I have a question for the hive mind. I own a 1993 K2500 (3/4 ton 4X4) Suburban with a 454. I tow a single axle 6X10 enclosed trailer on occasion. I recently had a motor swap done, and had a used engine installed. The oil used after the swap was Valvoline 10w30. Upon startup, oil pressure climbs to ~45 psi (gauge has been tested and is accurate). After the engine warms up to operating temp, the oil pressure starts to fluctuate. While running at interstate speeds, pressure stays around 40 psi. However, when the vehicle slows to idle, the pressure drops down to about 5 psi. It has been suggested to me that the problem may be having the wrong viscosity oil. Does this sound right to y'all, and if so, what viscosity should I be running? Thanks for y'all's insights.
Oil Pressure oddities
- Thread starter Alispark
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5psi at hot idle os more indicative of motor problems than it is of using the wrong oil.
Sorry.
Sorry.
I'd do a compression test before anything else, cheap and easy to do and will tell a lot..
Sounds like worn main bearings. I'd replace the oil pressure sender first to confirm.
I think the oil light will come on below 5 psi by the way.
One last thing, in a quick Google:
Possible causes for low oil pressure:
1. Improper oil viscosity
2. Malfunctioning oil pressure switch
3. Not enough oil
4. Clogged oil strainer
5. Deterioration of oil pump
6. Worn oil pump relief valve
7. Excessive clearance in various sliding parts (e.g., bearings)
Possible causes for low oil pressure:
1. Improper oil viscosity
2. Malfunctioning oil pressure switch
3. Not enough oil
4. Clogged oil strainer
5. Deterioration of oil pump
6. Worn oil pump relief valve
7. Excessive clearance in various sliding parts (e.g., bearings)
Sounds like a typical worn out motor to me.....put some thicker oil in it and drive it till u figure out what your gonna do with it....
a lot of those engines did that the 350 was also one of them it will run fine i saw tons of them with this and they all still ran well..
Originally Posted By: crazyoildude
a lot of those engines did that the 350 was also one of them it will run fine i saw tons of them with this and they all still ran well..
I agree, Where would you find a used under 200,000 mile '93 TBI 454 these day's, It may be worn....If it ain't knockin' don't worry about it!
a lot of those engines did that the 350 was also one of them it will run fine i saw tons of them with this and they all still ran well..
I agree, Where would you find a used under 200,000 mile '93 TBI 454 these day's, It may be worn....If it ain't knockin' don't worry about it!
Originally Posted By: jdavis
I'd do a compression test before anything else, cheap and easy to do and will tell a lot..
a compression test will tell you how the rings and valves are but not the main,rod or cam bearinga
I'd do a compression test before anything else, cheap and easy to do and will tell a lot..
a compression test will tell you how the rings and valves are but not the main,rod or cam bearinga
Put in Shell Rotella 15w40 , maybe even Mobil 1 15w50 , BBC's dont mind thicker grades
Oil Pump clearances or worn main bearings.
All SBChevy and BBChevy motors will show x PSI per 1000 RPM. I like about 30 PSI at idle and +5 PSI per 1000 RPM (so 50~60 PSI @ redline).
But ... these motors are amazingly tolerant of a wide variation in oil pressures. I've seen examples with low idle pressure like yours go another 100,000 miles.
You could drop the pan and measure your main bearing clearances. Rebuild or change out the oil pump, screen, and make sure that the pickup is not picking up air at the same time. No need to pull the motor. The level of the pickup should be checked and set (brazed or staked) during installation, maybe that wasn't done properly.
All SBChevy and BBChevy motors will show x PSI per 1000 RPM. I like about 30 PSI at idle and +5 PSI per 1000 RPM (so 50~60 PSI @ redline).
But ... these motors are amazingly tolerant of a wide variation in oil pressures. I've seen examples with low idle pressure like yours go another 100,000 miles.
You could drop the pan and measure your main bearing clearances. Rebuild or change out the oil pump, screen, and make sure that the pickup is not picking up air at the same time. No need to pull the motor. The level of the pickup should be checked and set (brazed or staked) during installation, maybe that wasn't done properly.
Originally Posted By: Chris142
Originally Posted By: jdavis
I'd do a compression test before anything else, cheap and easy to do and will tell a lot..
a compression test will tell you how the rings and valves are but not the main,rod or cam bearinga
Right, and if those are in good shape then it's not out of the question to drop the oil pan and replace the bearings from underneath without having to replace the motor.
Originally Posted By: jdavis
I'd do a compression test before anything else, cheap and easy to do and will tell a lot..
a compression test will tell you how the rings and valves are but not the main,rod or cam bearinga
Right, and if those are in good shape then it's not out of the question to drop the oil pan and replace the bearings from underneath without having to replace the motor.
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Step 1 would be to verify the pressure with a mechanical gauge. Have you done this?
1) mechanical gauge
2) Clogged Oil Filter
3) Worn out Oil Pump
4) Worn crank and rod bearings..dont forget the cam bearings.
5) Complete Overhaul
6) Install used or reman engine when yours stops pumping oil at all.
7) Sell As Is/Where Is.
Those are pretty much your options.
2) Clogged Oil Filter
3) Worn out Oil Pump
4) Worn crank and rod bearings..dont forget the cam bearings.
5) Complete Overhaul
6) Install used or reman engine when yours stops pumping oil at all.
7) Sell As Is/Where Is.
Those are pretty much your options.
Originally Posted By: Alispark
Unfortunately, dropping the pan on this requires either raising the motor, or removing the front axle. Not something I can do in the driveway.
Why ARE so many vehicles made where you have to basically pull the engine to get at the oil pan? Do they not want us removing them?
It just seems terrible when a plug gets stripped and swapping pans could be an easy fix......or putting on a new gasket to fix a leak could be a few minutes and a few dollars.
Unfortunately, dropping the pan on this requires either raising the motor, or removing the front axle. Not something I can do in the driveway.
Why ARE so many vehicles made where you have to basically pull the engine to get at the oil pan? Do they not want us removing them?
It just seems terrible when a plug gets stripped and swapping pans could be an easy fix......or putting on a new gasket to fix a leak could be a few minutes and a few dollars.
I'd run M1 15W-50 in it and call it a day. Don't worry about it until it starts knocking. Use a cheap non restrictive oil filter like the OCOD. The 6x10 trailer is nothing - a BBC laughs at that. My 92 Suburban BB sees a little under 30psi at hot idle on 10W-30, but it's a low mileage engine that's had synthetic oil it's whole life. Most of the miles have been hard though, towing a 12,000 lb trailer.
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