Head gasket failure or something worse??

andydunn2 · 30-04-13, 08:46 PM

Ok I think one of the head gaskets has failed on my 2.8 cabbie (using water and mayonnaise in the filler cap).

BUT I'm also getting low oil pressure 0.5bar when hot and oil warning light, is this connected to the head gasket or is something more serious going on

missfire · 30-04-13, 09:26 PM

Head gasket's pretty serious isn't it!.

i doooo hope you are not driving it?

andydunn2 · 30-04-13, 09:36 PM

Quote:

Originally Posted by missfire

Head gasket's pretty serious isn't it!.

i doooo hope you are not driving it?

Head gaskets I can deal with, if its bores, rings etc i am getting out of my league don't want to change the head gaskets and still find I have low oil pressure.

No she is a driveway queen at moment while i get the other jobs done to her...

missfire · 30-04-13, 09:39 PM

It'll lose oil pressure through the gasket though, won't it?

TeXerv · 01-05-13, 01:09 PM

Normally the head gasket gets burned between the pot bores and / or the coolant bores. Sometimes the oil return is leaking at the gasket. But I'm not sure whether the pressure circuit might fail at the head gasket. So you should have visible oil leaks, excessive oil consumption, or a clearly recognizable coolant / oil blend.

andydunn2 · 01-05-13, 09:01 PM

Quote:

Originally Posted by missfire

It'll lose oil pressure through the gasket though, won't it?

Not sure as almost all other head gasket failures I have had over the years has been a catastrophic cloud of white smoke rather than what I have on this which is some coolant loss mayonnaise on the filler cap and low oil pressure..

.

andydunn2 · 01-05-13, 09:04 PM

Quote:

Originally Posted by TeXerv

Normally the head gasket gets burned between the pot bores and / or the coolant bores. Sometimes the oil return is leaking at the gasket. But I'm not sure whether the pressure circuit might fail at the head gasket. So you should have visible oil leaks, excessive oil consumption, or a clearly recognizable coolant / oil blend.

The only oil/water mix I am seeing is mayonnaise on the oil filler cap. No obvious external leaks that I can see...

TeXerv · 01-05-13, 09:27 PM

Quote:

Originally Posted by andydunn2

The only oil/water mix I am seeing is mayonnaise on the oil filler cap. No obvious external leaks that I can see...

Mayonnaise might also appear under cold and wet weather conditions when the vehicle is mainly operated on short trips. So the engine doesn't reach it's serious operating temperature.
Due, oil might be thinned with condensates, causing declining oil pressure.
I would change oil an filter first.

andydunn2 · 01-05-13, 09:32 PM

Quote:

Originally Posted by TeXerv

Mayonnaise might also appear under cold and wet weather conditions when the vehicle is mainly operated on short trips. So the engine doesn't reach it's serious operating temperature.
Due, oil might be thinned with condensates, causing declining oil pressure.
I would change oil an filter first.

Yes my brother suggested that as well, car has been off the road for around 2 years prior to me buying it so oil could easily be goosed.

Will give it an oil change at the weekend and see what happens...

fj1200 · 02-05-13, 12:22 AM

Going back to my days at the dealer now. We did MANY head gaskets on 12V v6 engines, was always oil leakage. Usually they leaked when piping hot at RPM. The place to look is in the valley between cylinders 4 and 5 (front two of your passenger side). Get it good and hot, clean aggressively and hold engine at 3K revs. Watch for oil forming at head to gasket joint.

The other common failure is the oil cooler, check the overflow bottle for oil residue. Due to differential pressures the two fluids go either way (kinky, no?). When the engine is running the oil pressure is higher so oil migrates to the coolant. After shutdown the cooling system pressure is higher so coolant migrates into the oil.

Hope this helps, Cheers.

Dan

30-04-13, 09:26 PM	#2
missfire making wooden things Classic Audi Club Member Join Date: Dec 2009 Location: cow land Posts: 8,156	Head gasket's pretty serious isn't it!. i doooo hope you are not driving it?

30-04-13, 09:39 PM	#4
missfire making wooden things Classic Audi Club Member Join Date: Dec 2009 Location: cow land Posts: 8,156	It'll lose oil pressure through the gasket though, won't it?

01-05-13, 01:09 PM	#5
TeXerv Grown up member Join Date: Oct 2011 Location: Northern Krautland Posts: 241	Normally the head gasket gets burned between the pot bores and / or the coolant bores. Sometimes the oil return is leaking at the gasket. But I'm not sure whether the pressure circuit might fail at the head gasket. So you should have visible oil leaks, excessive oil consumption, or a clearly recognizable coolant / oil blend.

02-05-13, 12:22 AM	#10
fj1200 Grown up member Join Date: Feb 2011 Location: Shrewsbury, MA U.S.A Posts: 21	Going back to my days at the dealer now. We did MANY head gaskets on 12V v6 engines, was always oil leakage. Usually they leaked when piping hot at RPM. The place to look is in the valley between cylinders 4 and 5 (front two of your passenger side). Get it good and hot, clean aggressively and hold engine at 3K revs. Watch for oil forming at head to gasket joint. The other common failure is the oil cooler, check the overflow bottle for oil residue. Due to differential pressures the two fluids go either way (kinky, no?). When the engine is running the oil pressure is higher so oil migrates to the coolant. After shutdown the cooling system pressure is higher so coolant migrates into the oil. Hope this helps, Cheers. Dan