P38 v8 Petrol Overheating

liners can slip after an overheat or they can slip after a crack appears in the block. i don't know if a slipped liner can cause a crack.
you can have a crack without the liner slipping, but a liner slipping without a crack won't enable the passage of exhaust gasses to the coolant

is it time to do another sniff test? ask your friendly MOT guy if he'll wave his analyser over your coolant tank

will do that today, thanks

A slipped liner will usually give you a constant tap tap tap at engine speed. Liners usually slip when the block cracks through a water passage behind a liner, allowing coolant to come in contact with the liner, lubricating it and allowing it to slip. Following that, you end up with coolant creeping up the liner and getting into the combustion chamber.

Have you checked your spark plugs to see if any are steam cleaned?

Someone has told me that a blocked heater matrix can cause overheating, do you know of this happening?

madbrit said:

Someone has told me that a blocked heater matrix can cause overheating, do you know of this happening?

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I can't see that. The front of the inlet manifold passes some coolant to the heater and the rest to the radiator. If you blocked the heater (which doesn't do much during the summer) then all coolant will go to the radiator

That’s what I thought. But reading up it is an important part of the cooling system. Hot water is always going through the matrix. It’s only the flaps left and right that stop hot air coming into the car and regulated. The water to the matrix is not regulated at all and is constant

madbrit said:

That’s what I thought. But reading up it is an important part of the cooling system. Hot water is always going through the matrix. It’s only the flaps left and right that stop hot air coming into the car and regulated. The water to the matrix is not regulated at all and is constant

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Yep that's true, but it's not dumping heat anywhere when the blend flaps are closed, so it's not aiding in the engine cooling. Equally it's not causing a restriction and heat buildup if it were blocked. At least that's my view

I have now bypass the matrix and off for another trip soon, see what happens, just trying everything before I start stripping the engine, like getting my other P38, 1998 2,5 DSE MOT's that's Thursday, so a days just checking it through tomorrow

madbrit said:

disconnected the water pipes from the gas system, still loosing water and overheating, so put back together, gas solenoid seems ok

Could this be a slipped liner, what would the symptoms be ?

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You'd hear a metallic tapping.

No tapping at all

madbrit said:

No tapping at all

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Do what @Marshall8hp suggested and check the condition of the spark plugs, keep them in order so you know what cylinder they came from in case any are steam cleaned.

Thanks, that is a job for tomorrow, along with compression test and pressure test each cylinder to see if any leaks back to cooling system

tomcat59alan said:

Do what @Marshall8hp suggested and check the condition of the spark plugs, keep them in order so you know what cylinder they came from in case any are steam cleaned.

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If one is steam cleaned, I'm not sure you'll care about plug order unless you're going to take the cylinder out to fix it

All depends on what I find today. But good idea to keep them in order

kermit_rr said:

If one is steam cleaned, I'm not sure you'll care about plug order unless you're going to take the cylinder out to fix it

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But it will help to isolate the cylinder/cylinders at fault so you know where to look when you pull the heads.

didnt get round to it today, as have more problems with the 2.5 diesel, started another post to do with airbag warning light

can anyone suggest the best head gasket set to put in this V8 doing it Monday

Ta

madbrit said:

can anyone suggest the best head gasket set to put in this V8 doing it Monday

Ta

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Elring..

And if you can budget, a set of ARP studs too.

Henry_b said:

Elring..

And if you can budget, a set of ARP studs too.

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Where sells them, do you know?

any idea who sells them ?