P38 Block or heads thats the question.

Willos · May 21, 2010

Here we go.
Has a misfire and heads leaking through the gaskets as smoke coming out when cold start. Engine top end strip new gaskets water pump and belt.

After rebuild full compression in cylinders. stil loosing a little water. New Rad and thermostat replaced.
Still a misfire on cold startup then ok.
Went for a test on the expnsion tank and Oh No combustion gas in the water

.
so where to go from here. Could take plugs off one bank fire her up and test for gas but how to stop the fuel in that bank pumping down the cat.
Whats the poceedure for checking if its the block or heads.
In what cylinder do the blocks crack. When i took the heads off no sign of any steam cleaning in the cylinders. No water in the oil.

j the range · May 21, 2010

did you get heads skimmed?

Willos · May 21, 2010

no bu checked with an engineers rule. 155 psi compression though

Irishrover · May 21, 2010

Remove the plugs and see if one looks as though it's been washed. The heads should be flat within about .003"

Willos · May 22, 2010

Where is the most areas of cracks in the blocks as I recal there are weak areas of the block ?. If you give answers in plug numbers that would be helpful.
Will take plugs out to have a look at the colour. Trouble is its running its best , but i'm suspecting the drivers side head (sods law the exhaust manifolds a dog to get to ) as the bolts in the middle of the head were not ver tight. There was no evidence of steam cleaning when I took it off the first time. Im just hoping its a head and not a block as the cars worth the same with an engine fault and repaired with a new engine.

wammers · May 22, 2010

Willos said:
Where is the most areas of cracks in the blocks as I recal there are weak areas of the block ?. If you give answers in plug numbers that would be helpful.
Will take plugs out to have a look at the colour. Trouble is its running its best , but i'm suspecting the drivers side head (sods law the exhaust manifolds a dog to get to ) as the bolts in the middle of the head were not ver tight. There was no evidence of steam cleaning when I took it off the first time. Im just hoping its a head and not a block as the cars worth the same with an engine fault and repaired with a new engine.

When you checked heads with the engineers rule did you put a feeler under it, or just do it by eye. If you take the plugs out and one is clean you most likely have crack in the inlet side on that pot. Any cracking in the block means water can only come in past the liner, so combustion pressure can pass the other way and you would have pressurising of system. If you have no pressurising of system it can only be a cracked head inlet side. If the head was warped you would also get pressure build up.

robp38 · May 22, 2010

mine looked straight but the engineer took 8 tho off the heads.

rewmer · May 23, 2010

I'm going with Rob. I had an engineers rule once that was 2mm short. If they cant get the basic measuring thing right, what are the chances of it being bent ?. I am sure if you lift them off again you will find another blow. Get them machined.

Irishrover · May 23, 2010

Personally, I would think that a couple of thou of warp would pull down when the head bolts are tightened. I think that the cause is more deep seated. Obviously people want to hope for the least expensive and psychologically (Long word..hope I've spelt it right !!) more pleasing result.
The V8 blocks are known to be a cause of probems and are well documented. If the heads are flat to spec. then there is no other option than to look elsewhere. My first experience of suspected head gasket failure related to a 3.9 Vogue and I replaced them twice within as many weeks. The heads were flat, used a surface table to check them and it was only after contacting RPI that I decided, at great expense to replace the short engine..problem solved.
My 4.6 a few years on showed the same symptoms and I again replaced the short engine..problem solved again.
I don't want to appear to be a prophet of doom, but you have to make yourself aware of the options..as bad as it sounds.
:behindsofa:

Willos · May 23, 2010

Thats what i was thinking. The head gaskets did need changing as i was leaking out the side on cold start up. This is where i thought the misfire was comng from but its still here on startup and still loosing water. must be leaching into a cylinder when colling and making it damp enough to stop firing until the coolant is exhausted.
in the moening I'm going to pull the fuses for fuel pump and coils and turn it over a few times and take out the plugs o find out where the leak is.

Irishrover · May 23, 2010

On my 4.6 I found the problem was worse when the engine was hot and switched off. Obviously the aluminium block expands more and the cooling system is pressurised, those two factors will force the coolant through the weak spot..either into a cylinder or in some cases into the sump. In the case of my 3.9 it was into the sump, but with the 4.6 it was into one of the cylinders. The result was that one of the spark plugs looked as though it had been washed clean. When the water had been ejected from the cylinder, it ran on all 8 pots smoothly but the exhaust was throwing steam out like a train if it was revved after idling for a bit. On start up the engine felt as though there was a brick in one of the cylinders, this was the water causing the piston to lock up on the compression stroke.

P38 Block or heads thats the question.

Willos

Active Member

j the range

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Willos

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Irishrover

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Willos

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wammers

No longer with us, RIP

robp38

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rewmer

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Irishrover

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Willos

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Irishrover

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