DIY: 1998 BMW 528i 160K Replacing AC Compressor

[cnn]

DIY: 1998 BMW 528i 160K Replacing AC Compressor

- At 160K miles, the AC Compressor was making "marbles in a can" sound, it was the beginning of a disaster (Google "AC Black Death"). Replaced with brand-new Denso Compressor ---> all is quiet now!

- AC work is complex, so if you read this DIY, it means you are an advanced DIYer.

- I replaced the Denso Compressor in my 2007 Honda Odyssey a few years ago, in that thread, you will find tons of useful AC info (the Physics, Chemistry, ideal gas law etc.), so please READ this link first:

http://www.odyclub.com/forums/52-200...placement.html

http://www.odyclub.com/forums/52-200...istry-fun.html


- The gauge set, make sure you watch this video by "EricTheCarGuy", so you know how to use it:

https://www.youtube.com/watch?v=lglPJuBXVeE


- The AC Compressor for E46 video by "bimmermerchant", note the locations of the 3 mounting bolts:

https://www.youtube.com/watch?v=IoAix_b-JYU



PARTS/TOOLS

- AC Compressor is Denso 471-1119 (7SBU16C type) for $225 on Amazon dot com.

- Specs for 1998 528i (later years are different): R134a = 43 oz; PAG Oil = 6 oz.

- Re PAG Oil: some forums say PAG 46, some say PAG 100. My research tells me that: PAG 46 (thin), PAG 100 (medium), or PAG 150 (thick) is almost like the oil analogy of let's say 5W30, 10W30, 10W40 and all that jazz. Many shops use only PAG 100 as "Universal Oil":

http://www.underhoodservice.com/ac-o...essor-failure/


- So I used PAG 100 oil. Don't trust Denso instructions that came with the compressor or published online: "Denso compressor is shipped with appropriate amount of oil".
This was simply WRONG for both my 2007 Honda Odyssey a few years ago and for my 1998 528i. All I could find is 1/2 oz of oil when I drained the brand-new compressor to verify!

- Remember PAG oil is only needed in the compressor, anywhere else (condenser, evap), it is a nuisance. Six (6) oz is factory fill from dry, so when you replace only the compressor, I think 4-5 oz is fine.

- After I drained the new compressor, only about 1/2oz came out. I filled the new compressor with about 5 oz of PAG 100 oil:

http://www.bimmerfest.com/forums/sho...d.php?t=525280

- Four (4) cans of R134a is good enough. In fact, I filled with only 3 cans 36 oz and it is ice-cold. My theory is: at factory they filled to max a system can handle (in my case 43 oz), knowing that every year, some R134a escapes the system (a molecule here, a molecule there). So when the system gets below a certain threshold, let's say 24 oz, then it is not as cold. It will take 20 years to get there. The analogy is like a tire, let' say a tire pressure below 20 psi is bad, so at factory, they fill the tire to 40 psi, knowing that some air will escape slowly, and it will take many years to get down to 20 psi…...anyway just an analogy.

- Wrench is 13-mm for the three (3) bolts holding the compressor.

- The fittings on top of compressor: 6-mm Allen socket.

- Small screwdriver to undo the electrical connector.

- The AC Tensioner: mine is hydraulic type, so I used the 8-mm Allen socket to undo the AC belt. Those with mechanical tensioner: use Torx key. Tons of info in those "cooling overhaul" threads.

- Special AC Tool to change the gap of the clutch.

- ZipLoc and rubber bands to seal tube ends!

- Eye Goggles for safety reasons.

- O-rings: even with correct VIN in realoem, I got the wrong O-rings for later years! So I ended up using the original O-rings (Green color), not a big deal but I now know what to buy. To correct the error in realoem, this should be the info:
* Up to mfg date Aug/1997: 64508363041 and 64508390603
* From mfg date Sept/1997: 64508375741 and 64508374959



PROCEDURE

- A note on Denso instructions, throw it away, none of it is correct!

i) Measure your own PAG oil (PAG 46 vs PAG100), do not trust what they say.

ii) The compressor didn't come with new O-rings, I bought new O-rings, only to find out they were the wrong type b/c my car was built during the "transition period of mfg date 09/1997". Even with the correct VIN number in realoem dot com, I got the wrong O-rings. So if you have the earlier type, use mfg date of Aug/1997!

iii) Gap was wrong from factory: it was 1.0 mm, I had to reduce it down to 0.5 mm or so.


- Look up the torque values, I just tightened the bolts hand tight and give it a "twist" to snug it down.

- Do NOT do this on a humid or rainy day to avoid moisture in the system. Tip: as soon as the ends are disconnected from the compressor, IMMEDIATELY cap the ends with ZipLoc and rubber band to prevent moisture from getting in.

- Front ends on wood ramps, and splash shield removed (Phillips screwdriver). Search forum for photos.






1. Go to a shop and ask them to evacuate the R134a for you. This is about $75 or so.
Many shops claim their machine cost $10K and can detect contaminant in the recovered R134a.
- In fact, after they saved the old R134a, they re-used it and put it back in your car. I am kind of worried about this claim, so I only use the shop to evac. I didn't want to use the shop to add R134a simply b/c it came from the common tank, and who knows what is in there.
- For Vacuuming and Recharge, I rented the tool from Autozone for free and bought 4 cans of Dupont Suva R134a at Oreilly Auto for $10/each. But you can buy Dupont Suva R134a online (ebay, amazon) in bulk for about $4-$5/each.


2. Verify that pressure in the system is 0 psi.


3. Basic anatomy and tools:






















4. To prep the new compressor:
a. Factory clutch gap was 1.0mm! To reset the clutch gap down to 0.3-0.6 mm range, you need the special tool to hold the clutch while undoing the 10-mm bolt. I used a bit of Loctite during installation. If you don't extra washer, you can file the washer down a bit to achieve the correct gap of 0.5 mm.
b. Only 1/2 oz of PAG oil came with the compressor. Go back to the Honda Odyssey link above and watch that youtube video on how to drain oil, measure and add PAG oil. Cleanliness is important. I added about 5 oz of PAG100 oil (rotate the clutch back and forth to distribute the oil), then close the ports immediately to avoid dirt, moisture in the system.
















5. Three (3) 13-mm bolts hold the compressor. Loosen them but don't remove the compressor yet:





6. Undo the 6-mm Allen bolts and disconnect the ends. Cap the ends immediately with ZipLoc and rubber band. You must re-use the factory 6-mm Allen bolts. The bolts that came with the compressor have the wrong length and they are used only for shipping purpose.




7. Only small mount of oil came out of the 160K compressor, I think some may have leaked out over the years (see the black grime/dirt on the compressor). Note the electrical connector…...use a small flat-blade screwdriver to gently pry it out:




8. Now remove the compressor from below. Make sure the new compressor has proper gap and proper oil before install. Reconnect the fitting ends. In my case, I bought the wrong O-rings for later years, it was the weekend, dealer was closed, so I re-used the factory O-rings (Green color), no issues so far.


9. Now, the vacuuming part is tricky, make sure you watch the video links above.
- Before going to the shop for evac, static pressure was close to 100 psi:





10. I am at 1000 feet elevation from sea level, so I got about 27 inches of Hg on the vacuum pump. I vacuumed it at 27 inches of Hg for about 45 minutes.










11. To add the first can of R134a, with engine OFF, attach the can as shown, pierce the can and slowly turn the handle CCW so R134a can flow from the can to the system. Turn the can upside down so the liquid can flow in. Turn the AC compressor clutch by hand CW to suck the liquid in. You can see static pressure is about 75 psi after the 1st can:




12. For the next 2 cans: I turned the engine ON, AC ON (The AC system needs some pressure to activate the sensor, this is why you need to install the 1st can manually). For these 2 cans, I leave the can upside UP to allow only vapor to enter the system (I don't like the idea of liquid being sucked in quickly when engine is on and AC is ON, this can cause hydrolock, however rare it is!). Just use some heat (your bare hand) and place the can on top of the exhaust to increase the pressure in the can (which is about 100 psi). Once the compressor is engaged, pressure on the low side is about 35 psi, with the can at 100 psi, there is differential pressure for a flow of R134a into the system.

*** When switching between cans, you must disconnect the hose from the system first to avoid losing R134a! Wear goggles!


3. After 3 cans, I get a "Temp Drop" of about 35F after a drive around. The industry standard is 30F-40F "Temp Drop".




That is all boys and girls, STAY COOL!!!
Total cost:
* Denso compressor $225
* Four (4) cans of R134a ($20 for 4 cans on line)
* One (1) 8-oz bottle of PAG 100 oil ($10 at Autozone)
* TOTAL = $255

But it is your labor though...


-----

I forgot to mention a few things when renting tools from local store...you never know who used it before you, so:

1. Check the Vacuum Pump to be sure it has oil.

2. The gauge set hoses have O-rings in them: in my case, a few O-rings were damaged (i.e. not a good seal), I replaced the O-rings in some hoses.

3. The Quick Connect (Round Circles in the photo below) ---> pay attention:

- First, turn the BLUE or RED knobs CCW to lift the pin upward, this way when you connect to the fittings in the car, there is no vacuum connection with the car yet.

- Now turn the BLUE or RED knobs CW all the way down, this will protrude the pin and OPEN the valve at the end of the fitting. This ONLY establishes a connection between the car's AC system and BLUE/RED tubing + the gauges and that is it.

- On the Gauge Set: a) turn the BLUE or RED knobs CW to disconnect the connection between the YELLOW hose with the BLUE or RED hose; b) Turn the BLUE or RED knobs CCW to establish the connection between the YELLOW hose with the BLUE or RED hose.

Anyway, it is just common sense: there are 2 "air connections" you need to make: at the car and at the Gauge Set.

[Ed CT]

Again, a great detailed write up, cnn. I did this task a few years ago. The compressor was making "the noise", and AC cold would only work when rpms were up. We had a trip to Atlanta scheduled, and there was no way I was going there without AC. I also changed out the dryer and expansion valve while I had the system open. In hindsight, the expansion valve was probably fine and could've been left alone. The PAG oil thing had me doing research, too, and ended up draining the new Denso with little oil being expelled, and using the 100 to the 4-5 oz. spec.

Next weekend, it's the rear bearings, using your write-up. Hope that inner race comes off without issue...

[philly98540]

Excellent DIY again! You got a great knack for writing up tasks that are clear and very easy to follow! I'd suggest to do the dryer while at it and confirm high and low side pressures against a R134A table. Checking vent is likely just fine though as long as not overcharged. Experts will chime in to use a scale for fill.

[wfseward96]

Great detailed writeup. I just did a near complete rebuild of my '98 540, including the condenser, dryer, compressor and expansion valve, as I had the black death scenario. I wanted to replace the evaporator as well but after looking at DIY and the 20-30 hours of deconstructing the dash down to the bone, gave up on that idea. So I ended up having to flush the evaporator and lines. Tough messy job for sure. I ordered the complete O ring set from FCP Euro to put it all back together. One small note on installing O rings, most pro forums and tech docs mention using a non-hydroscopic mineral oil to lube O rings instead of PAG OIL as PAG is hydroscopic and can lead to corrosion at the fittings. Might be a bit anal, but I found some of the recommended 525 SAE mineral oil on Amazon (TSI Supercool MO-500-GM Premium Mineral Oil). I also installed an inline filter on the high side pipe going to expansion valve as I'm sure there is still some crap in the system from compressor failure. My plan is to run the system for a few weeks, then have evacuated by shop. Then open and clean inline filter, replace the dryer (its only around 30$ at FCP) and vacuum and fill again.Right now Walmart has the pure Dupont SUVA refrigerant for under 5$ a 12Oz can. My system takes about 3 1/2 cans and makes it a cheap follow up flush.

There is a lot of information to absorb when doing a system like this, and a TON of misinformation out there. Good DIY's like yours are much appreciated. The Bentley manuals are not comprehensive regarding this, especially on specifics for adding PAG oil. I had to go into the TIS to figure out how much total oil is in the 540 system (8OZ). They do recommend adding oil to components replaced, as the oil gets distributed throughout the system in addition to oil added to compressor. Also, you where right to be conservative in adding refrigerant, as under filling a bit is not and issue, while overfilling can kill the system. Topping off a system where you don't know the actual volume is a crap shoot. I see the DIY's showing dude with walmart AC fix in-a-can, with leak stop and oil added pumping into low side, with crap gauge showing only low side pressure. Pressure reading will not show you system volume. Full confession, Ive done this myself, but knowing it was only buying time to get through south Florida summer. But really, paying a shop to evacuate and refill is the way to go.

[groundhogdmd]

my 1997 e-39 compressor just failed,...vin # IJ4GZ4855WC197069,....I understand '97's are different from other e-39's,...??? What's different?

[effduration]

AS it pertains the AC system, Your ‘97 should be very similar to the ‘98 that used for this excellent DIY.
To make sure, compare AC diagrams and part numbers for both a ‘97 and a ‘98 on RealOEM