Overheating and engine surging

mercanlandy · Sep 3, 2019

Hi I am having an overheating issue on my P38 2.5 diesel auto which has now developed a second problem of the engine surging from tick over. When you take foot of throttle the revs drop to normal then engine starts surging uo to about 1500 rpm. I am suspecting it may be the gead gasket failing and engine oil is being forced into cylinder/s. I have recentky fitted a bew radiator, water pump, thermostat, temp sender and viscous fan after I suffered s split hose and overheat 6 months ago. But I have found engine always runs hot since then. It does seem to over pressure the water system, now this surging problem seems like over fuelling. What do you reckon?

wammers · Sep 3, 2019

Unlikely to be head gasket. More likely a cracked head. For the surging. Have you cleaned the intercooler out? If not check for oil in the turbo pipes Year would be good. You have obviously not read the first post in this section.

Henry_b · Sep 3, 2019

When the M51 overheats the head turns to margarine..

I would be racking my brain as to why you'd keep knowingly running it hot.

brianp38dse · Sep 3, 2019

Did you check the new rad had the baffle fitted in the top.

wammers · Sep 3, 2019

brianp38dse said:
Did you check the new rad had the baffle fitted in the top.

Good point. And we still don't know what year it is.

Datatek · Sep 3, 2019

brianp38dse said:
Did you check the new rad had the baffle fitted in the top.

^^^^^^^ +1 to that.

mercanlandy · Sep 3, 2019

it's a 1995 m51 engine.

Datatek · Sep 3, 2019

mercanlandy said:
it's a 1995 m51 engine.

So pre EGR, that eliminates one more source of problems.
Need to check the RAD has the baffle in place and that there is no air in the system, you also need to check the viscous fan is working correctly with the newspaper test.

mercanlandy · Sep 3, 2019

Datatek said:
So pre EGR, that eliminates one more source of problems.
Need to check the RAD has the baffle in place and that there is no air in the system, you also need to check the viscous fan is working correctly with the newspaper test.

mercanlandy · Sep 3, 2019

I am getting to the point now of pulling the cylinder of it and getting it checked out for damage or cracks (if that is possible to prove it's the head) or buy a recon head and fit that. Car is very good for it's age . Anybody recommend where to get the head checked or buy a recon one from. I live in Anglesey North Wales (currently in Cornwall with a sick P38)

mercanlandy · Sep 3, 2019

All hail Green Flag

brianp38dse · Sep 3, 2019

Check the free- cheep stuff first like the baffle and the viscous fan they will cause over heat.

RangeRoller dt · Sep 4, 2019

Another DT???

If you take the head off you can use a dye (red I’ve seen). it will wash off but remain in tiny tiny cracks making it visible. Gets bloody everywhere though.
New head is expensive but should be plenty cheap enough off existing vehicles like scrappers and ‘the bay of e’.

I’d rule out few other things before going balls deep as mentioned.

Datatek · Sep 4, 2019

As others have said, you need to look at the cheap obvious things before removing the head.

mercanlandy · Sep 4, 2019

Datatek said:
As others have said, you need to look at the cheap obvious things before removing the head.

I am going to take the stat out and drill an 8mm hole in it to see if it helps
(this is the 2nd brand new stat tried in past 2 months). I was wondering if the surging could be caused by having to much engine oil in sump? The level on the dip stick is about 8mm above the high level mark. If the engine has been over pressurising due to an air lock can this be forcing oil where it's not meant to be? I am going to drain oil and refill correctly once I get back of holiday. Car got recovery this morning for it's ride of shame on the recovery truck

Datatek · Sep 4, 2019

mercanlandy said:
I am going to take the stat out and drill an 8mm hole in it to see if it helps
(this is the 2nd brand new stat tried in past 2 months). I was wondering if the surging could be caused by having to much engine oil in sump? The level on the dip stick is about 8mm above the high level mark. If the engine has been over pressurising due to an air lock can this be forcing oil where it's not meant to be? I am going to drain oil and refill correctly once I get back of holiday. Car got recovery this morning for it's ride of shame on the recovery truck

Before you drill a hole in the stat, test it by putting it in boiling water and see if it opens, if it does, no point in drilling a hole, if it doesn't it needs replacing. The stat should already have a small hole which should be at the top when fitting the stat, it aids bleeding the air out of the system.
Over pressuring cannot force oil where it's not meant to go.
An airlock can cause overheating and pressurising,
You still need to check the viscous fan and the baffle in the RAD.
Over filling the sump with oil is dangerous.

mercanlandy · Sep 4, 2019

in disgrace again

mercanlandy · Sep 4, 2019

Datatek said:
Before you drill a hole in the stat, test it by putting it in boiling water and see if it opens, if it does, no point in drilling a hole, if it doesn't it needs replacing. The stat should already have a small hole which should be at the top when fitting the stat, it aids bleeding the air out of the system.
Over pressuring cannot force oil where it's not meant to go.
An airlock can cause overheating and pressurising,
You still need to check the viscous fan and the baffle in the RAD.
Over filling the sump with oil is dangerous.

mercanlandy · Sep 4, 2019

I will do all the checks once I get home after weekend.

Thank you all for good advice

Henry_b · Sep 4, 2019

So..

It keeps overheating.

Oil level is rising.

Etc

And it's driven 'till it stops?!

Ahh!

Overheating and engine surging

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