OIl pressure help

Tyson

Well-Known Member
Posts
597
Reaction
0
Would anyone on here local to OC (HB would be rad) happen to have a mechanical oil pressure gauge and wants to drink some beer and help me out for a couple hours?

I Just bought this 90 Chevy blazer and after rebuilding the transmission, fixing the wheel that fell off driving down the road, I am starting to notice that when I'm driving the oil pressure gauge is around 30. However, when I stop it drops to the "zero" line. I am very hopeful that it is a bad sending unit cause the truck seems to be running fine. To all of the people that I have talked to they say to grap a mechanical oil pressure gauge and see if my stock gauge is taking a crap (hopefully).

Any help and/or advice is appreciated.

Thanks

Look at me, I can fly

Check It</font color=red>
 

Stan

Well-Known Member
Posts
308
Reaction
0
Yeah, make sure you check it with a mechanical gauge first. Since I didn't have access to a gauge at the time, I just replaced the sender and the sender is not the problem. But I've also been running around on 0 psi the last two years according to the stock electrical gauge.

I'm not here, nor was I here, nor will I ever be here.
 

gary

Well-Known Member
Posts
2,057
Reaction
13
i think i can tell the problem from here....IT'S NOT A TOYOTA!!!!!!
 

drtdevil93

Well-Known Member
Posts
1,769
Reaction
11
what weight oil is in it? putting a thicker oil (20w50) will bring it up.

erik
 

rdc

- users no longer part of the rdc family -
Posts
5,788
Reaction
7
IS IT AN S-10 BLAZER OR A FULL SIZE CAUSE MY FREINDS WOULD ALWAYS DROP TO ZERO WHEN HE CAME TO A STOP BUT IT ALWAYS HAD PRESURE HIS WAS AN S-10 BLAZER WITH A 4.3 V-6
 

jeff

Moderator
Posts
7,422
Reaction
314
Thick oil is even thicker in cold weather and is a bad idea. 5W-30 is better in cold weather than 10W-30 because it will initially act as a "thinner" oil and flow easier throughout your engine. In theory the two oils will have a similar viscosity and protection once they warm up. If you live in a really cold climate you can actually destroy an engine if you run the wrong oil and attempt to run it. A bunch of Corvettes that were being moved in a parking lot snapped their crankshafts because of a cold weather oil related problem. That's when the Vette switched to synthetic oil... Orange County and the surrounding area does not count as a cold climate though. If it were my vehicle I would NOT run a high viscosity oil to make up for lost oil pressure... I'd try to figure out why it's not maintaining a sufficient pressure and then fix it the right way.

Or... run it til' she blows!

Aloha
 

hoeker

Well-Known Member
Posts
2,004
Reaction
101
if the engine is getting old and a little tired, a heavier weight oil is a viable means to increase oil pressure. engine builders will "loosen" an engine up depending on the oil you are planning to run. with age engines naturally loosen up a little. i would have total confidence running a 20w 50 in a 100,000 mile engine that required 10-40 when new. synthetics also typically reduce oil pressure.

if the engine is fresh or low miles definitly try to find the problem.

remember higher viscosity oil costs horsepower too, so thicker oil is not necessarily better, even in race applications.

The people who are crazy enough to think they can change the world, are the ones who do.
 

ntsqd

Well-Known Member
Posts
2,429
Reaction
27
See, now if you'd bought an earlier truck the gauge would have been mechanical which guaruntees absolutely nothing. :)

Be choosy about the mechanical gauge you use for comparison. Not all of them are accurate either. If you find a liquid filled gauge that isn't a 'race' gauge (i.e. is an industrial part) the odds of it being a decent gauge are with you.

TS

I used swerve around my halucinations, now I drive right thru them.
 

Dave_G

Well-Known Member
Posts
2,859
Reaction
307
More than likely it's the cam bearings. Too much clearance and the oil pressure at idle goes in the toilet. Small block chevys are famous for this especially if this is a rebuilt motor. Most rebuilders don't bother checking the cam journal clearances after installing the bearings. They just hammer them in and go with it.

Just my $.02 worth...

Dave

"I know it all, but I can't remember most of it..."
 

Tyson

Well-Known Member
Posts
597
Reaction
0
So if that was the case Dave, then what is the solution? Is this something that will end up grenading the motor or something that will last? As far as I know this was a new motor 8K miles beofre I got it and I have put on maybe a thousand.

Thanks

Look at me, I can fly

Check It</font color=red>
 

Dave_G

Well-Known Member
Posts
2,859
Reaction
307
RE: "So if that was the case Dave, then what is the solution? "

If in fact the cam bearings are the problem you would need to install new ones and check the clearances before reassembly. When I built my 400 motor I built a fixture and custom machined and fitted the cam bearings to the block and cam. But before you do all that I would investigate the systems oil pressure with a mechanical gauge first to verify that the system really is low at idle and not just bogus readings from the sender or stock gauge. Try that first and see where it leads you.

Dave

"I know it all, but I can't remember most of it..."
 

hoeker

Well-Known Member
Posts
2,004
Reaction
101
not an expert on small block chevy's, but i was always told the single biggest cause of low oil pressure was the rod side clearance. since the engine was recently rebuilt, the guy that ground the crank could have made the journals too wide. definitely check the pressure with another gauge first, but at least rod side clearance can be checked easily by dropping the pan in the truck, and using feeler gauges. while the pan is off, you could also check your other bearing clearances and know what you have. peoples definitions of rebuilt vary drastically, especially when selling a truck. maybe they just threw new bearings in and rings and called it rebuilt, not making sure tolerances were right.

while definitely not good, there ale a lot of vehicles that ran for thousands of miles that way.

The people who are crazy enough to think they can change the world, are the ones who do.
 

Tyson

Well-Known Member
Posts
597
Reaction
0
Well I am definately going to do the gauge test first and go from there. But the guy I bought the truck from is a friend and I just found out that it was a crate motor direct from Chevy, so who knows maybe it's still under warranty?? That would be cool huh.

Look at me, I can fly

Check It</font color=red>
 

hoeker

Well-Known Member
Posts
2,004
Reaction
101
just wanted to provide a little information from Autometer on racing gauge accuracy. autometer is the world leader in aftermarket race gauges, and while they sponsor my team, i would not use their product if it wasn't accurate and consistent. autometer is located here in the midwest, and therefore maybe not as popular on the west coast, but they are the best.

<font color=blue>Auto Meter gauges and tachometers are calibrated to a SAE (Society of
Automotive Engineers) Class A specification at the factory ( this is the
highest level established) . Class A is the standard that test equipment
is built to.
The environment in which a gauge lives, has a huge part to play in the
accuracy and life span of the gauge. High vibration, dirt and moisture
can be detrimental to the accuracy and service life of a gauge.

Mechanical gauge technology has been around for approximately 100 years.
Auto Meter standards have brought this technology to it's highest level
of quality. Only so much can be done, we have done it ! We have
manufactured our products to be accurate to SAE standards, affordable,
and available.

We have been manufacturing gauges that are more accurate. Our electric
full sweep gauges have greater accuracy through out the full sweep. This
is new technology, and of course is more expensive, but yet still
affordable.

You cannot seriously race with test equipment, you would give up
numerous benefits : durability, affordable pricing, availability, choice
of sizes, style, service, contingency programs, sactioning body approval,
and warranty just to name a few</font color=blue>

The people who are crazy enough to think they can change the world, are the ones who do.
 

ntsqd

Well-Known Member
Posts
2,429
Reaction
27
This disclaimer: "The environment in which a gauge lives, has a huge part to play in the accuracy and life span of the gauge. High vibration, dirt and moisture can be detrimental to the accuracy and service life of a gauge." is why I advocate the use of a gauge known to be good and has not been in a vehicle for any period of time.

I don't know what the name of the stds industrial gauges are held to is, but I doubt they are SAE. A friend works in instrumentation at a local power generating plant. 4000 psi, 800-1200 degree liquid steam. He recently bought a master temp gauge that cost something like $1200. This is the gauge that they use to calibrate every other service gauge to. I doubt that the Autometer gauges can match it's repeatability and accuracy. It isn't that the Autometer gauges are bad, they are reputable gauges known for quality, it is that they couldn't afford to build such a gauge to be sold for vehicle mounting at a Summit price.

TS

I used swerve around my halucinations, now I drive right thru them.
 
Top