I had a intake manifold gasket (coolant leak)replaced on the 5.7 lt engine in the 95 suburban 4X4 about 30 days ago. After picking it up from the repair shop I noticed the oil pressure seemed lower than normal. I checked the level and looked at the sending unit, both looked OK. I dont know my way around a GM engine very well but I dont see anyway for the tech to block a port or a oil return by screwing up the intake gasket job, is there ?
I called the guy who did the job and he said the inside of the engine was clean and the job he did shouldnt have anything to do with a possible loss in oil pressure. He asked was I even sure it was too low ? The truck has a gauge and it was reading around 14 psi at idle and 45 psi at 2000 rpm. He said that was in spec. To be honest I couldnt tell him what is was before the repair, it just seemed lower now.

Well that was 30 days ago, now its a different story. It is getting lower daily. I pulled the sensor and put a gauge on it. It drops to 5 to 8 psi range in gear when hot and this is too low.
I have no reason to distrust the work done right before this started but I wanted someone else to check it. I brought it up to the local chevy dealer and had them check behind me and they agree, low pressure and I should start seeing the check gauge warning light on SOON. The dealer said 20/50wt oil  would help but short of a new long block they dont want to touch it.

Any GM tech's have any suggestions other than pulling the pan and checking the strainer ?

I dont have time to do a rebuild or a short block. Well I guess I could do a short block but with the miles on the engine it seems a better case for a long block.
Oh the engine has 151215 mile on it.  

I am open for suggestions

[s]The best line from Apollo 13 was Kraft asking, "Is this an instrumentation problem, or are we looking at a real failure here."[/s]
Read better...

The 5.7 uses sealer instead of gaskets on the end rails of the engine block.  Could the mechanic have dropped the old pieces he scrapped off the block down into the engine?  Or could he have used too much sealer on the end rails when he re-installed the manifold?  If excess sealer dropped into the engine for any reason it will get sucked up against the screen of the oil pick up and could restrict oil flow causing low oil pressure.  It is also possible that the engine is just tired with over 150,000 miles on it.  

The place were I had the work done is a corner Exxon. I had a little coolant leak and it looked like a bypass hose from the water pump so I trusted them to replace the hose. I dropped it off on my way to work in the AM and they called and said it was the intake gasket and they could still knock it out that day. Against my better judgement I said yes. I know I should have done it myself, I am just getting lazy.
The tech is pretty good one and I trust him for normal stuff but internal engine work, NO.
So I cant rule out the possible pick up clogged and extra sealant stuck were it doesnt belong.

I am not blaming the Exxon, it is just so soon after a repair it makes me wonder ?  
It is possible the motor is just tired.

It is common for the intake gaskets to leak on the 5.7s  I have a 97 Tahoe and mine was leaking also.  It is not a bad job, but you have to be careful when setting the manifold in place so that you don't knock the sealer off the rails.

A plugged pick up screen is the only thing I can think of that would be a direct cause from having the work done.  Now you need to decide if it is worth pulling the oil pan off to have a look, or is it better to just get another engine.  My 97 has 130,000 and is still running strong, and I know of many 5.7s that have gone well over 200,000 miles.  It all depends on how well the engine was maintained during it's lifetime.

Did they change the oil after doing the job ?

If not, then whatever cleaner/chemical they used to clean the gasket surfaces could have thinned the oil enough to show low pressure. Brake Clean and Carb Cleaner will do this...

If they DID change the oil, it's possible they put cheap low viscosity bulk oil in it...

I wouldn't panic just yet...
First thing I'd do is dump the oil & replace the oil filter. Try a little heavier oil in an older motor...

It's also possible they dislodged sludge from the intake galley, and it found it's way to the pump pickup screen, or clogged the oil filter...

They changed it when they did the gasket, I dumped the oil and changed the filter a couple of days after the job was done too. The oil didnt look too bad at all.

Anybody know what the book pays for R/R the oil pan on a 95 4x4 suburban ?

Is it a pain ?

Chevy Suburban 1500 4WD

R&R oil pan 2.7
with skid plate add.4
with oil cooler add .5


Chevy Suburban 1500 2WD

R&R oil pan  4.9
with skid plate add .4
with oil cooler add .5    

I've got a '94 K1500 with a 5.7.  I understand that the changeover from TBI to EFI was '96.  Do you know if the TBI manifolds are subject to leaks as you say the EFI ones are?

Thanks, Roadhawk.

3.6 hr it is.

I guess its the next step.

Anyone know if there is a Pan Gasket or is it sealant ?

From what I understand, the problems started with the 1995 model year.  The 3.1 V6 Gm engines also have this problem.

The oil pan has a rubber formed gasket.

Roadhawk is correct.

Arent these the same engines that have been identified with the piston slap?  The engine sounds like a diesel when its cold in the effected engines.  Very hard to sell a truck when it makes all sorts of weird noises.  

Just a guess, but my money is on the strainer being partially plugged.

Danny

Sorry to hear of your situation. I've seen
things similiar to this happen before.  Ask the
technician if he cleaned parts with "surface
conditioning discs" etc. Those made of plastic
fingers are relatively harmless but if they contained aluminum oxide they can destroy bearings in few hundred to a couple thousand
miles or so. The abrasive eats bearings alive.
Cleanliness and attention to detail is very
important. It may be other items that were
previously mentioned as well. Just food for
thought.

Dustdevil out........

[:D]

I have no suggestions other than; pulling the pan, inspecting the pump pick-up and as long as your that far, replacing the pump no-matter.

What is the condition of the rest of the vehicle?

I have a '92 4x4 suburban with 150,000 miles that reads relatively low oil pressure. It is really not that big a deal. With that many miles the cam bearings get a little worn and you are not getting as much pressure up top where the gauge is. Keep an eye on it and make sure pressure is consistant and not jumping around.

Just keep your oil changed and I'll bet you.ll go another 100,000 miles.

BTW, intake leaks on small block Chevrolets are no new problem. They have been leaking since 1955.

With that said, I had a '77 F-150 4x4 (351M)that never had a OP since i got it with 113k on it. It lasted another 50k+ and was sold in decent running condition.  Gotta love those Ford "low" and "high" gauges however they are all relative so one could say the numbers are useless.

Hmmm, I could'nt get the intake to seal on a SB Chev with World Product Heads, I thought it was the castings.

Glad I read this thread...I just did the first oil change since I bought my 1995 Suburban.  Right after I bought it I had an engine oil flush and had them put in Mobil-1 10w30.  The oil pressure was okay--maybe a little lower than I'd expect when the engine is hot.  After the oil change (again Mobil 1 10w30) I have higher oil pressure but now it appears I put in too much oil--5 quarts instead of 4.9 quarts.

I am learning not to pay huge amounts of attention to the dash oil guage.  My old van has had pretty low oil pressure when hot as long as I've had it (6 yrs), and it's way over 200k miles now.  The one time pressure went to zero it was because the sending unit had died.

GunLvr

The electronic gauge isn't the gospel of oil pressure. The key is too make sure it is fairly consistant when it is hot and cold. When it starts going way up and down sporadically you may have problems.

P.S..

You have a LT1 series 5.7...

They were known for minor coolant/oil leaks due to the use of RTV in place of rubber gaskets (as mentioned earlier)...

The biggest problem with oilpan removal is the mess, although transmission pans are worse (no drain plug)... If it's not in the screen or pump area (and it's not just different weather or paranoia), then you're not going to be able to find the problem affordably...

What are you guys talking about?

The oil pump SUCKS oil through the pickup screen.

It would either get sucked up to be cycled to the filter, or fall to the bottom to be removed with the oil change he said he did.

Besides, I would think a oil passage that's plugged up would show HIGHER pressure, not lower.

Debris from engine repairs including gasket material, silicon sealing agents, debris from 3-m discs can and do plug up the screens of the oil pick-up tube. Cavitation can result and can damage an oil pump. Trash can and will stick the pressure relief valve open causing loss of oil pressure. The oil goes first through the strainer, then the pump, then the filter.

Been there and seen that.

Danny

The sensor is post filter. Any debree clogging the pickup or the filter will not promote a higher oil pressure indication and even if it did, the problem still exisits.

I recently replaced the oil pump on my 89 350 4x4 p/u.  Had about 180k on it at the time.  Started having wierd oil pressure gauge reactions, dropping to 0 and then gaining and then to 0 but not related to the rpm. Then steady low pressure.  My mech who is a neighbor pulled the pan and found that the pickup did have some fouling the pump was worn.  Said it was one of the first wearing out oil pumps he had ever seen.  Think he replaced one rod and rod bearing.  Said everything else was fine (a little surprising because I dodn't baby that thing.)

My gut feel is that oil pick-up is partially clogged and you might have some crud in there.

In any case a couple of $20 oil and filter changes might be a cheap double check.  Make sure they put the right weight in.

Man o man, sorry to hear about your problem with your repair job. Did you say Exxon station? Was the mechanic wearing a felt hat with triangular scallops cut out of the brim and a grease rag hanging out of his back pocket? I'll lay you odds he first used a whiz wheel (die grinder with abrasive disc attached) to remove the old gasket and well you can guess where all the debris went. I would pull the oil pan before matters become worse. And stop calling him a technician!

I still wouldn't trust a factory gauge, he's fine. He even said he didn't know what it was before, he just knows it's lower. The numbers he told us are in spec.

I just replaced my engine in my S-10 blazer (4.3 vortec) and it took me 3 times to get the lower intake correctly.

It wasn't till I laid the fattest bead across the back and front block valleys did it finally seal. I also RTV'd the distributor gasket on the third attempt.

I didn't have any of these issue you guys are speaking of after 3 lower intake pulls, but then again, the oil passageways in my engine are brand new.

And, pumps don't suck!

Pumps like these create a low pressure, oil under atmospheric pressure is drawn into the pump.

I used to think they sucked too.

If you ever have a oil pan off, replace the pump as well. Don't replace it with a high volume-high pressure one either.

Asking for trouble.

Danny

It's basically 2 gears drawing oil towards itself.

In [s]theory[/s] guesstimation, yes. In reality NO.

An engine oil lubrication system is no different than a hydraulic system and to throughly understand the operation of such system requires hands on training and actual experience.

I'm not knocking anyone here, at all. His problem simply could be a small piece of trash under the relief valve in the oil pump itself, causing some of the flow to run back into the pan.

Pumps create flow and not pressure BTW, pressure is created by resistance to flow.


Danny

I picked up the truck this AM, NO CHARGE !!!! WTF

I asked the service advisor why NO CHARGE and he said they couldnt do any thing for me so no charge. I asked him if they checked the pressure with a gauge and he stated YES .
SO I popped the hood and looked WAY back to the sensor and it hasnt been touched ? I dont see anywere else they could have taken it from. Am I missing something ????????? Damn I cant even GIVE money away.

Picked up a pan gasket while I was there. I am going to pull the pan and replace the pump while its down.

[b]What is the condition of the rest of the vehicle?[/b]

It runs like a top but its got some dings and I would rate it at FAIR, book wise.

Thank for the advise, I just picked up a pan gasket and I am going to swap out the pump while I am there too.

Your Gomer Pile picture doesnt match up.
The tech is a ASE master, what should he be called. He worked at a new car dealer for 10 years before the Exxon. Be careful you could fall from that high horse your on, the higher the fall the more it hurts [;)]