Automotive Air Conditioning Information Forum

Hello,

I am a DIY'er and experienced a compressor failure on my truck last year. While I do replace the receiver dryer, I cannot really replace every other component in the system to get the dreaded black death crap out of the system. So now I am faced with another compressor replacement.

I am using an air conditioning Pipeline Cleaning Tool canister tool to perform the flush. I have tried using 2 quarts of AC flush but obviously the system still has contamination in it after flushing as it burns out the next compressor after short usage.

My technique is that I inject the clearer in the opposite direction of system flow. I do disconnect all the lines and flush at each connection.

What volume of flush is required to clean out a truck system? This next time I have 6 quarts on hand. What air pressure should I be using when I squirt the cleaner in?

Any words of wisdom would be most welcome!

Flame Red wrote: Tue Feb 11, 2025 8:41 am I am a DIY'er and experienced a compressor failure on my truck last year. While I do replace the receiver dryer, I cannot really replace every other component in the system to get the dreaded black death crap out of the system. So now I am faced with another compressor replacement.

What is the make, model, and year of your truck? Also, what type of refrigerant does it use (R-134a or R-1234yf), and how many miles has it logged?

In addition, several thoughts and considerations immediately occur to me in addition to those referenced in the post just above:
— Typically, compressor manufacturers require that the condenser and receiver/dryer (R/D) be replaced. Most condensers, particularly the parallel-flow type, can't be flushed. Neither can a R/D. A tube-and-fin style condenser can be flushed, but it's always best to replace any condenser with a new one whenever a new compressor is installed.
— The evaporator probably will have to be flushed in situ because in most instances, it is too difficult and labor-intensive to remove and replace it with a new part. In addition, the metering device (TXV) must be removed beforehand. Consider replacing the TXV with an OEM part, if available, depending on its appearance when removed. Also remove and set aside (do not flush) a POA valve if the truck has one.
— Used compressors can't be solvent-flushed. Instead, they can be flushed a few times using the same type of oil that the system uses.
— All flushed components (except the compressor) must be thoroughly purged of remaining solvent using dry shop air or nitrogen. If any residue remains in the system, the solvent will contaminate the oil and ruin the new compressor.
— Any lines and hoses having mufflers (can-like devices in the line) can't be flushed and must be replaced.

Flame Red wrote: Tue Feb 11, 2025 8:41 am What volume of flush is required to clean out a truck system? This next time I have 6 quarts on hand. What air pressure should I be using when I squirt the cleaner in?

Six quarts of flushing chemical should be more than enough. One gallon is probably sufficient. See the instructions that came with your flushing tool for the recommended air pressure. If none is specified, 125 PSI sounds about right.

Be sure to thoroughly evacuate the system before recharging it to ensure that all the solvent, air, and moisture are removed beforehand.

Thank you for all the replies!

I removed the old compressor and immediately found the problem! Seems that when I installed the suction side connection, I failed to notice that the o-ring seal dropped out of the fitting and was sitting just below the compressor on the AC bracket. And I over tighten the fitting to get it to seal. Amazing that it did not leak at all without a o-ring! Anyway, I found the male end on the compressor cracked on the end and pieces of aluminum broke off and went into the system - bye, bye compressor!

All I can say is Do'oh!

So I have a new compressor, o-rings, receiver-dryer, and six quarts of the good stuff flush.

The system is an aftermarket R134 on an old Army truck.

I am well practiced now at replacing compressors and can do it record time, for me! This time, I will be very careful and make sure the o-rings go on properly! Do'oh!

JohnHere wrote: Tue Feb 11, 2025 9:11 pm See the instructions that came with your flushing tool for the recommended air pressure. If none is specified, 125 PSI sounds about right.

Thank you for the pressure recommendation. I was thinking that blowing the cleaner liquid through at high pressure, which is what I did previously, did not give it a lot of time to work. It is like a machine gun, a quart goes in pretty quick! Then I would blow it out with air at high pressure to make sure I got all the solvent out. I was thinking maybe I did it wrong and should have just injected the solvent with a very low pressure, and dry it out with high pressure.

Flame Red wrote: Wed Feb 12, 2025 9:25 am I removed the old compressor and immediately found the problem! Seems that when I installed the suction side connection, I failed to notice that the o-ring seal dropped out of the fitting and was sitting just below the compressor on the AC bracket. And I over tighten the fitting to get it to seal. Amazing that it did not leak at all without a o-ring! Anyway, I found the male end on the compressor cracked on the end and pieces of aluminum broke off and went into the system - bye, bye compressor!

Since the system is now contaminated with metal particles, I strongly suggest replacing the condenser, which acts as a filter for the rest of the system. If you have a parallel-flow condenser, the particles will lodge in the micro-tubes. For all practical purposes, any debris that gets caught-up in a PF condenser can't be flushed out.

Flame Red wrote: Wed Feb 12, 2025 9:25 am I am well practiced now at replacing compressors and can do it record time, for me! This time, I will be very careful and make sure the o-rings go on properly!

I like to use a dab of Nylog Blue on each o-ring and threaded connection to help ensure a leak-free seal.

Flame Red wrote: Wed Feb 12, 2025 9:25 am Thank you for the pressure recommendation. I was thinking that blowing the cleaner liquid through at high pressure, which is what I did previously, did not give it a lot of time to work. It is like a machine gun, a quart goes in pretty quick! Then I would blow it out with air at high pressure to make sure I got all the solvent out. I was thinking maybe I did it wrong and should have just injected the solvent with a very low pressure, and dry it out with high pressure.

Curious, I went out to the shop, got out my flushing tool, which I haven't used in some time, and re-read the instruction sheet. It says to fill the cylinder with up to 32 fluid ounces (one quart) of flushing chemical, connect it to regulated, clean, and dry shop air at 90-125 PSI, and reverse-flush each component, repeating until all debris and contamination are removed.

Flame Red wrote: Wed Feb 12, 2025 9:25 am I am well practiced now at replacing compressors and can do it record time

The goal is to do a job correctly, not in record time. You seem to be learning this.

Just wondering out loud - Is there any kind of in-line "filter" that is designed to prevent compressor failure?

Flame Red wrote: Thu Feb 13, 2025 7:19 am Just wondering out loud - Is there any kind of in-line "filter" that is designed to prevent compressor failure?

Yes, although they have their "pros" and "cons." ACKits.com, this Forum's sponsor, lists OEM filters for both GM and Ford vehicles that might fit your truck. Aftermarket filters also are available, I believe.

Just a mention: When your system is filthy with debris. You can catch and filter your flushing agent a few times when getting the larger particles out of the system. Just use a clean flush on the final passthrough.

Thank you all very much for the useful information.

I performed the flush using six quarts. There is still residue coming out with the shop air. I will continue to air flush till it stops. I am giving my compressor a rest.

Not having professional machines it was quite the mess. Attempting to recover the flush fluid was ineffective. It exited as a high pressure stream that more bounced out of the bucket than stayed in. Then the exit hose flopped around. And the end the pressure knocked the bucket over! So not much left to reuse.

I am looking at the filters on this website. Hopefully I can find something I can adapt.