M38A1 engine oil leak from bell housing

giacomo · Post by **giacomo** » Fri Jun 17, 2016 1:42 pm

[quote
Hi all,

I have this leak of engine oil from bell housing, and as I think I should replace the crankshaft rear oil seal bearing, I would kindly know if I should remove the crankshaft and if this work you can be done with the engine in situ
thank you

Giacomo[/quote]

4x4M38 · Post by **4x4M38** » Fri Jun 17, 2016 2:14 pm

Giacomo,
If you search in the articles you will find a lot of information about oil coming from the bellhousing. It could be the rear main seal, and it could also be the rear cam welsh plug.

Yes, I believe you could address the rear main seal by laying on your back and working the old seal out and the new one in, but I believe the consensus is you really want to determine if all sealing surfaces are not damaged and the cause is something else besides just the damaged seal.

Be aware there are two types of seals and you need to make sure you get the proper one.

So yes, it can be done. But in the end maybe not the correct way.

Take care,

Post by **wesk** » Fri Jun 17, 2016 7:46 pm

A proper job of seal replacement means remove the engine and place it on an engine stand and rotate it upside down and remove the crank. As mentioned above there are three possible sources for engine oil to leak from your bell housing. The rear main seal, the rear oil gallery welch plug and the rear cam journal welch plug. It is really a PITA to lay on your back and do a poor job of seal replacement just to find out your leak is not from the rear seal.

Also there are two styles of rear seal. The older rope style seal.

Here's a good explanation of how to change a rope seal.
http://hainesgarage.proboards.com/threa ... ine?page=2

And the newer preformed seal:

There are two or three different production preformed seals. Those produced during the 80's/90's had serious fit problems. Be sure to stay with new production seals.

Also the seal surface of the crank needs to be in good shape. This usually means polishing that surface.

Here's an example of a crank you Should Not Use without Polishing out pits.

Many old gurus will tell you no worries they have installed many seals withe crank still in the engine using seal pullers of various types. What they don't tell you is how long each lasted.

Finally there are two different cranks out there. The early rope seal crank cannot be used with the new preformed seals unless you get the seal surface of the crank machined down to the correct diameter.

giacomo · Post by **giacomo** » Sat Jun 18, 2016 5:02 am

Hi wesk,

thank you for reply,as usual, accurate, fast answers and very technical

the two types of seal are interchangeable ?
if I have the older rope style seal I can mount the newer preformed seal ?
I have to remove the crankshaft in order to install the rear seal halves to block ?

Giacomo

Post by **wesk** » Sat Jun 18, 2016 10:14 am

That is not correct. My post explained that you can use the rope seal on the newer crank that is machined for the preformed seal but you cannot use the newer preformed seal on an older crank that is not machined to fit the preformed seal.

giacomo · Post by **giacomo** » Sat Jun 18, 2016 11:02 am

Ok
and as regards the second question ?
thank you

Giacomo

Post by **wesk** » Sat Jun 18, 2016 7:23 pm

It is preferable to remove the crank when replacing either seal. This insures a proper conditioning of the crank's seal surfaces and the proper fitting of the seals both rope and preformed.

Also important is separating the engine and bell housing so you can ascertain exactly which of the three possibilities is actually leaking.

giacomo · Post by **giacomo** » Wed Jun 22, 2016 2:22 am

Thank you wesk,

but if the leak comes from rear cam welsh plug or rear oil gallery welch plug,
one can intervene in the rear part of the engine block after removing the bellhousing , but without disassembling the camshaft ?

Giacomo

Post by **wesk** » Wed Jun 22, 2016 8:42 am