A defective thermostat can produce this problem by not being open fully at rated temp (88-90C) This will restrict coolant flow and allow heat to accumulate. Your fan clutch should be at least partially engaged at about 90C. You can tell by bringing the rpm's up to about 2000. with a good fan clutch, you will definitely hear the fan working. If you keep it a 2000 and the temp starts to drop to the 86-88C range, the fan will begin to declutch and become quieter. Oil pressure will drop in an inverse fashion with increasing temp. It gets thinner when hotter and pressure goes down. You may have some air in your cooling system, your radiator may be partially occluded. If your aux fan is coming on and it's still hot, then something is wrong. Start with thermostat, fan clutch, air in sysem, radiator. You should be able to find the culprit. Good Luck..
1987 BMW 325
[This message has been edited by jeffsr (edited 04-09-2000).]