A/C Compressor Removal

[emerydc8]

Hello:

I am about to replace the a/c compressor on my 1994 E420 and was hoping that someone here has gone through this on his 500E and could offer some advice on what to look out for, what could make the job easier, etc. I am presuming the 500E and E420 is virtually identical as far as removing the compressor. Thanks!

 

[Tonyetee]

just did it last week drop the sway bar pull the belt 1 13 mm on the lines 4 13mm on the compressor pull it out took about 30 minute to replace.

 

[emerydc8]

Great! Thanks for the reply. You have no idea how much better that makes me feel. When you drop the sway bar, do you remove the whole thing or just the front brackets and pull it out of the way? I have been procrastinating for several days because I wasn't looking forward to doing this job.

 

[samiam44]

Get a vacuum on it quick after R&R the compressor. You can borrow one from autozone(and probably other parts stores). Maybe hoses(?). I'd have it connected up and pull it down for 3-4 hrs EVEN if you are taking it in to get it re-charged at a shop.
You want to get the moisture/air out ASAP. The oil is hygroscopic (absorbs moisture from the air). Wouldn't be a bad move to put a new dryer on it at the same time.

IF the compressor died from a mechanical failure internally- you need to flush the system. That's NOT hard, but not a fun job either.


Michael

 

[emerydc8]

I have a vacuum pump that is driven by an air compressor but it is a cheap Chinese Harbor Freight model and, if I remember correctly, I can't get more than 15" of vacuum. I will see if I can rent a better unit. It is so dry here in Tucson that I once didn't evacuate an a/c system (I didn't have the pump) and the a/c ran great for years. That's not what I plan to do this time, though. The compressor is being replaced because the clutch will not engage. Actually, I think it's partly stuck as you can see from this video because it will not let go either. This occurs whether calling for air or not.

If, when I remove it, the compressor looks to be ceased or damaged I will look at replacing lines too. I did order a receiver/dryer and will replace that regardless.

 

[gsxr]

The compressed-air-driven vacuum pump IS NOT adequate for A/C work. Not even close. It's handy for creating vacuum for testing engine and chassis vacuum items (i.e., EGR valve, etc) but that's it. You need a proper A/C vacuum pump (like this one). You may be able to rent one.

FYI... you can replace the clutch without replacing the compressor, if the clutch is the only problem... no need to break open the refrigerant lines for clutch work.

 

[emerydc8]

Thanks. I will definitely rent a pump this time. I already bought the compressor and r/d because I was told that replacing the clutch with the compressor on the vehicle is difficult. Also, I felt that the likelihood of me getting a new clutch installed and adjusted correctly was slim. With over 200,000 miles on the compressor, I decided to go ahead and replace it. Hopefully, the compressor itself is not damaged so I won't have to worry about contamination of the whole system.

 

[gsxr]

Replacing the clutch on the vehicle isn't too bad, probably no worse than full compressor replacement! The bigger problem is the cost of the clutch. It's usually cheaper (a lot cheaper) to buy a complete compressor with new clutch, rather than just the new clutch by itself. Makes no sense at all, but that's what I found about 2 years ago when I needed a new clutch. You are probably right that with 200kmi, proactively replacing the entire compressor ain't a bad idea.

Cap off any open lines when removed, keep the "system open" time to an absolute minimum, and I'd replace the drier and red pressure switch while it's all apart. Cheap insurance! Then pull vacuum for a few hours and re-charge with fresh R-134a.

 

[emerydc8]

I got a new Denso compressor from AutohausAZ for less than $300. I'm not sure what the difference in quality is between the Denso and NipponDenso (OEM) or whether they are even the same company. Do you happen to know if I have to drop the whole sway bar or just the front part in order to get the compressor out?

 

[samiam44]

Sounds like you have a good plan. I have no idea on where the Denso's are made and if quality is similar. Generally, clutch failure is due to more internal friction which means your at the end of a Compressor's life. I think that's the right decision.
FYI last year you could get the compressor on Amazon for less. Borrow one from autozone. Make sure whom every you borrow or rent the vacuum pump from- the oil should be clean/clear. Check before hand.
R134a in cans was the cheapest at biglot earlier this year.
I think his reference was to drop the front of the sway bar lower(remove from mounts and just twist it down.

FSM has notes about how much new oil to add with a compressor replacement. Generally, teh dryer you add 1 oz. Buy the correct grade and throw it away when you are done with the project. PAGXXX? Cannot remember the correct weight off the top of my head. Dave?

 

[emerydc8]

It has been several years since I bought R134 and I couldn't believe the price. It was $5 a can a few years ago. Now it's $15. I already bit the bullet and bought four cans from Autozone. I haven't even checked on the exact amount I need considering the new r/d but I read that it was in the four can area for the whole system. I'm pretty sure the oil was already pre-added to the new compressor, but I hadn't considered adding any to the r/d. I think I'll add an ounce there just in case.

I will have to leave the car on ramps instead of jacking it up because I think there is a load on the sway bar when the weight is off the wheels. Hopefully I can get away with just dropping the two front brackets and pulling down.

Autohaus seems to be pretty competitive with the free shipping and they usually get it to me in a day or two. They were good about returning a Uro blower motor last year that was so noisy that I couldn't hear the engine. I learned my lesson about Uro parts for sure.

 

[Tonyetee]

I got a new Denso compressor from AutohausAZ for less than $300. I'm not sure what the difference in quality is between the Denso and NipponDenso (OEM) or whether they are even the same company. Do you happen to know if I have to drop the whole sway bar or just the front part in order to get the compressor out?

.

Pull the whole bar off 2 17mm on the the bracket arms and 4 13 mm on the the clamps the whole bar will fall out.

 

[emerydc8]

Will do. Thanks again guys.

 

[emerydc8]

Well, it took about an hour to get the compressor off and 15 minutes to bolt it back in. It was a lot easier than I anticipated. The sway bar came right off and there was only an oil cooler flex line and a plastic tube that Mercedes calls the "air supply pipe for the left engine bearing." (What's that all about?) The Denso compressor from AutohausAZ came with oil in it so I just turned the clutch about ten times to prime it. There is a face plate where the high and low lines connect that must be reused from the old compressor, but it was very easy to swap out (four Allen bolts torqued to 24 nm). The replacement O-rings seemed to by slightly smaller than the ones that came off, but I attributed it to swelling of the old O-rings over time (I hope). I was able to draw a vacuum of 25" with a 2.5 CFM pump that I bought on sale at Harbor Freight for $89 and it held for 30 minutes after turning the pump off. I am at 3,000' MSL so I don't think I could get much more than 25". All-in-all, it was an easy job. Thanks for the help and advice guys. I tried to attach some pictures but for some reason they wouldn't upload. Have a good weekend.

 

[samiam44]

That's great news to hear it went so well=0) THe airsupply line is to cool the motor mounts as the engine is so tight in the engine compartment there is not much airflow. Removal makes getting at the motor mount bracket on that side (front 2 bolts) much easier.

 

[emerydc8]

So the motor mounts really do get that hot that they need air flow. Who'd have thunk it (other than the MB engineers). I did the mounts last year and, if I recall, it was easier to remove the four bolts that held the mount bracket to the engine on one side (can't remember which) and on the other side it was easier to remove the big 17mm bolt through the mount. Thanks again.

 

[M104-AMG]

Great notes. I'll be doing this soon. Also, just learned about di-ether, aka "double end-cap" PAG oil having superior corrosion control; lubricity; and less-affinity to water than "normal" mono-ether PAG oil.

FWIW, FCP Euro carries it.

PAG-Oil 46 A/C Compressor Oil (8 oz.) - Santech MT3012

PAG-Oil 46 A/C Compressor Oil (8 oz.) - Santech MT3012

www.fcpeuro.com

neil

"The performance of oil for HFC-134a refrigeration lubricant in an automotive A/C system is effected by the end group and main chemical structure of PAG [oil]. Di-ether PAG, without the hydroxyl end group is less hygroscopic than mono-ether PAG with hydroxyl end groups. Therefore, end capped PAG provides proper rust inhabitation and lubricity and is the preferred oil for automotive A/C applications."

https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=2250&context=icec

 

[gsxr]

Neil, the double end-cap PAG oil is definitely the way to go. However, the Santech / MasterChem oil sold by FCP is made in China and comes in a plastic bottle, which doesn't give me warm fuzzies. I bought a bottle last year but I don't know if I'd use it with a new compressor & new receiver-drier.

Although the cost is substantially higher, I plan to use genuine Denso double end-cap PAG oil, ND-OIL 8. This is made in Japan [see post #21 below], and comes in a metal can. See attached PDF file with detailed technical explanation as to why Denso thinks their product is superior. Not many major vendors carries this stuff though. No affiliation with the vendors below. Denso is sold in a 500ml / 8oz can (p/n 999-0101). Avoid the Toyota-branded ND-OIL 8 which is a 40cc / 1oz can for crazy prices.


https://www.ebay.com/itm/193002665232

https://www.amazon.com/gp/product/B0049GED1S/

https://www.densoproducts.com/denso-999-0101-ac-compressor-oil

https://www.abilenemachine.com/denso-nd8-pag-oil-46v-amx10272

https://www.finditparts.com/products/5416599/denso-9990101

Edit: I bought mine from Rock Auto, see post #20 below:
https://www.rockauto.com/en/moreinfo.php?pk=9551944&cc=0&pt=6928&jsn=57

 

[M104-AMG]

Dang no local shops have the Denso product.
Here's an experiment on synthetic PAG vs Double-End Cap (DEC) PAG (which is also synthetic):

PAG Olis - Do I need DEC? - Automotive Air Conditioning Information Forum

Moderator edit: Link above is broken as of summer 2023, use the archive link below:

https://web.archive.org/web/20220817074343/https://www.autoacforum.com/messageview.cfm?catid=20&threadid=17571

Spoiler:

Conclusions:​

​

If you must use PAG, make sure that you are using DEC [Double End Capped] PAG. If you open a PAG system, be sure you have flushed it to bare metal before you re-assemble it.​

 

[gsxr]

Rock Auto claimed to have the Denso ND-OIL 8 for ~$14/can plus S&H, however the photo showed an O-ring. I gambled on buying that and it is the wrong photo, they will ship the correct Denso oil in a metal can (500mL / 8oz).

There is no COO on the label however, I'm not sure where the oil is produced. It's a metal can with screw-top and a reusable seal plug. Edit: It's made in Japan, see next post.

I'll get some high-res photos eventually, but in the meantime, here's a link to purchase:

https://www.rockauto.com/en/moreinfo.php?pk=9551944

 

[M104-AMG]

It was hard to find, but I did locate the COO below the "First Aid" section:
"Contents made in Japan"

Also, it comes with a re-useable plastic seal cap.

neil

 

[gsxr]

COOL! Thanks for the update, Neil! And yeah, I need to get my eyes checked...