E34 525i Coolant / Oil Headgasket Fault?

[bmnut]

My M20 525i has a problem with disappearing coolant. It does not leak, there is no white smoke, and until now it was not going into the oil. I am having to top up the coolant every 3 days.

The head gasket was replaced 2 months ago (head pressure tested and skimmed) along with the water pump and timing belt etc.

I always do my own repairs so I believe it was done properly.

After the head gasket was replaced it lost a very small amout of coolant every week (not unusual as it has done this for about 5 years). This slowly turned into a large loss (still no leaks). Now there is coolant in the oil.

Has anyone seen this fault before? Is there a common fault I don't know about?

I would appreciate any help or advice. Thanks

[Ausmpower]

Your head probably has a crack inside one of the exhaust ports.

Was it badly overheated before the head gasket was done?

Either that or the installation of the head was dodgy.

Torqued to Spec? OEM head gasket? Corrosion in the head? Cracked block? Block deck not clean?

Got any pics of the job as it pogressed?

[bmnut]

Sorry don't have any pics.

It has not overheated.The only time the temperature went near the red line was while bleeding the system after the head gasket was replaced.

I took a lot of time to replace the gasket so am pretty sure it was done correctly (I'm a fusy Toolmaker by trade).

The gasket was not OEM. Will this have made any difference?

I'm 100% sure it was torqued correctly. There was very little corrosion in the head.

The block was thouroughly cleaned and all traces of old gasket removed.

Would a crack not have been detected when it was pressure tested?

Thanks for the reply, these are the type of questions I need to be asked.

[Ausmpower]

Because they pressure test the head when it's cold.

Incorrect torque proceedure can cause a small leak from the get go.......They always get worse like your has.

[Bill R.]

Oz but the ones here use hot water and they circulate it under pressure for about 30 minutes if the test is done properly, that way it brings the head up to the same temperature as the hot water, the heads are quite warm at the end of the test... many years ago as a grunt at a machine shop this was one of my most hated jobs.




Because they pressure test the head when it's cold.

Incorrect torque proceedure can cause a small leak from the get go.......They always get worse like your has.

[Ausmpower]

Oz but the ones here use hot water and they circulate it under pressure for about 30 minutes if the test is done properly, that way it brings the head up to the same temperature as the hot water, the heads are quite warm at the end of the test... many years ago as a grunt at a machine shop this was one of my most hated jobs.

Cold as in not at "real" operating temp Ie exhaust ports are no where near their normal temps.....

I have a Fiat (i know!) X1-9 that was pressure tested O.K. but still drank water like a fish......... Had it crack tested and lo and behold 2 exhaust ports were cracked from around the valve guide stem across the roof of the port.....

[bmnut]

What do you think about additives(Cargo seal, K-seal etc) that are supposed to seal any small cracks or gasket leaks?

Do these products work? or do they screw up your cooling system?

[Ausmpower]

Sorry but there are no cheap fixes for head gaskets.....

[632 Regal]

were the cylinder head bolt holes cleaned? If they had any coolant or oil in it then it can hydrolock the block causing cracks too.

good luck on your venture.

[bmnut]

Sorry but there are no cheap fixes for head gaskets.....

I think I have spent enough time on this engine. Time to replace it.

Will a 24v engine fit straight in?

What are my options?

[gmannino]

Sorry to say but Oil and coolant mixing is never a good thing. I think someone named it the chocolate mix of death. Anyways, If you did not have your cylinder head pressure tested for leaks then you should have. When my m20 had oil and coolant mixed, i inspected the head very closely and it looked like it was in great condition. After having it tested, it was obvious that it was severely cracked. So have the head tested for cracks.
Also its important to clean out the bolt holes with an air compressor to make sure the block doesnt crack.

Good luck man.