Blown head gasket, BMC 1.5

[SimonA]

My head gasket appears to be cream crackered, I'm getting lots of bubbles in the coolant and if I run the engine with the cap off the bowman heat exchanger the coolant overflows from the filler, I'm also losing coolant at a fair rate inside the engine. No other symptoms, engine starts without any problems. Oil looks thin and watery, but the level hasn't been going up so I don't think the coolant is going in the oil, and no mayo under the oil cap.

Has anyone changed a head gasket in a BMC Diesel engine? I'm not a hugely competent mechanic but can follow instructions, not sure if this is a DIY job or something I need to leave to a mechanic. Would the timing need to be set up after removing the head? (I've only ever taken the head of a petrol engine).

Does it require a crowfoot spanner for the head bolts under the rocker?

Finally has anyone tried something like Steel Seal or K Seal, or are these a complete no go for boat engines?

 

[RichardS]

Don't know the engine but if you've done a head gasket on a petrol engine you should have no big issues provided access is OK.

Before going ahead I would ask a boatyard how much for a compression test. Should not be expensive and might clarify the issue.

Richard

 

[Mrnotming]

Hi Simon A ,
As Richard says no real differences from replacing the head gasket on a petrol engine.
I only did it once years ago,when the symptoms were as you describe.I left the injectors well alone,and the glow plugs.There are no timing issues,the chain driven cam is beneath the area.no disturbance of the diesel pump is necessary.
I think I checked the head and block for warping.xthe head was checked on a sheet of plate glass with some light grease as a tell tale.As there did not seem to be any distortion, I just replaced the gasket,tightened the bolts or studs to the right torque, and reset the rocker clearances.Having reassembled the diesel feeds to the injectors,and bled the system,also connecting the glow plugs,a fill of coolant completed the job.
The engine ran as long as I had the boat,and was the most reliable engine I'd ever had!
If you are bringing the head to be skimmed,clean it up well,as the engineers prefer clean bits to work on!
Good luck with the job.

 

[SimonA]

Brilliant, thank you.

 

[Jcorstorphine]

As others have said. not a lot of difference between your engine and the petrol engine (1498 Morris Oxford) which is the base unit other than the design of the head. Might be prudent to change the glow plugs while you have the head off. The reason I suggest this is that sometimes a glow plug can break when being replaced and the heater section has to be drilled out and the indirect combustion chamber cleaned out.

 

[TQA]

Not unknown for these heads to crack into the water jackets. Clean the surface and inspect very carefully.

A DIY crack test kit is a worth while investment.

 

[PCUK]

I thought it was the 1.8s that cracked, not the 1.5.

 

[TQA]

I thought it was the 1.8s that cracked, not the 1.5.

Both the 1.5 and 1.8s were known to crack.

These are the Goto people for the BMC 1.5 diesel. They can even supply reconned 1.5 heads for £600. http://calcuttboatsshop.com/epages/c3a6cb0f-3e0f-4132-9636-974f7502e04d.sf/en_GB/?ObjectPath=/Shops/c3a6cb0f-3e0f-4132-9636-974f7502e04d/Products/BMCYL1.5ASSYREC

 

[SimonA]

Both the 1.5 and 1.8s were known to crack.

These are the Goto people for the BMC 1.5 diesel. They can even supply reconned 1.5 heads for £600. http://calcuttboatsshop.com/epages/c3a6cb0f-3e0f-4132-9636-974f7502e04d.sf/en_GB/?ObjectPath=/Shops/c3a6cb0f-3e0f-4132-9636-974f7502e04d/Products/BMCYL1.5ASSYREC

They rebuilt my engine six years ago, not cheap. I'm hoping it's just the head gasket this time.

 

[TQA]

I will keep my fingers crossed for you.

 

[Jim@sea]

Don't know the engine but if you've done a head gasket on a petrol engine you should have no big issues provided access is OK.

Before going ahead I would ask a boatyard how much for a compression test. Should not be expensive and might clarify the issue.

Richard

Not only would a compression test clarify the issue it would tell you which cylinder was effected. I would also suggest having the head examined (and skimmed if necessary)
When I wanted to have the compressions checked on the BMC engine in the boat I had just bought I used a mobile mechanic (£30 an hour no Vat)
And if the head has to come off, if he is the sort of mechanic to have a compressor with an air wrench he will have the head off very quickly and probably know who to take the head to for checking.