AC Compressor Oil Leak - Help Appreciated

[Sniff38]

Search didn't turn much up so I figured I'd start a new thread. I noticed a drop of oil collecting at the wiring plate on the bottom of my AC compressor (green circle). The AC works perfectly fine other than this small oil leak. I'd characterize it as the next step above sweating . . . but not a major drip. The rest of the fittings attached to the compressor appear to be bone dry. The previous owner had the original compressor replaced with a new Denso unit in July 2015 (less than 600 miles ago) and it is still running R12.

My questions:
1) How do I go about fixing this leak? I am hoping all I have to do is remove the two hex nuts holding the sensor in place and replace an O-ring (if only I were that lucky).
2) If the oil level in the compressor is low, do I risk damaging the compressor even if I don't turn the A/C or defrost on?
3) Can this repair be done with the unit mounted on the car or am I looking at a complete rebuild on the bench?
4) Will this repair cause me to lose all my refrigerant and require a recharge?
5) How do you go about adding oil to an AC compressor?

Any advice you can give is greatly appreciated.

Sean

[Timm]

The lubrication for the compressor is PAG oil - and that is added when the system is regassed. The system is designed so that if there is a leak and the refrigerant pressure drops the compressor will be disabled - there is a double-switch in the system that checks for under-pressure (in which case the compressor is disabled) or over-pressure (in which case the auxiliary fan runs at full speed to reduce system temperature and pressure).

Your leak looks like CHF (Central Hydraulic Fluid) rather than anything that might pop out of the compressor.

Does your A/C system actually work?

[Sniff38]

Your leak looks like CHF (Central Hydraulic Fluid) rather than anything that might pop out of the compressor.

Does your A/C system actually work?

Yes, my A/C system is working perfectly fine . . . but then again it's basically brand new. I've spotted a drip of clear brown oil that collects at the wiring plate located at the bottom of the A/C compressor (the area I circled in green) which I thought could be PAG oil. There also is some slight wetness on the wiring surround that extends from that connection, but it only goes up an inch or so. I wondered how oil could travel up the wire, but I figured it was probably getting splattered up there from wind caused by the radiator fan.

Are there power steering/hydraulic lines routed above and/or near the A/C compressor in the 850? I'm not sure where the CHF fluid would be coming from. The rest of the compressor is essentially spotless.

I'm no detective, but it appears they re-used the switch (what I've referred to as the wiring plate) from the original compressor when they installed the new Denso unit in my car 1.5 years ago. I looked at RealOEM and that switch is NLA. I'm making this assumption based on the fact there is cosmoline on the plate while the rest of the compressor is perfectly clean. If that's the case, is there a gasket in there that can be replaced? If it's perished, will PAG oil leak from this location?

Sean

[sleepy81]

Your leak looks like CHF (Central Hydraulic Fluid) rather than anything that might pop out of the compressor.

As Timm says, it appears the leak is elsewhere down the side of the compressor from above. Check fittings above compressor.

[Sniff38]

As Timm says, it appears the leak is elsewhere down the side of the compressor from above. Check fittings above compressor.

As I mentioned in my original post, all the other fittings into the compressor are bone dry.

Does anyone know if PAG oil can seep out of that bottom switch plate?

Sean

[wolfebrian2120]

Your leak looks like CHF (Central Hydraulic Fluid) rather than anything that might pop out of the compressor.

Does your A/C system actually work?

Timm... I don't think it could be CHF if his car is LHD. the compressor is on the other side of the engine from all the power steering components.

OP, I suggest you clean the oil off with a rag and see if it reappears. You say the oil looks kinda brown, maybe its engine oil. I'm not sure what the color of the PAG oil is. If there is a leak in the AC you should be able to detect it with an AC manifold and see the pressure drop or have a shop check it.

[Sniff38]

Thanks for your comments. If it is engine oil, I can't fathom where it would be coming from or how it could only collect at the bottom of that switch plate. That entire area of the engine, subframe, etc is clean and bone dry.

I may have jumped the gun a bit describing the fluid as clear brown. I think the cosmoline on the switch plate gives it that allusion. I think it's more clear, but it's hard to tell because there is not a lot of it.

Does anyone out there know if it's possible for PAG oil to leak out of the switch plate (the area circled in green)? Again, I think the switch may be a 25-year old original as it still has cosmoline on it and everything else on that compressor is perfectly clean.

Also, is it even possible to leak PAG oil and still hold a charge? My A/C works like a champ (at least for now).

I sent an email to Denso describing my situation but I am not confident I will hear anything back from them.

Sean


[Timm]

No, you're right - I was confused by the green circle - my brain immediately thought green fluid....

[Sniff38]

No, you're right - I was confused by the green circle - my brain immediately thought green fluid....

Timm -- It appears we've ruled out green CHF. Do you know what color PAG oil is and if it's possible to leak from the compressor while still holding a charge?

My research discovered there is only ~ 5 ounces of PAG oil in the system . . . not very much. That is why this leak has me concerned. I don't want to run a new compressor dry.

Sean

[Sfdon]

Any AC shop can run dye into your system and tell you where it's leaking.

[Timm]

Nah, the PAG oil won't come out without the gas coming out before it - and it doesn't take much before it will just inhibit the compressor.

[8eights]

Sure the oil isn't from the Timing chain tentioner?

[Sniff38]

Sure the oil isn't from the Timing chain tentioner?

I'll go take a look next time I'm in the garage. Thanks for the tip.

Just curious, how involved of a job is it to replace the timing chain tensioner on an M70?

Sean

[8eights]

You just replace the parts BIG Money, Almost Twelve Bucks ,) Takes about 20/30 minutes

Scale of 1/10 about a 3 because of the tight space, You have to apply pressure while trying to get a good thread on reassembly, That spring inside could make you swear!

[Sniff38]

You just replace the parts BIG Money, Almost Twelve Bucks ,) Takes about 20/30 minutes

I just read an old thread that said the "V12 camchain tensioner is spring loaded, not hydraulic." If that's the case, could I still leak oil?Sean

[8eights]

Yes, Plenty when it's in really bad shape.

[Sniff38]

I just pulled the RealOEM diagram. If this is the source of my leak, am I correct in assuming I'll need to replace items 16-24? Do they make an assembly with all the individual components together?

http://www.realoem.com/bmw/enUS/show...diagId=11_4904

Sean

[8eights]

I believe I changed out 19-20-21 and 24

19 was the cause of the leak, there is a upgraded o-ring from Gault BMW.

[Sniff38]

OK, thanks for all the info 8eights. In a way I hope it is my timing chain tensioner and not anything to do with my A/C compressor. The previous owner paid nearly $1300 to replace the compressor and recharge with R12 a little over a year and a half ago.

I'll take a look at it sometime tomorrow and report back.

[Sniff38]

Well 8eights was on to something. I just took a look at my timing chain tensioner (see photo) and it's wet and dirty . . . so to speak. I'm surprised I didn't see that when I was looking at the top of the compressor.

I read a couple of threads that briefly touched on the timing chain tensioner, but none included a detailed replacement procedure. Anyone know what I need to remove to get into that cramped space? Any tips someone can provide would be greatly appreciated. I remember reading something about needing to prime these tensioners. Am I correct in assuming that was only for the hydraulic ones (on the V-8's)?

As far as parts, they seem to sell the entire assembly for the 840, but not the 850. Is this because the 850 tensioner is spring loaded while the 840 is hydraulic?

Sean

IMG_0841.JPG

[PabloRock]

Did you ever find write up on this? Looks like I have the same issue. Just like you, thought it was a leak at the bottom of the AC, but after a cleanup, noticed it dripping down from above (was about to post the same pics as you). Any suggestions appreciated. Thanks. Paul.

[Sniff38]

Did you ever find write up on this? Looks like I have the same issue. Just like you, thought it was a leak at the bottom of the AC, but after a cleanup, noticed it dripping down from above (was about to post the same pics as you). Any suggestions appreciated. Thanks. Paul.

Hey Paul -- I did confirm the leak was coming from my timing chain tensioner and not my A/C compressor (thank goodness). I asked specific questions on another thread which you can reference. https://www.bimmerforums.com/forum/s...er-Replacement

Here is a link to the RealOEM diagram so the parts #'s make sense.
http://www.realoem.com/bmw/enUS/show...diagId=11_4904

You should be able to stop the leak by replacing the rubber O-ring (#19) and the aluminum sealing ring (#20). I had to purchase the rubber O-ring on eBay (for $8.00) because it was the only place I could find a single. ECS Tuning only sold them in bulk and none of the other parts places I shop even had it. I'd also recommend you purchase a new black plastic protection cap (#24) as I completely destroyed mine pulling it out. I had to snip off little pieces with an extra long set of needle-nose pliers until the thing came off. The cap has "barbs" inside which allow it to slide on but not back out. In one of my posts I equated it to those Chinese New Year finger toys you may have played with as a kid . . . you easily insert a finger into each end of the tube, but when you try to pull them out, you can't.

I also replaced my spring (#17) and the sleeve (#21), but that's because the parts were cheap and I wanted them on hand since I didn't know what was bad. In hindsight, I probably could have done without them.

To gain access to the tensioner, I removed the passenger side airbox and the MAF. I also had to disconnect some of the vacuum lines so I could get better access. Once you are in there it's pretty straightforward what you need to remove. My biggest concern was making sure the forks in the piston (#18) were oriented properly to engage the tensioner (#12). I marked the piston with a permanent marker to show "North Up." As you push the piston in and twist ever so slightly, you will feel the piston engage the tensioner. Attached is a photo of how the piston engages the tensioner.

So far I have no leaks and everything is working fine. I was worried when I started the car for the first time that I'd get a lot of noise from the chain as the oil that spilled out was replaced. I heard nothing abnormal and the car started as usual. I have not installed the plastic cap yet because it's a "one-use" item as far as I'm concerned and I wanted to make sure there are no leaks over time.

Since I never did a job like this before, I did quite a bit of research on the subject. I put together a PDF file from all my research so I'd have something to reference out in the garage. Perhaps you will find it useful.

Sean

[Sniff38]

Could not seem to add a PDF and a picture in the same post. Here is the timing chain tensioner replacement PDF I mentioned.

[PabloRock]

Thanks for the info Sean. That's a nice write up. I am pretty sure that is what's leaking. At first I thought it was the AC, but I sprayed the area with degreaser and the next day noticed a drip down the side of the compressor and the end of that cap. I am currently in the middle of trying to seal my intake manifold gaskets and paint my valve covers, so I should have plenty of room to get at it (going slower than I had hoped for varied reasons). I think I have a power steering leak as well (and thought this was it until I realized that was the compress and not the power steering pump), but haven't found it yet. I seem to lose steering fluid, but not oil. While my car is out of commission, I figured I would take care of some of these other issues at the same time (have had spots on my driveway for some time now). But the list is starting to get a little long, so I may have to stop adding to it (have a couple of active threads). I'm going to remove the lower shield so I can get at my power steering pump and drain that system. Hopefully I will be able to see a leak there.

I noticed the 20 pack at ESC as well, but found all 3 parts at FCPEuro for $10 (but shipping is $8). I haven't used FCP yet, but they are in state, so shipping stuff should be quick. All these tasks are new to me as well (learn as I go), so I hope you don't mind if I PM you on this one if I run into any issues.

Thanks. Paul.

[PabloRock]

Finally, a task that went as expected! It took me about 30 mins. A couple of tips for others that may attempt fixing timing chain tensioner leak. On mine (91 850i), there was an electrical connection in the way. The front pulls out with a squeeze, and the part attached to the bracket has a tab on the bottom that you push and pull it up. When removing, I used a piece of wood as a lever to help with preventing damaged fingers. When it's loose, put that against the socket and twist it by hand. This way your hands are out of the way when it pops out. Putting it back in trying to compress that spring was a pain. I put it on the socket and put it back without the spring to see the angle it should be at so I don't have to search for the thread while holding that spring in.