Mayonaise colour oil cap for TT
Discussion
Could be HGF, but equally *could* just be crankcase condensation, especially this time of year.
Check for oil (mayo/sludge) in the coolant - that is definitely a sign of trouble. If that's clear then take the car out for a good run of an hour or so to get it really hot, and see if the sludge clears up.
Check for oil (mayo/sludge) in the coolant - that is definitely a sign of trouble. If that's clear then take the car out for a good run of an hour or so to get it really hot, and see if the sludge clears up.
Adam77 said:
I have tried taking it for long drives, the mayonaise gunk eventually comes back.
Not sure what you mean by that. The gunk (water/oil emulsion) will form when the engine is cold, and boil off when it is hot. If you have HGF putting coolant into the oil it will form continually even when the engine is hot. So, it coming back when the engine has been cold is normal. It remaining while the engine is hot, isn't.I am so confused. Before I think I had any problems I used to drive the car for around 15-20 minutes and the temp indicator would go to the correct spot which is 90 degrees and stay there. I never noticed it flutuating before I tried to top up the oil and saw this yellow stuff around the cap. I you feel i don't have an issue no worries. I don't know much about engines and have been stung by Audi for hundreds of pounds just to carry out diagnosis checks at £135 plus VAT per hr!
i would guess on the head gasket, when the engine warms up the water pressure increases and a small amount passes through the gasket into an oil channel, hence the mayo, your engine temp goes over normal because it cant pressurise correctly due to the leak, eventually the engine temp reaches a point where expansion through heat of either the gasket,block,or cyl head seals the leak allowing the cooling system to operate correctly and bring the temp down to normal operating temp, you need to borrow/buy a coolant pressure testing system for an hour, simple bit of kit and very easy to use, probably cheaper than an audi diagnostic, but then again i could be wrong.Good luck with it anyway
twistedsanity said:
i would guess on the head gasket, when the engine warms up the water pressure increases and a small amount passes through the gasket into an oil channel, hence the mayo, your engine temp goes over normal because it cant pressurise correctly due to the leak, eventually the engine temp reaches a point where expansion through heat of either the gasket,block,or cyl head seals the leak allowing the cooling system to operate correctly and bring the temp down to normal operating temp, you need to borrow/buy a coolant pressure testing system for an hour, simple bit of kit and very easy to use, probably cheaper than an audi diagnostic, but then again i could be wrong.Good luck with it anyway
Not sure I agree, I think you have two issues not related, 1 - condensation in cold weather, which is very common this time of year if you are only driving 15-20 mins at a time. it will reoccur very quickly if the top end of the engine isn't getting warm enough, 20 mins is not enough.
2- failure of the temperature sender unit ( very common on the VAG engines around this time,) does the temperature go up ok, then when you are on a faster road, it drop slightly?, then back up to 90? that sounds like the sender or a thermostat issue.
only real way to test for a HGF is an emissions test on the coolant.
Adam77 said:
Ive just checked it, its a pinky kind of colour and it is clear.
If you had oil in the coolant, that would be pretty conclusive proof of gasket failure, probably a head gasket.Since the coolant is still clear, this isn't proof that there is no leak but it's a pretty strong indication that there's no leak.
The fact that (if I've understood you correctly) the emulsion is boiled off after a hot run and only returns slowly after subsequent short runs is consistent with simple condensation so there is no firm evidence of head gasket failure here.
You could get additional confirmation that it's OK by running the engine with the pressure cap off and confirming that when you rev the engine you don't get froth going round with the water, and (if you're still in any doubt) getting the coolant tested for HC contamination. This would test for a leak between the chamber and the cooling system, which is very common after head gasket failure.
Unless you get some other evidence suggesting head gasket failure, my conclusion would be that this is simple condensation. You'll probably find most cars have it at this time of year.
The unusual temperature gauge reading may just be a consequence of the recent cold weather, or the thermostat starting to play up, or the sender.
Keep an eye on it, if it seems to be getting worse go back and do the other checks again, but I wouldn't spend hundreds of quid getting it investigated just based on the evidence you've told us so far.
I am so grateful for all your replies. I do really hope its not a HG problem. The pure fact that it never over heats is probably a good sign, although having mayonaise coloured gunk on your oil cap is slightly more worrying. I will arrange for a test to be carried out on the coolant and also to get the sender/thermostat to be checked.
What has annoyed me is that 2 weeks ago I took it into Audi because my engine management light came on, after being at the garage for ...45minutes I got charged £182incl vat for replacing a coolant sensor apparently!!
Once again many thanks for your prompt responses.
What has annoyed me is that 2 weeks ago I took it into Audi because my engine management light came on, after being at the garage for ...45minutes I got charged £182incl vat for replacing a coolant sensor apparently!!
Once again many thanks for your prompt responses.
Adam77 said:
I am so grateful for all your replies. I do really hope its not a HG problem. The pure fact that it never over heats is probably a good sign, although having mayonaise coloured gunk on your oil cap is slightly more worrying. I will arrange for a test to be carried out on the coolant and also to get the sender/thermostat to be checked.
What has annoyed me is that 2 weeks ago I took it into Audi because my engine management light came on, after being at the garage for ...45minutes I got charged £182incl vat for replacing a coolant sensor apparently!!
Once again many thanks for your prompt responses.
having just replaced the sender in a golf ( same part), parts cost was £32, and took exactly 3 minutes to change.What has annoyed me is that 2 weeks ago I took it into Audi because my engine management light came on, after being at the garage for ...45minutes I got charged £182incl vat for replacing a coolant sensor apparently!!
Once again many thanks for your prompt responses.
madrob6 said:
Another thing worth checking is the oil cooler.
Don't know much about the TT engines but the oil coolers on Passats are a fairly common failure which would let coolant into the oil supply.
Not sure how you would get water into the oil, usually the oil pressure is higher, therefore would tend to get oil in the water system, rather than the other way around. Don't know much about the TT engines but the oil coolers on Passats are a fairly common failure which would let coolant into the oil supply.
phumy said:
madrob6 said:
Another thing worth checking is the oil cooler.
Don't know much about the TT engines but the oil coolers on Passats are a fairly common failure which would let coolant into the oil supply.
Not sure how you would get water into the oil, usually the oil pressure is higher, therefore would tend to get oil in the water system, rather than the other way around. Don't know much about the TT engines but the oil coolers on Passats are a fairly common failure which would let coolant into the oil supply.
madrob6 said:
phumy said:
madrob6 said:
Another thing worth checking is the oil cooler.
Don't know much about the TT engines but the oil coolers on Passats are a fairly common failure which would let coolant into the oil supply.
Not sure how you would get water into the oil, usually the oil pressure is higher, therefore would tend to get oil in the water system, rather than the other way around. Don't know much about the TT engines but the oil coolers on Passats are a fairly common failure which would let coolant into the oil supply.
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