Just an information post that may be helpful to someone.

I search for days to find internal photos of the denso compressor with no luck so I will post them here - why? I was trying to work out what could possibly be making such a noise internally.

My car has this shocking noise (Ref mp3 attachment), it's actually very loud - you can hear the car coming from the end of the street.

From all my research and own experience the alternator and the power steering pump can all make a similar noise and can be hard to pin down. I was concentrating on the power steering pump in my case as it had the wrong fluid and was also making noise.

Anyway after lost of stuffing around and diagnosis it was coming from the compressor.
Removed and stripped the unit down to find internal damage from I think lack of oil.

Turns out the pulley bearing was making 90% of the noise. Off the car it's sound slightly noisy but nothing too major. Very odd in my opinion - bad bearing do not generally make a consistent whining noise - please correct me if I'm wrong here.
I put the unit back on the car with the compressor shear plate off (so the compressor will not turn) and wow what a noise. The later cars do not have a clutch so you cannot just turn off the compressor as such.

In my case the compressor will need to be replaced as there is quite bad scoring of the cylinder bores and the swash plate is damaged. I would rather replaced the unit now than have a major repair later when it lets go completely.

I am trying to locate a replacement OEM Denso compressor great difficulty finding and stock so need to keep driving to car until I locate one.
The new type of compressors cannot be left running with no or very low gas in the system as they require this for continuous lubrication.
An alternative to removing the hub is to use a shorter belt depending to the type of engine you have.

Will post some pictures of the pulley and bearing when I pull it off again.


Cheers,

 

beautiful post. thank you very much for the awesome pics and audio reference

 

No problem. I have used these and other forums so much in the past and find them extremely useful even if it's for something as simple as a photo.

Cheers.

 

Just wondering for future reference, how difficult was it to remove the compressor from the block? Looks pretty buried down in there

 

Hi, the sub frame is very close and just opposite to the compressor so space is at a premium.

A one thing that was quite difficult for me but would have been easier with the right tools was loosening two of the three mounting bolts with too short an E12 spanner (no room for a socket and ratchet).

Next a Ratcheting ring to get the bolts all the way out as they were tight all the way due to a bit of corrosion and thread lock - very tedious moving a 1/4 turn with each spanner repositioning.

Just a side note: no disrespect to anyone here but I have long skinny hand so not too hard for me to get access but other people may find it difficulty to squeeze up near the chassis.

There is a bit of per-disassemble:

Remove front under tray
Drain coolant
Remove thermostat housing extender (black aluminum section the upper radiator hose connects to)
Remove cooling fan assembly.
Remove serpentine belt

The only other hitch was the bolts cannot be removed from the compressor while it's in place (no room) and must come out together and go back the same way. I used a bit of insulating tape to hold them in place when I was reinstalling the unit to make it easier to position and stop them falling out and catching on the chassis.

In my opinion the M273 V8 engine bay is not too bad for space - seen much worse: newer Porsche's for example.

Cheers.

 

nice thnx for the info and post!!!

 

There was a Mercedes service note on this some time ago. While I don't have the reference to the bulletin directly, there is a video on how to remedy ths: Unfortunately es ist nur auf Deutsch.

 

Small update: finally got a replacement compressor after lots of pain with Denso equivalents listing problem.
I pulled the old one off again so here is a picture of the problem bearing.

As the video above shows, most of the time only the pulley needs to be replaced. You will also need the hub removal tool (ref photo) while the compressor is on the car.
In my case with it off the car I just used a Dewalt impact driver and it come straight off without a problem. Note: you need to remove the hub snap ring first.

Also a word of caution on removing the snap: the edge of the pulley is made of very brittle plastic and is easily damaged as I found out.
If you have a new pulley to replace the old one it will not matter but if like me it was necessary to temporarily disable operation by removing the hub it's best to take care.

More to follow.

 

Hello Greglig.
nice reference.but i have a question that i don't understand.
i disassambled my mercedes compressor that is identic as yours but i don't know how the mechanism of the pistons is?when i rotate it by hand the pistons don't move in the cylinder.it rotates easily by hand.and another thing.when i rotate by hand i don't feel any compression in the suction and discharge port.so if anyone can explain please how it works.maybe is the refrigerant gas pressure the moves the pistons?do they move all at the same time inside the compressor.so i can test it only mounted in the car? Really?Thank You

 

Hi Marjus, it varies the angle of the plate with the control valve in the back of the compressor but needs to be pressurized to make it work.
Look here (detailed explanation) :


To all on on mbworld: I have not been able to post on forums as have been struck down by an awfully debilitating pain my joints (especially hands). I have not been able to walk let alone type.
Cars are easy to fix compared to this type of problem which has the doctors and specialists scratching their heads. It seems to be slowly improving on it's own as nothing the doctors have given me seems to make a difference.

Cheers.

 

greglig glad you seem to be on the upswing

hope you are 100% soon

thanks for posting the info on the compressor

 

Thank You Greglig for your explanation and i am sorry for your health problem.hope you are fine soon.i understood it now.just another last thing.could you please tell me the order of the valve plates because they are 4 and i dont want to put them in the wrong order.if you help me with the order which is first and last.Thank You another time

 

Where does one find this clutch tool. It doesn't look like a regular clutch removal tool.
Also is there a nut at the front of the compressor that you removed with a socket?
Up close in the video it doesn't look like there is a nut. What's actually turning? When the mechanic places the tools it kind of blocks what's actually turning. I know you've added alot of content but you be more specific in how to remove the pulley.

 

where can I find the hub removal tool?

 

Hi, sorry for the late reply been busy. I had a bit of of a look online and could find much in the States although UK and Netherlands seems to have more.

I did find one but am not 100% sure it's right.

http://www.ebay.com/itm/CLUTCH-HUB-I...276744&vxp=mtr

Another one that might be right:

http://www.ackits.com/mastercool-ser...dkszexel-24315

You would need to ring them and confirm as the 7SEU model is not stated but inferred. With this set total length could also be a problem with the compressor still on the car.

It also may be possible to get direct from Mercedes depending on the price. I'd need to dig up a part number. if anyone's is interested.

As to whats being unscrewed: there is no nut, it's the compressor input shaft rotating and unscrewing from the hub. As you rotate the shaft while holding the hub stationary the hub moves out and away from the pulley.

Cheers.

 

yes please. I cannot find the tool anywhere.

 

I found the part here in the US. special order from autozone. the a/c compressor pulley was indeed the culprit