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post #1 of (permalink) Old 09-13-2000, 03:25 PM
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oil pressure

Can someone tell me what my oil pressure should be on the guage at idle for an 87 GMC Jimmy with a 2.8 in it? Also what should it go up to when I get on the gas?

Thanks,
John

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post #2 of (permalink) Old 09-13-2000, 04:00 PM
 
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Re: oil pressure

I can tell you my 87 GMC Jimmy 4x4 2.8 auto with 147K on it, Starts out the day at around 60[img]/wwwthreads_images/icons/smile.gif[/img],
then when it warms up and driving down the freeway stays around 40[img]/wwwthreads_images/icons/crazy.gif[/img],
but in stop and go city driving with the AC on, and the engine it gets hotter like 210/220, it drops down to around 20 sitting at a light[img]/wwwthreads_images/icons/mad.gif[/img],
but as soon as I hit the gas it jumps back to 40[img]/wwwthreads_images/icons/smile.gif[/img].
what does yours do????

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post #3 of (permalink) Old 09-13-2000, 06:06 PM
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Re: oil pressure

I'd say mine has a problem then. It has 124k miles on it. Its a 5 speed manual. I'm getting a check guages light. My oil pressure is around 15 at idle. I have enough oil in it. It never gets higher than 40. My engine runs at about 180-185 at the most no matter what the conditions. It was running at 245 under heavy load on a hot day but my thermostat had almost gone bad. I replaced it and it runs a lot cooler now. I'd say it may be time for an oil pump. I hope I just have some trash in it or something. I need to change the oil anyway. I just got it put back together three days ago. I hit a tree doing 40mph when I swerved to miss a large deer that ran out in front of me. It hit on the left headlight. It bent the frame in two inches. I got the frame straightened at a shop and put the rest of it back together myself. I got everything to line up great and you cant even tell it had been wrecked.

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post #4 of (permalink) Old 09-13-2000, 06:23 PM
 
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Re: oil pressure

It could also just be your "sending unit" or your "Gauge" if the valves aren't ticking you are probably OK. you may want to try a little thicker oil, that may bring it up some.

About 5K miles ago my oil pressure sending unit came apart and shot oil all over the place[img]/wwwthreads_images/icons/frown.gif[/img]about 2 or 3 quarts in less than 1 minute!
Luckily I was in my driveway when it happened, if I had been driving down the freeway it probably would have seized the engine before I noticed it. I did a post about this awhile back called "Oil pouring out the bottom of my engine"
and several others said theirs had done that too, so you may want to change yours out. It might fix your low reading? and it may prevent a bigger problem down the road? I think it was about $30?

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post #5 of (permalink) Old 09-13-2000, 07:42 PM
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Re: oil pressure

If you have that many miles on it and the new sending unit and changing the oil doesn't do it, then it's probably the cam bearings. They are the most overlooked part in a motor. I've seen more guys do a quick overhaul, like yanking the oil pan, changing the bearings, oil pump, and new rings with a hone job, and maybe a timing chain & cam in the process with out pulling out the motor. And when they fire it up the oil pressure is still down with all new stuff. That cam spins more revolutions than the crank and those bearings always go 1st. Like they say, go to a 40 wt oil and see what happens. Not 10W-40, but 40 period. If she doesn't start knocking later on and you don't have clattering of the valvetrain as they said, then blow it off. She probably has 10-20,000 more in it. When that starts going on, then a bearing will be next to raise it's ugly head. Also, if you overheat that baby too much the oil rings go weak and the blowby will cause a loss in oil pressure too. Tom

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post #6 of (permalink) Old 09-13-2000, 11:20 PM
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Re: oil pressure

Thanks guys. You have been very helpful. I will check on the sending unit first. I did have some valvetrain clatter but it went away. I am still getting a check guages light. It shouldnt be running to hot at around 180. Thats the highest I have seen it get up to. Normally its around 145-150. I have 10w-40 in it right now. I will try just SAE 40. How do I need to check the sending unit and where is it located? Or do I just need to go ahead and try replacing the sending unit?

Thanks again
John

post #7 of (permalink) Old 09-14-2000, 12:30 PM
 
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Re: oil pressure

The sending unit is right by the filter, I don't know anyway to test it's accuracy.
You have to remove the filter to get to it, so it would be a good time for the oil change anyway[img]/wwwthreads_images/icons/wink.gif[/img].
Drain your oil.
Remove the filter.
Unplug the wires from the sender. (three wires on a plug, so they all unplug together)
Unscrew the sender. (you will need to have a very short 15mm open end wrench for this, since there is NO room, I had to cut a wrench in half to do it, and the best way to get at it, is through the drivers side fender well). Good luck, and let us know if this fixes.
(if it doesn't I still don't think it was a waste of money because it may have broken soon and caused more serious problems)
As far as oil straight 30wt or 40wt is a little drastic, straight wt's like that don't lubricate well with a cool engine so you really may get some clatter on start-up[img]/wwwthreads_images/icons/frown.gif[/img]
I would just try some 20-50wt

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