V6 Head Gasket Failure Symptoms

[Fylnn]

So what are the symptoms of a failed head gasket on a V6 Alfa?  I have no water in the oil, or oil in the water.  On the last rally it was run in 38 deg C heat and it did not overheat.  It does not use water or oil.   I did notice before the event that there was some very minor bubbles in the radiator bottle but since I had just replaced the heater and dropped the radiator water I suspected it was residual air.

So what am I worried about.  During the event it started to fluff and and was reluctant to run cleanly at low revs, and it was not too keen at high revs.  Pulled alright in the middle, but it did get worse as time went by.  I do not have a compression tester so no idea on what the cylinders are doing.  Engine was running strongly until the fluffing started.  It goes back to the fuel injection tuner next week to be retuned with new injectors and to try and diagnose the issue.  But trying to understand any possible mechanical causes should that not prove fruitful.

[MD]

Flynn,

The symptoms are not that different to any water cooled engine.

A couple of ideas to start with.
1 Spark plug that looks super clean in comparison to others is often a tell tale sign of where the water is getting into.
2 Initially, if the coolant is getting into the combustion chamber, there is not likely to be oil in the water or vice versa.This will change as the condition gets worse.
3 Pressurising the radiator to see if it will hold pressure or not will also show a defective head gasket. You may need to visit a radiator works for this "tool" to be used unless your mechanic has one.
4 Removing one high tension coil at a time (using insulated tool)will show the chamber contributing the least to the running of the engine (there can be other causes for this but it is still worth doing)
5 Bubbles observed in the radiator can be (not conclusive) indicator of combustion pressure leaking into the coolant galleries.

Start examining the spark plugs..this will cost nothing.

[310]

hi Flynn
check spark plugs clean one mean water is entering into combustine chamber as the water will be cleaning the carbon away.
also you should be able to drop into repco or burson and purchase a tee- kay tester or you should be able to drop into a workshop and have the test carry out. the fluid is blue if it turns green to yellow it means a combustine leak is evident.
and the final test is a compression test leak down. turn engine over till valves are shut in each compression chamber and fill with compressed air a good sealed chamber should not leak into coolant system.

[Fylnn]

Sounds like the spark plugs are the place to start.  I have not noticed anything untoward, but will check again.  I suspect the real issue is injection related, but whilst sitting here on holiday waiting for parts, just covering the bases.  It has always been my experience that leaking head gaskets which produce bubbles in the radiator also lead to coolant loss, and there is no evidence of that either.

[Mick A]

The lack of power you described sounds like a possible problem with the Air Flow Meter.

Did it backfire or surge?

If it backfired, it's more likely an ignition problem, spark cutting in and out whilst fuel is still in supply causes backfiring.

If it just cut out, then came back again, or lost power then gained it again suddenly with no splutter or backfire, it is likely a fuel problem.

-mick

[Al Campbell]

Could be AFM Issue. One dtimeon my car It was running ok whne taking ot slow but If I tried decent accelerator shove would run like an absolute pig, rough as... Ease off and it'd be ok again. I'd been working on the car the day before. Popped the bonnet for a look, I hadn't reconnected the AFM   Not saying this is your problem but bloody surprised that my car would run ok just tootling with no AFM electronics. So... Sticky flap? Carbon track buggered?

Also maybe there is bigger coolant air issues - I remember something about bleeding trapped air being a real bugger sometimes, around the thermostat and Water temp sensor, if you're getting air around the sensor it'd be telling the L-Jet lies.

[Fylnn]

Thanks guys, the car runs a Haltech with a MAP I think in place of the AFM.  I suspect the issue lies in the electronics.  Big problem now apparent is the old style injectors run low impedance which even with a shunt in place to drop it to 9V means something like 5 amps going to each injector.  The Haltech can't really handle it and goes into protection modes when it overheats.  The more modern injectors run much high impedance, like 16 Ohm which means more like 0.8 amps which is what the Haltech is designed for.  I have subsequently changed over to later style high impedance injectors and about to get the shunt removed and the injection retuned.  The tuner did not quite understand until another car came back with the same sort of issues. 

So find out for sure next week but just wanted to have the knowledge if the 'it is in the engine' issues get raised.

[Al Campbell]

Well there's quiet a few Haltech systems running around out there so if you do enough searching and asking you should be able to find someone who knows the workable combo and eliminate that.

[Mick A]

Thanks guys, the car runs a Haltech with a MAP I think in place of the AFM.  I suspect the issue lies in the electronics.

Mate, maybe next time mention this sort of shit in your initial post?