D612 PNT One of these days...

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D612 PNT One of these days...

Postby ACourtney » Wed Jun 08, 2016 7:58 pm

I almost called this post Waking Sleeping (Black) Beauty, but in truth it was more like waking a grumpy teenager. Every time I thought that this car was ready for its MOT another little problem would show its head. And so a quick job, that was only going to take a month, or so, has lasted nearly 14 months. However, D612 PNT has been coaxed, persuaded and sworn at until, like that grumpy teenager, it has risen from its slumber and is now tested, taxed and insured and ready for a summer of motoring.

The story started back in 2013 when the owner of D612 PNT, Chris Nicholls, first approached me about helping to resurrect his Midas Gold Coupe. However, at that time I was too busy and couldn't have looked at his car. I was still too busy through 2014, but Chris waited patiently and kept in touch. In fact if anyone was hassling me about the car it was Tony Moss. Quite often Tony would visit my workshop and his route from Coventry would take him past Wellesbourne, where Chris was then living So Tony would start a conversation with " as I drove past Wellesbourne this morning, I wondered when you were going to make a start on Chris's car". So if Chris had lived in Kineton, or Snitterfield, i.e. just off Tony's route, his car might still be sitting under the dust sheet right now. Then early on in 2015, with the club getting ready to celebrate its own 30th anniversary and that of the Gold Coupe, I realised that I had a bit of free time and space in the workshop and that it might just be possible to get the car ready for Stoneleigh (well we got the car there and it was running, but not ready to go back on the road).

Chris has owned D612 PNT since it was new in 1988. He had the optional rear seat fitted, along with children's seat belts in the back, so that he could use it as family transport. He also had MED upgrade the engine to 1380cc, fitted a higher lift cam with roller rockers and a gas flowed head. So pretty fast family transport at that. However, a back injury meant that he couldn't comfortably drive the car, or work on it, so he laid the car up in his workshop for when his back got better. Chris's back did get better, but his life also got busier and so his Midas remained under that dust sheet. Fortunately, the workshop where D612 PNT was stored was kept warm and dry and the dust cover meant that the bodywork and interior was protected from damaging UV light. In fact you couldn't have asked for better storage conditions, unless you had thrown in a rolling road to keep the car exercised on (well some classic car owners do that!). Chris had regularly run the engine, up until five, or six years ago, when the car had refused to start. The result is that Chris's cars is one of the most original Midas Gold Coupes around. Its Black gelcoat is still shiny, if showing a few faint scratches and a bit of print-through from the woven rovings in the roof. While the interior is still just as it was in the late 1980s. However, after nearly 18 years of storage, all the mechanical bits would need checking over and revitalizing, where necessary.

As Wellesbourne is just off the M40, I called in to take a look at the car on one of my trips past. Although Chris had a boost starter, the engine barely turned over and it wasn't possible to start the engine. It also quickly became apparent that the fan belt was missing (why do I still call it a fan belt when it doesn't drive the fan?). In fact both the water pump and alternator were seized solid so it looked like it might need a new starter, whilst it definitely needed a new battery, alternator and water pump. I agreed to collect the car in early April, so I had four weeks to get the car running before Stoneleigh.

When I collected the car Chris had already bought a new battery for it, whilst I had got my hands on a replacement water pump and an uprated alternator - a new 70amp alternator of the type used on post '89 Minis actually worked out to be cheaper than the 55amp version of the Metro. So when I got the car back to the workshop my first job was to see if the engine would fire up. I had already checked that it would turn freely, by rocking the car in second gear, but I needed to find out what all the problems were and what was preventing the engine from starting.

ImageReady to get stuck in by Alistair Courtney, on Flickr

With the car off the trailer and on my scissor lift I was able to take a better look. With the new battery connected up the engine turned freely and the ignition was even giving a fat spark. However, no fuel was getting through to the carb so it seemed that a new fuel pump would be required. The piston of the SU carb was stiff, the oil in its damper pot having become waxy with age, but I squirted some fuel past it and tried the starter again. This time the engine fired and ran for a few seconds until the small dose of fuel had been used up. So far so good. The starter motor was working fine with the new battery and the ignition was working as well. I had agreed with Chris that I should give the car a thorough service, with new oil, oil filter and spark plugs then a 2 stage chemical flush of the cooling system and new coolant as well as the new water pump, alternator and drive belt (that's what I should be calling it instead of fan belt!). I had now added to that list, a new fuel pump and a service kit for the carb (which would prove to be even more necessary than I had imagined).

ImageRusty steel and crusty ally by Alistair Courtney, on Flickr

That seems like a good place to leave the first installment of the story. There is plenty more to come, so I will deliver it in small doses.
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Re: D612 PNT One of these days...

Postby ACourtney » Tue Jun 21, 2016 5:41 pm

I hadn't intended to leave it two weeks before continuing the story, but I seem to have been very busy again.

The first job was to fit the new fuel pump. This was the standard SU mechanical fuel pump, which is more than adequate for a 1380cc with a single 1 3/4" SU. The new pump only came with one gasket, so I looked out a second one for the other side of the spacer. I also added an inline filter before the fuel pump, which proved to be a wise move. With these fitted I tried the engine again and this time it fired into life. However, there was a puddle of fuel appearing under the front of the car, pouring out the carb's overflow pipe, so I quickly turned it off again. Just as well that I had bought that carburetor service kit from Burlen Services when I bought the pump!

ImageCarb about to be serviced by Alistair Courtney, on Flickr

The most common reason for SU carbs to overflow is that the float valve is leaking, either due to something getting in between the needle and its seat, or the needle itself is worn. However, as soon as I started to strip the carb down the real reason was immediately apparent: the float itself was stuck to the bottom of the float chamber by some dried up fuel residue.

ImageBefore cleaning by Alistair Courtney, on Flickr

After stripping down and cleaning all the parts, I rebuilt the carb using the SU service kit and some fresh oil in the damper pot. Once the carb was primed with new fuel from the pump, the engine fired up again, but this time with no fuel puddle forming under the car.
This took a fair amount of cleaning, but it was worth the effort and I soon had everything back together, with the new float valve, emulsion tube and seals fitted.

ImageAfter by Alistair Courtney, on Flickr
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Re: D612 PNT One of these days...

Postby coh1952 » Thu Jun 23, 2016 9:28 pm

1. My Mark 2 also refuses to fire up with no fuel being delivered to the carburettor. One of these days ... I have not moved the trailer from in front of the garage sop there is room to park the Midas there. Maybe tomorrow ...
2. On alternators: When I built the GTM Coupe, I found that the alternator for a Sherpa van delivers more voltage at lower revs than the Mini ones, which are designed to operate at a faster speed. Something to consider if you are fitting very high final drive ratio to reduce engine speed for quiet cruising.
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Re: D612 PNT One of these days...

Postby ACourtney » Fri Jun 24, 2016 5:42 pm

With the engine firing up and running, I thought that it was time to do the full service and the coolant flush. Changing the oil and filter was problem free and the oil was relatively clean, but at nearly two decades old the oil needed to be replaced.

I had bought a new water pump from Minispares, one of the high capacity pumps with the glass-filled plastic impeller and a three year warranty. I was a bit reluctant to fit it before doing the chemical flush. Not because I feared that of the chemicals themselves might damage the pump, but because I have seen large flakes of rust become dislodged when flushing A-series engines in the past. So I had been working at the old water pump with some WD40 and had managed to free it up. The downside of this was that it had started to seep through its seals, but the leak was relatively small and I was going to be watching the engine temperature carefully throughout the flushing process so I decided to keep the old pump on for the flush.

ImageWater pump kit by Alistair Courtney, on Flickr

Before starting the chemical flush I did a good old fashioned hose pipe flush, flushing in both directions to get rid of any loose sludge (why waste good chemicals on debris that is easily flushed out): First I removed the thermostat (another debris trap) and refitted the empty housing. Then I disconnected the pipe from the top of the cylinder head take-off. Then using two lengths of hose pipe, I connected one pipe from the tap to the engine (cylinder head take off) and the other from the engine (pipe) into a bucket. I used a white bucket which would let me see the debris coming out. The first flush took nearly ten minutes before the water came out clean and then I reconnected the hose pipes around the other way to reverse flush and remove any debris trapped by the first direction of flow - the heater matrix is the worst remaining place for trapping debris and in really bad cases it is worth disconnecting the pipes and flushing it separately. The second flush was over much quicker and the debris collected from both flushes wasn't too bad. Mainly small flakes of rust of around two to three mm in size. So it seemed that the cooling system hadn't fared too badly over the extended lay-up, but I thought it was still worth proceeding with the chemical flush. I used the Holts two stage flush - the first stage is the active flush that removes limescale and surface rust and the second stage is a neutralizing stage that is meant to prevent further corrosion and condition the rubber pipes and seals. Experience has taught me that it is also worth doing another hose pipe flush in between the two stages as the first one will free up a lot more loose particles. So, what with allowing for the engine to cool down again between treatments I allowed plenty of time to complete the job.

The first step involves filling the cooling system with the stage 1 liquid and clean water and then running the engine for thirty minutes. This seemed to be going well and the leak from the old water pump wasn't too bad, until after around five minutes the engine spluttered to a halt. I had been working on another car just a few feet away and the way that the engine spluttered had made me think immediately of a fuel feed issue. I had filled the tank with fresh petrol, so when I looked at the fuel filter I was surprised to see that it was full of a bright green fluid. I disconnected the fuel pipe from the pump to the carb and pointed it into a jam jar. Then I cranked the engine over and started to fill the jar with the strangely green and very pungent smelling liquid. I can't describe the smell, but the slightest whiff was choking.

ImageStrange green liquid by Alistair Courtney, on Flickr

I carried on cranking the engine over and pumping the green liquid through, filling the jar up completely twice - just as well that Chris had supplied a new battery for the car! In the end I must have removed over a pint of the green liquid before fresh, clean (and healthy smelling) petrol came through the pipe. This still left the float chamber filled with the green stuff, but by squirting clean fuel into the carb I was able to get the engine to fire up briefly and after three false starts it took hold and continued to run for another 25 minutes, or so. I have been told that the green liquid is just one of the chemicals that is found in petrol and if stood for long enough (try 18 years!) petrol will separate out into its constituent parts.

After leaving the engine to cool down I drained out the stage 1 flushing mixture and then repeated the hose pipe flush procedure until the water was running clear and I was happy that I would get no more debris out. I then filled the system with the stage 2 liquid and topped it up with fresh water before running the engine for another half hour. Then when the engine had cooled down again, I drained out this liquid and set about replacing the water pump. With the pump removed I could see into the water jacket of the block and could see how effective the flushing process had been.

ImageBlock face cleaned by Alistair Courtney, on Flickr

The gasket face cleaned up nicely using a plastic scraper and WD40 to loosen up the remaining traces of gasket. I then gave the sealing area a wipe with some acetone and fitted the new pump with its new gaskets assisted by a thin smear of blue Hylomar. I then refitted the thermostat with some new gaskets and filled the system up with some new Bluecol antifreeze mix.

ImageAll back together by Alistair Courtney, on Flickr

With the drive belt back on and the new new alternator connected, the only remaining job on the engine was to clean the K&N air filter. The K&N filter is a cotton gauze filter that uses an oil film to trap dust, which can be washed off and replenished. A K&N service kit had been purchased consisting of two spray cans, one of cleaning fluid, the other of the filter oil. I'm told that the filter can also be cleaned in a washing machine using a boil wash, but I haven't tried that myself.
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Re: D612 PNT One of these days...

Postby ACourtney » Thu Jul 21, 2016 8:34 pm

I seem to have been rather busy since the last post. I'm afraid that its more words than pictures this time.

The engine was now running, if not ticking over particularly cleanly and it now had new oil, oil filter, spark plugs, rotor arm and distributor cap to go along with the new water pump, coolant, drive belt and alternator and a clean and freshly oiled air filter. The next thing to tackle was the brakes.

Chris had used Silicone brake fluid (SBF) from the start, which doesn't take up moisture from the atmosphere. So in theory the brakes should be in a better state than would be expected with conventional fluid. SBF will float on water and thus any water in the system would find its way to the lowest points. If anywhere was going to suffer then it would be in the traditional Midas brakes problem area of the rear slave cylinder. One neat feature with SBF is that it loses colour with age. New SBF is purple in colour and when that has faded it is time to renew the fluid. This makes bleeding extremely easy as you can quickly see when all new fluid is coming out of a bleed nipple. Unsurprisingly, after 18 years the fluid in the ca was almost clear.

One advantage of having the car up on the scissor lift was that I could take off all the wheels and check over the brakes before bleeding them. The discs had some fine surface rust, so I gave them a quick once over with some a small abrasive disc in my mini air sander. I slipped the pads out and they looked okay, if around half worn. I gave the pistons and seals a look over using a torch and a dentist's type mirror and they looked okay, so I then put the pads back in. At the back it was a similar story. The drums had some fine surface rust, that I cleaned off with an abrasive drum (one of those Scotchbrite wheels) in my power drill. The shoes looked okay, so I took them off to access the rear slave cylinders. I peeled back the dust covers at each end of the cylinders and all looked okay. No signs of rust or any leaking fluid.

So it all looked okay and in fact once it was all back together the brakes all worked, even if the pedal was very spongy. It looked as if just new fluid would be needed. Before starting on the bleeding process. I used my hand operated vacuum pump to remove all the old fluid from the reservoir. This gave me the opportunity to clean up a small amount of dark residue from the bottom of the reservoir before refilling with new SBF.

Tony Moss had called by so I roped him in to pump the pedal. I have a Gunson's eazibleed and the vacuum pump can be used to suck the fluid through the system too, but I still prefer to have a human foot to operate the pedal if one is available. In fact we had only bled enough old fluid out from the N/S rear to fill the 18" length of clear pipe, that I was using to observe the fluid, before Tony shouted "that's a good solid pedal now". I replied "it shouldn't be, the bleed nipple is open!" Nothing was coming through so I opened the valve up as much as I could, without it coming away, and asked Tony to give it a good hard push. Suddenly a clump of brown debris, around an inch long, shot into the pipe.

We carried on bleeding and now the fluid was coming out easier and the old clear fluid was quickly replaced by new purple SBF. Apart from the brown debris, that looked like a collection of flakes of rust, there had been no air bubbles present. So we moved on to the O/S rear and that too quickly bled through, with clean, bubble free, purple SBF. The fronts all bled up quickly and then we really did have a good firm pedal. The only hiccup being the rusty debris. Judging by the amount of fluid that came out before it blocked the nipple, I suspect that the debris had collected in the rear brake restrictor. However, it all came out as one plug and was not followed by any flakes, or air bubbles. So I can only assume that the rust had formed, or collected in the valve over time and simply travelled down the pipe with the fluid.

It was a quiet Sunday afternoon and with the brakes and engine all working, the next thing to do was to give the car a little road test around the estate. Starting gently, I gave the brakes a tentative test and it immediately became obvious that the brakes had more bite than the 18+ year old tyres could cope with. They may have had good tread and crack free sidewalls (thanks to careful storage), but they were as hard as billiard balls. Also on this test it became obvious that there were problems with the gauges and warning lights. One gauge didn't seem to move though, the fuel gauge. It had been reading 3/4 full from the first time I had got the engine running and it was still reading 3/4 full, which was odd as a) I had only put a gallon and a half of fuel into a supposedly empty tank and b) I had extracted around one pint of strange green fluid (probably residue of some additive that had been released by the fresh fuel) and run the engine for over an hour.

On returning the car to the workshop I crawled under the back and disconnected the wires to the sender gauge. I connected it up to the sender gauge from my spare tank and, no real surprises, I could make the duel gauge go up and down by moving the float. So evidently the one in the tank was stuck in the 3/4 full position. (at last a chance for a photo - the sender unit)

ImageDSC_0151 by Alistair Courtney, on Flickr

Well, I had just about run out of time for today and I've just run out of time tonight, but perhaps I can continue the story tomorrow evening.
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Re: D612 PNT One of these days...

Postby ACourtney » Fri Jul 22, 2016 9:49 pm

So with one week to go before Stoneleigh (2015) the position was that the engine was running and the brakes were working. However, the engine wasn't ticking over nicely and the tyres were so hard that there was no way they would grip the rollers to pass an MOT test. Furthermore, the instruments and warning lights were behaving strangely, except for the fuel gauge that was reading 3/4 full irrespective of how much fuel there was in the tank. I had also noticed that the headlights were misbehaving, sometimes they would come on and some times they wouldn't.

Chris Nicholls came over to look at the car and discuss what we could do before Stoneleigh. It was clear that the car wasn't going to be ready to pass an MOT in the coming week, so we agreed that I would take the car there on my trailer on the Saturday and then Chris would tow the car home on Monday, before bringing it back over to my workshop the following week. With that agreed, we decided that the first thing to investigate was the fuel sender gauge.

After loosening the rear exhaust mounts and undoing the fuel filler neck we were able to drop the tank out. Actually there was a little more to it than that as two of the fuel tank bolts had to be accessed from under the rear seat. Chris had opted for the full rear seat in his Gold and his daughters had made good use of them, but now the seat was in our way. This was the first time I had worked on a Midas with the proper factory rear seat so it was useful to have Chris there to guide me.

ImageDSC_0169 by Alistair Courtney, on Flickr

We soon had the tank out and once I had undone the retaining ring we were able to see what the problem was with the sender unit. It was encrusted with brown goo, the same sort of brown goo that I found in the float chamber. The float was simply locked in the 3/4 full position. Not only that but the tank itself had a layer of brown goo, probably around 1/4" thick, at the bottom and powdery white stalactites hanging from the top. This didn't look too promising, cleaning a float chamber out is one thing, but a fuel tank is a totally different proposition. Fortunately, Chris knew of a Marine Engineering company that could steam clean the tank, so our next decision was to fit my spare tank so that the car could be run over the Stoneleigh weekend. With my spare tank fitted Chris took the car out for a quick drive around the estate, the first time he had driven it for over 18 years.



He returned with a smile on his face, but agreed that the old tyres were a lost cause. He also felt that the wheels looked a bit tatty. So if we were going to fit new tyres then we might as well take the opportunity to refurb the wheels at the same time.

As those of you who attended Stoneleigh in 2015 will know, we followed the plan and I took the car along by trailer on Saturday. It spent the night in the MOC marquee and on the Sunday it took part in the group photo shoot for Complete Kit Car Magazine. Chris came along on Monday with his wife and took the opportunity to drive her around the showground. He also turned down an offer of £6000 for the car, although he did give it some serious consideration.

ImageCKC Cover July 2015 by Alistair Courtney, on Flickr
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Re: D612 PNT One of these days...

Postby ACourtney » Tue Jul 26, 2016 8:46 am

During one discussion at my open day last Sunday, it occurred to me that I hadn't adequately covered the initial starting up procedure from when the car first arrived at my workshop.

Although Chris had periodically run the engine and warmed it up during the early days of storage, he could not remember how long it was since he had last done so. I thought that I should treat it like any engine that has been stood for a long time, which meant removing all the spark plugs and squirting some oil into each bore before even thinking of trying to turn the engine over. If you look around the internet I'm sure that you will come across this procedure and will see recommendations for anything from a teaspoon to a tablespoon of oil. I don't find it very easy to pour oil into a spark plug hole using a spoon so I just gave each cylinder three good squirts of oil from my oil can.

With the oil inside I then turned the engine over slowly by hand. That isn't that easy on a Metro sourced A-series as the aluminium engine mount stops you from getting a socket onto the crank pulley nut. In this case the drive belt was missing so I used my belt-type oil filter wrench around the crank pulley to slowly turn it over. It turned over quite easily and smoothly so I then felt safe to proceed and try the starter motor. As you will have read above, that is when the problems started!

Another thing that I didn't mention was that I had also checked the compression on each cylinder. The first time I did this was in between the first attempt to start the engine, when the fuel pump was not working and the second, after replacing the pump. The cylinder pressures were all quite high, between 200 and 215 psi. Adding some more oil in the bores put them up by around 10 psi each, which is a smaller increase than I would normally expect. Some months later, when trying to sort out a fuelling issue, I checked the pressures again and they all lay in the range 170 to 180 psi when cold and squirting in oil added another 25psi or so to each cylnder. I suspect that the when I first checked the pressures the cylinder rings were probably holding some residue of old oil and fuel which was improving the sealing. This will have been burnt off after we had run the engine for a couple of hours, or so, returning the cylinder pressures to a more normal reading.
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Re: D612 PNT One of these days...

Postby ACourtney » Thu Jul 28, 2016 9:10 pm

Chris returned the car to me the Friday after Stoneleigh and took away the wheels to have them refurbed. The car was still on its original Revolution RFXs with polished rims and black centres. The rims were starting to show oxidation through the clear lacquer and the black spokes had various marks on them, so Chris decided to have them shot blasted and powder coated by a company in Redditch that he knows well. For any owners in the Midlands looking for powder coating, Washford Finishings are situated on the Washford trading estate in Redditch and also have a sister company, Blackpole Powder Coating Ltd in Worcester. Chris chose a silver powder coat finish all over, rather than the two colours of the original:

ImageDSC_0119 by Alistair Courtney, on Flickr

Whilst the wheels were away we got on with swapping the fuel tanks again. Chris had the tank steam cleaned by a marine engineering company. Although the tank was returned spotlessly clean, there were a couple of signs of rust spots starting to appear. Particularly around the joint of the filler pipe. So Chris also treated the rust and then sealed the surface of the tank with a tank lining paint. Chris already had some going spare, so I'm not sure which one he used. However, I have had good experiences with the POR15 fuel tank sealer that Frosts sell. Whilst Chris had been getting the tank ready, I had cleaned up the old sender unit and obtained a new sealing ring from Mini Spares - fortunately these are the same as used on all the later Minis. So it all went together very easily, we even found time to spray some extra stone chip on the more exposed underside of the tank. And then the car fought back: Chris refitting the filler cap after I had reconnected the neck to the tank and it literally fell apart in his hands.

After a quick discussion, the obvious solution was to fit an MGF fuel cap. Anyone who has seen this update will know how well the MGF cap follows the curves of the Gold's rear wing. It is almost as if the designer of the cap had a second life in mind for the caps in case the MGFs they were fitted too all ended up being scrapped! The key to getting this to work is to use an MGF filler neck as well. This involves removing the original flange and relocating it to fit on the underside of the wheel arch. To get the flange to sit snugly the underside of the wing needs to be ground flat to create a 20mm wide flat ring around the opening. On the Coupe, this may involve breaking through and then having to patch up the inner wing with glass loaded filler. I didn't take a photo of Chris's car, but here is one from an earlier car.

ImageIMAG0187 by Alistair Courtney, on Flickr

That photo shows the original flange being reused, but since then I have had some new flanges laser cut from slightly thicker steel. Apart from being thicker, the hole cut in the centre is rounder and cleaner, so the flange is easier to braze in place. Previously I had used Charlie Dodd's technique for positioning the flanges, which involved using some welding clamps and a large jubilee clip around the tube to hold the clamps. However, I found that if I really wanted to get the cap to fit well then the flange was never square to the tube and that was difficult to achieve using Charlie's method. My new method is simpler: I clamped the new flange in place using the two screws that will locate it, then I pushed the filler tube into place with the cap fitted. I then got the outer face of the cap positioned how I wanted it and taped it in place with some masking tape. Then from the underside I applied four big blobs of non-runny epoxy adhesive to join to temporarily join the flange to the tube. Once the epoxy was set, I undid the cap, undid the screws and took the flange/tube assembly over to my vice. I then carefully locate the tube in the vice so that the flange was fully supported and brazed the flange into place. The epoxy melts with the heat and just blows away with the flame from the torch. So it is vitally important to locate the assembly in the vice carefully to ensure that the flange does not move from its desired position.
After brazing I retouched the paint on the neck with some fuel resistant paint - Eastwoods Extreme Chassis black - before refitting it.

Image2015-05-24 12.45.00 by Alistair Courtney, on Flickr

The sharp eyed will notice that I also modified the breather tube. The MGF breather has quite a large radius that creates a clearance issue with the Gold, but in this case there was another issue that we only discovered later. More of that in another posting, but in the meantime this is the finished result:

Image2015-06-05 15.53.31 by Alistair Courtney, on Flickr
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Re: D612 PNT One of these days...

Postby Geoff Butcher » Fri Jul 29, 2016 8:20 pm

I have found recently that my MGF filler neck has gone rusty at the top where it contacts the rubber seal, so there is slight seepage on left hand bends. It's rather annoying that almost the newest thing on the car has deteriorated so soon.
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Re: D612 PNT One of these days...

Postby ACourtney » Sun Jul 31, 2016 8:14 am

Geoff Butcher wrote:I have found recently that my MGF filler neck has gone rusty at the top where it contacts the rubber seal, so there is slight seepage on left hand bends. It's rather annoying that almost the newest thing on the car has deteriorated so soon.


Hi Geoff,

The filler neck has a very light zinc plating under its original paint. Zinc has a low melting point (around 400°C IIRC) and so the zinc is easily damaged during the brazing/soldering of the flange to the tube. It will certainly be burnt away on the inside of the pipe adjacent to the braze spots. It is also easy to damage the plating around the top when removing the original flange. Especially if you are trying to make a fine cut to re-use it, which is one reason why I now use a new flange each time.

I now re-paint the necks with a zinc rich primer, before applying the petrol resistant top coat. I make sure to paint both inside and outside of the tube, which isn't that easy. I wedge the non-return flap open before painting to make sure it doesn't get glued shut by the paint.
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