Oil leak on 240z with a L28 block and transmission?

Graeme - CZ

Club Member
Hello everyone,

One of my final jobs is to fix an oil leak coming from the engine. No idea yet specifically where. I'm wondering if there are common culprits for this and also how difficult a job this is going to be? Lastly, what should be on my parts list? I already have the rear main engine oil seal.

Thanks for any tips before I attempt this job.

Regards, Graeme
 

jonbills

Membership Secretary
Site Administrator
There's a crank seal at the front as well as the rear one you've got. There's also seals for the rear main bearing cap.
It could also leak from the sump or the the timing cover or even the head gasket.
Best to figure out what and where its leaking before buying parts I think.
Changing the crank rear seal means lifting the rear main cap, and then you think about changing bearings and then you're onto a full rebuild :)
 

Ped

Club Member
Mine looked like it was coming from the head gasket joint, but it was running down from the rocker cover gasket.
 

Graeme - CZ

Club Member
Mine looked like it was coming from the head gasket joint, but it was running down from the rocker cover gasket.

That’s interesting re rocker cover. I’ve just replaced the gasket. Notice one of the bolts snapped, so it’s not getting the best seal. How did you spit it in the end?


Sent from my iPhone using Tapatalk
 

Graeme - CZ

Club Member
My hunch is it’s coming from the rear of the engine. Underneath I see a cover that appears to bolt onto part of the gearbox (bolts missing). Definite signs of oil coming from here.

36587a47bff487f13ea96a9f9336028e.jpg



Sent from my iPhone using Tapatalk
 

Graeme - CZ

Club Member
There's a crank seal at the front as well as the rear one you've got. There's also seals for the rear main bearing cap.
It could also leak from the sump or the the timing cover or even the head gasket.
Best to figure out what and where its leaking before buying parts I think.
Changing the crank rear seal means lifting the rear main cap, and then you think about changing bearings and then you're onto a full rebuild :)

Time for a proper investigation by the sound of things.



Sent from my iPhone using Tapatalk
 

jonbills

Membership Secretary
Site Administrator
My hunch is it’s coming from the rear of the engine. Underneath I see a cover that appears to bolt onto part of the gearbox (bolts missing). Definite signs of oil coming from here.

36587a47bff487f13ea96a9f9336028e.jpg



Sent from my iPhone using Tapatalk
It's just a dust cover really, that plate between the gearbox and engine - no oil seal. If oil is coming out there between gearbox and engine, first thing is to figure out if its engine oil or gearbox oil (the seal on the gearbox input shaft can fail).
 

Huw

Club Member
I had a slight oil leak in the same place. I thought it was the crank oil seal as it was engine oil not gear box. Turned out to be the sump gasket at the back of the sump that butts up against the engine/gearbox cover. Just needed to slightly tighten the sump bolts down slightly.
 

Graeme - CZ

Club Member
I had a slight oil leak in the same place. I thought it was the crank oil seal as it was engine oil not gear box. Turned out to be the sump gasket at the back of the sump that butts up against the engine/gearbox cover. Just needed to slightly tighten the sump bolts down slightly.

Good tip. I’ve got a new sump gasket already. I’ll clean up everything, replace sump gasket and put back together. At least that’s a simple job to rule that out and I have the part.




Sent from my iPhone using Tapatalk
 

jonbills

Membership Secretary
Site Administrator
Good tip. I’ve got a new sump gasket already. I’ll clean up everything, replace sump gasket and put back together. At least that’s a simple job to rule that out and I have the part.




Sent from my iPhone using Tapatalk
Just FYI, changing the sump gasket isn't completely trivial with the engine installed.
 

240L31

Club Member
I didn't have any issues with removing my oil pan at all. Cyl 1 needs to be at TDC, though.

I had a similar leak, the issue were the main cap side seals. I did replace them without pulling the engine or gearbox.
 

jonbills

Membership Secretary
Site Administrator
I believe it's something to do with the front possibly catching on the cross member before the sump has cleared the intake strainer
Yes, that's it. You have to lift the engine a bit to get at all the bolt heads too.
I know some people have removed the oil pickup and strainer before taking the sump off completely, but not sure if that's making it any easier overall.
 

240L31

Club Member
I only can repeat myself :D I did this some weeks ago, there is not plenty of room, but you can slide out the oil pan if Cylinder one is at TDC. It needs only a little wiggeling.
 

Graeme - CZ

Club Member
Think I’ve tracked down the leak to the sump cover / seal. Now just need to suss out the removal / refit process. Any further tips on that?

881541c341cb15c74f9d9cae2a8cf1a0.jpg



Sent from my iPhone using Tapatalk
 

Graeme - CZ

Club Member
I only can repeat myself :D I did this some weeks ago, there is not plenty of room, but you can slide out the oil pan if Cylinder one is at TDC. It needs only a little wiggeling.

Hi. So if I’m understanding correctly, you didn’t jack the engine at all? You were able to access all the bolt heads ok? Dumb question: what’s TDC?


Sent from my iPhone using Tapatalk
 

toopy

Club Member
Hi. So if I’m understanding correctly, you didn’t jack the engine at all? You were able to access all the bolt heads ok? Dumb question: what’s TDC?


Sent from my iPhone using Tapatalk

TDC, top dead centre, basically the piston is at the top of its stroke, so if no1 piston is at the top of the bore, the crankshaft immediately below it wont be protruding into the sump, therefore making removal easier at the front.
 

Graeme - CZ

Club Member
TDC, top dead centre, basically the piston is at the top of its stroke, so if no1 piston is at the top of the bore, the crankshaft immediately below it wont be protruding into the sump, therefore making removal easier at the front.

Is piston 1 at the front? I assume you just need to remove the spark plug to check if the piston is at the top?


Sent from my iPhone using Tapatalk
 
Top