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Oil pressure

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by yotapunk, Jan 3, 2003.

  1. yotapunk

    yotapunk Registered Member

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    First off hello, My name is Tyson and I'm new to this forum. Now my question (and yes I did run a search but did not find what I was looking for)
    I recently purchased a 90 Blazer with a new 350 and rear end. The tranny was shot so I had it rebuilt and installed a tranny cooler. However, now after the truck is warmed up and I stop a signal (in gear) the oil pressure gauge pulsates to 0. This worries me cause I don't want to blow up this motor since this is now my daily driver and tow truck. Is this normal for this to happen? I read in another post that when you drop the tranny and put it back in you have to redo the timing and the vaccum lines?

    Thank you in advance for any solutions that you can think of.

    Tyson
     
  2. Klink K5

    Klink K5 1/2 ton status

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    Try a new oil sender first. Does the engine make any rattling noises at idle? If the engine is new, you shouldn't have any problems with it. What is oil pressure at crusing speed? We'll see what happens!
     
  3. Dale fan

    Dale fan 1/2 ton status

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    Put a mechanical gauge on to really check your pressure. Take it to a shop close by if you don't have one around. The gauges aren't the most accurate things anyway and usually it's just the sending unit is bad. If it's really jumping around then that's probably what it is. Of course if you had 0 pressure you should be hearing some funny noises.
     
  4. yotapunk

    yotapunk Registered Member

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    Rattling noises hmmm, not that I can think of. I did pop the hood yesterday while it was running and heard a little rattling inside what sounded like the valve cover but not loud. It could have been a loose wire holder in the engine compartment.
    At cruising speeds the gauge goes up to about 30. And if when I'm stopped and the gauge shows it going down I can put it in Neutral and give it a little gas and the gauge goes up, sooo? I will take it to a shop I suppose to see if they have an actual gauge cause I would like to put my mind at ease.
     
  5. Klink K5

    Klink K5 1/2 ton status

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    Try a sender first, if that dont show any diffrent, put a decent mechanical gauge on it. That will show you accucal oil pressure. /forums/images/graemlins/thumb.gif Good luck /forums/images/graemlins/k5.gif
     
  6. Dale fan

    Dale fan 1/2 ton status

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    A light tapping in the valve covers isn't the best thing to hear. I'm assuming there is the correct amount of oil (that's probably the first thing you checked). Usually if there is low pressure or low oil you will hear tapping in those valve covers. Take it to a shop before you drive it much.
     
  7. BlaznRebel

    BlaznRebel 1/2 ton status

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    you know its a strange thing but i drove a friends truck for awhile when i was getting my blazer back on the road and when the oil got low his guage did the same thing. When i added oil everything was back to normal. Might check that also. but you probably already have.
     
  8. yotapunk

    yotapunk Registered Member

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    Yeah the oil level was the first thing that I checked so I did add a quart and I am going down now so that I can change the oil. I am going to see if I can get my hands on a mechanical gauge so that I can be sure. I will let you know later this evening if I got this taken care of. Thank you for your ideas.
     
  9. rlepage

    rlepage Newbie

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    rule of thumb is 10# for every 1000RPM. But 30psi is too low for my taste. I run 30psi at idle and 65psi at 2000RPM. The rattling in the valve cover area is probably lifter noise, not enough oil pressure for the lifters. I'd say either the bearing clearances are way too loose or you have a leak in the oil pump pickup or the oil pump gasket. Check the pressure with a good gauge and if it is as low as you say the motor needs to come apart for repair.
     
  10. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Wouldn't the ECM be rather displeased if you took off the electric gauge in lieu of a mechanical one. I think it needs a pressure signal in order to activate the fuel pump. Thats why TBI motors seem to take forever to start when its cold. You could use a tree kinda setup to be able to run the electric gauge and the line for the mechanical. There's also a little plug on the side of the block above the oil filter that would work for tapping into. Its a bear getting them out though. Does the gauge slowly fade back, or does it kinda jerk and twich while its going to 0. The pulsates word is what got me going on that line. Tick tick tick, is a good indication that you have low pressure. Those are the lifters making that noise. Knock knock knock, is when you've got a rod bearing out. /forums/images/graemlins/crazy.gif That should fade out though when you rev it up.
     
  11. yotapunk

    yotapunk Registered Member

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    Well it kind of jerks back to the "zero" line. I am hoping that it is the sending unit though makes sense that the lifters are the cause for the little tick tick tick inside the valve cover. Also found out today that the water pump is leaking. . .Gonna have to go all through this truck like I should have originally.
     
  12. BIG STEVE

    BIG STEVE Registered Member

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    By now im sure you checked it with a manual gauge
    (note)always recheck oil psi with another gauge even if
    stock one was manuel specs for a 90 are 35-55psi at 2000rpm
    with 18psi min at 2000rpm /forums/images/graemlins/shocked.gifyes i know some people
    will freak at that but at idle even 6 psi is ok ideal no.
    But ive checked oil psi on hundreds of eng. from 3hp b&s
    to 2500hp cummins
    if it is truley low put another oil pump on easy on 4wd
    blazer BUT DONT GET A HIGH OUT PUT ONE they are not capatible in a stock motor and your just robing power.
    Old Heavy eguiptment mechanic
    90 jimmy 85 jimmy 02 GMC HD
    outrages insurance payments /forums/images/graemlins/mad.gif
     
  13. yotapunk

    yotapunk Registered Member

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    Actually I still have not been able to check the oil pressure with a mech gauge, but have high hopes for tomorrow.
    ALso I think this is good news the noise coming from the valve cover is not the rockers its actually coming from the vaccum line that hooks into the valve cover. Whether this is good or bad I'm not sure but I'm thinking that its better then rocker noise caused from lack of oil. Yes No maybe so ???
     
  14. yotapunk

    yotapunk Registered Member

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    Quick update and a ?
    The clicking was coming from the PVC valve that hooks into the valve cover, replacing that tomorrow.
    On the oil pressure if the engine oil pressure was actually going down that low after the engine was warmed up. . .wouldn't the water temp be going up? I would assume that if the motor is not getting the right amount of oil then the friction would start to build up correct? I know that the best way to tell is to get a mech oil pressure gauge but do you know where it plugs into the block at? Sorry for not knowing this truck as well as I should but like I said I did just buy this truck and have to make sure the eng, trans is in good working order before I start lifting the thing.

    Thank you in advance, and thanks for all the previous posters for answering my rookie questions.

    Tyson
     
  15. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    It will be at the rear of the engine next to the distributor. You'll have to access it from the driver's side and if it has cruise, you may have to take off the cruise control vacuum module. Take off the air cleaner also. Not a whole heck of a lot of room either. There will be an elbow type attachment there, with an electrical hookup going to it.
     
  16. wrathORC

    wrathORC 1/2 ton status

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    Below 10psi stock hydraulic lifters will start to get soft and next thing you know you will have all sorts of nifty noises. Not long after those nifty noises the valvetrain will start complaining about abuse.

    At 10psi you aren't guaranteed the front two rod bearings or the second from front main bearing is getting enough oil. 18-20psi is the minimum to keep damage from happening. Running at 10psi for prolonged periods is bad.

    A high volume pump does rob horsepower but it's a nice safety device for sloppy bearings. I can't see the purpose of a high pressure pump in anything that doesn't see 6000-8500 rpm all day.
     
  17. wrathORC

    wrathORC 1/2 ton status

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    You've got a thermostat, a radiator, and a fan that is going to do its best job to keep the motor cool.

    You can find the sender for the gauge next to/behind the distributor just out of sight. If you've got cruise control there isn't much room.

    You can always stick a second gauge next to the oil filter. I can't remember, but that might be where the computer gets its oil pressure from.
     

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