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Thread: High oil pressure problems

  1. #1
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    Question High oil pressure problems

    2000 S-10 4.3

    A few weeks ago I noticed my oil pressure was really high when I first start my truck. I mean like the gauge was up to 80psi. The more the engine warms up the lower the oil pressure gets until it finally settles around 40psi (middle if the gauge) Under load it would go up slightly but then back down at idle. Last week I started my truck up and the oil pressure gauge was on zero. I immediately shut it off. Checked the oil and it was slightly lower than usual but still within the hash marks on the dipstick. I looked underneath and saw a puddle of oil. I tracked it down to the oil pressure sensor/switch behind the distributor. After changing the oil pressure switch and topping off the oil I then had oil pressure on startup but it was high like it was before. Tonight coming home from work the oil pressure dropped to below 30psi on the gauge and I could smell oil burning. The oil was again coming out of the oil pressure switch and dripping onto the Y-pipe and burning. Could a bad oil pump cause the oil pressure to be so high that it cracks the plastic oil pressure switch? Anyone ever have an issue like this? I can't seeem to find anything online about it.

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    Re: High oil pressure problems

    Bad sender again, sometimes you get an faulty one new.
    D.J.

    Typing on a phone, my fingers are bigger than the keys. I also can't spell for crap. Excuse any errors done by stupidity or otherwise.

    Quote Originally Posted by oddball View Post
    1st gen are like the old mutt that hangs out on the front porch,aggravate the crap out of ya,but ya love 'em to death.The ONLY way I will have a 2nd gen is if they a almost giving it away.

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    Re: High oil pressure problems

    I'm going to try a new oil pressure sending unit and hope you are right. I have bought new parts in the past that did not work so it's possible. I may try to find a oil pressure tester to find out exactly what the oil pressure is.

    I guess high oil pressure is better than none at all but I know it's not normal.

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    Re: High oil pressure problems

    Yea prob bad switch. Even if it was 80, the switch should be fine up to tht pressure.
    My Trans Am ran stock 305 gauge/sender about 40. After the 355 build and installed, the new Melling Hi Volume/Press oil pump shoots the gauge over 80 which is about maxxed out for the stock cluster. I have never had the sender leak because of it.
    And I have replaced the sender B4 in the past with an Advance Auto Parts brand ('Wells' maybe at the time). The old sender was leaking at the plug connector area BTW.
    Where is yours leaking?
    2003 S-10 ZQ8 - 262/M5 1986 Pontiac Trans Am - 355/A4

  5. #5
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    Re: High oil pressure problems

    I never had a problem with a defective sender like you have, but I did have a Blazer here a few years ago with a high oil pressure problem.

    When I first got the Blazer it suffered from lifter tick when you first started it each day. It went away in a minute or two and it didn't do it again all day as long as you used it from time to time throughout the day. I bought some STP OPil Treatment to cure the problem and it worked great ....for a while. A few months later I was getting ready to pull out of the driveway one morning when I noticed there was no oil pressure. I checked the oil and there was nothing on the dipstick so I put a few quarts in (3 I think). As soon as I started it it dumped all the oil out the bottom of the engine. I shut it office and got it into the garage so I could take a look and see what was going on.

    What I found was that the oil filter was loose and the o-ring gasket was blown right out. I changed the oil and filter and started it back up. The oil pressure went right up to 80 and it blew the o-ring out again. I took the filter off, fixed the o-ring and re-installed it ...this time over tightening it. Same thing happened again, and again, and again, and ...well ...you get the idea. No one had any ideas other than made a stuck valve in the oil pump, but the Blazer was 2WD so pulling the engine to get the pan out was a last resort.

    I finally remebered putting the STP Oil Treatment in the engine and started to wonder if it was making that pressure valve stick so I changed the oil again except this time I used 4 quarts of oil and 1 quart of Marvel Mystery Oil. When I started it up the gauge went right back up to 80, but this time it didn't blow the gasket out. I let it sit and idle for a while and gradually the oil pressure came back to normal after about 10-15 mintes. I ran it for another hour and then did another oil change with regular oil.

    I already had the Blazer sold when this happened so I told the guy that was buying it what had happened and that I would give him another engine if anything went wrong. I was in touch with him for a few years after he bought it and he never had another problem.

    Don't know if you have a similiar problem, but I hope this helps!
    Stu
    www.s10shop.com
    Middleton, NH

    "You can never have too many S-10s!"

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    Re: High oil pressure problems

    Id check it at the sending unit port using a mech gauge. If its still real high, like over 80psi, you may have a problem. There is a bypass for if the filter is clogged, if it doesnt open pressure will jump up. Id bet you have a faulty switch though.

    Oil pressure over 80 psi is too much, filter will blow off around 100 psi. Ask me how I know. HV pump has no bussiness in a street motor, where you bearing clearances are probably tight. Hence making your pressure stupid high. HV pump is for a "loose" race engine, looser bearing clearances. I dont know why people always just assume HV pump is needed in their mild street app?

    I seen a cam failure create too much metal in the oil, clogged the filter, bypass didnt open, filter blew off. It was in a circle track car.

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    Exclamation Re: High oil pressure problems

    How many miles are on this??.

    If the oil pressure reading is correct(again check that with a mechanical gauge)then the percentages are good it is the pressure relief valve in the oil pump.Fixes in can are short term if at all.I was a life long user of Fram filters until I read and cut open one.Cheap oil filters can and will cause problems.I since have moved to Wix filters.

    Bypass valves being clogged is a symptom and not a cause.You need to find the cause.The main/rod bearings play a large role in oil pressure.....as well as the main oil passage.It doesn't take much to clog those.The only engine we lost in over 30 yrs of racing was one we found a pc of lint from a oil rag.A very expensive lesson.

    You want what everyone wants.To turn the key with confidence to go where ever you want.The oil/oil pressure being the life's blood of any engine,you might want to consider taking it apart to fix it so your sure you can do that.Once you have done that(checked the rod/main bearing)post what you have found.

    We all can suggest tons of checks you can do,but until you take it apart,none of that is fixing it.

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    Re: High oil pressure problems

    The truck has 106,xxx miles on it. I have always used AC Delco pf-52 oil filters.

    Anyways, I took out the old pressure sending unit and it was covered in oil as was the electrical plug. I cleaned the plug and wiped off the sending unit just to look at it. I didn't see any cracks or anything unusual. It was just covered in oil. The manual pressure tester I bought didn't have any fitting that would fit my engine so I couldn't manually check the pressure.

    I went to o'reillys and bought a new sending unit, oil, a new oil filter and a 16oz. bottle of marvel Mystery oil to help possibly clean the oil passages. When I drained the oil it looked clean. The oil in the old oil filter was clean as well.

    I installed the new sending unit and changed the oil and filter. After starting the engine cold (it had been sitting overnight) the gauge read about 40psi. The oil pressure would go way up to 60psi or higher when I rev it up. At 2000 rpm it was maxed out to 80psi or higher on the gauge. No oil leaking but something just doesn't seem right. I'm going to see if I can find another manual tester that has the correct fitting for my engine. That is the only way to know exactly what the oil pressure is.

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    Re: High oil pressure problems

    Agreed.You need to nail down a confirmed oil pressure.Also if you would please follow this logic,the high pressure at one time and than normal oil pressure lends it's self to deduce a defective part.

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    Re: High oil pressure problems

    Quote Originally Posted by 1gary View Post
    Agreed.You need to nail down a confirmed oil pressure.Also if you would please follow this logic,the high pressure at one time and than normal oil pressure lends it's self to deduce a defective part.
    I understand what you are saying but I don't think the oil pressure is what I remember as "normal" at all. 40psi at idle doesn't seem right. 60-80psi at 2000-2500+ rpms definately is not normal. I've searched online and in my repair manual and I can't seem to find what the normal oil pressure should be. I even called the dealership but they were no help at all. The manual only shows what the minimum oil pressure should be at certain rpms. I checked autozone and o'reilly's and neither sells an oil pressure tester. Autozone has an aftermarket manual oil pressure gauge that you wouldinstall if you didn't have one on the dash but it only has a maximum of 40psi. I need one with up to probably 100psi.

    Anyways, thanks for the help and I'll post up anything new.

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