How many miles does it take for a differential leak to show?

[Submariner1]

I would be grateful for some info.
I have resigned myself to replacing the drive sharft seals on the diff.
As it appeared to be leaking imo horribly.

Wierdly when I wiped this off I expected the kitchen towel to be soaking. In fact
Yes it went a little dirty, but only in 2 places both about 4mm x4mm did it go translucent. So it looked a lot worse than it was.
I had it looked at by the local main dealer, who said it wasnt bad, and they didnt check the level as they doubted it had leaked much. But they determined it was leaking from the top of the seal.

Because I am having it replaced by my indy some 70miles away, and have it booked it for next Thursday; I wanted to work out if it needed topping up before making the journey. I dont want to drive 70 miles on a 1/2 empty diff!

So I thought I would clean it all off with kitchen towel and brake cleaner. Which I did last night.
I drove 30 miles today and just checked the diff.
It looks bone dry.



I was surprised as I expected some kind of slight weep.

By coincidence a friend of mine has a work colleague who also has a CL500 and he had a leaking diff!
and likewise had what appeared to be not a massive leak.
But naturally he changed the driveshaft seal.

Ironically after changing the seal it leaked again, so they thoroughly cleaned the diff.
This time, Although there was no nasty leak at the bottom, there was significant misting around the breather.
They changed the breather and no more misting there !!
And he has had no further problems.??

As you can imagine the second time around, he asked how come it leaked badly and then only slightly. He told me they didnt really have a decent explanation.

Yes I was surprised to find that diffs even have a breather.

Putting 2 and 2 together to make 10!
I had a look and yes mine does have a breather right above the leak!
The oil mist looked lighter around the top of the seal / breather area, than the bottom of the seal / drain plug.

So you can imagine my dilemna, is it the driveshaft seal as the Maindealer says , or is it the breather directly above that seal?

Hence I would like to know

How many miles would it take to show if it was a driveshaft seal leak?
I.e will it show within 100 miles ? I,e. Before I get to my Indy

What makes a breather leak and apparently no longer leak?
( no idea how they work).

I would much rather pay my Indy to upgrade my bixenons to the Gen 2 versions.

Is it significant that a few months after my build the breather part no and breather cap was changed?

Does one clean out a breather or do you just replace it?

Am I right to assume 30 miles is not enough to let the leak manifest itself.

 

[LostKiwi]

How long is a piece of string Sub? Seriously thats pretty much the answer.
The time required will depend entirely on the size of the leak.
It will take a major leak for the diff to lose enough oil on a 70 mile drive to be noticeable and if it was that bad you would see oil on the ground under the car after only a few minutes stationary.

Any part of a car that is 'sealed' and suffers large temperature variations in use must be able to relieve the internal pressure form expansion of oils and air. Thats why the gearbox and diff have breathers.
My Defender had 4 transmission breathers - one for the main gearbox, one for transfer box, one for each differential.

 

[Submariner1]

How long is a piece of string Sub? Seriously thats pretty much the answer.
The time required will depend entirely on the size of the leak.
It will take a major leak for the diff to lose enough oil on a 70 mile drive to be noticeable and if it was that bad you would see oil on the ground under the car after only a few minutes stationary.

Any part of a car that is 'sealed' and suffers large temperature variations in use must be able to relieve the internal pressure form expansion of oils and air. Thats why the gearbox and diff have breathers.
My Defender had 4 transmission breathers - one for the main gearbox, one for transfer box, one for each differential.

Thanks LK for the reassurance.
I can understand even for someone experienced in diff leaks, how much in how many miles is very difficult to assess.
Blimey what do I do if when I get to the Indy its still bone dry. :-/

Strangely I can not find how to replace or clean the breather in WIS. Yet it is on EPC, with the associated replacement part #.

I sort of wish I had not heard about this guys problem.
It seems so similar, just a faint misting at the top, and yet covered 1/2 the bottom quite clearly but no drips on his garage floor.
And when they tested it, the level had hardly dropped in the casing.
His theory is ... at some time the breather started blowing out oil mist, it sank down the side of the casing, around the seal.
His was discovered at a service, and then they changed the seal. When it was checked later there was still so e misting at the top, but hadnt dropped down onto the seal . Then they changed the Breather. And no more problems.
What he felt was odd was how it let out a fair bit and then later just a little. His garage reckoned he must have pushed the car very hard on a hot day and the oil expanded enough to decide to to dump some oil.

Unless mine clearly comes out of the breather again, I will just have to go through with the seal replacement. Becuase I cant go crawling under the car every few days, nor do I want to run it under capacity .... kinda defeats the maintenance ethos of changing all the fluids on time.

I got the oil from a main dealer, who checked it was the right one. And the Indy also checked it. So thats a double check. And it was genuine MB oil. So no worries on that front.

 

[Craiglxviii]

It is worth pointing out that a "MASSIVE" oil leak can be nothing but a few ml spread 3-4 molecules thick. Oil has a wonderful propensity for spreading over nearby surfaces especially where there is airflow assistance. It also picks up all forms of airborne cack which makes it look far worse than it is.

For now I'd say, monitor it weekly. Check your driveway daily for spotting.

 

[brianbrian]

As above, as that looks like a weep you have.The oil in the back axle is some thing like e90 so quite thick, but not so thick summer time or after a long run.You will not even get a weep of oil winter time.If you had a table spoon of oil and poured it out on the floor you would see what a mess it would make. I don,t like cars that leak oil on the road for safety reasons for other users. But what you have I would not worry about it.

 

[Wighty]

I did suggest last week to clean it and monitor it , as has been said above a tiny amount of oil can cover a large surface area . If every six months the diff just needs a wipe then I don't think hundreds of pounds to repair it is worth it ??

 

[Submariner1]

It is worth pointing out that a "MASSIVE" oil leak can be nothing but a few ml spread 3-4 molecules thick. Oil has a wonderful propensity for spreading over nearby surfaces especially where there is airflow assistance. It also picks up all forms of airborne cack which makes it look far worse than it is.

For now I'd say, monitor it weekly. Check your driveway daily for spotting.

Thanks
No spotting on driveway. And when I first wiped it down, I was surprised only in 2 places (and only about 3x4mm ) did it make some quilted kitcHen paper go translucent. So it seemed an extremely thin coating.

 

[Submariner1]

As above, as that looks like a weep you have.The oil in the back axle is some thing like e90 so quite thick, but not so thick summer time or after a long run.You will not even get a weep of oil winter time.If you had a table spoon of oil and poured it out on the floor you would see what a mess it would make. I don,t like cars that leak oil on the road for safety reasons for other users. But what you have I would not worry about it.

Thsnks, Good point.

 

[Submariner1]

I did suggest last week to clean it and monitor it , as has been said above a tiny amount of oil can cover a large surface area . If every six months the diff just needs a wipe then I don't think hundreds of pounds to repair it is worth it ??

I did pay heed, one of the reasons I cleaned it off. Mainly to double check It hadnt got worse while it waits for its day in the shop.

But now I am wondering is it this £5 breather?

Mending something so minor is a thought. But most of my issues were down to the original owner toleratiG things .... and then you get an accumulation of issues that need resolving ..
And being a tad older its a pain crawling around underneath checking it.
The new House will have a 2 post lift
I see £3,000 in the context of the value of a house a wise investment ... balanced by not taking the massive depreciation hit of buying new cars.

 

[Wighty]

I did pay heed, one of the reasons I cleaned it off. Mainly to double check It hadnt got worse while it waits for its day in the shop.

But now I am wondering is it this £5 breather?

Mending something so minor is a thought. But most of my issues were down to the original owner toleratiG things .... and then you get an accumulation of issues that need resolving ..
And being a tad older its a pain crawling around underneath checking it.
The new House will have a 2 post lift
I see £3,000 in the context of the value of a house a wise investment ... balanced by not taking the massive depreciation hit of buying new cars.

The two post lift sounds wonderful , why don't you leave it until then , and the added bonus of having room to replace the breather as well

 

[Submariner1]

The two post lift sounds wonderful , why don't you leave it until then , and the added bonus of having room to replace the breather as well

Undoing all those struts and folding down the wheel carrier is outside my comfort zone, so having MBS doing it.
Plus it will be at least a year, and they will use the garage for storage during the build .. so its one of the last things in.
Course having the floor reinforced before that with 500mm cubes of concrete under the posts when they do the floor.

 

[Submariner1]

Been down to MBS ... great service
All sorted