Paul Type R

Hi,

Can someone help please??

Got a problem with my Audi A6 2.8v6 Quattro.

BAsically the other day, it over heated. AA man reckoned it is the head gasket.....so he towed me home (better safe than sorry)

Today I did a compression test and got 14bar in each cylinder. This is normal, theres no gunk in the filler cap and no oil in the header tank. To me this say's the head gasket is OK.

So...got two things left - Water pump and the thermostat. How can I tell which is faulty?? and where are they?

Cheers,

Paul.

J4CKO

iTrader: (1)

What about the rad ?

Paul Type R

I *Think* the radiator is OK as it's getting hot..

MGJohn

Overheating? In stop-start traffic. At motorway speeds or what?


Are you losing coolant?

A damaged head gasket may not show up on any static engine test. In traffic or at high sustained speeds, compression gases can pass into the cooling system over-pressurising it but not at other times. If really bad, this could show as coolant escaping somewhere ... any tell tale coolant stains? Similarly, coolant can pass into the combustion chamber via a damged gasket and thus expelled through the exhaust without any tell tale signs except a 'damp' exhaust and coolant loss.

My test for over-pressurised cooling system resulting from damaged (they rarely actually fail) head gasket is to remove VERY CAREFULLY (use thick, protective gauntlet type gloves just in case) the coolant expansion bottle (header tank) cap. In a healthy fully warmed up (hot) engine, there should be a gentle 'shuush' as normal coolant pressure is released. In a over-pressurised system, that 'shuush' will be a much more powerful one as the extra (extreme) pressure is released. In a really bad case that pressure build up is excessive resulting in a large quantity of VERY HOTcoolant being expelled or released DANGEROUSLY! So do be VERY CAREFUL and if you dont fancy doing it yourself, perfectly understandable, entrust the job to the professionals. Ask them to do that hot engine pressure test soon after switch off whilst the pressure is still present in the hot engine. Allowed to cool, the pressure may reduce to 'normal' level.

Is there any 'previous' with V6 Audis giving head gasket troubles? After all, it now appears that many german cars are not 100% bullet proof reliable as once thought.

"Honest John" in the Motoring Telegraph keeps a dossier on all the various models and their recalls, faults etc. I believe he has an email adds or site... worth a search and check.

Good luck.

Paul Type R

Hi

The car has over heated just this once on the motorway, doing about 90mph. I pulled over and the water was boiling (so squirting out of the valve in the header tank)

The coolant level doesnt appear to be dropping and there is no steam coming out of the exhaust.

I've tried the test that you mention and I do get a gentle shush out of the header tank.

Is it normal for the coolant to be under high pressure when the engine is running? I've tried opening the header tank at full temp with the engine running and the collant squirts out. I take it this is normal?

there is another problem now too. Since the water boiled, there appears to be a air block in the coolant system as the heater does not get warm. Any idea how to bleed the system?

Cheers,

Paul.

mas58

Several years ago I had a XR2 (no comments please), the thermostat closed when driving down the motorway and resulted in an overheat. This was some 60 miles after initial warm up. Replaced thermostat problem went.
To get rid of the air lock, idling car without radiator/ pressure cap can help. You can also apply vacuum system to cooling system to draw off air.

the moose

Sounds to me like it's the water pump - running at 90mph you're unlikely to need assistance from the thermostat, so long as water is being pumped round.

As for V6 Audis having head gasket problems - not aware of any, and mine's now onto 153k. Give The Auto Pool (01753 655011) a call - I've no connection them other than that they service my Audi and can usually help out on technical queries. Very honest/reliable bunch, and relatively inexpensive (though I'm dreading the 160k cambelt change service ....)

Paul Type R

Surely if the thermostat is gone then the water wont be pumped around?

Paul.

Diesel

Steamy exhaust = water in cyl

water in cyl = wet spark plug

wet spark plug = missfire

missfire = emissions fail

Check for emulsified oil/combustion by-products in coolant.

Check for water pump failure by removing top hose and spinning engine (never tried that one though - just thought of it)

Yours could just be a sticky stat or an airlock - there will be bleed screw somewhere on a 'high' pipe or a 'auto-bleed' pipe from top of rad to the expansion bottle that you should blow through before re-filling.

My 'blown head gasket' was a cracked block - NICE!!!! Good luck!

Diesel

PS where are The Auto Pool (google gives me swimming pool cleaners!)