E39 540i A/C compressor replacement

Wow, Alex. Good luck getting an answer to this. If no one on the board can help, you might get in touch with a place that rebuilds A/C units. Denso is a pretty widely used brand, I believe, and so there should be lots of places to try for a bit of quick, over-the-phone advice.

I have absolutely no experience with this; but, in the hopes of helping with someone else's reference, here's what is in the bestlinks put there by others:

(in order of occurrence, with duplicates and dead links not culled out yet)
A/C hose rebuilding service
AC compressor rebuild
Patrick Parish's air conditioning page
Poor A/C performance and R134a pressures
R134a conversion information
- Air conditioning compressor knocking sounds (1)
- Air conditioner compressor replacement DIY (1) & AC refrigerant & PAG oil to use (1)

I don't know the answer but this is very interesting, to see the inside.

Here are a couple of fun and informative videos:

I'm shopping for a dryer, since it also has to be replaced. I'm somewhat confused which one I should get. I looked up the part number from Tischer (getbmwparts.com) and the BMW part comes to around $180. The same part but by Behr on Pelican Parts is $35. The huge difference in price is puzzling although there are some people that say that Behr part is good quality and does what it's supposed to. Do you guys have any opinions/experiences on this? Behr supposedly is one of the major brands and the part should be ok, it's just why the BMW part is so much more?

Wow, that's quite a differential. I will say that when I talked to Bavarian Professionals about installing my coolant reservoir (I was debating having them install all the parts and adding the Evans NPG+ coolant) they said they wouldn't install the Behr replacement because it's different from the Behr BMW part, and they didn't want the liability of installing the non-OEM part. It's weird because I can't tell the difference between the previous tank and the non-BMW replacement. At any rate, they said that the factory-spec Behr parts are different from the Behr after-market parts for the same application.

I don't know what to think. They weren't trying to sell me a tank themselves. They didn't care if I bought it elsewhere, but they'd only install it if it was a Behr/BMW part.

Almost makes me want to get that $35 part, take it apart and compare against my old one.

Uh-oh.

The TIS calls out the need for DIS to measure the evap exhaust temp, which is the final arbiter of proper charge.

Edjack, notwithstanding the TIS, doesn't the system tolerate a fair amount of imprecision? In other words, if the charge isn't precise, can't it still be effective, but simply less than optimum? That to me is the implication of the second video that 540Alex posted, which involved a Denso compressor.

After a lot of painful consideration I've decided to go with the OEM dryer. It's good if things go well with the aftermarket part, but if you have a problem later, you'll wonder if things were different with the OEM part.

I also got a replacement compressor from a 740i on eBay. The ports were different so I had to swap them. Also when it came, the clutch plate had an impact impression, and I swapped that too (got a post-sale discount from the seller because of this). Attached are a few comparison photos of the two compressors. The one with the red label is my old failed one.

Interesting, Alex. I'm surprised at the differences in the plumbing ports. Are they from different years?

It came from a 1997 740i with 86K miles out of Florida. The same model was meant for cars built until 09/98 (my car was built 10/97), but for 7-series, I guess that's the reason for the difference in ports. I believe they had the same engine, but maybe different engine mounts, since 7er is wider then 5er.

Hi guys , I was reading this post and looks like I have exactly the same symptoms with my AC unit (E38). I decided instead to go with a new unit ($230). I have read a little bit around (AllData and couple threads) and I was thinking to share what I am aware so far :

The Dryer unit (bottle) does not have to be replaced at a regular service intervals or if your system does not leak.

The Dryer unit (bottle) needs to be replaced if you have leaks in your system, for a system opened for more than 24 hours (during a repair), there is dirt in the system (compressor has seized). Dryer , when open it will absorb dust particles from air and it will make it inoperable. Also if you discard your pressure suddenly (release one of the hoses under the pressure) something in the dryer (a membrane?) breaks an will not be good anymore(this I was told by several indies) . So with a little care you can save money.

E39 filling AC capacities :

Refrigerant oil type PAG BMW part # 81 229 407 724 or equivalent ,
160 ml +/- 15 ml for Nippodenso , and for Seiko seiki 180ml +/- 20 ml.

Refrigerant type 134 A (of course)

for models up to 09/98 (M52, M62) - 1225 g +/- 25 g

for models from 09/98 (M52.M62, S62) -750 g +/- 10 g.

If I were your I would blow with air the compressor unit , and the lines from the car until I see no more freon/oil coming out , and I will fill with the right capacities and fresh oil.

Quote :

Caution :

When starting out a new compressor for the first time it is absolute necessary to Cary out the following break in procedure :
-Switch ON AC system.
-Set all vents to open
-Start engine and let it stabilize at idle
-Set blower to minimum 75% output of max
-Switch the AC system to OPEN and let it run at idle speed for at least 2 minutes (risk of damage at higher speeds ! )

When evacuating the AC system, refrigerant oil is also extracted and collected in the oil separator unit of the service station.

Hope this Helps !

I know you are still working @ your heads this time... In the mean time I changed my AC compressor (refurbished for $205 @ rockauto) and I would like to ask the guys around here :
What should be the good pressure readings for AC system on the low & high side?

BTW : I was quote $100 for the system vacuum only so I decide to buy the tools for $150 from Harbor freight and do it myself. I went @ the shop and pay $20 so they will catch the old refrigerant. I have not replaced the dryer,(since the job took me about 3 hours and the BMW TSB says not to change it unless is left open for 24h) I did replaced all the O-rings, I vacuum the system for an hour and know is quiet and works nice. Still I would like to know what the pressure readings should be. If anybody knows...
THX!

Never mind...I found it in the mean time : compressor discharge pressure should be at least 10bar.

Did anyone notice if their failed/failing compressor significantly reduced fuel economy (MPG)? I get 29.5mpg highway without ac but only 19mpg with it on. Belt and tensioner are both new. AC works 100%, at least that I can tell. i.e. works when I turn it on. Also other aux belt, tensioner, idler are both new. all 4 o2 sensors replaced, plugs, and plug boot replaced, along with Vanos most recently. Nothing has helped mileage. Car runs great for an 02 525i e39. Someone suggested a failing compressor could decrease mileage. But I found nothing about that online.

AC Compressor Replacement succesfull

1st I want to thank everyone who posts to this Forum and especially this thread. I have an E39 540i sport which I love. Everything below I did myself or with help from a friend. There is no reason a somewhat mechanically inclined person cant do this procedure. I was fortunate as my system still had a charge of R134. There are people on these forums that make this sound like you are removing a part from the space shuttle but it's not that bad. Keep in mind my pump had oil in it so I didn't need oil.

1. AC clutch failed and nearly fell off. This was a year ago.
2. Mid Atlantic weather (Maryland) got very hot so I quickly needed a clutch or AC pump replacement.
3. I could not afford to pay someone to put a pump in my 540i.
4. Purchased a rebuilt Compressor off of ebay.
5. Luckily the system still had pressure.
6. If your system is pressurized take your vehicle and have the AC system evacuated. I'm not saying I did or did not. Make sure the pressure is relieved very very slowly or you can mess up the system drier (or so I read).
7. Use eye protection and remove the electrical wire and the Refrigerant lines to the pump. Cap with a bag etc immediately. It is of extreme high importance that dirt, dust, water/moisture, etc not enter the ac lines.
8. Remove the pump (this sucks). Remove 2 front bolts than the rear bolt.

At this point I realized my old pump inlets and the rebuilt one didn't match. I cleaned the old pump and then swapped the inlets. If you do this remember CLEAN, CLEAN, CLEAN! Do not allow dust, dirt or moisture to enter the internals of the pump.

9. With intake/exhaust holes capped put new pump on. Again do not allow any dirt, dust, etc to get inside the pump.
10. Make sure AC lines and pump intake/exhaust holes are clean and carefully insert the lines into the compressor. I used an AC vacuum pump to remove moisture etc and to create negative pressure. I left the pump on for 1/2 hour and had -30.
11. I added R134 till about 35PSI. My system blows cold and has for 2 weeks now. Blows between 41 and 45 degress.

When I charged the system and everything worked I was very happy I went this route!

Old thread...

But, this is a fairly straight forward procedure. I had the dreaded "Predator" sound - death rattle - of the Denso 7SB16C AC compressor. I never used it much so it wasn't an issue. But, the sound kept getting worse, and the prize for delay is a destroyed refrigerant system. This is on a 1998 528i with production date of 09/1997.

1. Bought a used Denso 7BSU16C - reed design flaw was fixed in this next generation. Pulled the clutch and pulley and put in a new pulley bearing;

2. Bought a new dryer /receiver - Behr. It's a dryer receiver after all. No need for $100 diff in price to get OEM.

3. Evacuated the system at an Indy for about USD$25 equivalent. I'm not impressed with the job because they didn't leave a mild vacuum. There was still some pressure on the high side - ask me how I know, and R134a is poisonous. Always wear gloves, glasses - and (lol) hold your breath when taking off the first pressure line in a system rebuild or part replacement.

4. The right front headlight has to come out to remove the dryer/receiver. There are 4 x 8mm screws/bolts that come out easy (used a socket on a screwdriver attachment) - remembering to disconnect the 3 wiring sockets at the 3 lights - regular, high beam, and turn signal. Then the base for the headlight has to come out, which is 2 x 8 mm bolt /screws. Now the receiver / dryer is accessible.

5. 6 mm allen socket to take out the pressure plate bolts (2 of them) holding the lines in. This is where I experienced my refrigerant / oil geyser. The high pressure one that runs from the firewall is held against the fender, near the compressor, by a simple-to-open clip. This should be undone because this whole section has to be moved up to get the dryer /receiver out.

6. 6 mm allen socket to take out the two pressure plate bolts holding the lines to the compressor.

7. All refrigerant lines, when they came off, we're either capped or wrapped with saran wrap and elastics if too big to cap.

8. Holes were plugged with saran wrap to avoid any oil leakage when removing - especially the compressor - and transporting.

9. Before doing this step, make sure that the AC compressor drive belt is removed. I was able to do this from underneath. I popped the two plastic rivets holding the fan shroud in place and lifted it from the slots on the sides and bottom. Then I was able to get a long breaker bar up between the fan shroud and the radiator to put the allen socket into the tensioner wheel - that's the type I have on my car (hydraulic) with a single allen bolt in the middle.

There are only 3 bolts holding the Denso 7SB16C (and 7SBU16C) to the engine. 2 of them are accessible from the top. I found it quite easy to drop the belly shield/pan and get at the third one from underneath. There is a single bolt on the back end (nearest the firewall) of the compressor that is under the low pressure line where it comes into the compressor. After the line was disconnected in step 6, this bolt was accessible from above, as well as from below. I used a 13 mm socket to crack these. There is a video video here on what this looks like on a stand-alone engine for visibility. It's an E46 but the general idea is the same.

10. After the bolts were out, the compressor stays on the engine because there is a lip around the bolt hole on the bracket on the engine. It takes a screwdriver to pry it out - it's easy so only gentle force is needed - from above. I removed the compressor from underneath by turning it vertical and moving it towards the front of the car until it could be lowered down. The replacement compressor went in the same way.

11. I put 4 oz of PAG 46 in the replacement compressor (there was minimal oil in it to start) as per other threads - in the larger hole (low pressure side). One is supposed to measure the oil in the old one and add that much. I put 1 oz in the dryer / receiver as per the TIS. Directions are here and here. I made sure the plugs that came with the dryer/receiver were put back in place. I turned the clutch a bunch of rotations until the oil cycled through and started to be visible / come out the high pressure side which is the small hole. I plugged both holes again and put the compressor into place with the reverse of the removal.

12. the compressor goes in place from underneath. I held it vertically and moved it up through the same space near the front of the car, twisted it to be horizontal and put it in place by lining up the back bolt channel on the compressor and on the bracket. Because of the lip around the bolt hole, it was able to hold in place - after all it did take a bit of leverage to get it off, no reason why it shouldn't hold on its own. I cleaned every bolt off with brake cleaner and put blue lock-tite on the threads. I put lithium grease on the rest of the bolt to protect it from corrosion and put them in place. I did one bolt from the top - it's obvious which one this is, and the other two from the bottom. No torque spec, I just made sure they were tight + a little bit with a socket

13. I changed all the o-rings on the 4 lines (2 to the compressor, 2 to the receiver dryer). I put NYLOG Blue on them just before putting the lines in place. In the meantime, all were kept covered in one form or another to avoid the entry of humid air. Each line had a black plastic-y grommet on the end as well. I didn't have replacements so I made sure that they had a thin coat of NYLOG blue as well. NYLOG blue provides a safe non-reactive elastic seal. PAG 46 and mineral oil have a tendency to break down the o-ring over time - or so I've been told.

14. I dropped the dryer /receiver into place and screwed it in place. It looks like, for my car, that the three screw holes are set up so that it can only be oriented in one way in order for the refrigerant lines and pressure -plate bolts to line up correctly. I popped the plastic caps off the lines, NYLOG'ed the ends, pulled the plastic plugs from the receiver dryer and pushed everything down into place. I snugged it all down with the two 6 mm allen bolts that were removed earlier.

15. I repeated the process for the two lines to the compressor - remembering to take the saran wrap out of the compressor holes. Then I put the drive belt back in place, and put the fan shroud back - securing it with the two plastic rivets.

16. I had bought a manifold and a vacuum pump for this purpose; here and here. The pressure manifold did not come with a can tap - so I had to scramble around to find one and wound up buying one with the stupid hose and cheap gauge on it that goes right to the low pressure schrader valve. d-oh. For future work, I've now ordered a basic can tap valve with a t-connection so that I can hook an refrigerant cans up to my full manifold system.

17. Vacuum was applied for about an hour - even though the product I was using for refrigerant wasn't reactive with moisture. R134a and R12a react with moisture - which is absorbed by the oil - to create acids which are not kind to the inside of the AC system. I waited 1/2 hour afterwards seeing the vacuum hold = no leaks. Great! While this was going on (the 1/2 hour vacuum test), I put the headlight back in place - took 5 minutes and if there was a vacuum issue, it was easy to take out again.

18. I turned the car on, put the temp down low, and the fan on low. I had disconnected the manifold and put my refrigerant (hydrocarbon based) onto the low pressure side. I had the cans in warm water which helps keep the refrigerant in gaseous form and makes it easier on the compressor to pull in. Nonetheless, because my product had oil in it as well, I needed to hold the can upside down and gently shake it just like in all the videos. NOTE that the pressure on the low side rises initially until the new refrigerant is processed and cycled through by the compressor. This takes about 5 - 10 seconds by my estimate.

19. I focused more on the weight of refrigerant that I was adding, as per the green sticker, than the pressure - but I was happy to see that it always returned to the blue after adding a new can. I used my manifold to get a proper reading off the low pressure port once I was done. It was about 35 psi - which I was happy with because this product is one that runs at lower pressure than R134a - which I believe is beneficial for the system as a whole.

20. Took the car for a drive. Sweet.

I love this thread, and was just about to cross reference it to whatever the canonical air conditioner replacement DIY thread was, when, to my shock and horror, I realized all the air-compressor replacement diys in the bestlinks refer to off-site threads, which can't be updated...
- BMW E39 V8 air conditioner compressor replacement DIY (1)

So, without further ado, I will ADD a new cross reference, pointing to this thread, so that, in the future, we can both point others here, and update as needed with new and cross referenced information.

See also:
- BMW E39 V8 air conditioner compressor replacement DIY (1) & a Pelican a/c compressor rebuild (1) & an ac hose rebuilding service (1) & what air conditioner refrigerant & PAG oil to use (1) & how to refill your A/C system (1) (2) (3) (4) & what to use to rid yourself of the BMW gym sock stink (1) & how to diagnose A / C compressor knocking sounds (1)

Bluebee, you've just gotta watch those recursive links. lol. I've spent a few hours at various times running around in circles from one thread to another, then it refers back to the first thread and so forth. The worst is a recursive link that goes through several threads in a row before bouncing back.

ON another NOTE: Does anyone know the part number for the 6 mm alan head bolts used to hold the air-conditioning lines to the compressor, the dryer/receiver etc? The only thing I can find that's close is the ISA screw (Part of number 4) at this REALOEM link. I've searched online and realoem and can't seem to find a part number.

Old thread but this talks about what I'm doing, which is replacing the original dryer and noisy a/c compressor on my 97 528. I had the a/c system evacuated by Firestone. Now after I replaced the dryer and compressor, asked them if they can charge the system. I asked them what type of refrigerant oil and they didn't know what I was talking about. Called Indie (well respected Strictly BMW Bellevue) and they too were asking what refrigerant oil I was referring to. Both said they just charge with R134a.

So does R134a already have refrigerant oil in it or what? If the system were recharged with R134a that already has oil in it, won't the system then have too much refrigerant oil?

I replaced the compressor and dryer in my '97 BMW 528i and the compressor was shipped dry ( no oil) . Most auto parts stores stock the correct oil . I added the small quantity of oil specified and then had the system recharged by the shop that did the evacuation . It has been trouble free for three years now .

Finally got an Indy who truly understands auto a/c systems. Firestone simply discharged/depressurized the system (I paid $29 for this service) which, if any, results in negligible lose of refrigerant oil. He says I just need to ensure the compressor and dryer have appropriate amount of refrigerant oil per TIS specifications and bring the car over to him. He will vacuum the system ( to remove moisture etc) and recharge with R134a (1,225g). Since there was no catastrophic failure of the old compressor such as seizing, there's no need to evacuate/flush the system. My old compressor was working fine but noisy (marbles noise).

I know this is an old thread but I have a related question about the dryer. I had to replace the bracket that holds the dryer and was able to do it from underneath without opening the refrigerant system. The dryer on my car has a bracket around it that tightens around the cylinder. I'm trying to find out where on the dryer (how high up) the bracket needs to be so the dryer will sit properly in the bracket.