"Black Death" found when when flushing. FULL COLOR PHOTOS - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 08-12-2013, 11:06 AM

Warning: The photos are color photos NOT black and white!

I am doing a Sanden retrofit on my neighbors 1980 300TD. The compressor (original) was locked up. I removed all the compressor hose assemblies, compressor, drier, and mounting bracket. I proceeded to flush the evaporator and condenser. After pouring a couple ounces of flush in the high side hose going to the evaporator, I got a LOT of what they call the "Black Death":

Flushing more:

And more:

When I got done, I noticed this puddle on the ground (I thought the rags got it all):

I did not get much out of the condenser, and it cleaned out fine. It is amazing what happens when an R4 fails, and I have never seen anything this bad.

1project2many · #2 08-12-2013, 11:23 AM

That's pretty bad. I wonder how long it's been since the last recharge? That "black death" is almost always the result of moisture in the system. R134A plus H20 yields HF , Hydroflouric acid. HF is highly reactive, to the point that it will etch glass and cause stainless steel to "bubble and foam." Older systems built for R12 frequently use dissimilar metals which only aggravates the problem. For many years I worked on R4's in R12 equipped vehicles and they typically didn't produce the same quantities of black garbage when they failed.

ROLLGUY · #3 08-12-2013, 11:58 AM

Quote:

Originally Posted by 1project2many

That's pretty bad. I wonder how long it's been since the last recharge? That "black death" is almost always the result of moisture in the system. R134A plus H20 yields HF , Hydroflouric acid. HF is highly reactive, to the point that it will etch glass and cause stainless steel to "bubble and foam." Older systems built for R12 frequently use dissimilar metals which only aggravates the problem. For many years I worked on R4's in R12 equipped vehicles and they typically didn't produce the same quantities of black garbage when they failed.

That is interesting. We were not able to charge the system yet, but will later today. We are going to vacuum for at least an hour to be sure no moisture remains. I hope there is no leaks, especially in the evaporator.

vstech · #4 08-12-2013, 01:17 PM

if you are unsure if it's leaking, putting the system in a vacuum is a BAD idea.

you should pressurize the system and VERIFY it is leak free first.

ROLLGUY · #5 08-12-2013, 02:00 PM

Quote:

Originally Posted by vstech

if you are unsure if it's leaking, putting the system in a vacuum is a BAD idea.

you should pressurize the system and VERIFY it is leak free first.

Yes I know, and told him (my neighbor) that we need to pressurize the system first and check for leaks. My bottle of CO2 (all I have) is low, so we will need to get it filled first...Rich

Whiskeydan · #6 08-12-2013, 02:53 PM

You will never get all that stuff out of the system. I had one we flushed, with a flush gun about a dozen times. Last of the flush was coming out clear. Still, I ran the system for three weeks and replaced the dryer as freon is pretty good at cleaning one up as it operates. The receiver dryer will load up quick.
I ran this for another year with no problems although it wasn't as efficient as the other AC on the 'Black' '85 300SD. Both cars have identical components.
A month or so ago the condenser developed a leak so I replaced it. I took the old one open and stuck a swab in one of the tubes.
You would be amazed at how much is still coating the walls. I suspect once the system sufffers "Black death" from a compressor failure the system efficiency drops due to this coating on the walls of the condenser and evaporator.

I don't know of anything other than scrubbing that will remove it.

panZZer · #7 08-12-2013, 02:57 PM

Quote:

Originally Posted by Whiskeydan

You will never get all that stuff out of the system. I had one we flushed, with a flush gun about a dozen times. Last of the flush was coming out clear. Still, I ran the system for three weeks and replaced the dryer as freon is pretty good at cleaning one up as it operates. The receiver dryer will load up quick.
I ran this for another year with no problems although it wasn't as efficient as the other AC on the 'Black' '85 300SD. Both cars have identical components.
A month or so ago the condenser developed a leak so I replaced it. I took the old one open and stuck a swab in one of the tubes.
You would be amazed at how much is still coating the walls. I suspect once the system sufffers "Black death" from a compressor failure the system efficiency drops due to this coating on the walls of the condenser and evaporator.

I don't know of anything other than scrubbing that will remove it.

Ide do some tests with the residue to see what will cut it.

Whiskeydan · #8 08-12-2013, 02:58 PM

Rich, Id suggest you run that system for a couple of weeks and take a sample of the oil off the hi side port.
If there's any sign of discoloration open it up and flush again. At least replace the dryer after a few weeks of operation.

ROLLGUY · #9 08-12-2013, 03:02 PM

I think we will run it for now, and later put in a new PF condenser and drier. Then we will flush it again until clear.

vstech · #10 08-12-2013, 03:17 PM

do you have any idea what the "BLACK DEATH" is?

in an electrical compressor, black death is from the winding insulation burning inside the compressor... there is no winding inside an automotive compressor...
the aluminum and copper if corroded from acid should form either a green or a white sludge... what's left to make black slime? the rubber hoses... so... they should be replaced. and modern hose has a "barrier" that keeps the pag and 134 from attacking the hose and leaking out.

My thought are that the rubber hoses should be replaced, and the metal parts flushed and filtered.
the "dryer" in an automotive system is nothing more than a can with a tube in it, and a desiccant bag inside to absorb moisture. it has zero filtering capabilities. if the system has black residue in it, a LIQUID line filter needs to be installed in the line between the dryer and the condenser. this will polish the oil and remove all traces of black death.

Whiskeydan · #11 08-12-2013, 03:25 PM

Black death is why the R4 comp gets such a bad reputation. Typically what happens is a poor R134 retrofit was done using either non-compatible oil or incorrect oil. The compressor then fails and spews its guts and charred remains of oil throughout the system.

The replacement R4 now has to pump this abrasive soot and it soon fails.

The R4 on my Black SD is over ten years old, is quiet and will make ice on the suction line. It's beginning to leak more at the front seal so someday I will do a Sanden conversion since she Sanden is a bit more robust and requires less hp.

panZZer · #12 08-12-2013, 04:27 PM

chemtool carb cleaner will probably cut it--ide fill the condenser full, let soak and clean it out.

1project2many · #13 08-12-2013, 04:28 PM

Quote:

the aluminum and copper if corroded from acid should form either a green or a white sludge...

Aluminum will form a dark grey to black oxide.
Hydrochloric acid vs. Aluminium foil - YouTube

Quote:

what's left to make black slime? the rubber hoses

Some flush solutions can damage the inside of old R12 hoses. They will also strip out mineral oil left over from the R12 system which saturates the rubber hose and forms a barrier that slows or stops R134 leakage. Picking the wrong flush can do more damage than no flush.

Quote:

My thought are that the rubber hoses should be replaced, and the metal parts flushed and filtered.
the "dryer" in an automotive system is nothing more than a can with a tube in it, and a desiccant bag inside to absorb moisture. it has zero filtering capabilities. if the system has black residue in it, a LIQUID line filter needs to be installed in the line between the dryer and the condenser. this will polish the oil and remove all traces of black death.

A very thorough and professional solution.

ROLLGUY · #14 08-12-2013, 07:03 PM

I used professional A/C flush solvent. I have heard of a liquid line filter, and agree that it would be the best thing to add, since there is a new Sanden in the system.

Air&Road · #15 08-13-2013, 08:20 AM

You should replace the rubber and THEN flush, flush and flush.

You don't need to buy all new hoses, it would cost a fortune. Take them off and take them to your hydraulic hose shop or local automotive a/c shop. Either of them can replace the rubber portions of the hoses.

While the hoses are at the shop, thoroughly flush and THOROUGHLY blow out the flushing agent from the components. About the only components to flush will be the evaporator, condensor and expansion valve.

After everything is back together, put the filter drier in place as the very last step, but don't do it until you have the vac pump in place and ready to go. As soon as you tighten the connections on the filter drier, turn on the vac pump.

Good luck with it.

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