P38 v8 Petrol Overheating

Have you taken the rad off to check the condition of the fins and to see if it's blocked?

tomcat59alan said:

Have you taken the rad off to check the condition of the fins and to see if it's blocked?

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Brand new rad fitted todat

madbrit said:

not sure what is meant by "NOT POSSIBLE ON THE THORE ENGINE"

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of course anythings possible, but you can't just 'take the thermostat out'
you could put it in a pan of boiling water then put a bolt through it so it jams it open

madbrit said:

Confused as to why the water should be cold on the bottom of the rad ?

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its cold on the bottom because the radiator is doing its job, only when the thermostat is fully open (over 96c) will the temp eventually equalise because its cutting off the bypass which is straight from the engine at 90+c
this might help...

Thanks for that, I have an old thermostat and I have managed to stick it open, and the temp gets up to normal (about half way on the gauge and stays there, not ideal, but its proving a point to me at least

Is the thermost fitted correctly?

Mark Piercy said:

Is the thermost fitted correctly?

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Always a possibility but the hoses are all different sizes (should be)

HUmmmm a possibility, but the two smaller top hoses of the thermostat are slightly different sizes, but I will check today

Thanks

The bypass is the important one, goes to the small connection in the centre

Which one do you call the bypass, the one feeding down from the top hose, or the one feeding the thermostat from the heater matrix ?

One thing that is happening, is the heater sometimes goes cold

Sorry, the bypass is the one that T's off the top hose
The other small one is the heater return. If these are the wrong way around then that could explain the heater blowing cold when the engine gets up to temp and the thermostat opening, which in turn closes off the bypass. Have a good look at the diagram i posted, hopefully helps make sense of the nest of snakes

I'll have a look at mine over lunch see if i can get a pic for you

Unfortunately ,heaters going cold is a sigh of gasket failure as air in the system finds the highest point , the heater matrix ,causes an air lock ,air expands with heat ,water gets pushed out ,try running it with the cap slack loosened might let some pressure, air out ,,I see you said you tested the water for gasses ,but iv never really trusted them ,if its an old test kits....

ok got you, I have replaced that hose at the plastic T snapped.

I will force feed the matrix system with water today as well, see what happens.

I also ordered a brand new head gasket test kit, should come today

Wondered if its worth getting a cylinder pressure tester to see if any air comes back through water system? I have a compression tester

You can run up to 90c with the cap off, there shouldn't be any bubbles

As I said before I have had the head gasket done or rather head gaskets a few months ago and it’s been running fine but it is bubbling with the Off and pushing water out or was until I forced water through the matrix going for a drive now see if makes a difference

just a thought, if the head gasket is to blame, would there be bubbles and expansion even when cold ? with a permanently opened thermostat i mean

I'd think you'd get bubbles all the time.
If you run it from cold with the cap on for a few mins then leave over night, is there still pressure in it? If so that's the tell

kermit_rr said:

I'll have a look at mine over lunch see if i can get a pic for you

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Can't get a pic but it should be quite obvious i think if it's wrong
Hope you have good news after your drive

On a separate note had random issues which i didn't prove, but narrowed down to a crack in the block that only leaked exhaust gases into the coolant over about 85c. The thermostat was drilled and engine temp rarely got over 70c