Advice from Pacific Oil Cooler Service Website
see
http://www.oilcoolers.com/article_oil_cooler_woes.asp
_________________________________________
DAMAGED THREAD ISSUES
.......................
VERY IMPORTANT:
......... In fact, throw all aluminum fittings as far away as you can from the work you are doing - and use steel fittings instead. Steel fittings, when installed with some type of lubricant on the threads, will almost never gall, bind up, or damage the threads of an aluminum oil cooler. In addition, steel fittings will un-screw cleanly from the cooler - even many decades later. None of these things can be truthfully said about aluminum fittings.
Steel is the fitting material of choice if you want to avoid damaging the threads of an aluminum oil cooler. Additionally, steel fittings will un-screw from the oil cooler cleanly and with no thread damage, even many years later. No matter what they?re made of, never ever screw fittings into an aluminum oil cooler without first applying some form of thread lubrication - and use aluminum fittings only as a last-ditch resort.
If you must use aluminum fittings for some reason, make sure that the threads are clean and defect-free, use Teflon tape or an anti-seize lubricant made for use on threads, and work slowly and carefully as you begin screwing the fitting into the oil cooler (and cross your fingers, also).
When pipe-threads are involved, be sure that the fitting is going to snug down and achieve a seal before the shoulders above the threaded portion of the fitting come in contact with the top of the boss on the cooler. When the shoulders on the fitting touch - or come anywhere close to - the top of the oil cooler?s boss before a seal is made, it means that the threads in the cooler have lost their taper and the cooler must be replaced.
________________________________
Bill Brooks
Ottawa, Canada
RV-6A finishing kit