Small amount of coolant under 1.8T today...

Veero

Veero

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So drove about 10 miles today into town and whatnot, went to change the driveshaft on the missus' 306 and noticed a small puddle under my A4...

Had the pink tinge like the coolant and sure enough the level was just under the Min mark.

Let it cool for a few hours, jacked it up, popped the under tray off and started up but no obvious pipes leaked at all. Loosened the header tank cap and there seemed to be a fair amount of pressure built up in only 10-15 mins (hadn't even warmed to 90°) and it spooged some coolant again, leaking into the same place it appeared to have leaked from before judging by the marks on the undertray.

So, headgasket on the way? :(
 
could be a stuck stat
 
Had the stat replaced when the cambelt was done only a few months ago.

Every morning last week it warmed up to and stayed dead on 90° within 5 mins. Wouldn't have thought it would go already.
 
I am also experiencing the same problem. I had the timing belt and water pump changed last year. I'm going to a mechanic tomorrow to get it inspected. I'll keep you guys posted...
 
Remove the header tank and check for a crack.Mine had one at the back.New tank about £12
 
Doubt its the headgasket mate. Possibly leaking from the changed water pump ?
 
Just ran it up nice and warm and took it for a spirited drive, stopped several times to check, no dripping. No obvious cracks in the header tank or any leakage from any hose at all. No steam/clouds out of the exhaust.

Will just keep a bottle of water with me this week and keep an eye on the levels.

Hopefully just a funny five minutes...
 
could it have just been over filled at all
 
But I hadn't touched the coolant system at all since owning the car. Last time it would have been topped was 2-3 months back when the cambelt/pump/stat/tensioner etc were changed by my local garage and I've done all sorts of journeys since. Long drives, short trips to town etc.

Strange...
 
Give all the pipework a good going over.

I know the G12 coolant has additive in it to attepmt to seal small leaks.
So you may have had a small leak and the G12 has sealed it - this happened on my Seat Ibiza Cupra, it was obvious where it had leaked from as the coolant had made pink foam where it had plugged the leak.
 
Well been watching the level like a hawk all week. It hasn't budged. Every day I've got to work it's been bang on Max. Every day when it's cooled down and I leave to go home it's 5mm above Min, with no obvious signs of any leakage.

So 1 minute from work today and 'Coolant' appears on the DIS. Limp it to work in 6th pop the bonnet and the level is on max. Some fairly noisy gurgling and bubbling sounds coming from the engine though.

Could the water pump have gone like Mark suggested above and the coolant's not circulating properly? Waterpump was changed when belt, tensioners and stat were done. I would be fairly angry if the pump had gone already. Can't remember if it was a metal or plastic impeller version.

I'm out of ideas...
 
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My new water pump failed within 20k of changing it, didn't leak till it was left stood with engine off but the bearings had collapsed
 
Were there original VW waterpump parts........aimed at both of you?
 
Sadly not. Surely it would be making lots of noise if the water pump had failed that badly?

When I turned the engine straight back on this morning the DIS check came back OK so maybe I've had a faulty coolant level sensor that leaked slightly then sealed and is now playing silly buggers. Going to pop to my local garage on the way home and have them check it.
 
Veero said:
When I turned the engine straight back on this morning the DIS check came back OK so maybe I've had a faulty coolant level sensor that leaked slightly then sealed and is now playing silly buggers. Going to pop to my local garage on the way home and have them check it.
Click to expand...

but then what would cause the gurgling and bubbling sound you heard?


 
It would overheat if the pump failed.Might just be some muck in the system
 
It was gurgling a bit before. On the way to the garage last night the temp shot up to 120°C and the coolant temp warning came on.

Ran it through the diagnostics and there's a short on the + terminal on the ECT sensor, also top rad hose felt airlocked, so left it with them for today.

Water pump must be doing something as all the heater matrix hoses are hot, so seems unlikely the pumps failed seeing how old it is.
 
I got mine checked out, and unfortunately it is the water pump! I only got the timing belt and water pump changed almost a year ago. I've been told its the water pump but luckily it's still under warranty.
I don't think mine was a genuine Audi part :(
 
i had a problem with mine where i was loosing water and i hadn't touched the coolant system but it was leaving a few drips on the floor.

bout a week later i looked again to check levels and noticed where the leak was coming from, it was coming out the rail that runs along the top of the engine under the engine cover on the top of that is a bleed screw, well the top was still on but had cracked off and it was leaking up the thread when the preasure built up.

you can't buy the bleed screw separately and you have to buy the part from audi £50 just glad i found it as little leaks are annoying.
 
Well a new ECT sensor later and it now behaves gauge wise.

The old sensor had signs of evaporated coolant on it, so the suspicion is that the sensor leaked slightly causing the very small puddle and the electrical fault/incorrect reading fault causing the coolant temp warning.

The garage bled it too as the top rad hose is now definitely liquid filled and there's no gurgling. Problem seemingly solved.

Cookies I'm sure that screw is available separately from somewhere, I doubt Audi would go to the trouble of custom manufacturing a bleed plug so if it did break you had to buy a new pipe too. Should be easy enough to determine what the thread is by measuring the OD of the thread and measuring the TPI (Threads Per Inch) with a thread gauge, providing of course you can get the plug bit out.
 
Hmm not solved, coolant temp wanrings come on a couple times again, despite a 300 mile journey where the temp stayed rock solid on 90°C.

If I stop when the coolant temp warning comes on and the gauge creeps up to 120°C, the top rad hose is not too hot to touch and the heaters blow out lukewarm air. Gotta be pump not pumping or stat not opening I guess...
 
Are your cooling fans working? I am not 100% sure of the 1.8t but i presume its the same as my diesel with electric fans?
Also does the top hose go rock solid?

Easy way to check if the water pump is working ok is to see if in the header tank the small return hose to it has a flow of coolant which should be regular. Might be worth taking the hose off and popping it into a clear bottle and just run the engine for a minute.
 
I would still be dubious about the waterpump.

I had a similar issue on my Ibiza Cupra 1.8T - the standard water-pump had plastic impellers - one broke off which caused it to become less efficient - it was replaced for a revised version with metal impellers...
Not sure if the standard pump on Audi's is plastic or metal but the symptoms sound similar.
 
Well the garage rang, same fault on the diagnostics with the temp sensor as before which now seems to be the temp sensor on the thermostat housing which was replaced in May.

Top rad hose definitely had water in it, but just wasn't as hot as the temp gauge and coolant warning would indicate. Both rad fans come on full blast so a temp sensor somewhere is working properly.

The thermostat housing is this one. Why would a thermostat housing have an electronic temp sensor? I thought thermostats were just mechanical spring loaded diaphragms to allow water to circulate to the radiator once up to operating temp...

The odd thing is though the warning doesn't come straight on. I have now driven it gently on several short journeys from cold keeping revs below 2.5k. Each time it warms to 90°C in 4-5 minutes and sits on 90. Another 3-4 minutes and it starts creeping up. With blips of the throttle the temp seems to increase quicker, resulting in the warning coming on. If it is the water pump it almost seems like it pumps normally to start with and then once it gets hot it gradually seems to stop pumping as well.

Either way it seems likely to be the water pump or thermostat, so it's got to come apart one way or another. I think I'll ask if the garage are prepared to dismantle it and see what looks faulty. I guess a water pump will be obvious.

But what I can't understand is why a faulty temp sensor on the thermostat housing would cause this issue.. I drove it 300 miles at the weekend and it was fine.
 
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The coolant temp sensor is in a housing at the back of the head. This thermostat is in a housing on the right hand side of the engine where the bottom rad hose connects. VW/Audi engines are odd like this with the thermostat in the bottom hose.

Was the coolant temp sensor a genuine one? There is many pattern ones out there that fail quickly. I have never had a problem with a genuine one yet.

That link you posted to a thermostat from Euro car parts doesn't look like one fitted to a 1.8T engine I have seen before but I maybe wrong. Sounds to me like the water pump has failed. I know a lot of people slate the standard VAG plastic one but least when it fails it doesn't cause any damage to the engine, I have heard of metal impeller ones having the bearings fail and scoring the engine block with the impeller meaning a new block has been required.
 
The temp sensor behind the head was replaced. Not sure if the one that had leaked was a genuine one, also not sure if it was replaced with a genuine one or not.

I was going by the picture on the ECP website regards what thermostat housing (apparently the actual thermostat itself is not available like every other car I've ever replaced a thermostat on) shows, the picture could be wrong I guess, I didn't look at it.

The water pump was a KWP plastic impellor version. Makes sense actually now you mention it, last thing you want is bit of metal being rammed into the block, if a plastic one fails it will at least be less destructive...
 
Well local garage replaced for a genuine thermostat last week and it's been spot on ever since.

Top rad hose is warm now instead of being cold when the coolant temp warning comes on and I'm getting proper heat in the cabin heater, so must have been a dodgy stat.

Good as gold now.
 
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