Chevy & GMC Vans

I've got an issue where oil pressure drops quite a bit after the van is fully warmed up. Maybe it's normal, but I doubt it.

When cold the van will run a pretty steady 40 psi regardless of RPM, changing slightly with load and RPM. Once fully warmed up the pressure drops to about 20psi at idle and 38psi at cruising RPM.

I'm thinking this means an oil pump replacement is in my near future.

Will I have to remove the front differential on a 2000 AWD to pull the pan? I've done some searching, and there seems to be conflicting answers.

Can I just swap the pump? It seems like there's a high volume pump that requires a new shaft, but would the standard pump just swap right over? I don't want to have to deal with removing the distributor.

The engine's got about 150,000 miles on it, and seems to run really well other than this. I'd like to swap it out before the engine gets starved.

What is more relevant to oil pressure is bearing wear.<mains/rod bearings>

I would not suggest a high volume pump on a engine with 150,000 miles on it because the potential of oil drain back issues.

20psi hot given the miles on it isn't too bad.You'll have to take out the dizzy if you swap out the pump to prime it anyways before the first start-up.

Maybe a better tactic would be a heavier oil.

smd3 wrote:Will I have to remove the front differential on a 2000 AWD to pull the pan?

Yes

I would not trust the oil pressure gauge that is on the dash, use a proper gauge to check your pressure, don't look for trouble, check first .

okie1 wrote:I would not trust the oil pressure gauge that is on the dash, use a proper gauge to check your pressure, don't look for trouble, check first .

An oil pressure tester will run me about the same as an oil pump, if I didn't have to remove the front diff, I'd probably just put one on. I don't think they're available as loan-a-tool's from the auto parts stores. I'll check, but I didn't see it listed online.

I'm military, so perhaps the auto-hobby shop on base has one.

Also, I hadn't considered the bearing wear, that's a good point. I can test the compression to get an idea of the health of the motor, but I can't think of any way to get an idea of the bearing wear.

I guess I'll check the sender/verify the pressure, then move on to a compression test. If compression is good, I'll throw a pump on it and hope for the best.

Where should I tap in to for the oil pressure, should I pull the sender and test it from there?

My 2005 has about the same oil pressure drop when it's warm. I think GM's spec is 6 psi at 1000 rpm warm. Personally with 150k on it, if it was faulty it would have died by now I think.

Have you found out any more on this?
I too can say that the OP drops down noticeably when its hotter.

Are you running 10-30 oil?, maybe try 10-40, or even 20-50 if its summer.
See what diff it makes. Personally, I wouldn't change out operating oil pump unless it dropped to lot less than 20 psi.
Also, Ive heard of starvation issues from the HV pumps.
The regular pump should be more than adequate.

That sounds normal. I wouldn't worry about it. It's a lot of work to change it when it's not really necessary.

IF the oil pressure drops when you step on the gas and goes back up when you ease off, the bearings are bad. If that doesn't cause the gauge to move you shouldn't worry about them. The person that asked what weight oil you are using probably is closest to the problem unless you're already using heavier than new car recommendations.

THanks for all the input, after the post above that said 6psi for every 1000, I stopped worrying about it.

However, I changed my oil this weekend and now my pressure seems to be high. Up to 60psi under load on cold starts. It settles down to a somewhat normal level when warmed up.

I also noticed something disturbing, it looks like someone over tightened the drain plug and snapped the head off. The just pushed the threaded portion into he pan

When I drained he oil, I definitely saw some sort of bolt, minus the head in there.

It would be heavy enough that it won't bother anything. I would plan at some point in the near future to drop the pan just to have a look for peace of mind. You may not need to remove the front diff if you can get the rear of the pan to drop enough to slip your hand into. You could always unbolt the motor mounts and lift the engine from above pivoting on the tranny mount.

I know this is old but since he mentioned conflicting info...on a 2004 AWD you only have to remove the 2(?) bolts to the differential to lower it an inch or two, you do not actually remove it. The other components will hold it in place, your really just lowing it a little for clearance. What you most likely have to do is spin the balancer to get the crankshaft out of the way as that was catching my oil pan, and then you can drop down the pan no problem. Maybe the older vans are different, if that is the case go buy a 2004!

Thanks for the tips Wiley. I'll be replacing oil pan gasket sometime so that helps. What did you have your oil pan off for?

it think it was leaking oil...it got bashed pretty hard a few times during my trip south. I had oil all over my engine so couldn't say for sure, and I also re-fixed my oil cooler lines at the same time so its possible it was fine all the time. Since I had temporary access to my parents garage before coming out to Cali where I knew I wouldnt have one I decided to drop it and seal it with rtv while I could. It lasted about 4K miles including a cross country trip but now I have oil leaking again and think it may be the pan again, but I haven't had a chance to really look, and at the time I didnt know about the front crank seal, so it could be that.

I only sealed it at the 3 places the manual says too. Any reason I cant try encircling the entire pan with the sealant, aside from the pain to clean it would be if it comes off again, I would feel better applying it all around the entire edge.

Many of the machine shops here in town I know.Without question all of them have commented about the Chinese import oil pans for fit,seal,durability.Spend the money for a GM OEM pan is my suggestion.Also there is at your local parts store a die kit with a black light the eliminates the guess work about the source of leak.You clean up everything and add the die.