Oil pressure

Yesterday while driving home I noticed that when I am just idling at a light or push in the clutch my pil pressure gauge drops to zero. I stays between 20-40 while driving but once it warmed up it drops to zero at an idle. It seemed to stay at about 20 when idling cold though. It is an '89 with 201,000 miles. Do to leaks I have replaced the rear main, oil pan gasket, valve cover gasket, and the oil filter o-rings. The slowed down considerably but still leaks a little and now I am having this pressure issue. Any ideas what might be going on and advice as to what weight oil I ought to be using as well. I live in Denver if that makes any difference.

dh, you can get along with low pressure at idle, but NO oil pressure is bad. You might change the sender unit, or connect another gauge to it, to verify the zero pressure.

It sounds like the main bearings are getting worn. Pulling the pan and installing new bearings is an option, if the rest of the engine seems sound. A new oil pump wouldn't hurt either......

what do you mean by "another gauge"? is there some sort of tester I can connect to it. I actually replaced the sender on it about 8 months ago because the old one starting blowing oil all over the place. How hard is replacing the main bearings. The engine seems to run well and doesn't smoke at all so if it is something I can do myself I am game.

dh, I meant a mechanical gauge that would read the true pressure. It has a tube that carries the pressurized oil to the gauge. That type is usually more accurate than the electrical type which we have. Since you've already changed the sender, your pressure reading is probably accurate.

Do a search on "main bearings". There is plenty of info on changing them. It's not hard; you will need a torque wrench and plenty of shop rags to wipe the dripping oil out of your eyes. You just loosen all of the mains and replace the bearing inserts one journal at a time. If the engine isn't knocking, chances are the crank journals are still in good shape. A set of new bearings should give you more oil pressure. I would also replace the oil pump.

You did clean the oil pump pick-up screen when you did the other work, right? Sometimes a clogged screen will reduce the oil pressure.

My XJ with over 200K used to do the same thing. Changing the oil always made the problem go away for at least 3K miles.

I decided to replace the rod bearings and when I took the pan off the problem was obvious. There was at least a full handfull of small pieces of gunk in the bottom of the pan and in the pickup. I cleaned it all up and haven't had a problem since.

But, if you checked you pickup while the pan was off then this isn't your problem.