1.5 leaking sump gasket?

[David Mutch]

Hi all. Been chasing oil leaks round my 1.5 for a while now. Have replaced rocker cover and gasket, side cover gaskets and leaky breather hose, but there's still oil coming for somewhere. There always seems to be oil on the lip around the bottom of the block, directly under the lift pump, but no obvious sign of how it got there. It doesn't seem to be running down from the lift pump, side covers or rocker cover and my air filter doesn't drip, as the breather isn't routed into it. Is it possible that it could be wicking upwards from a leaking sump gasket? If so, any tips for replacement? If not, any other suggestions where to look? Thanks

[bigste]

Oil leaks can and often do show up in all directions. Don't just assume they go downwards, although it will be much worse below the leak. With that last bit in mind you should be able to spot the leak. Thoroughly degrease the area and keep a close eye open. There is always a way.

[Tony Brooks]

The lift pump may have a small breather hole in its base. Get a torch and mirror to look at the bottom of the pump.

 

I think the easiest way to do the sump gasket is to take the engine out but check the tightness of the sump bolts first. 7/16" AF I think but might be 1/2"

[David Mutch]

Oil leaks can and often do show up in all directions. Don't just assume they go downwards, although it will be much worse below the leak. With that last bit in mind you should be able to spot the leak. Thoroughly degrease the area and keep a close eye open. There is always a way.

Thanks. Thought this might be the case!

The lift pump may have a small breather hole in its base. Get a torch and mirror to look at the bottom of the pump.

 

I think the easiest way to do the sump gasket is to take the engine out but check the tightness of the sump bolts first. 7/16" AF I think but might be 1/2"

Thanks. There's a fair bit of space around/under the engine (big cruiser stern). Is there any particular reason why the engine would need to come out if there is space to get to bolts/drop the sump?

[mickp]

I had a oil leak on my lift pump a few years back and was hard to trace ,like you i changed other gaskets first then i renewed pump and leak free since

[bizzard]

As long as you have about 10'' of space below the sump and a foot or so at one side or the other, it should be doable, remove the dipstick first. I must have renewed dozens of sump gaskets on vehicles in the past. Its being careful with offering the sump back up with new gasket and sometimes seals that is the tricky bit as you can end up with a worse leak than you started with.

Its quite common for mechanical fuel pumps to leak oil from the vent hole underneath as TB mentioned.

[bigste]

Not familiar with BMC engines but if there is a breather check it is not blocked otherwise your repair will be in vain.

[bizzard]

Not familiar with BMC engines but if there is a breather check it is not blocked otherwise your repair will be in vain.

Indeed the crank case breathers are a sore point on those engines but he said he'd renewed the side plate gaskets, on one of which the breather resides so I presume he's cleaned it out.

[Chalky]

I'b about to pull the engine out of my car (1.8 petrol B series) for the same problem. The petrol engine has a a number of common leak points and I assume that they're common with the diesel since the basic engine design is the same - with the exception of things like the pump. Most BMC petrol and diesel engines of this vintage were based round a common architecture and tend to have the same problems.

 

You've identified the tappet chests. On the petrol engine it's common to fit a rubber gasket to the rear cover and a cork one (off an MG A) to the front due to the different cover designs (crank case ventilation). Also you need to change the O-rings in the bolts that hold the covers on.

 

Other common leak points

Oil filter housing / bypass pipe - on some versions the bolt holding the filter housing works loose and causes a leak. If there's an external bypass pipe these can leak at the ends.

Crank shaft oil seal. Runs down engine back plate and can look like a leak at the sump. - very common. On the petrol variant the seal is in the back plate and there's a gasket to seal the two together. If the gasket has failed then this can also leak a lot of oil.

Timing chain cover and oil seal

 

If you remove the sump make sure its flat round the bolt holes. If not gently flatten the relevant area of the flange with a hammer and a hard surface. Be careful when removing the sump. The main bearing caps at the end of the block seal to the block using cork blocks. Make sure these are back in otherwise it will leak - lots.

 

There are a number of bolts (oil pressure relief valve) and plugs that seal oil ways however these usually don't leak.

 

If you google MGB oil leaks you'll find lots of details about how to identify and fix them.

Edited June 9, 2016 by Chalky

[Tony Brooks]

Thanks. Thought this might be the case!

 

Thanks. There's a fair bit of space around/under the engine (big cruiser stern). Is there any particular reason why the engine would need to come out if there is space to get to bolts/drop the sump?

 

I think there may be a couple of cork seals on no.1 and no.4 main bearing caps that I would not like to have to fit without a good view and access but I am not sure. I think BIzzard, Richard etc. have messed with 1.5 diesel far more recently than myself so take their advice.

 

If you did not clean the breather when you have the side plate off it would definitely be a very good thing to do now.

[Bee]

I've done one of these, easiest way if you do have to get the sump off is to disconnect everything then just tip the engine up on its nose, I would not really think its possible to do the job by 'feel'

[p6rob]

I currently have a bmc 1.5 in bits, so if it's any help, I can take pictures of any components.

 

 

Rob

[Chalky]

Possibly relevant discussion on another forum about someone who has a leak in the same place. Caveat - it's the petrol version not diesel.

 

http://www.mgexp.com/phorum/read.php?1,3284524

[David Mutch]

Thanks very much all. I'm hoping it's the lift pump now, as the sump gasket sounds trickier than I had imagined! Will check all the other possibilities too. Photos/videos of any jobs on the 1.5 (or similar engine) would be a great help, thanks Rob!