My B20B is quiet when cold, but when the engine has warmed up it sounds like one of the tappets is out of adjustment. The sound follows the revs, and stayes at the same volume. At around 2500 revs or so (no rev counter) it suddenly starts going quiet and at say 100 revs higher it is gone. Any ideas? My thoughts are that valve clearance would decrease with temperature. The car does mostly short distance, and is running cool due to a wrong thermostat to be replaced this weekend, but I suspect a higher temperature would make it worse since the car is quiet when cold. It actually sounds very good when cold!

Driving about 3 or 4 km at a time to work in cold weather (15 deg.C max), so there is definately water/condensation in the oil. Could it be that when cold the oil is so thick that it lubricates properly, but when warmed up there is insufficient lubrication due to the water and at higher revs the oil pressure comes up? (Not intending to fit an oil pressure gauge.) Now that I've got rear safety belts fitted, we will drive longer distances with the kids.

I would like to solve this before fitting the warmer thermostat this weekend, and your thoughts would be much appreciated.