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Overheating Tin Top


Guest timswait

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Guest timswait

I got the replacement coolant reservoir from Audi, fitted it in less than half an hour. There were not obvious cracks in the old one, although it was extremely discoloured compared to the new one. I plugged in the laptop took the car for two runs up the road that's caused problems in the past (out of Sheffield from Eccie road into the peaks, it's not steep but it climbs constantly and is twisty but fast, especially if you wait for a long gap in the traffic so you can push hard without catching anything up!). As expected the gauge on the dash didn't move off 90C. On the first run I drove in high gears keeping the revs low and making it labour, the ECU measured temp reached a max of 92.7C. On the second run I drove hard, revving to the redline on each gearshift and foot flat to the floor as much as possible, that time it only reached 90.9C. The only issue was when I stopped at the top after the second run to turn round I did see it briefly spike to 96.3C, but it was only brief, so I think it was heat soak and the effect of suddenly dropping to tickover after loading it heavily.

So in summary it appears fine, but I am touching wood as I say that because it also seemed fine after changing the thermostat. I need to carry on monitoring it for longer until I can really be sure. The water pump theory also looks less likely as if it was going to slip then I would expect it to slip most at high rpm when it's trying to push the water round as fast as possible, but actually that run was slightly cooler than the low rpm one when it wouldn't have been spinning as fast.

So thank you to everyone who's contributed, especially richyb66, it is looking like you hit the nail on the head (again touching wood here!)

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  • 4 weeks later...
Guest timswait

Well, it wasn't the expansion tank. Or the radiator. :( after a few days of driving after changing the expansion tank it was apparent it was still loosing coolant. So changed the radiator, and same. The gauge never moves off 90 (once it's warmed up) but the only trace of coolant I can ever find in the engine bay is around the vent on the expansion tank, so it is boiling off. Every time I had my laptop plugged into it then it behaved itself however hard I thrashed it, so I got a bluetooth adaptor to leave permanently plugged in and now every journey I take I monitor the coolant temp on my phone. 99% of the time it is completely normal, but just occasionally it will really spike. Today I was driving in the peaks and got to a moderate but short hill which I drove up normally and it suddenly shot up from 90 to 100 by the time I'd got to the top (dash gauge still on 90). The next hill which was steeper and longer I thrashed it up redlining each gearshift and it stayed around 88-90! It doesn't seem to like labouring at low revs, but even labouring at low revs up a hill won't do it every time. It's so intermittent I'm running out of ideas. Maybe it's the water pump. Maybe it's the head gasket. I'm thinking of giving it to a garage to change both as I really don't have the time, but it'll be a lot of money and I'm not sure it'll fix it. I just don't have any other ideas, I've run out :(

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A work colleague had a strange overheating issue with a golf tdi which turned out to be corrosion blocking the metal tube connecting the header tank to the cylinder head/thermostat housing. Cleared the pipe and the issue went away

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What replacement stat did you fit? Audi one? Might be worth repeating that for the cost is not much and it's an easy fix. We have all know new parts supplied duff. Certainly worth pulling it out and trying it in a pan on the stove just to reassure yourself the new one is working properly.

 

Nigel

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Guest timswait

There don't seem to be any metal pipes in system, everything is rubber or plastic. The coolant has been changed twice now, once by the garage when they changed the stat and once by me when I changed the rad. Both times it's appeared clean and clear with no signs of corrosion.

I changed the stat just over a year ago when it had been running cold (according to the dash gauge) that one wasn't a genuine Audi part. When I took it to the garage they took it out and tested it and said it opened and closed, although possibly slightly more slowly than they'd like, but they thought it was fine. I told them to replace it anyway and they used a genuine Audi one, so now it has an OEM one. So I don't really think it is the stat as it's had two, one of which was only a year old and definitely opened and closed the other of which is a brand new OEM part. On the other hand they are pretty cheap and quick enough to change that I can find time to do it myself, and it did seem to improve if not cure the situation when the garage swapped the last one (although with the intermittent nature of the fault I wouldn't swear it definitely did improve even).

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Guest timswait

A little bit more testing today and I can see some consistency in pattern of temperature of coolant according to ECU. It is definitely related to low RPM. Going up even a moderate hill at 1500-2000 RPM at half throttle (not really labouring) will get the temperature ramping up rapidly to 98-100. Dropping down a gear or two to rev it to 3000+ RPM and the temperature immediately drops to 88-90. Even going up steeper longer hills and flooring it, braking hard flooring it again it won't go above 90 as long as I keep the revs up.

Steve: There is a metal pipe, I see what you mean, it was under a plastic cover. I'll take it off and clean it tomorrow, although as I say the coolant looks very clean so I doubt there's significant corrosion anywhere in the system.

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Guest timswait

Took the metal pipe off that Steve described. As expected no sign of corrosion or any other blockage. So looks like I'd better bite the bullet and book it in for water pump to be changed, may as well get them to do the timing belt while they're at it (it's a timing belt driven one). The only question is should I get them to change the head gasket too? Does anyone think that's at all likely to be an issue. If it does need changing then it obviously makes sense to get it all done in one go. The car has 185000 miles on the clock.

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Guest Getting There

Hi

 

There are well known problems with the water pumps with plastic impellors which begin to spin on the shaft. I had exactly the same issues on my Octavia with the same engine. Low RPM mid load would get hot. Its not hard to change just fiddly.

 

HTH

 

Chris

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  • 3 weeks later...
Guest timswait

Good news and bad news! It seems I may finally have identified problem. I bit the bullet and changed the water pump (and timing belt), meaning having to take most of the front of the car off. Once I got to the water pump there was a pink stain coming down from it, I'm pretty sure it had been leaking. Probably only a minor leak when pressurised, hence no puddles on the ground, but it's the first thing I've found in the system that's clearly at fault (and I've already changed almost everything else!!).

However the bad news is that I seem to have messed up the timing :( I didn't have the cam and crank locking kit, but I was so careful to make marks on the old belt and new belt, corresponding marks on the sprockets, counting the number of teeth between the marks, taking photos of the marks before removing the old belt and checking everything three times. I've done other engines this way before and they've been fine, but on putting it back together it's very noticeably down on power (although starts easily, runs smoothly and without smoke) and diagnostics gives an error 012296 P3008 - 000 - Camshaft Position Sensor (G40): Signal Out of Range, which a bit of Googling seems to be due to camshaft misalignment. The recommended procedure involves using the locking tools and loosening the cam sprocket on the shaft so it can be moved by fractions of a tooth. I hadn't thought that was necessary if I put the new belt on in the same position as the old one (and I'm pretty sure I did), but it appears it is necessary :( So I now need to re-do the job, using locking tools this time :( I don't suppose there's anyone around Sheffield with a set of VW/Audi TDi locking tools is there?! :)

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Guest nippynick

I would test the rad for a blockage. get the car up to temperature then turn it off and leave to stand for five minutes if the centre of the rad matrix is still cold its almost certainly blocked.

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What engine code is it? I've done probably 7 cambelts on 1.9 Audis and VW's and all I've ever done is set the engine at TDC using the pointer in the bellhousing and sticking it in first gear.

 

I lock the injector pump with a (think it's) 7mm drill bit and I remove the cam cover and use a stack of steel shims to lock the cam against the gasket seal face of the head using the groove in the back of the cam Probably needs about 6mm thick steel strip 25mm wide 120mm long at a guess.

 

I've never had a problem getting everything to line up but if you need to adjust the cam you have to loosen the cam sprocket bolt slightly, use a 2 leg puller to break the taper between the sprocket and the nose of the cam and then align the cam before you re-tighten the bolt.

 

As I said I've not had to adjust the cams ever on a 1.9tdi and never had a problem but I did have the adjust the cams when I did the belt on the quad cam 40 valve V8 in my S6.

 

The process is basically same - get all the marks somewhere near, lock the crank, lock the injector pump, lock the cam (breaking the taper if you have to). Fit new belt and tension it correctly. Re-tighten cam sprocket bolt. Obviously don't loosen the cam sprocket bolt loads so the sprocket is flapping around. You just want it to be able to turn on the taper when you tension the belt.

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