How do you flush after a A\C compressor failure? - PeachParts Mercedes-Benz Forum

badgator · #1 09-16-2007, 01:53 PM

How do you flush after a A\C compressor failure? Or back flush from compressor? My 85 300sd compressor locked up and belt broke Friday, still full of 134a. PO installed a rebuilt r4 compressor, drier 3 years ago, was working OK for Florida. I always do my own A\C work, have guages, vac and sniffer.

loepke72 · #2 09-16-2007, 03:48 PM

Flushing an A/C system involves forcing a solvent under pressure through the condenser, evaporator, and any lines that are not going to be replaced. In a pinch, something like mineral spirits or other solvent followed by compressed air will get most of the oil and crud out. Pay the most attention to the condenser since that is where most of the metal trash is going to wind up. Replace the drier since it can't be flushed effectively and also has most of the debris. Any hoses that have a muffler will need to be replaced as they also can't be flushed effectively. Be sure to pull a real good vacuum to get as much solvent residue out. Then charge with the oil and refrigerant of your choice.

badgator · #3 09-16-2007, 03:54 PM

How do you you back flush it from the compressor? Ex- force 1 quart mineral spirits? into low pressure side, let soak 1 hour then apply 50psi? Until dry.

loepke72 · #4 09-16-2007, 04:05 PM

Not quite sure what you mean, but like I said, flushing involves pressurized solvent through the system (minus the compressor, of course). So, what I would do without the specialized equipment is to pour in enough solvent to fill the component being flushed, let sit, then blow out. Since you're not using a flush machine I recommend disconnecting the hoses at the components (they can remain in the car, though) and replacing the O-rings when reassembling. That should allow you to not contaminate various other parts. Pay attention to what comes out when blowing out the solvent. You may need to do this more than once depending on how badly contaminated the part is. Sorry if I wasn't more clear the first time. I believe I have seen aerosol A/C flush cans at the auto parts stores. This can be something to consider as well. They would just attach to whatever you were trying to flush. Preferably to back flush like you said. That means you would be working from the receiver-drier side of the condenser, for example.

badgator · #5 09-16-2007, 05:14 PM

I want to reverse / back flush the a/c system as to hopefully blast out any crud, crap, chunks of the failed a/c compressor.

sailor15015 · #6 09-16-2007, 05:19 PM

You can buy cans of solvent that are pressurized and come with a little hose to put in whatever you're flushing. My local Autozone has them.

tangofox007 · #7 09-16-2007, 06:45 PM

Quote:

Originally Posted by badgator

I want to reverse / back flush the a/c system as to hopefully blast out any crud, crap, chunks of the failed a/c compressor.

Flushing (or backflushing) is best done one component at a time. You do not want to flush the entire system at once. And the compressor is not involved in the process; evacuate the refrigerant, then disconnect and remove the compressor. Don't install the replacement compressor until the flush is complete. Also remove the receiver/drier; don't flush the old one.

Considering that you have a known compressor failure, a professional flush might be worth considering. A good a/c shop will have the equipment necessary to take the guess-work out of the process.

badtrukrisin · #8 09-17-2007, 05:58 PM

Buy a couple gallons of mineral spirits and flush let soak and flush again. Then repeat in opposite direction. Then use a good grade brake cleaner spray to soak again and then blow all out with compressed air(dry). Especially the condensor coil. When blowing out with air, use an old white sock over the outlet and then inspect sock for debri. You will know when it is clean. Good luck.

Bud

rrgrassi · #9 09-17-2007, 06:09 PM

You first need to either buy or rent a flush gun.

Remove the compressor and the drier, remove the expansion valve. Flush all the lines and items that remain. You will be flushing the lines, evaporator and condensor.

Diesel Giant has a good pictoral on this at his website. http://www.dieselgiant.com

I bought two gallons of methanol to flush with, and ended up using about 1 1/2 gallons. You have to be careful, and make sure you do not create any sparks, as methanol's flames are nearly invisible, but the stuff works great!

Yes, you do need to flush, then dry with shop/compressor air. You will be flushing the

Also, find a local BG Lubricants distriutor in your area and buy the 8 oz bottle of Frigiquite oil. It's $10-12 instead of Diesel Giant's $39.00.

Try to buy a Hodyon (Hancock Industries) compressor and replace the drier and expansion valve while you are at it.

Check the replacement compressor, as it may have stepped ports also make sure the clutch coil eletrical connector is "clocked" at 3:00 as viewed from the front.

JimmyL · #10 09-17-2007, 10:11 PM

What Ralph said above is THE way to do it. Others above had also told you what to do, yet you keep asking the same question. Inspect the above answers carefully, and fully, and you have your solution.
No short cuts or you will just be wasting time and $$$$$.