To flush or not to flush. That is the question that comes up a lot.
Unfortunately, there is no easy, cheap answer. There is an easy, expensive answer, and that is to never flush a muffler - just replace the hose assembly that contains the muffler. The problem is that sometimes the hose assembly is not available at any price and other times the cost of the hose assembly is more than the the rest of the AC repair parts put together, sometimes more than the value of the vehicle. If we had Superman's x-ray vision, life would be simpler - at least with respect to flushing mufflers.
One mid price answer is to cut out the muffler and have an aluminum welder splice in a piece of straight pipe. Most folks won't know the difference on 99% of the AC units in operation.
I recently flushed a muffler that was on a 1970 Impala for 23 years with no evidence of any type of AC failure, and then in my attic for ten years. I rebent the aluminum lines to fit a 1972 El Camino because the very complicated hose assembly for the 72 is not available any more. The 33 year old hoses look as good as new! I used lacquer thinner and a LOT of air from a 17.5 scfm compressor at 125 psi. I was assuming that the Impala muffler was just an empty can based on it size and inlet/outlet configuration.
Then I found a very large muffler with right angle inlet/outlet attached to a mid 70s Oldsmobile A6. I cut it open and was surprised at the internal intricacy - 7 baffled chambers of decreasing volume from in to out.
It was almost perfectly clean inside except for some a light black carbon film in a few locations. This muffler didn't even need flushing, but if it was flushed to remove old oil and properly dried out, it would work fine. The problem is that if it had been in a system that had a major compressor failure with resulting shrapnel or a system with black death, it probably would be impossible to clean it all out.
So to paraphrase Google - Are you feeling lucky?
First pic is of 1970 Impala muffler. Second pic of cut open 70s Oldsmobile muffler.
Edited: Sun April 13, 2008 at 12:24 AM by Automotive Air Conditioning Information Moderator
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