Coolant loss

bear1

Hi guys, have a bit of an issue. At the beginning of last month I noticed the temp gauge acting funny and jumping around a bit but never went past the normal temp.
Next day my coolant level warning lit up and when I stopped it was practically empty.
As the water pump hadn't been changed in years before I bought it I brought it to the mechanic who changed the timing belt and water pump.
All fine until I noticed yesterday the level was at the min mark and today the coolant level light flashed up.
Checked and yet again it was practically empty.
A few days ago I checked the oil cap and it was clean, by clean I mean no mayo colouring.
I dont recall leaks under the car but cant be sure.
The mechanic was a vw specialist company and they did a full service as well and nothing was noted about any leaks.
Booking the car in again this week but has anyone any other suggestions?
VW Passat b6 170bhp 2007.
No white smoke, no back pressure when opening the coolant tap, no rough running so it doesn't sound like a hg issue.

biko

Yeah, headgasket is the big worry but it's rarer than you think.

For coolant to vanish this quickly there has to be a leak.
Is car parked indoors at night? Can you leave a newspaper under it see where leaks comes from?

Alanstrainor

biko wrote: »

Yeah, headgasket is the big worry but it's rarer than you think.

For coolant to vanish this quickly there has to be a leak.
Is car parked indoors at night? Can you leave a newspaper under it see where leaks comes from?

It can be tricky as the coolant can sometimes pool on the undertray under the engine.

But yeah, there is most likely a leak somewhere, rad, expansion tank etc are common areas to check in all cars. I'd be wary driving too far in it's current state.

GM228

biko wrote: »

Yeah, headgasket is the big worry but it's rarer than you think.

A friend of mine had the exact same problem with his Passat and eventually turned out to be the head gasket.

bear1

Yes the car is parked 99% of the time in the garage so ill give that a go.
Expansion tank is new as the mechanic said that the old one was so destroyed they couldn't see the coolant levels so the replaced with a new one.
Knowing my luck it will be the hg but surely that would show in the oil? Or at the very least when they changed the oil.
I get the impression it may be the rad as forums are saying they are a known week point.

George Dalton

Leaking EGR coolers are also a known issue with this engine and won't show any external signs of leaking.

bear1

George Dalton wrote: »

Leaking EGR coolers are also a known issue with this engine and won't show any external signs of leaking.

Interesting, how would one do a basic check on this?
Is it specific to certain engine codes?

John T Carroll

bear1 wrote: »

Interesting, how would one do a basic check on this?
Is it specific to certain engine codes?

Son in laws EGR Cooler went in 2013 on a 2010 Golf 1.6 TDI, a bit strange but he wasnt losing any water, the car was losing a bit of power and a warning light then came up on the dash and was diagnosed by the main dealer.

George Dalton

John T Carroll wrote: »

Son in laws EGR Cooler went in 2013 on a 2010 Golf 1.6 TDI, a bit strange but he wasnt losing any water, the car was losing a bit of power and a warning light then came up on the dash and was diagnosed by the main dealer.

The OP's PD engine is an older design where the EGR and cooler are separate, unlike the combined unit that gives so much trouble on the newer common rail engines. So the cooler on the PD engines can be leaking without any external signs.

Because of this it can be pretty much impossible to pin down the EGR cooler as the cause of the leak so it is very often a case of ruling everything else out first then replacing the cooler.

bear1

George Dalton wrote: »

The OP's PD engine is an older design where the EGR and cooler are separate, unlike the combined unit that gives so much trouble on the newer common rail engines. So the cooler on the PD engines can be leaking without any external signs.

Because of this it can be pretty much impossible to pin down the EGR cooler as the cause of the leak so it is very often a case of ruling everything else out first then replacing the cooler.

I'm praying its the radiator tbh. Few forums are mentioning that they are a weak spot in the engine and prone to start leaking.
Have the car parked up now with paper under the engine but I'm fairly sure it doesn't leak with the engine off.

George Dalton

bear1 wrote: »

I'm praying its the radiator tbh. Few forums are mentioning that they are a weak spot in the engine and prone to start leaking.
Have the car parked up now with paper under the engine but I'm fairly sure it doesn't leak with the engine off.

To be honest with you it seems to have all the signs of the EGR cooler being the cause. We have had loads of these in for investigation over the years and you can leave the pressure tester on the cooling system all day with no drop in pressure. Yet when the car is being driven the coolant drops regularly. It seems that they only leak when they are at full operating temperature, the coolant disappears into the exhaust where it is burnt off and exits via the exhaust with no visible steam or other signs due to the high temperatures.

bear1

George Dalton wrote: »

To be honest with you it seems to have all the signs of the EGR cooler being the cause. We have had loads of these in for investigation over the years and you can leave the pressure tester on the cooling system all day with no drop in pressure. Yet when the car is being driven the coolant drops regularly. It seems that they only leak when they are at full operating temperature, the coolant disappears into the exhaust where it is burnt off and exits via the exhaust with no visible steam or other signs due to the high temperatures.

Which would "possibly" explain why I'm not seeing any signs of hg failure.
Are they a big job?

George Dalton

It's a pretty awkward job and the part is expensive. We haven't done one recently but the cooler itself is in the region of €375 ex VAT IIRC.

bear1

George Dalton wrote: »

It's a pretty awkward job and the part is expensive. We haven't done one recently but the cooler itself is in the region of €375 ex VAT IIRC.

Mighty are those coolers specific to a certain engine code?
I.e. Mine I believe is BMR and I'm seeing parts listed as BKP etc.
Or does being the 170 engine have a different cooler to the 140.
Sorry for the questions.

George Dalton

I think the 170bhp part is different yes. I'm not 100% sure though.

bear1

George Dalton wrote: »

I think the 170bhp part is different yes. I'm not 100% sure though.

Just my luck. Thanks for that

bear1

Guys, what about an air lock? Doing some reading and it seems like a possibility.

bear1

Further update, it would seem my thermostat is probably causing this issue.
Takes ages to get up to normal operating temp and it will only stay at 90 degrees if I stay at a highish constant speed. Say 120-140 and above.
If though I slow down then the temp starts to drop to 80/85.
In the morning it will take at least 10mins longer than usual to start warming up.
No leaks under the car, no oil in the coolant, no steam, no mayo under the oil cap...
Temp never goes above 90 btw.
Is it possible the stat is stuck?

John T Carroll

bear1 wrote: »

Further update, it would seem my thermostat is probably causing this issue.
Takes ages to get up to normal operating temp and it will only stay at 90 degrees if I stay at a highish constant speed. Say 120-140 and above.
If though I slow down then the temp starts to drop to 80/85.
In the morning it will take at least 10mins longer than usual to start warming up.
No leaks under the car, no oil in the coolant, no steam, no mayo under the oil cap...
Temp never goes above 90 btw.
Is it possible the stat is stuck?

Its possible that the stat is stuck in an intermediate position but I would think its unlikely to cause the coolant loss for two reasons, one is that you should see obvious signs around the expansion bottle top where the relief valve is and two the temperature gauge should reflect this. The VW temperature gauge is conditioned to read exactly 90C between 75C and 107C, as the relief valve will not lift until well above this (107C) temperature then you should have noticed it and a audible alarm and a red light are also annunciated. I have heard of cases where the plastic impeller has broken up on the water pump but if this was the case then you should get overheating problems very rapidly and anyway your water pump was renewed.
Here is a link to the VW (VAG) temperature gauge which you might be interested in.
http://www.boards.ie/vbulletin/showthread.php?p=93946262

bear1

John T Carroll wrote: »

Its possible that the stat is stuck in an intermediate position but I would think its unlikely to cause the coolant loss for two reasons, one is that you should see obvious signs around the expansion bottle top where the relief valve is and two the temperature gauge should reflect this. The VW temperature gauge is conditioned to read exactly 90C between 75C and 107C, as the relief valve will not lift until well above this (107C) temperature then you should have noticed it and a audible alarm and a red light are also annunciated. I have heard of cases where the plastic impeller has broken up on the water pump but if this was the case then you should get overheating problems very rapidly and anyway your water pump was renewed.
Here is a link to the VW (VAG) temperature gauge which you might be interested in.
http://www.boards.ie/vbulletin/showthread.php?p=93946262

Yeah, at this stage I think I'm looking at two faults.
I opened the expansion tank last night and it had some mayo coloured crap under the cap but no oil in the tank and no coolant mixed with oil under the oil cap.
Then this morning I opened the bonnet again and checked the levels, now it's between max and min so during the night the level went down.
Looked under the car and this time I noticed moisture on the ground and some drops and directly above the drops a sort L shaped pipe which was moist/wet at the bottom plus what seemed to be a droplet about to fall.
Now, this could possibly be where my coolant is goin but it also seems strange that the temp gauge is acting strange and would suggest that both the thermostat and the leak happened at the exact same moment.. Unless it is indeed the thermostat leaking as from what I've read it's on the same side of the engine.

Idbatterim

if its running out quickly, put water in it, turn on the engine and in very good light, simply open the engine bay and see where it is leaking from, it should be fairly obvious when the system is under pressure...

bear1

Idbatterim wrote: »

if its running out quickly, put water in it, turn on the engine and in very good light, simply open the engine bay and see where it is leaking from, it should be fairly obvious when the system is under pressure...

Thing is it seems to take a few hours for this drop to occur, the coolant is circulating correctly but there is an area where this circulation is leaking and finding it is the bastard of it.
Car booked in for next week.

Fuelwatch

George Dalton wrote: »

Leaking EGR coolers are also a known issue with this engine and won't show any external signs of leaking.

Hi George,
I have a 2010 Passat CC losing coolant, have to top up every 4 weeks,no sign of coolant leaking anywhere,bone dry,mechanic pressure tested system, no sign of any discolour in the oil, do you reckon it could be egr cooler?

Thanks

George Dalton

Your car has a different setup to the OP. Leaking EGR coolers are common on the newer CR engines like yours as well but generally the leak is external and easy to spot. Leaking water pumps are also a common issue on your car, more so than the older models.

bear1

UPDATE: Mechanic called and said it was the pipe.
It was some non OEM pipe which wasn't the right size at all so coolant was coming out through cracks and what not.
New pipe has been ordered from VW so car should be ready by tomorrow.
All in all 80e so I'm happy out with that.

biko

What pipe exactly? So it was a pipe installed by someone else at some point?

bear1

biko wrote: »

What pipe exactly? So it was a pipe installed by someone else at some point?

Directly below the engine which is coming from the lower end of the rad to the engine.
Someone had replaced it at some point with some ****ty quality pipe which didn't even fit properly.
And to hold it in place they also strapped it to the boost pipe.
Job well done right there. Doesn't even seem like the pipe was for that car even as it just hung way too low.