944 Oil Pressure
 

I am having oil pressure problems with my 86 944. I recently had the water pump, timing belt and accessory drive belts changed. After driving the car less than 100 miles the oil pressure gage flickered and went to zero. If I shut the engine off and then restart the pressure comes back up to normal. My mechanic changed the oil pressure sending switch and the Oil Pressure Relief Valve, but the problem is still occurring. (My mechanic said he put a mechanical gage at the sending unit location and that the pressure was actually going to zero when the gage does.) When I picked the car up after the OPRV was changed I drove less than 10 miles when the problem resurfaced. The oil pressure is normal otherwise. I found that this occures at about 2100/2200 rpms. I also found that if the rpms are increased slowly the pressure remains steady until about 3200 rpm, when it suddenly goes to zero.

I returned the car to the mechanic the following morning and the car operated normally, without a problem. (The only difference between the trips was the outside temperature, 80 vs 60 degrees.) The mechanic said that he ran the car for an extended period yesterday and the problem returned, this time around 3200 rpm. He is rechecking the torque on the front crank bolt now. He said he is questioning the oil pump drive, but seems at a loss. The temperatures, and pressure are normal otherwise, and I didn't notice any unusual noises the first time around. I thought there was some noise in the top end when the gage zeros now, but it could be my immagination.

Help, ideas, suggestions?

Craig