I have a 1986 GT with the 2.8 stock engine with 89,000 miles on it. I am seeing low oil pressure at idle when the engine is warmed up. I removed the Oil Pressure sensor and installed a mechanical gague and observed that it is in fact running at 40 PSI normally and 6-10 PSI when idling at high temperature. The oil pressure comes back when the engine is revved up but I am concerned about the drops in pressure. I believe that 5W30 is in there but I am not 100% sure as the oil was changed at a quickie-lube and you never know if they grabbed the right hose or even greased all 10 fittings under the car.

Is this normal for the 2.8 to have somewhat low oil pressure when hot?

I do not notice any other effests of real loss of oil pressure like tempreature soaring, noise in the motor (I do have an exaust leak at the header giving me a "tick" noise.) or loss of power.

Welcome to the forum, That 6-10psi scares me some at idle, with a mechanical gauge (good choice) on your part, might be the screen is clogged, low weight could play some factor, you could try a change, if that doesn`t help would be worth taking the pan off and having a look around down there, misewell replace the pump while its off, lots of things could cause this--but you pretty well nailed it down by using the mechanical gauge . Does the light come on?

Does it happen to be an auto? The high revs or that fact that Fiero's do get drive Sunday church style the bearings that a beating.

90K their probably getting a little loose and your pressure is getting low. Like 3800 says pull the pan (fun job shile in the car) and check the pickup screen but I bet it's ok. While your there put in a high volume oil pump. Be sure and set the pickup to pan height for about 1/4" clearance and you should buy yourself some time before you have to do major work. If you want to spend a couple extra bucks you can replace the crank and rod bearings while your there and get the pressure up even more. Doing it yourself it only adds about $60 or so to the total.

To check the pan clearance I usually dry the pickup and stick a piece of molding clay on the front and back edge of the pickup and then push the pan tightly in place and remove to check the clearance.

Good luck.

[This message has been edited by Dodgerunner (edited 07-21-2006).]

Yes it is an Automatic.

I have no idea as to the history of the GT as it was purchased from a friend who bought it from someone who had it sitting in their back yard for 6 years. Overall the car is in fantastic shape for a michigan car and sitting forever uncovered outside under the eave of a house so all the rain and snow and elements are concentrated on it's roof (caused a sunroof leak that went unchecked for a few years)

I am planning on going through the car completely anyways, but was hoping to put off the engine internals for a year.

I wonder if I can get away with switching to 10W40 for the little bit of driving it will get for the next year or so. I hate doing things like that as pressure is not the same as getting lubrication to everything that needs it.

I usually run the 5-30W in winter and 10-30W spring, summer and fall with just a little bit of Lucas oil treatment for flavor. I have Rodney's magnetic drain plug and I always use a larger filter (P-53 IIRC). About 15K ago (at 85K), I installed a high pressure oil pump and new lower bearings, oil psi at idle did improve for me, sorry I didn't take readings with mechanical gauge.

My thoughts would be to change out the oil yourself to a heavier weight and check it again at 500 miles, then go from there. To my surprise, the oil fill cap on my 86 says 5-30W and my 87 says 10-30W, that could be confusing enough, let alone what a oil change shop manual would list, (if they would even look it up).

If you're not getting any hard psi drops during left hand turns or noise yet, you're catching this early. Let us know the results after your oil change, ok?

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jetman
Silver 86 SE 2M6 4-speed, with "check wallet light"

drop the oil pan, polish the crank, clean oil pickup, and put new rod bearings in. $20 and a days work - mostly polishing
do a search in the TD&C Archives - much stuff on dropping oil pan & low oil pressure - usual cause is bad rod bearing - and for some reason - on cyl #4?

I have a similar problem. I switch to 10-30 and my pressure went up about 5psi at hot idle. When the motor is below 220 and idling pressure is usually fine but once it's starts baking in traffic and peaks over 220 the pressure will drop to 25-30.

Anyway to tell a bad bearing without dropping the pan?

I too have this problem also an 86GT with high mileage engine. I have seen this many times and it is almost always related to bearing wear. Things just wear out. You can try different weight oil etc. but in the end you will replace the bearings or rebuild the entire engine.

I finally got around to changing the oil to 10W40 in the 86GT. Interestingly the new oil in there from the recent oil change only 86 miles ago was very dirty already and the filter looked pretty dirty after I cut it open. I am wondering if the oil change loosened up a bunch of crud. Oil pressure before change to 10w40 was 20psi cold and 6-8psi warm. Oil pressure after changing to new 10W40 and a new filter 55psi cold 25psi warm.... well actually hot. It's 90 degrees out and I drove it for a good long drive the fans were kicking in at stoplights on my way home. Typically I almost never have the fans come on because the radiator is so effective. Temp never went much higher than the fan trip point and went down fast after the fan came on.

So now I am confused. Was it bad oil from the oil change place? was it a plugged oil filter from having a large amount of crud letting go in a dirty engine that has been sitting for years? or am I simply seeing what heavier weight oil does to a car with worn bearings?

Your are seeing the effects of heavier oil. You can run it year round, just warm it up for awhile when it's cold outside.

.

[This message has been edited by Fiero2M6GT1 (edited 03-14-2007).]