1275 Oil Leaks again

[jaguar68]

Hi chaps,

I think I still have an oil leak problem on the 1275 A+ engine in my '69 4 door. The sump seals have been replaced and the cork gaskets replaced with rubber ones. The engine still appears to be leaking oil from the rear of the mounting plate and is pooling beneath the car and producing yet another slick on the road outside the house. Oil pressure on the engine is good, between 50-70 psi according to the gauge and the car is now running a breather from the rocker cover as well as the front engine plat

Also, the bottom of the gearbox is wet with oil. I don't know if this is a separate leak from the gearbox (I hope not) or whether its a "referred leak from the engine when the car is moving.

Is there anywhere else obvious that the engine could be leaking oil from?

Regards

John

[bmcecosse]

Pressure in the crankcase will push oil out the rear labyrinth... To test - hot engine after a spirited run - - remove the oil filler cap and rev up - is there a plume of smoke/fume?

[jaguar68]

Hi Roy,

I've taken the car out for a good run, 20+ miles with around town speeds and a couple of 50-60 mph runs. Taking the oil filler cap off and revving the engine doesn't produce any smoke or fumes from the rocker cover and I can't see anything from the exhaust. Is this where I would be expecting to see the smoke?

If this isn't a breathing problem what could be a possible cause and any cure available?

Regards

John

[bmcecosse]

Hmmmmm - well engine sounds good. Could be worn labyrinth I suppose - or worn main bearings flooding the 'seal' to the point it just can't cope. Leak from this area should be coming from the jiggle pin in the base of the bellhousing (assuming Minor gearbox...). There is an aftermarket seal kit sold by some - which runs on the tail flange of the crankshaft - which of course needs to be perfectly round and machined/polished to a nice smooth finish..... You could try that - not inexpensive I believe, and mixed reports.......

[Declan_Burns]

You could also try fitting a PCV valve and a flame trap between the inlet manifold and the crankcase breather. I did this on my MG TD, (TD's are notorious leakers) over the weekend as an experiment and it reduced a torrent to a dribble. I measured the crankcase pressure with a U-tube and it is now running at -11mbar. The carb will need resetting. Experiment ongoing.
Regards
Declan

[bmcecosse]

Yes - well worth doing -because that valve connects the crankcase directly to the inlet suction. I have done it without benefit of the valve, on a Mini engine. That (ie no valve) upsets the idle slightly (but it was bad anyway with long camshaft) - and certainly cured the oil leaks for me on that engine.

[Declan_Burns]

Here's a photo of the test Installation. The PCV valve is from a Ford part no.13H55191 (£5.49 on ebay). The flame trap is from a Landy discovery (£4.50 on ebay) and the rubber glove to seal off the oil filler cap is from Aldi . The pressure can be measured by removing the bung on the U-Tube. It really works!
Regards
Declan[frame][/frame]

[bmcecosse]

Just measure the pressure by how much the glove inflates.......

[Declan_Burns]

Exactly,
That's how low pressure industrial transmitters work-they sense the deflection on a diaphragm.
Regards
Declan

[philthehill]

If the engine oil is not coming from the rear crankshaft bearing and past the return scroll and not from the rear sump seals it can only come from the following:-

1. The rear oil gallery plugs.
This is highly unlikely as it would be coming down the front face of the rear engine plate unless you have a cracked rear engine plate and MG 1275cc are prone to cracking if that is what you have fitted.

2. The oil pump cover.
There are different sizes of cover and oil pump (diameter and depth) and it is important that the oil pump cover is matched with the oil pump and rear engine plate otherwise the cover will not sit right between the rear engine plate/gasket/engine block and you will get a leak from around the cover. There is a drain between the cover and the crankcase and oil thrown into the oil pump housing should drain out into the sump. If there is a problem with the oil pump cover oil could drain into the bell housing instead of going back into the crankcase/sump. If the mating surfaces of the rear engine plate and the oil pump cover are clean there should be no need to use a sealant when assembling although I have found sealant between the cover and rear engine plate when stripping 1275cc engines.