Yet another P38 2.5 Diesel overheating . Different symptoms!!

Its the old faithful problem again I think.

Can will sit ticking over without any problems.
When it is driven for approx 10 miles. the temp goes very quickly up into the red. It is an automatic and goes into limp home.

Before it over heats the temp sitS nice in the middle of the guage. hot air from the internal heater. Then no hot air and temp off the scale.
Has a new thermostat fitted and a new water pump. although old units seemed ok.

when you check the temp of the hoses when over heating, the hose from the radiator to the thermostat os cool and the other hose to the radiator is very hot. Also seem like they have a fair bit of pressure in them.

System has been bled to get all the air out of it .

Any thoughts? .

I would have siad that the thermostat was not opening sometimes, but that would not stop the water flowing through the internal heater matrix I dont think.

Airlock is possible but I think the rad may be either blocked or the centre baffle has failed. Warm the engine up and feel the bottom of the rad, if it's cold you have no flow through the rad. Do the marble test, with the rad off the car, drop a marble or small stone in one hose entry, tilt the rad and see if it comes out of the other hose entry, if it does the rad is stuffed. If that test is OK, get the marble out of the original entry point and flush the rad.
The other thing to check is the viscous fan, if the coupling is shot it will not cool the engine.

Don't keep overheating it because if the head is not already cracked it soon will be!

I will check the radiator, Flushed it out today and ran water through it until it ran clear. not debris , only pink antifreeze. but will check the baffle. would expect both hoses to be about the same temp if the baffle was missing? or could it come loose and block the outlet port?

brisca943 said:

I will check the radiator, Flushed it out today and ran water through it until it ran clear. not debris , only pink antifreeze. but will check the baffle. would expect both hoses to be about the same temp if the baffle was missing? or could it come loose and block the outlet port?

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Sounds like a circulation problem. Can only think the stat is stuck shut. Take it out and test it. New water pump could have failed but that is less likely than a duff stat, most are made in wongawanga land these days from pressed camel droppings or beer cans.

Some more info. Checked the stat and all seems ok. water pump been removed and all ok.

Checked the pressure in the system and up at approx 18-20 psi and then the relief lifts on the cap with temperature in the healthy zone .

Occasionally here a strange "woosh" noise coming from the engine like something is letting go. head gasket??

have not done a comp test yet will do that in the morning.

Are they prone to block or head failures?

brisca943 said:

Some more info. Checked the stat and all seems ok. water pump been removed and all ok.

Checked the pressure in the system and up at approx 18-20 psi and then the relief lifts on the cap with temperature in the healthy zone .

Occasionally here a strange "woosh" noise coming from the engine like something is letting go. head gasket??

have not done a comp test yet will do that in the morning.

Are they prone to block or head failures?

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They crack heads if overheated

Think I have found the problem.

After removing the cylinder head i have found a crack between the injector base and the centre of the valves on two cylinders. Also starting to show signs of a crack on a third cylinder.

Will post photos later, suspect this is the problem so I am now looking for another cylinder head if anybody has one for sale.

Thanks again for all you help.

brisca943 said:

Think I have found the problem.

After removing the cylinder head i have found a crack between the injector base and the centre of the valves on two cylinders. Also starting to show signs of a crack on a third cylinder.

Will post photos later, suspect this is the problem so I am now looking for another cylinder head if anybody has one for sale.

Thanks again for all you help.

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Howdy mate, any pics yet.

Sorry forgot about the pictures.


Still looking for another head if anybody has one for sale.????

brisca943 said:

Sorry forgot about the pictures.


Still looking for another head if anybody has one for sale.????

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Have you had it pressure tested?? im sure your right and id say the same if i looked at it but you get the exact same cracks on v.w 1.9 diesel heads but they are fine and well known for it (i specailise in vw diesels) but im not too sure for the BMW engine im still learning, im sure some one on here will be along to help on the subject. Good luck
Also mightt be worth giving Joe a ring at Emmots of Colne, hes got everything for P38's.

Anyone thought of getting the cracks welded up?

brisca943 said:

Sorry forgot about the pictures.


Still looking for another head if anybody has one for sale.????

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There is one on eBay at the moment.

thought about welding them up as I haave an AC tig for alloy but may be more hassle than getting another.

As for if this is the problem , Not 100% sure but there is a plug for the water gallery directly above the crack and when this is removed the water gallery seems to be directly above the crack. So can only assume this is the issue.

Any thoughts welcome though.

does anybody know if the BMW 325 diesel cylinder head is the same??

Thanks

brisca943 said:

does anybody know if the BMW 325 diesel cylinder head is the same??

Thanks

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If it's the M51 engine I think it should be, it was fitted to the Opel Omega as well

brisca943 said:

thought about welding them up as I haave an AC tig for alloy but may be more hassle than getting another.

As for if this is the problem , Not 100% sure but there is a plug for the water gallery directly above the crack and when this is removed the water gallery seems to be directly above the crack. So can only assume this is the issue.

Any thoughts welcome though.

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I have the same symptoms.
Were the cracks in the head the problem? Also do you remember if the temperature went down when the revs were over 2000?
Thanks

Have you checked the Viscous is working properly? Newspaper test?