2 leaks on diff - DIY repair/seal replacement NCV3

mugget

Member
Hi folks,

To give some background it's a 2006 NCV3, currently has 309,000km on the odo. So it's coming due for the rear axle oil change (does this mean the diff?) and coolant.

Just noticed some oil on the outside of my diff in the last week, thought I'd better get it taken care of… freaked me out at first since I've never had cars before (I'm a bike guy), but looking around it seems like it's just a simple seal replacement? What is the general feeling for a differential-n00b to take this on, easy DIY job?



There also seems to be a 2nd leak towards the back of the diff:



I guess there is just another gasket/seal that needs to be replaced there? Unless that could be indicative of other problems?

There seems to be a couple of dings on the bottom, not sure if that could have caused it?



Also just wondering what else I should look for if I go ahead and take the old seal out? Any chance there will be bearings that need replacement? Or are they usually okay? On my bikes I would just check for bearing play by hand, not sure if the Sprinter bearings need more specific measurements taken?

Looks like I have a leaking shock on the rear, another job to add to the list.

Cheers for any advice on the diff leaks and ease or difficulty of the seal replacement. :thumbup:
 

Eric Experience

Well-known member
Re: 2 leaks on diff - suitability for DIY repair/seal replacement?

Mugget.
Looks normal to me, you need a small amount of oil to lubricate the seal. Just give it a good wash and monitor it. Eric
 

4wheels

Well-known member
Re: 2 leaks on diff - suitability for DIY repair/seal replacement?

Those dents are the cause of the leaking .. I had it on my 08 at 50k . So just clean it with pressure washer , then take a hammer and hit that diff. cover , where it was bent . Also , check if the bolts are tightened. Then check the fluid level . That is what I did , no more leak , the diff. is dry now . I bought a new gasket but never used it . I also changed the fluid out .
 

mugget

Member
Re: 2 leaks on diff - suitability for DIY repair/seal replacement?

Cheers Eric, glad to know that the seal looks like a normal type thing. I am not usually this paranoid, but this is completely new to me.

4wheels, do you mean to hammer the dents to bring them back closer to original shape? So an outward/downward force? (Or hammer onto the cover in the same direction as the bolts are installed?) And do that while the cover is still installed, or remove it?

I was looking for the torque specs on those cover bolts, in case I have to remove it, found some "official" info on the pinion seal sweating - like Eric said, perfectly normal.

Xentry supports Carl's guidance



Here is the full MB document LI35.31-N-048694

View attachment 35834

This is the meat:

Cause
Before starting repair work to rectify leaks, carefully check what type of leak is present at the affected major assembly.

Moist areas from which no fluid is dripping off or draining away do not represent cause for complaint. These are caused by the phenomenon of "sweating" (see attachment).
This "sweating" cannot be avoided with the current state of the art and does not have any negative effects. This sweating may also be caused by pregreasing of the pinion sealing ring.​
----------------
Remedy
Repairs due to sweating only produce an aesthetic improvement and are not justified.

To perform a precise check, clean the affected area thoroughly with a cloth and monitor over an appropriate period of time (approx. 1 week or max. 1000 km).

If necessary, check the rear axle oil level and the housing ventilation up to the frame crossmember.

If fluid is dripping or draining off visibly, a leak is present which must be eliminated by performing appropriate repair work as described in WIS.

If a leak is present, also replace the standard oil drain screw with a magnetic oil drain screw A 000 990 58 17.​
----------------
Here are the repair instructions

View attachment 35833

-Jon

PS: I forgot to include the attachment to LI35.31-N-048694

Here it is:View attachment 35836
Another thought - maybe that oil only leaked out during the initial impact that caused the dents, may not be actually leaking right now. Could be possible because I've driven maybe only 1,000km since I've had the van. But also perhaps that's not very likely because there does seem to be some gunk built up.

Anyway, it would be great if anyone could clarify where the hammer comes into this - don't wanna go hitting stuff randomly.

And I didn't end up finding the torque specs for the cover bolts, does anyone know? I'm just interested to find out now.

Cheers :thumbup:
 

lindenengineering

Well-known member
Re: 2 leaks on diff - suitability for DIY repair/seal replacement?

My torque tables show 65nm for cover bolts or 48lbf ft.

This seems a bit high so go easy as you tighten it up.
In any case I always go easy on use again bolts since they get stressed over time.
The maxim "tight is tight" and "too tight is over-tight"; often repeated to me as an apprentice when asking the same question many years ago.

As for re-sealing the cover, simply clean it off both faces that is---degrease with some brake cleaner, apply a goodly layer of automotive silicon sealant to the cover and a light smear on the axle face, let it congeal for a few minutes then directly apply the cover without making it slide.
Install the bolts and tighten up.

Dents you can pound out with a hammer on a wood anvil or block, just go easy so that you don't deform the face, which is the important bit. Although that stated silicon can take up a lot of face deviation which is why it is so popular as a manufactures' first when selecting a suitable joint sealing medium.
Dennis
 

mugget

Member
Re: 2 leaks on diff - suitability for DIY repair/seal replacement?

Cheers for that info. Just wondering is there any point to pound out the dents, since it's the face that seals?

I was planning to change the diff oil anyway, just went to look at the fill hole to make sure I have the needed tools. Pried up the rubber hole plug... then oil started trickling out so I just put it back in (not much oil lost, then!). So I don't have an actual fill hole bolt?? Is that normal? I didn't check if it's threaded there because oil was leaking onto the grass and I wasn't ready for it.
 

220629

Well-known member
Re: 2 leaks on diff - suitability for DIY repair/seal replacement?

... Just wondering is there any point to pound out the dents, since it's the face that seals?
Yep. It's good to hear that the method works. Certainly worth trying. If it doesn't work (continued seeping) then there doesn't seem to be any downside because you can just go ahead and do the full repair.
...So I don't have an actual fill hole bolt?? Is that normal? ...
Very normal. OEM.

vic

P.S. - The level should be at the fill hole. Unless the differential is hot, or the vehicle isn't level then popping out the rubber plug shouldn't cause fluid to flow out.
 

mugget

Member
Re: 2 leaks on diff - suitability for DIY repair/seal replacement?

Okay cheers, good to know I'm not missing a bolt!

Yeah it wasn't parked on level ground, wasn't expecting to actually open the fill hole, just wanted to check the bolt head size.

Sorry just one more question - should the diff oil be drained after a drive (while it's hot)? Or does that not apply so much to the diff?
 

220629

Well-known member
Re: 2 leaks on diff - suitability for DIY repair/seal replacement?

...
Sorry just one more question - should the diff oil be drained after a drive (while it's hot)? Or does that not apply so much to the diff?
My opinion, not fact.

I get it warm first. The differential fluid is quite viscous. The warmer it is the more readily the residual oil will shed off the case walls and such for draining. My guess is that when it is warm it may also carry debris with it more readily.

I'm certain that at dealerships most differentials, and engines for that matter, get drained cold because they sit in the lot until taken in for service. For that reason I doubt that it really matters. vic
 

mugget

Member
Re: 2 leaks on diff - suitability for DIY repair/seal replacement?

Just to update the thread and give some additional info for anyone who is thinking they need to do the same thing.

I cleaned around the cover and drain bolt, then used a 14mm Inhex socket to remove the drain bolt.

Then removed the cover bolts using a 13mm socket. A warning/heads-up for anyone who hasn't done this part before - I think the bolts have some kind of interference fit, so they take a bit of force to move, but then really soon after they start they become much easier. So if you expect that and don't go at it with a big push/pull action then you might just save yourself from skinning your knuckles on the sway bar...



I usually wear nitrile gloves when working with any greasy parts or oils, for easy cleanup and to keep the stuff off my skin, gloves probably would have saved my skin as well.

With the bolts removed the cover was still stuck pretty good because of the sealant. I wound up using a plastic trim lever to work my way around the edge and pry the cover off.

You can see the bottom edge where the dents were - the seal must have been broken because you can see the not all of the face is clean in that area. And I didn't take a picture, but when I was re-installing the cover I happened to look right along the face of the cover and could see that the dented area fell away noticeably. So that explains the slow leak.



And here with the cover off, you can see the dented area where the sealant has lifted.



Once I got it all cleaned up I could see that the same area where the sealant had lifted wasn't finished like the rest of the face, it doesn't have those sanding marks. So I took some 80 grit paper and sanded that area so the entire face was more uniform, give the new sealant something to grip to.



I wonder if the dents wouldn't have caused the leak if that straight painted area wasn't on the face?

I used some old Threebond 1104 liquid gasket that I had sitting around to reassemble the cover. I used 25ft-lb for the drain plug and 45fl-lb for the cover bolts. I wasn't sure what torque would be right for the re-use of those bolts, so just guessed at that.

Leaving it overnight for the Threebond to fully cure (not sure that it really matters though since it's tack-free in about 5-10 mins) then I'll refill the oil and let it sit, and look for leaks. But pretty confident that it's all sealed up good again.
 

mugget

Member
Another update: it was a few days before I got around to putting diff oil back in, when I checked out the cover there was a drop of oil and droopy, sagging Threebond along with it on the bottom of the cover/diff case. So I guess that although no oil was running out when the cover was off, there must have been enough that when the cover was reinstalled it bled across and interfered with the Threebond cure.

So I removed the cover again and cleaned it up. That stuff is harder to remove than silicone, thankfully acetone will just wipe it off. Not wanting to risk any more problems I went and bought some RTV sealant specifically for diff covers. I also wiped out the bottom of the diff case as much as I could. I installed the RTV sealant as per these particualr instructions (finger tighten the bolts until sealant squeezes out, then come back after an hour to fully tighten/torque it down). Next day I filled it, and it's oil tight - no problems since.

Since I had the cover off again I snapped a pic of the dented/warped face area. You can just make it out... but it's good to know that silicone sealant will deal with that kind of gap/warping with no problems.



Now just to make sure that it never gets dented again... shouldn't be too tricky, I think that as long as I don't drive over any boulders I should be fine!
 

bkhi

New member
Re: 2 leaks on diff - suitability for DIY repair/seal replacement?

My torque tables show 65nm for cover bolts or 48lbf ft.

This seems a bit high so go easy as you tighten it up.
In any case I always go easy on use again bolts since they get stressed over time.
The maxim "tight is tight" and "too tight is over-tight"; often repeated to me as an apprentice when asking the same question many years ago.


Dennis
I know now that it's not 48lb ft. , snapped one of the bolts Sunday. Does anyone know the size bolt it is supposed to be? I took another out but I cannot find a matching thread size.

At least the one I snapped was the top most bolt
 

Dingo

New member
I think you will find the 8.8 on the head of the bolt refers to its tensile strength .

If you used a 13mm socket to undo the bolts your thread would be 8mm , a 14mm socket would be 9mm BUT as with American threads (UNF/UNC) you have two different pitch sizes for metric bolts & there is a not a great deal in them . Hope this is of use to you

View attachment metric thread.pdf
 
Last edited:

Dingo

New member
Me again , sorry lads , just done a quick check and an 8mm 8.8 tensile bolt dry should be tightened to 18.7 lbft , you could safely tighten to 20lbft . Way short of 48lbft in the manual . Just remember it is only holding on a pressed steel pan , not your steering gear to the chassis :professor:
 

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