With credit to Ric Stephens for this original question:
Gentlemen, I need to have my oil cooler flushed. Can an automotive
shop (like a radiator shop) cook it out or do I need to have an “aviation” shop do it?
Thanks! Fly Safe. Ric Stephens A23-24
Ric, I saw Bob Steward’s good advice about the need to have this done. To add to his comments, you should be aware that a proper shop that is equipped to flush and repair aircraft oil coolers uses very different techniques and compounds versus an auto radiator shop.
An aircraft oil cooler requires very high pressure, high-volume flushing with a special, high specific gravity, high-detergent cleaning compound. That is the only way the shop can be certain that all the tiny bits of heavy metals, embedded in sludge in all the nooks and crannies of the cooler, will get carried out. If the cooler is just flushed with standard solvent, such as mineral spirits, some of the sludge gets carried out, and the metal fragments get exposed or loosened but most remain behind. Then when the cooler goes back on your engine, the much heavier oil picks them up and takes them into your engine for you. As Bob notes, the cleaning compound cannot contain any caustic or acidic products, as they will attack the aluminum cooler. You can easily see that normal light solvents won’t remove metal fragments. Try using mineral spirits to rinse some metal filings from a metal pan or similar (just file something or scrape it with a hacksaw). Most of the metal will stubbornly remain in the pan. You can imagine how hard it is to remove debris from the nooks and crannies of an oil cooler.
Note that proper oil cooler flushing is an often overlooked step in an engine overhaul. Too many field overhaulers just flush it out locally with solvent, if they do it at all. As noted above, this can do more harm than good. Most coolers also get a healthy dose of vibration during their lives, and a good examination on a clean cooler, followed by a proper pressure test, might just avoid total oil loss on a newly overhauled engine. Wouldn’t that be depressing,
just to save the cost of a proper cooler inspection and overhaul?
An auto shop is equipped to test radiators to perhaps 25 PSI. A proper aircraft oil cooler shop will test your cleaned cooler to 150 PSI or more, as your engine’s cold-oil redline on oil pressure is 100 PSI. This may sound high, but you’ll find that a great many aircraft are set to this upper 100 PSI pressure limit, and will experience it on most takeoffs on a cool engine (first flight of the day).
Here is a listing for a shop I have used in the past (but not for some time now). They are located in Dallas, TX:
Southwest Cooler Service: (Tom; 214-330-7214); oil cooler cleaning
and re-certification. www.swcservice.com
CAUTION! The FAA just issued an unapproved parts notice for SWCS (May 2006). Investigate further before having any work done there!
There may be other references in the Links section for good shops that are closer to your location.