Coolant leak ABY Avant

[Jonas_R]

Why don't you put some pressure in the system and see where it leaks?

0.5-1 bar should be enough to find a leak. Just disconnect the overflow hose at the expansion tank and plug it. Then put a little pressure in the expansion tank and see where it leaks.

[Steve770]

So not really had much time with the car recently but not sure I am actually losing coolant. The main problem seems to be the fluctuating level in the expansion tank. I've been through the guide on here to bleed the coolant system but not really sure what the issue is - an air lock somewhere? At no point has the car been overheating and no low coolant warning (not sure what the threshold is here?).

Basically the coolant level behaves in the exact opposite of how it should. The car will be at min mark when cold but drop when warm rather than increase - the level returns back to min once it's cold. I went out this morning and bled the coolant system again using the radiator bleed valve to release the pressure and all seemed well. Drove for about 30 mins and again coolant level had dropped. I let it cool for a bit and then removed the header tank cap. I then fired up the engine and it immediately jumped up to between min and max then again dropped back to min once cool - as it should. Another 30 min drive after that and it's back below min mark...

I did notice looking through pictures of when I first bought the car the level was already low - think I missed this due to the min marker being much lower on the V6 saloon - basically where the coolant level was on the S2 - so I assumed at a glance this was the correct level.

Surely if there was a leak it would continue until there was no more coolant? The level never gets lower than about an inch and a half below the min marker.

The car is running great otherwise and while this doesn't seem to cause any problems it's bugging me

Any ideas guys?

[Steve770]

Why don't you put some pressure in the system and see where it leaks?

0.5-1 bar should be enough to find a leak. Just disconnect the overflow hose at the expansion tank and plug it. Then put a little pressure in the expansion tank and see where it leaks.

Cheers. I've ordered a kit so will check do a pressure test next week.

[newsh]

If you’ve got a small leak at the turbo causing the bubbling, or somewhere else low down, maybe it draws air in as the system cools..

[Steve770]

If you’ve got a small leak at the turbo causing the bubbling, or somewhere else low down, maybe it draws air in as the system cools..

Yeh, that could be it. It's a small leak but it's clearly leaking from there. Either way it makes sense to sort that before looking at anything else.

Had a better look today - putting pressure in the system holds fine but does make the leak look a lot more obvious when it's cold. Lost about 0.1 bar in about 15 mins so leak is minimal. You can see it starting to pool at the bottom of the coolant return pipe.

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I'm guessing it's the o-ring that's perished? Number 6 on the diagram. Shouldn't be too difficult to replace.

[newsh]

Looks like a copper washer, might just need tightening.
Try slacking the union nut, tighten the adapter down to crush the washer a bit and then retighten the upper nut.
You might want to anneal the copper washer first though by heating till it glows and quenching in water.

[Chris5044]

Places I’ve had water leaks.

1/ Underneath the header tank where the hose joins on, there was a crack in the tank, this one cost me the head gasket when I got stuck in traffic in the A40 into London. Knew I had a leak but couldn’t find it.

2/ Bottom of the rad where the rubber mount it’s fixed, badly soldered mount bracket.

3/ Afterrun pump

4/ Turbo cooling pipe at turbo

5/ Turbo coolant feed at front of water rail there’s a short rubber section (not included in the original samco water kit)

6/ Core plug at rear of head rusted through

7/ Plastic water take off flange at rear of head to heater hose, replaces with one of Rusty’s billet alloy jobs

8/ Water pump, leaking down inside cambelt cover.

I think that’s it

My car has done over 250,000 miles though

Massive thank you for posting this dude!! I currently have a coolant leak. I will continue my searching. It is a slow leak and when the car is hot and IM blast it, it can spill out.

[Ian Simmonds]

No 3 was mine….
Oh and the rubber hose on the coolant rail next to the block.