I completed an AC overhaul this week but now the compressor is making clunking noises. When I leave the air running but put it in the EC mode the clunking noise stops.

I had the dealer put in a new receiver-dryer and I put in a push button control and then the dealer pulled old refrig out and put new in. It has never made this noise before now.

Looks like compressor was replaced in 1994. It is the cheaper one.

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1982 300SD Light Blue
2002 Honda Accord SE
1974 Toro Wheel Horse Tractor
2000 Toyota Tundra Pickup

compressor never runs on the e/c mode so you wont hear the noise while on e/c, I would check on the high side pressure to make sure it is not overcharged. also check everything around the compressor to make sure the noise is actually coming from it. Sometimes people charge liquid refrigerant through the low side of the system and allow too much liquid into the system, that liquid refrigerant has to boil before it gets to the compressor otherwise it could have devastating effects on the comp since liquid doesn't compress. I'm not sure this is your problem but liquid in the comp can bend the valves and cause other problems without necesarily detroying the compressor. Hope is something simpler!

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87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

". Sometimes people charge liquid refrigerant through the low side of the system and allow too much liquid into the system,"

Any liquid refrigerant into the low side of the system is too much....The first thing it hits are the reed valves...and they go Kaput.....

There is no mechanism to allow for the boiling once it moves downsteam of the evaporator. Liquid refrigerant is always installed in the high side.

Yes, it could be overcharged, but if any bolts are loose it could cause the noise. Check the bolts for tightness.

Good luck,

Although I dont do it, if done carefully it is possible to charge liquid through the low side depending on the system and wether it has a liquid expansion reservoir before the compressor and you charge it in small burst, what I meant was that people just open the valve and let a rush of liquid in and that's it for the comp. I do agree that any liquid in the low side is too much but in practice that's not what happens

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87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

This is a Mercedes Diesel forum.... do any of our cars have that ?

I suspect not... and we have enough trouble getting people to believe that the rules should be carefully followed anyway.... people accuse us of trying to make it ' mysterious' when we are just trying to emphasis how important the rules are to longivity in a very harsh enviornment ( inside the system)....

And if you knew that a " liquid expansion reservoir " was needed to make the statement correct and safe for lay readers it should have been included in that post..

"but in practice that's not what happens " --- how about describing where you see this happening... and tell what the advantage is... compared to sticking it into the high side as the books suggest ?

It very much depends on the particular compressor. Some make and model compressors are very tolerant of this and some, such as the old York and Techumsehs will break a valve at the least little introduction of liquid.

As a general rule, just don't take the chance. If the system won't take gas, then warm the cannister, or if using cans, lower the can into a bucket of lukewarm water.

Good luck,

Maybe a loose belt. This may sound too simple, but best to eliminate the simple ones first. My compressor sounded like marbles rolling around in a coffee can. It cooled great, but at idle I could hear it above the engine noise. Thanks to a suggestion on the ShopForum, I tightened the loose V-belt and solved the noise problem. Be aware that my belt was not extremely loose, but just enough to cause the noise. Hope this works for you.

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Bruce

73 220D (never left Germany)
81 300D (totaled)
84 300D (Purchased '03, sold '17)
85 300SD (purchased 10/01/03)

They recovered the system, replaced the dryer and recharged refrigerant.

Point #1. If they did a fast recovery = system oil loss.
Point #2. When you replace the receiver dryer = system oil loss.
Point #3. It is possible the oil loss was not replaced.
Point #4. It is also possible the oil loss was replaced with too much oil.
Even if the system pressure looks right, if the oil loss volume was filled by extra charge = lubrication loss + system over charge = added stress and wear on the compressor + system cooling capacity loss.
Excess oil = compressor noise + cooling capacity loss.

This is all guess work without further data.

This is how we do it in the OEM climate control laboratories.
#A. Recover the system slow.
#B. Remove and drain compressor.
#C. Remove receiver dryer.
#D. Flush the system.
#E. Fill compressor with correct oil charge.
#F. Install compressor.
#G. Install new receiver dryer.
#H. Charge system with 110 psi nitrogen for thirty minutes = leak check.
#I. Vent nitrogen charge and vacuum system for thirty minutes.
#J. Charge system with fresh refrigerant.
At this point you will know the oil and refrigerant charge are right.

Roy, how do you do a leak check on nitrogen? Do you simply look for the system to hold pressure? If it does not hold, how do you locate a tiny leak, if you are leaking nitrogen??

Nitrogen is for gross leaks, but worst case for tough to find leaks = add half ounce of refrigerant to system for detection.

Most leaks are gross leaks.

Thanks, sounds like the ticket.

Hey all am saying is that people don't always do things the way they're supposed to and some systems do have "liquid expansion reservoirs" when I mentioned this I was referring to people in general and not diesel owners in particular.
"how about describing where you see this happening..."
I "see" it happening all the time when people hold the can of refrigerant sideways and start shaking it as opposed to holding it up where only gas will flow out.

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87 300d Turbo 241K with original #14 head (blue)
87 300d Turbo 198K will run great again someday (silver)
84 300sd sold ( buyer drove it to Paraguay )

The clunking can be as simple as a belt that lost a chunk out of it if its not new. My W116 did the very same thing...I though tthe compressor was about to self destruct and then I noticed the belt...then problem solved.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

boy, that's a good thought. makes a lot of sense, because the noise is load related on the system. BTW, BHD you win the prize for most improved Avatar. That is simply beautiful and mesmerizing.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.