Rearend Leak, where is it coming from, Help?

[cobrak]

I have a BDR with the BMW rearend. I have 1600 miles on the car and since day one the rearend has been leaking. It is not comming from the Diff, I know this because the color is not purple, it is the color of motor oil and all seals and plugs in the diff are dry. The area that is wet are the CV joints exactly where the spline head bolts are. The boots are not wet. It appears that during rotation the oil is flung onto variuos parts under the car, then drips off the frame onto the floor. It is the consistancy of oil, not grease.

Questions
1. Has any body else had this problem?
2. Is there grease in the CV joint that is breaking down with temperature and dripping out? Maybe the wrong grease was used.
3. Where could the oil be comming from?

CobraK

[Snakester]

CobraK,
I have the exact problem you just explained! From day 1 , just a drip or 2 after the car sits overnight. Looks like burnt motor oil instead of rearend grease.I also have @1600 miles on car ....I have checked the fluid level and is still full, so not much has leaked....What do we do?....I guess the only thing is to keep a close eye on it! Let me know if your leak gets any worst.
Snakester BDR261

[Hank Steckel]

CobraK and Snakester, I've got the same thing happening. I've got a little over 4K miles on my car and the leak has been getting worse. I wiped the frame down to see where it's coming from. The "spline" bolts just next to the diff (left side only) are really wet, but the CV boot is dry. There is nothing coming from the speed sensor, so that O ring is Ok. I found this diagram of a BMW rear axle parts diagram on the web: http://www.realoem.com/bmw/showparts...62&hg=33&fg=10
I don't know if it's the correct diagram, but it is for an E36 Bimmer.
I went to a friend's place Sunday and the car left a little 50 cent piece size drip of purple on the ground. Ok, so now I know it's Royal Purple differential lube.

I'll keep watching this thread. If I learn anything more, I'll let you know.

Hank Steckel
BDR #258

[cobrak]

Originally Posted by Snakester

CobraK,
I have the exact problem you just explained! From day 1 , just a drip or 2 after the car sits overnight. Looks like burnt motor oil instead of rearend grease.I also have @1600 miles on car ....I have checked the fluid level and is still full, so not much has leaked....What do we do?....I guess the only thing is to keep a close eye on it! Let me know if your leak gets any worst.
Snakester BDR261

Snakester;

What happens if the leak does not get any worse, but the oil/grease completely drains over time. I don't think the fluid is comming from the diff, so how does one check the fluid level?

CobraK

[cobrak]

Originally Posted by Hank Steckel

CobraK and Snakester, I've got the same thing happening. I've got a little over 4K miles on my car and the leak has been getting worse. I wiped the frame down to see where it's coming from. The "spline" bolts just next to the diff (left side only) are really wet, but the CV boot is dry. There is nothing coming from the speed sensor, so that O ring is Ok. I found this diagram of a BMW rear axle parts diagram on the web: http://www.realoem.com/bmw/showparts...62&hg=33&fg=10
I don't know if it's the correct diagram, but it is for an E36 Bimmer.
I went to a friend's place Sunday and the car left a little 50 cent piece size drip of purple on the ground. Ok, so now I know it's Royal Purple differential lube.

I'll keep watching this thread. If I learn anything more, I'll let you know.

Hank Steckel
BDR #258

Thanks for the information. My car seems to have the same leak, but mine is not purple and I know the rear diff oil that I have is purple.

CobraK

[Speedysnake]

C/N 291 checking in on this subject. I too have a little over 1600 miles on the car. I just crawled out from under it. There is a very slight leak on the right side of mine. It appears to be coming from the inboard end of the boot. I can press on the rubber & see fluid coming out from under it. It is not coming from the differential. It is not a heavy grease, but more like dirty motor oil.

Mr. Lucky, what do you think?

[Hank Steckel]

I had to have my right rear axle replaced. The inboard CV boot was torn (arrived that way new) and it slung oil and grease all over the place. It was definately black. As I recall, it was more like grease, but had an oil component to it as well. The grease probably heats up and thins as you drive. Can you tighten the clamp at the boot, or is it fixed and there is nothing to do? If it throws enough of the grease out, it will dry out and the CV joint will fail. Maybe a call to a friendly BMW wrench turner can give you some ideas. My RR axle was replaced under warranty by Cal Cobra, so maybe your dealer can help.

Hank

[cobrak]

Originally Posted by Hank Steckel

I had to have my right rear axle replaced. The inboard CV boot was torn (arrived that way new) and it slung oil and grease all over the place. It was definately black. As I recall, it was more like grease, but had an oil component to it as well. The grease probably heats up and thins as you drive. Can you tighten the clamp at the boot, or is it fixed and there is nothing to do? If it throws enough of the grease out, it will dry out and the CV joint will fail. Maybe a call to a friendly BMW wrench turner can give you some ideas. My RR axle was replaced under warranty by Cal Cobra, so maybe your dealer can help.

Hank

Thanks for your input. The boots can not be tightened. It does not appear that the boots are leaking, but I will double check.

CobraK

[jp65cobra]

Hank

I have my car in at Frank Fahey Motorsports right now for the tranny which is another story. Frank came recommended to me and he knows the suspension and rear end very well being a long time BMW guy and race driver. He gave my car the once over and found many interesting things. I have potentially a leak similar to yours and also left side. He tightened a few things and wiped it down and now we will follow up and see what happens. He pointed out that these rear ends and suspension parts are not new and maybe reconditioned. Basically it looks like they were cleaned up and then hand painted. Now I am wondering where they came from and just how reconditioned they were.

He also pointed out some other things to me that I will post and see what others have and how they compare.

John

[lovehamr]

John, what were Frank's observations? As a potential BDR customer I'd like all the heads up I can get.
Thanks, Steve

[jp65cobra]

Steve

Some of the things Frank went over with me are not a BDR issue but my car in particular. Here are some of them.

1. BDR: clutch hydraulic line positioning relative to the headers could lead to some of the clutch engage issues some other cars have been having after they get really hot.
2. BDR: the rear ends appear to be rebuilds and maybe the job was not well done and that’s why some of us are having leaks and other issues mentioned in this thread. He did mention that this is basically a great design and if put together right should be really good. Mine for example had the bolts holding the half shaft coupling almost come completely off after 2K miles. If I was going to buy one again I would go over the car from front to back and make sure every single bolt is tight and secure.
3. BDR: The very front steering U-Joint is at to sharp an angle for his liking. I honestly can’t remember what he didn’t like about it.
4. Mine: He did not like the driveshaft I have. It has non-sealed u joints and they have a lub fitting that he says is not located correctly. He would like to see a sealed one in its place. This is a drive shaft that replaced the one from BDR because that one caused a vibration.
5. BDR: There is no lock on the adjustment rings for the front shocks so it could easily change. This is an easy fix.
6. Mine: I may have blown my rear shocks due to bottoming out to many times and I may have broken seals. I need to get this adjusted and test the travel.

So nothing really outrageous and maybe things other guys would have looked into but I was very green last year but I am learning real quick. I would still buy a BDR but would do some things a bit different.

John

[SkipB]

John,

So it looks like Frank has had some time to find a bunch of things he would change.

I am familiar with the clutch/heat issue and have ordered a heat shield which I will install later. If this helps you may want to do the same to avoid boiling brake fluid.

The rear ends are from BMW E36 3 series which haven't been made for several years, so I am sure they are out of wrecks or rebuilt units. Very sturdy, so I am suprised to hear about the leaks. If anyone can fix that, it is Frank!

The steering U-joint at the rack is at a rather sharp angle for no apparent reason. Lessening the angle may or may not make much of a change in steering feel. I too wonder why they are made this way?

I have the original driveshaft, but I know others have had problems with theirs like you did. It appears the replacement may not be to Frank's liking, but is it worth replacing?

It looks like Backdraft relies on the weight of the car to hold the adjustment ring for ride height. A second one on each corner as a jamb nut would be a good idea, and a cheap fix.

My car had the sagging springs that are being replaced now. I'll bet my shocks are leaking too. I bottomed out many times. Of course, I had my suspension set really low because it looks good to me. I am having Frank put in the new springs, align it, and corner weight the car as well as adjust the ride height. Why don't you wait until mine is done before doing yours. Unless the shocks are shot and leaking.

I keep telling myself that these are really glorified "kit" cars and will constantly need upgrading and fixing. But, overall, I think we are both very satisfied with our cars.

[Barry Hall]

I have BDR #159. Ditto the small leak on the garage floor. Nothing major, just keeps happening. I have over 3000 miles on mine and check the fluids regularly.

[jp65cobra]

Skip,

I have the heat shield from Ed and will install it after I get the car back from Frank.

Yup I knew these were E36 3 series and I am also not convinced yet that mine is leaking. I suspect the oil is coming from another source. We are wiping everything down and will monitor closely. I guess my real concern is more about how these were reconditioned and what quality steps were taken and I am basing this on the leaks, the several cases of half shaft couplings coming loose and CV boots being bad from the start.

I agree on the driveshaft and it is something I will monitor but may not consider changing until I have other things done.

Yes I am going to wait and watch what Frank does on your cars rear suspension. It is on my list along with some other things.

I am happy with the car like you and I understand it will require some baby sitting.

[WOLFEMAN]

BDR #369 has 250 miles on it and the same leak from the rearend. I contacted Craig in Boynton Beach to see if they've identified the cause and a solution.

[RodW]

I have #186 and have not experienced a rearend leak. I did however shred the drive shaft....

Rod

[Nor Cal Al]

I've been away and just saw this thread. My car is #128. It had leaks from the beginning and I think the rear end was not a reconditioned unit. BDR replaced it. The leak spots I am aware of come from the seals where the half-shafts go into the differential. The newer/replacement seals are a 2-face seal whereas the older ones had a single face seal. If these seals are leaking there will be differential fluid thrown onto the frame on the inboard side of the drivelines.

I also had a small leak on one of the half-shaft boots that threw a thicker, darker grease. I do not think these boots were done if/when the rear end assemblies were reconditioned. Someone told me a smallhole in a boot can be fixed with Permatex black gasket sealer.