Coolant loss: Is the radiator the culprit?

timmus

timmus

A2OC Donor
Hi folks,

Over the last few months, I've been having to top up the coolant more and more regularly. It started around the time that I had my Webasto replaced, so initially I assume that I was simply replacing the fluid lost during the swap and topping up as the air bubbles made their way into the expansion tank. However, I've now poured a fair few litres into it and am convinced that I've got a problem.

There doesn't appear to be a pool of liquid forming anywhere easily visible. However, I seem to lose coolant much faster when I'm driving the car more vigorously. After a few hundred miles on the motorway, the fluid loss is fairly minimal. But after an hour of driving around the western fells of The Lakes yesterday, using higher revs (including going over Hardknot Pass in 2nd gear), I emptied the expansion tank completely.

Does this indicate that the radiator is the likely culprit? The thermostat will have been sending more fluid that way in order to keep the engine cool.

How do I proceed? What can a garage do to establish where the fault lies? It's at times like this when I feel like a complete newbie to cars. I might be a dab hand at retro-fitting, but I'm still fairly ignorant when it comes to the oily bits under the bonnet!

Thanks folks,

Tom
 
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The thing they can do is a pressure test this as it says on the tin, pressurises the system and they check for a drop this should show the leak. I take it you've checked the oil ?

Phil
 
the grim reeper said:
The thing they can do is a pressure test this as it says on the tin, pressurises the system and they check for a drop this should show the leak. I take it you've checked the oil ?

Phil
Click to expand...

Thanks Phil. I thought I'd read something somewhere about pressure testing.
Checking the oil... I presume this will tell whether coolant is getting into the engine, will it? What am I looking for?

Cheers,

Tom
 
terrywindy1 said:
Tom when did you last have the water pump changed?
Click to expand...

Awesome changed it in March of this year. The Webasto was replaced in May. In the intervening time, the low-coolant warning light didn't come on.
Where is the waterpump? What would help me spot problems here?

PS: The area around the Webasto is completely dry. I'm confident that this problem started around that time, but that it's not related.

Cheers,

Tom
 
terrywindy1 said:
After i had the waterpump changed i had a coolant leak turned out it was the gasket incorrectly fitted
Click to expand...

Did you lose coolant at a steady rate? My coolant loss seems to be noticeably tied to how hard the engine is working.

Cheers,

Tom
 
Look for "mayonnaise" on the oil filler cap/ dipstick. This can indicate water mixing with the oil forming an emulsion.
Also look for brown discolouration in the coolant header tank/ exhaust smell in the coolant header tank - these can indicate exhaust gas vapour getting into the coolant...

Another member Ashley's TDi has been using coolant of late and he also thought it was a head gasket but took it to a garage that I recommended to him the other day and they're suspecting water pump failure/ water pump gasket failure. I must admit I didn't think diesels warped/blew their head gaskets often due to the lower (relative to petrol cars) combustion temperatures and therefore lower head coolant requirements?
 
Hi Tom
The water pump is on the front of the cylinder block and is driven by the cambelt. Potential problems with the pump are - loose impeller, leaking impeller shaft seal, leaking O.ring seal where pump mounts to cyl block.
Other possible coolant leakage areas are - pressure cap seal, hoses, radiator core, cylinder head gasket. Note that Audi warn against using Radweld type products on engines fitted with a Webasto heater.
Troublshooting - As discussed above a system pressure is quite good for showing up hose and radiator core leaks, but not early stages of headgasket problems. Test is done by replacing the header tank cap with a gauge unit and hand pump. System is then pressurised with the pump and rate of pressure decay checked on the gauge.
A 'snifffer' test can sometimes detect headgasket leaks and is done by taking a sample of coolant and testing it for the presence of combustion gas residue.

Its normal for the engine to loose more coolant when its worked harder as more heat is transferred to the coolant and the system pressure increases.
Although not exactly a common problem, several members have had head gasket failures on TDis, possibly due to the combination of significantly higer compression ratio and turbocharging.

Cheers Spike
 
Wow, thank you! Thorough and well-explained is what I like. :)
With all this info, I'll take a look under the bonnet tomorrow and see whether I can find any more clues. I remembered I had another expansion tank cap in the cellar, so I've replaced that. I'll know whether it's done the trick within a few days.

Cheers,

Tom
 
Right guys, an update...

I found that the coolant loss problem was relatively easy to solve; the cap to the expansion tank wasn't sealing properly.
However, it's created new problems. The coolant that had leaked from the expansion tank has soaked the wiring running beneath, where a repair had been done on the ABS loom. So, my brakes are misbehaving. Mostly I love my A2, but sometimes... :mad:

I'm hoping that it'll dry out and that all with then be well.

Tom
 
Hi Tom I tried all of the above and I suspect the head gasket has gone. Its a very hard fault to find as most experienced garages will say its not the head gasket as they will pressure test it and it will look fine. I had my water pump changed as I had a cracked mount but this did not resolve the problem. On mine the system would pressure only under lots of load and push water out of the expansion tank pressure valve Id suggest putting something over it and see if water is escaping from there after a moterway run - if so Id suggest its the headgasket. Dan recommended a nice guy who was very well priced in Surrey. After mine was done no more annoying beeping when the water level was low so very happy again.
 
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