99 Suburban .. low oil pressure????? Help


dcaves2
03-16-2006, 01:38 PM
My 99 GMC suburban with a 7.4 and 119K, when started registers the oil pressure just over 40 - then when it warms up it goes to 7 on a idle. When I'm driving it it registers at least 41 or 39. I had the oil sensore replaced and no change. Could this be a bad oil pump? Is the oil pump worth changing? Does anyone think this is a urgent matter to do a overhaul right away or can I go for a while without blowing the whole engine up?

P.S Last tune-up all spark plugs were dry with no oil residue, and it passed emmissions with no problem. It also has a slight "rumble" after warming up and on a idle. What do ya think?

horse482
03-16-2006, 01:54 PM
What brand of oil filter are you using? What brand and weight of oil are you using?

dcaves2
03-16-2006, 01:56 PM
Im not sure on the brand of oil filter, I do know that I have a 10/30 penzoil in though. Oil was changed about 2000 miles ago.

Not_ Me
03-17-2006, 10:22 AM
My 99 GMC suburban with a 7.4 and 119K, when started registers the oil pressure just over 40 - then when it warms up it goes to 7 on a idle. When I'm driving it it registers at least 41 or 39. I had the oil sensore replaced and no change. Could this be a bad oil pump? Is the oil pump worth changing? Does anyone think this is a urgent matter to do a overhaul right away or can I go for a while without blowing the whole engine up?

P.S Last tune-up all spark plugs were dry with no oil residue, and it passed emmissions with no problem. It also has a slight "rumble" after warming up and on a idle. What do ya think?



Was down this road with my 99 only it is the 350. Had the pan pulled and found that the main bearings did not look as if any of them had a load but the front and rear. So it was pulled and sent off to the machine shop. Put it back in and in and no change. Now I am P OHD. Wait it gets better. Keep in mind that an after market warranty is paying for these repairs. The machine shop is the best in the world listening to them. In less than 300 miles it throws a rod out the bottom taking the block out on the way. Hauled it back to the shop. Not us, we just pulled it and installed it. Warranty says you must pay to find out what happened. If it is a covered part we will pay for the part. It was 1 full year before I ever drove it again. Turns out that the cam bearings in the first engine were worn letting the oil pressure drop. It only had 80,000 mi. at the time. The rod was the machine shops fault. Found the nuts for the number 1 rod in the pan. Machne shop says no not us we said it needed line bored and have new nuts? Warranty would not pay for this. Has anyone in this shop ever heard of a new invention called loctite? Loc what? The warranty says we will pay for the rod that failed and the cost to install it. Install it in what,there is a big hole in the block. Thats not our fault you drove the car after you knew there was a problem. What? Do you call coasting to a stop after the engine blows contuied use? Well ah um yeah,we will get back to you. Yes 1 freaking year. Lost 2 grand in value on the thing and could not even drive it.Anyway, You could have some worn cam bearings. As long as you have 35 psi at 2000 rpm it should be ok. The low pressure at idle is not very good. Try a real test gage on the system and see what you get. Mine showed 10lbs on the gage but was 19 - 20lbs on a test gage. There is a place by the oil filter you can access the oil pressure system. Good luck.

dcaves2
03-17-2006, 06:19 PM
Wow! Actually that was helpful. What causes low oil pressue exactly?

robos88
03-23-2006, 12:58 PM
Wow! Actually that was helpful. What causes low oil pressue exactly?

Worn out bearings... Bad oil pump...

dcaves2
04-03-2006, 03:16 AM
Is replacing an oil pump very difficult by a novice? Or expensive?

horse482
04-03-2006, 04:02 PM
To replace the oil pump you need to drian the oil, drop the oil pan and then pull the bolts that hold the oil pump in. If you don't get a new pickup you will have to pull the old one and put it in the new pump, they can be a bear some times. The hardest part is pulling the oil pan. Hope this helps.

aztecf
04-04-2006, 09:54 AM
Leave it alone!!!!, 7 psi at idle is more that plenty, as long as it goes up above 25psi while driving its fine>

Jeff

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