P38A intermittent coolant pressure issue

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It's back, again. Too much pressure.
Fished another stringy bit of silicon 'bath sealer' out of the expansion tank again so I'm convinced that's the root cause. Intermittent blockages.. somewhere!!
I suppose the next job is to drain the block and do a full flush.. is that easier said than done? How do i flush for foreign objects that may or may not be causing an obstruction?
 
Also, does anyone know if it's normal for the bottom of the radiator to be cold when the engine is running and at normal operating temp?
Ie. Can the radiator dump enough heat to go from 90c at the top to.. say 20c at the bottom? (Not measured)
I'm probably over thinking things here
 
kermit_rr said:
Also, does anyone know if it's normal for the bottom of the radiator to be cold when the engine is running and at normal operating temp?
Ie. Can the radiator dump enough heat to go from 90c at the top to.. say 20c at the bottom? (Not measured)
I'm probably over thinking things here
Click to expand...
Not normal on the diesel for sure. No idea about the V8 but doubt it's normal on that either. On the diesel it would suggest the baffle in the header has failed is is failing.
 
Datatek said:
Not normal on the diesel for sure. No idea about the V8 but doubt it's normal on that either. On the diesel it would suggest the baffle in the header has failed is is failing.
Click to expand...
Cheers, even though it doesn't overheat at idle or driving at any speed?
I think the radiator is coming off again anyways so I'll check it out
 
I've taken the stat off today, blown through all the smaller hoses/tubes and refilled, everything seems clear and refilled very easily. Fingers crossed!
 
Just got wait for it break down to sludge and find it’s way to somewhere you can get to it? Atleast if it was plastic impeller (my first thought) it would’ve lodged.

Regular changes all you can do? Hope it sorts itself out for you
 
RangeRoller dt said:
Atleast you are now well versed in p38 cooling :)
Click to expand...
Haha yes sadly true! Not sure silicone will break down that much though, just find its way through eventually to somewhere i can find it!
This last time I've not actually found anything though so put it back together in the same state apparently.
Will take it out today and see if it's any better
 
Still on going... Aaargh!!
Back to basics, expansion cap off, run up to 90c, get all the air out,, no more bubbles coming through into the expansion tank.. switch off and allow to cool
Go for a drive the next day and we're back to square one!! Once it gets up to 90, the pressure starts building!!
Pretty sure there's no coolant leaks now and the lpg is totally disconnected.
Tested for hydrocarbons in the expansion tank again, negative result but not much to test when there's no bubbles!!
I'm missing something really obvious here :(
 
kermit_rr said:
Still on going... Aaargh!!
Back to basics, expansion cap off, run up to 90c, get all the air out,, no more bubbles coming through into the expansion tank.. switch off and allow to cool
Go for a drive the next day and we're back to square one!! Once it gets up to 90, the pressure starts building!!
Pretty sure there's no coolant leaks now and the lpg is totally disconnected.
Tested for hydrocarbons in the expansion tank again, negative result but not much to test when there's no bubbles!!
I'm missing something really obvious here :(
Click to expand...

If you have bubbles entering the header tank. It is either combustion gas leaking into the coolant or LPG leaking into the coolant.
 
When it over pressures, it's either a result or consequence of air in the system.
Once is got that out with the cap off and at running temp, there was no further bubbles
 
If it’s leaking air can get in, this could be coolant sensor washers missing to holes/untight bung in the rad. Could be something simple like putting stat in wrong way by accident

Could be a blockage causing it to pressure up - more of that gunk - but that shouldn’t cause gas in header? Every time you work on coolant system you find bit more then it behaves while. There can only be a finite amount in there, try blowing it out like you did before?
 
kermit_rr said:
When it over pressures, it's either a result or consequence of air in the system.
Once is got that out with the cap off and at running temp, there was no further bubbles
Click to expand...

You need someone with a static test rig. It is over pressuring from somewhere. The previously mentioned are the only things that can cause that. Ambient air cannot be drawn it is not possible.
 
What do you mean by a static test rig? I have a pump and dial the screws in place of the cap, i pump it up and it holds pressure.. or do you mean something else?
 
kermit_rr said:
What do you mean by a static test rig? I have a pump and dial the screws in place of the cap, i pump it up and it holds pressure.. or do you mean something else?
Click to expand...

A test rig can be used in two ways. As you state and fit but do not pressurise and run engine. Engine should run with coolant at around 5 to 7 PSI when warm at idle. If it goes off scale you definitely have a leak in either the head gaskets or the LPG heater.
 
FINALLY found it!! Ran it up to temp again, no issue up until 94c. Only at that point did i see exhaust gases

Why on earth would it be ok when it's cooler? No idea but not happy and not sure what to do next.
Is the p38 scrap/parts?
 
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