Likely source of oil leak

[p6rob]

The trip from Mercia Marina down to Birmingham has been progressing slowly. The engine still isn't happy, it overheats, blows various shades of black and blue smoke, breathes smoke out of every orifice and isn't keen on starting. The conclusion is to take it out, strip it down and build it back up properly and add useful things like a rear mount for the alternator to stop it vibrating loose.

 

One of the biggest concerns is, or rather was, an oil leak from the back of the block. (Picture with the leak smothered in chemical metal attached hopefully)

 

Link to pic

 

 

There was a fine spray of oil coming from the join between engine and bellhousing just above where a clutch slave cylinder would mount. This leak was playing havoc with oil consumption and since filling the area with epoxy putty oil loss has been almost nil. I can't understand why there would be a pressurised leak there, unless the block is cracked maybe. Does anyone by any chance have a picture of the rear of the block to help fathom it out.

 

Thanks in advance

Rob

 

[RLWP]

It sounds possible that your head gasket has gone. Can I suggest that you take the head off before doing anything more drastic?

 

Richard

 

MORE: MATTY!!! I need my BMC 1.8 book back!

Edited April 24, 2013 by RLWP

[bizzard]

If you remove that cam follower side plate ''the one secured with the centre bolt'' with the pipe and clip attached going to the air inlet manifold which is the engines breather and clean it all out, it could well be blocked up with sludge and goo. If so that could cure most of you problems.

[Chalky]

If you remove that cam follower side plate ''the one secured with the centre bolt'' with the pipe and clip attached going to the air inlet manifold which is the engines breather and clean it all out, it could well be blocked up with sludge and goo. If so that could cure most of you problems.

 

It's a common problem. The tappet chest covers are sealed with rubber "O" (actually they're rectangular) rings which harden and split due to the heat from the exhaust. These then leak and you get oil in the bilge (or on the drive if its an MGB!) . One of the covers usually contains a metal gauze oil strainer and it's designed to catch the oil vapour and let the oil return to the sump, the rest of the crank case fumes then get fed into the inlet manifold and burned. If the gauze is sludged up or the pipe blocked then the engine can produce some interesting exhaust fumes. Checking this is cheaper than changing the head gasket.

[RLWP]

I like that. I don't have any experience of those side covers

 

Richard

[bizzard]

It's a common problem. The tappet chest covers are sealed with rubber "O" (actually they're rectangular) rings which harden and split due to the heat from the exhaust. These then leak and you get oil in the bilge (or on the drive if its an MGB!) . One of the covers usually contains a metal gauze oil strainer and it's designed to catch the oil vapour and let the oil return to the sump, the rest of the crank case fumes then get fed into the inlet manifold and burned. If the gauze is sludged up or the pipe blocked then the engine can produce some interesting exhaust fumes. Checking this is cheaper than changing the head gasket.

An older engine of this type would have cork sideplate gaskets. That's right, a blocked breather will put the whole engines internals under pressure causing oil leaks and smoke everywhere and can cause an engine to blow up once its blown all its oil out. It was always a common problem with these engines. In a vehicle those breathers would have needed removing and cleaning every 5000 miles.

[p6rob]

Thanks for the tips. I had been planning on taking the water pump off to check the state of the water jacket, head off and replace the timing chain. Then thought, if I'm going that far, it'd be easier if the engine was out with some decent access available.

 

I can't understand the cooling system at all. I haven't installed a thermostat yet and the skin tanks peak temperature is about 78 deg c whereas the engine temperature will basically keep climbing. We've been checking it with an infra red thermometer and stopping for a rest when the space between injector and glow plug reaches 90ish.

The suspicion is that the coolant flow isn't as good as it should be.

[RLWP]

Most likely you have an air lock somewhere

 

Richard

[Chalky]

There was a fine spray of oil coming from the join between engine and bellhousing just above where a clutch slave cylinder would mount. This leak was playing havoc with oil consumption and since filling the area with epoxy putty oil loss has been almost nil. I can't understand why there would be a pressurised leak there, unless the block is cracked maybe. Does anyone by any chance have a picture of the rear of the block to help fathom it out.

 

From memory there's an oil gallery in the rear corner of the block that feeds the head (at least there is on a 1.8 petrol and most of the base engine is common)

[Tony Brooks]

From memory there's an oil gallery in the rear corner of the block that feeds the head (at least there is on a 1.8 petrol and most of the base engine is common)

 

 

I agree with that and I think it was plugged with a brass plug in the rear block face. The end plate (or in this case the bell housing then goes onto the back of the block with a gasket.that surrounds the plug. Maybe the plug has worked loose or the gasket has failed. Certainly worth a good clean up and inspection.

 

If the engine is going to get overhauled I would buy some cheap oil and keep going until you get home.

[David Mack]

That's right, a blocked breather will put the whole engines internals under pressure causing oil leaks and smoke everywhere ...

I had the same on a Petter PH1 on a dumper truck. Oil was being blown out past the crankshaft seal into ther bellhousing. And when I took the dipstick out with the engine running I had an oil fountain.

 

The breather tube was completely blocked with oily goo. Cleaning it out solved the problem.

[p6rob]

With a little help from my friends the boat has now arrived in Birmingham.

Saturday morning I'll have a look at the breathers and re-torque the head nuts before carrying on through the next flight of locks.

 

Thanks again for all the advice.

 

Rob