1. I am getting ready to acid flush my engine and was wondering about the themostat. Do I remove the thermostat before the flush, or can I flush the engine with the themostat in if I warm up the engine first? Will the acid do any damage to the thermostat? Any precautions I should take, aside from the normal acid spill warnings?

It is best if you remove the thermostat and clamp off the by-pass loop so that all of the acid solution goes through the block and head. However, many folks do just warm the engine up first and then draw in the acid, and claim to have good success.

We've never heard of any damage of any kind resulting from the acid flush procedure, no doubt due to the very mild concentration of acid. - Updated: January 3, 2004