74 replies to this topic

[Spider]

Perhaps ask yourself here what's pushing the Oil out and where that pressure is or could be coming from.

The crankcase is basically a box with some oil being splashed around in it. In the upper part of the box, there's a moving seal, and on the other side of that seal, pressures considerably higher than the what's ordinarily in the lower part normally. 

So, what do you think is pushing the oil out ?

[PoolGuy]

My gut feeling is that the timing cover is filling with oil and obstructing the breather. Hence the suggestion made by Timmy to run the engine with the filler cap removed. IMO the timing cover breather is the last one to use, other breather locations are a much better choice. However, it does appear from information provided by the OP that the engine may be producing a little too much pressure below the pistons. 
 

A methodical approach is more important than knee jerk reactions though. 

[Lplus]

My gut feeling is that the timing cover is filling with oil and obstructing the breather. Hence the suggestion made by Timmy to run the engine with the filler cap removed. IMO the timing cover breather is the last one to use, other breather locations are a much better choice. However, it does appear from information provided by the OP that the engine may be producing a little too much pressure below the pistons. 
 

A methodical approach is more important than knee jerk reactions though. 

This is also my opinion, the timing cover is filling with oil to the level of the 3/4 in hole in the block face through to the crankcase - which is also the level of the breather hole in the timing cover.  It seems the OP tried taking the cap off and it didn't produce a huge amount of blowby. Given that this is a 100 mile engine which probably doesn't have fully seated rings any blowby is also passing out of the hole in the block face against the flow of oil back to the crankcase. I don't know how much the moving chain and sprockets would aerate the oil but it is likely to be somewhat frothy under these circumstances. quite why the oil can't get down out of the timing case through the two small holes I don't know - excess sealant? old gasket left in from cleaning the block face???

 

 

I suppose it's possible that the hole through the timing backplate and the block is covered by an incorrectly made gasket leaving the oil trying to get down through the maincap holes to the crankcase against the blowby....

 

Personally, I'd remove the rad and brackets then the pulley and the cover and have a look at the holes in the backplate/block and the two holes in the maincap.

[PoolGuy]

 

My gut feeling is that the timing cover is filling with oil and obstructing the breather. 

quite why the oil can't get down out of the timing case through the two small holes I don't know - excess sealant? 

 

Personally, I'd remove the rad and brackets then the pulley and the cover and have a look at the holes in the backplate/block and the two holes in the maincap.

 

It's not uncommon, think of how often you see sealant sticking out from gaskets. 

[DeadSquare]

I have never tried it, just seen it advertised, but what about that orange stuff from "Just Stop Oil" ?

[Earwax]

More clarification on the camshaft oilways.  ( and I could be wrong )

 

Some cams are rifle and cross drilled ( rifle drilled  along the centre longways : ) (cross drilled through each lobe that get fed under pressure)

 

There is sometimes a grub screw or similar to cap the oilway  at the timing end- so the oil builds pressure to feed throughout-from the centre cam bearing.  If it is leaking it might push oil into the timing cover 

 

So under the cam plate maybe an area of excess oil?   On further thought I doubt it possible to diagnose properly without engine out?? 

[imack]

I'd not considered that it may have a cross drilled cam shaft. My MED fia15 and my SW23 both have a grub screw in the timing gear end of the cam. If this was not fitted I'd imagine the timing cover would quickly fill with oil, I don't know whether it would overwhelm the breather hole in the end of the block, but it would probably fill to that level. If the breather canister doesn't have a pipe on it to extend the open end above the top of the fan in my experience then the fan can draw oil out of the breather canister, particularly if it's filling beyond it's designed level.

[lsto]

Just my 2 pence, if you don't want to pull the engine why don't you pop somewhere who can put a manometer on the engine and actually measure the crankcase blowby. At least that would give you a definitive answer on wether the engine will need coming apart or not.
I'd imagine if you phone around a few engine shops someone would be able to check for you. That is how we diagnose tired engines at work. It takes all the guess work away.
Good luck

[alpder]

Just my 2 pence, if you don't want to pull the engine why don't you pop somewhere who can put a manometer on the engine and actually measure the crankcase blowby. At least that would give you a definitive answer on wether the engine will need coming apart or not.
I'd imagine if you phone around a few engine shops someone would be able to check for you. That is how we diagnose tired engines at work. It takes all the guess work away.
Good luck

It's pretty easy to make one. At least, for use just in the workshop. But even that might be enough to get some indications. https://www.theminif...k/?hl=manometer

[BobbyMax]

It's one of the earlier star drive cams so definanly not X drilled

[BobbyMax]

I really thank you all for your input. And i have listened very gratefully to all of them. So I'm going to pull the engine after all the 🎄 is over. I'll keep everyone informed on the outcome but im pretty sure I've used to much of the blue stuff (gasket sealer) or ive left a bit of old gasket in the system thats causing problems.
Again thank you all and I'll keep you informed as soon as I've worked it out 🙏🙏🙏

Bobbymax

Edited by BobbyMax, 17 December 2025 - 07:05 PM.

[panky]

Just thought I'd mention what I did re-building my Morris Minor engine after advice from those that know over on the MMOC forum. I did't use any sealant on any gaskets but just smeared them in grease and after a few months of regular use there is not a drip of oil or coolant coming from anywhere and it used to mark it's territory everywhere. As long as the sealing surfaces are in good condition then you shouldn't need anything else consequently  there's no chance of anything blocking oil ways (except misalignment or error) 

[BobbyMax]

Thank you panky...much respect 👌

[BobbyMax]

OK so engine out.
My first question is, are the 2 inner small holes under the Crank, oil drain holes  20260107_133609.jpg   47.83K   27 downloads

Edited by BobbyMax, 07 January 2026 - 02:19 PM.

[Lplus]

OK so engine out.
My first question is, are the 2 inner small holes under the Crank, oil drain holes 20260107_133609.jpg

Yes they are, but they should be in a significant rebate below the level of the rocker cover gasket face.  There seems to be a very small rebate for the top half of the holes but this may not be enough especially if there's excess sealant..  Are you sure the main cap is fitted the correct way round?