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ksengage31, ASE Certified Technician
Category: Car
Satisfied Customers: 61
Experience:  Master Certified Technician Specialist in driveability and engine diagnostics.
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1992 Isuzu: head indication of bad bearings

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1992 Isuzu rodeo(3.1 V) had a coolant leak in the head gasket...
pulled heads and replaced gaskets....engine started fine....but I noticed the oil pressure
gauge was reading low..very low..close to idle
Before the gasket replacement it was reading 30 -50 or so...
Repalced oll pressure difference.....
What could cause the gauge to read so low after the work when before the work it was reading much highter...measured the pressure at the sending unit...and it reads in between..about 15 - 30

Engine runs real quiet and smooth with no indication of bad bearings or anything...

Any ideas...

ksengage31 :

Hi, my name's XXXXX XXXXX id be happy to offer you some assistance.

ksengage31 :

Im assuming you've changed the oil and filter after repairs completed, yes?

Customer: replied 5 years ago.
Yes, filter and oil changed
The best thing to do next, is test the oil pressure with a gauge set other than the one on the dash. You definately need to confirm if that psi reading is accurate or not. Most mechanical oil pressure gauge sets will have several adapters to use to thread in to the engine block with sender removed.

This will help you determine where to look. I agree that you would expect to hear some noise with a pressure reading that low, but its still possible the rod bearings have worn thin. Coolant has a tendency to errode the bearing material quickly, if there was coolant in the oil long enough this could very well be the case.
Customer: replied 5 years ago.

Yes, and I would beleive that except that the 20 -25 lb drop happened right after

the head gasket replacement...the first time I started it...I saw the pressure gauge way down...down about 20 lbs from where it was before...


and now here is exactly what it does...


--when cold and I start it the pressure gauge reads about 55

--iot stays there for about 5 minutes at road speeds and then drops to about 30 lbs.

--when it goes to this point it reads about 10 on gthe gauge...


The mechanical gauge shows about 15 - 20 at idle andXXXXXspeeds..


So my question there any thing in the oil path,,,,of the oil pressure sensor(like partially blocked with something) that can cause this erratic reading..or does it really just mean...the engine decided it was over after the head gasket repair?






You can check for a blockage in the passage under the sender, using some mechanics wire or similar. However it sounds like you just have some excessive wear to the bearings, either rod or camshaft. The general rule for oil pressure is 10psi at idle minimum, and 10psi more showing for every 1000 rpm above idle. Your just around the minimum spec, and while it sounds like there is some engine wear here i would suggest if no noises or other symptoms are present to drive the vehicle and just monitor the condition. If it doesnt worsen, you may have alot of use from this engine yet. Only other option is complete teardown, rebuild, or engine replacement.
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Customer: replied 5 years ago. noises..very smooth and quiet...


Thx. for your input....