Rear Leak Mystery Help?

[cp81]

I seem to get a small pool of oil on my garage floor, at the rear of the car on the drivers side. While in lock down and doing other jobs on the car I started to investigate. I found oil sprayed on the chassis around the drive joint, chassis and brake pipe area where it splits to feed to feed either side. I clean all the areas up, to hope to find the source of the leak.

All my fluids are new and clean, so it’s difficult to determine if it’s diff oil or brake fluid.

With the car jacked up, I got underneath and had my partner operated the brakes to see if leak was from brakes. Nothing seemed to leak out under pumping of the brakes. Is this the correct way to check?

After returning from over night, some more fluid again appeared on the drive joint:




Looking over the diff it seems all clean. Is there something I should check? Steve Bible references a breather for the diff??

Any thoughts and suggestions would be greatly appreciated.

[O mage]

The breather is on the o/s could be that and it can be extended higher but check its not just been overfilled first.

[cp81]

What’s the breather look like?

[O mage]

If you take the o/s/r wheel off you might be able to see, it's on top of the rear ally housing, it's just a small hollow stud with a loose metal cap on it screwed into the housing. The cap can be removed and then add a small length of hose and a clip to extend it slightly higher.

[Steve_D]

Wipe the oil on your finger and smell it. Diff oil has a very distinct smell. Brake fluid almost none. You could dip a finger in the brake master cylinder to get a comparison.

Steve

[TJC46]

cp81 said:

What’s the breather look like?

You can see the breather outlet on the top right side of the diff.I would expect to see some oil on the diff body also, if this has been blowing oil out.



Are all the bolts tight on the CV flange joint, driveshaft to diff. The grease around the CV joint, inside the rubber gaiter reaches pretty high temps and any

tiny gap in the joint will allow this to leak.

This will show up as spray on the chassis / underbody right above the flange. Another possibilty is the oil seal / seals on the diff itself, and this will also show as

spray on the chassis / underbody.

Edited by TJC46 on Thursday 4th June 09:03

[cp81]

Well firstly found the breather:



Felt around it and no oil. Is there a check I should do to make sure breather is ok?

Checked bolts on joint, these are solid, won’t tighten or loosen up. Even with Allen key and tube... sprayed some penetrating oil on them and will try them again tomorrow.

Steve there is no smell to the oil but diff fluid will have only done less than 100miles...

Pressuring the brake system should highlight a leak in the system correct??

Diff is clean and seems not obvious leak point...

[Dougal9887]

Sounds like the diff output shaft seal leaking. Oil can travel along the shaft and get sprayed out from the back of the flange without leaving much evidence.
It's easy enough to replace the seal in situ, although getting the shaft levered out can be difficult. Even if the seal has been recently replaced it will still leak if the shaft has a wear ring. A wear ring can be sorted DIY with a speedy sleeve or by metal spraying and re-machining, but I imagine that's pretty costly. I had 100% success with a speedy sleeve and new seal. Don't be tempted to re-use a seal even if it's very new, it will likely leak again. The shafts are made from unobtainium.

[Steve_D]

cp81 said:

..............Steve there is no smell to the oil but diff fluid will have only done less than 100miles...

Even more reason for it to smell. It is a very pronounced smell so if you are not getting it then it is not diff. oil.

Undo the level plug and put you finger in so you know what it smells like.

Steve

[cp81]

Steve, I will try that... had a non productive day trying to get window height adjuster to adjust but completely seized up. Had to take all the door apart and had joy of taking skin of my arm getting to the nuts...

Dougal I think you maybe right and probably have to go see local specialist as doing of axle stands is probably going to be too difficult and really haven’t the room...