Oil Pressure on my truck...Your Thoughts??

Jelly · Oct 16, 2003

Well, as some of you know, I'm running Pennzoil Long-Life 15w-40 with a SuperTech filter in my Chevy pickup with a 4.3L V-6. BTW, the oil pressure gauge shows 0 to 60 p.s.i.

Anyways, from startup and until the engine starts to warm up, the pressure runs anywhere from 40 to 50 P.S.I. depending upon how long the engine has been running and the R.P.M.'s it's turning.

When the engine fully warms up (which takes quite a while!), the pressure runs about 33p.s.i. or so.

Do you all feel this is too high??

JohnBrowning · Oct 16, 2003

No, Those pressures are not high at all. While they are just fine from a warranty stand point I personel like to see them higher then this.

From a warranty stand point anything above 6psi At idle and is acceptable as long as pressure comes up with RPM'S.

I like to see at least 65psi between 1800-2000 RPM with oil at temp with 10W30. When I was a young aprentice the rule of thumb was 20-35 PSI at idle with 10 psi per 1000 rpm's.

userfriendly · Oct 16, 2003

That rule of thumb has not changed, add another 50 PSI for Ford Clevlands.

The weak link in the even fire 4.3s are the cranks. When and if worked hard, such as in a marine application, rod and main failures may occure.
The standard low volume oil pump has its by-pass set for 35 PSI. When the oil is cold the pump by-pass port cannot lower the pressure to the factory setting.
The prefered fix for low engine oil pressure is to replace the low volume/pressure pump with a 63 PSI high pressure/volume pump and use the steel pinned pump drive.
Using a higher viscosity engine oil will also raise the oil pressure, but at the risk of lowering the volume of oil flowing to the rod and main bearings.

Schmoe · Oct 16, 2003

Got the same set up on my '93 GMC. Oil pressure runs about 50 when first started. But after it's been run to get to work, it drops to about 30-ish, at idle though. When it's running around 2K rpm, regardless of temperature, pressure still hovers around 50. If yours is doing that, I wouldn't worry about it. I'm running 10W-30 Pennz. in mine.

jason07-1zzfe · Oct 16, 2003

My car ('89 325is) specs 7-28psi at idle and 57-85psi at redline.
Right now with RL 10w40 idle is 12-15 hot, but with 10w30 is closer to 8-10. Goes up quick: 30psi @ 1.5k. 40psi@2k, 50-55@3k and then only increase a couple psi per 1k after that. Max seems to be no more than 65psi at redline.
So my concern is both idle and max are close to the lower limits. Does this mean the engine is worn or is there that much variation in new engines(why would they give such a big range). Engine has 182k so some wear is not out of the question

Just wonder why they give a huge range.

[ October 17, 2003, 10:42 AM: Message edited by: Jason Troxell ]

pmt · Oct 16, 2003

I have a new 2003 GMC Sierra 1/2 ton with the 4.3L engine - about 7500 mi on it now. With 5W-30 oil (whether synthetic or dino) with fully warmed oil - gauge reads 45 psi at 2000 engine rpm and 25 psi at idle rpm. Seems a little low, but owner's manual shows 40 psi as typical oil pressure when going down the road - so must be normal.
An off topic question: this engine in my truck has a narrow rpm band (about 1100 - 1400) that feeds a slight (but easily noticeable) vibration into the cab - steering wheel, etc. Other than that narrow rpm band the engine is pretty smooth. Has anyone else noticed this vibration on their late model 4.3L GM engines?
Thank you.

MRC01 · Oct 16, 2003

quote:

Originally posted by Jelly:
When the engine fully warms up (which takes quite a while!), the pressure runs about 33p.s.i. or so.
Do you all feel this is too high??

No problem at all. Ford's '96-'01 DOHC Cobra V-8 engines run around 85 PSI in the mid to upper RPM range when fully warmed up on 30 weight oil.

dickwells · Oct 16, 2003

PMT - I have a 2002 Silvo 4.3 with 41K miles and do not notice vibration. Is yours std transmission? Mine is Auto. My oil pressure runs at 60 going down the road 1500+ RPM. It will drop a little below 40 fully hot at a stop in gear.

Jelly · Oct 16, 2003

Thanks everyone for all your help.

Guess what made me worry is that the oil pressure gauge only goes to 60p.s.i.

During the first few minutes of operation, every time you glance down, you see the needle hovering near the upper end of the gauge...

BTW, another funny thing...like I said, it runs about 33p.s.i. or so when fully warmed up and driving along.

But when idling (and fully warmed up), it still runs 30p.s.i. Weird?

[ October 17, 2003, 01:22 PM: Message edited by: Jelly ]

pmt · Oct 17, 2003

dickwells - I have the 3.42 rear end. I doubt if is a AT problem, because with the tranny in neutral if I slowly bring engine RPM up into the 1100 to 1400 range, the vibration is right there - same as when I'm driving. But I suppose if the AT had a component out of balance, it could be the culprit. I think I'll stop at the GMC dealer's on my way home tonight.
Thanks all.

edhackett · Oct 17, 2003

Jelly,

Those are _exactly_ the same oil pressure numbers I see in my 1990 GMC with the 5.7L using Chevron Delo 400 15W-40.

dickwells · Oct 17, 2003

PMT - Thanks for the feedback, one more thing to try, take off the serpentine belt and see if the vibration goes away with it. If it does then the fan or some other accessory is at fault. Could also be a bad balancer but the shop would need to determine that. Good Luck, RW

Drew99GT · Oct 17, 2003

My Dad's 98 4.3L has the shakes as well, serious shakes at idle, and even worse at about 1200 rpm. It does however have over 130K.

As far as oil pressure, it has steadily gotten lower and lower with age. The dudes at the garage that fixed the intake gasket leak put in 5w-30 and the hot idle oil pressure is now below 20 after severe stop and go driving; around 15-18 psi I'd say. It still goes to about 35-40 psi hot when the rpms are around 2500. With 10w-40s and 15w-40 weights, the idle pressure never goes below 20 and usually stays more at around 25.

Gary · Oct 17, 2003

quote:

Originally posted by Jason Troxell:
My car ('89 325is) specs 7-28psi at idle and 57-85psi at redline. Right now with RL 10w40 idle is 12-15 hot, but with 10w30 is closer to 8-10. Goes up quick: 30psi @ 1.5k. 40psi@2k, 50-55@3k and then only increase a couple psi per 1k after that. Max seems to be no more than 65psi at redline.

Jason, my 330ti and 325 have 20 psi at cold/hot idle, 60/50 psi cold/hot above 3000 with the same rise, this with Amsoil 20W-50. GTX 10W-30 / ARX has idle the same, 3000 hot about 45-50 with quicker rise times. I'm going to 0W-30 afterwards.

Chris B. · Oct 17, 2003

My 2003 Silverado with the 5.3 V8 is at 45-50psi cold idle and 34-40 hot idle with 5 and 10w30. It goes up close to 80psi WOT and 55psi or so crusing at 2,500rpm.

pmt · Oct 17, 2003

Dickwells - I have the AT also. Maybe I should have the dealer's service shop check out my engine's vibration - predict they will say that "they all do that". But worth a try. Also, I don't know why your oil pressure reads so much higher - perhaps just cheap oil gauge variation in accuracy. I think the only way to know what actual oil pressure is would be to check with a known accurate external gauge. Thanks.
pmt

jason07-1zzfe · Oct 17, 2003

Sure it's not tranny shudder? Ours was starting to get that.

dickwells · Oct 17, 2003

PMT - What rear end ratio? Mine is a 3.42 and I don't think they offer the 3.08 or whatever with auto anymore.

Schmoe · Oct 17, 2003

I get the same shakes as well at idle. For a while there I thought that I had the wrong plugs in or something else. But it purrs along. Kind of wierd, but when you hit the gas, it smooths out. Makes me think back to the old days when you had a higher lift duration cam. But that was then, this is now.

Jason8691 · Oct 18, 2003

I have a 03 S10 with the 4.3L and on startup with GC 0W-30 the pressure is around 58-60. When the oil is hot and its idling in gear the pressure is around 26-27, idling in park its about 33.

Oil Pressure on my truck...Your Thoughts??

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