repost: Oil pressure light
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5.0 and 5.7 Discussion, repost: Oil pressure light in Cadillac Engine Technical Discussion; Ok so a new issue has been bugging me and i need suggestions.. Recently after my engine gets nice and ...
  1. #1
    walk3rb0h is offline Cadillac Owners Member
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    Angry Oil pressure light

    Ok so a new issue has been bugging me and i need suggestions.. Recently after my engine gets nice and hot my oil pressure light has been coming on when i come to a stop.. I have taken it into the shop and after some dye and a pressure test we are not able to find any leaks in the system. This only happens when the engine is hot.. I have also noticed that it become much more sluggish after it gets hot.. slow accelerations and such.. kinda wierd that it drives alot better cold eh?

    I know i need my TCC swapped out but this problem seems unrelated.. Happens if i drive at 30 miles an hour for 30 minutes too..

    Anyone got any ideas?

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  3. #2
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
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    Re: Oil pressure light

    I would get a gauge on the oil pressure right away.

    Swap to 15W40 oil and see if the problem comes back. How hot is "nice and hot"?

    How many miles on it? Is this the 88 Brougham? Olds 307?

  4. #3
    walk3rb0h is offline Cadillac Owners Member
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    Re: Oil pressure light

    yea its an 88 with a 307 and nice and hot as in been driving for atleast 15 minutes.. not sure on temo.. took it to a shop cant find a leak anyplace. and pressure seems good.

  5. #4
    carnut is offline Cadillac Owners Master
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    Re: Oil pressure light

    What is meant by "seems good" first thing a good shop would do with an oil pressure light on would be to verify oil pressure with a gauge screwed into the oil sender hole. On most engines the light turns on when oil pressure is below 5 lb. If the gauge reads above that when the engine is warm, then suspect the oil pressure sender is electrically faulty.

  6. #5
    joe_padavano is offline Cadillac Owners Member
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    Re: repost: Oil pressure light

    First, find a new shop. An oil pressure light is NOT an idication of low oil level, it's an indication of low oil pressure. A dye test looking for leaks is irrelavent and a waste of money.

    The first thing you should do is temporarily hook an oil pressure gauge up to the pressure port on the engine and see what's really going on. The oil idiot light is pretty worthless and the problem could be a faulty sensor or it could be a serious problem. If the gauge shows good oil pressure, a replacement sending unit is an easy fix. If the oil pressure on the gauge ever falls below 25-30 psi under any conditions, you've got a problem. It could be a worn oil pump, but if the motor has a lot of miles the more likely cause is worn bearings. As the oil warms up it thins out and low oil pressure is more likely under those conditions.

    Unfortunately, if it really is a worn bearing problem, you're looking at a new or rebuilt engine. In the meantime, you can try heavier weight oil (10W40 or 20W50) to try and bring the oil pressure back up and help the engine live longer.

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    walk3rb0h is offline Cadillac Owners Member
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    Re: repost: Oil pressure light

    the only reason for the dye is that ive been having a slow puddle under the car form over the last couple of weeks and something is leaking under the hood near the intake that is making an interesting smell and a small amount of smoke from time to time and I wanted to make sure there are no leaks.. the engine only has 80k on it so i really really hope its not berrings.. oil pump i can handle..



    as for the smoke im not a mechanic so i dont know what the part is called but there is a crome slinky type hose connected to what looks like the intake duct leading to the air filter that was clean a few months ago and now is covered in black nastyness that just so happens th be right in the location of the random smoke i get.
    we also added a die to the coolant to see if maybe that is the culprit.

    now ive been told that the only fuel filter in the 307 is in the carb is that true?

  8. #7
    walk3rb0h is offline Cadillac Owners Member
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    Re: Oil pressure light

    i think part of the problem they are having pinning it down is that it only seems to happen when the engine is hot and even the its not consistent.. happens more when the AC is on though..

  9. #8
    joe_padavano is offline Cadillac Owners Member
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    Re: repost: Oil pressure light

    Quote Originally Posted by walk3rb0h View Post
    now ive been told that the only fuel filter in the 307 is in the carb is that true?
    Yes, that is correct (well, not counting the plastic screen on the pickup in the tank). The small inline paper filter in the Qjet is not the best and many people add an aftermarket filter in the line from the fuel pump to the carb.

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    joe_padavano is offline Cadillac Owners Member
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    Re: Oil pressure light

    Quote Originally Posted by walk3rb0h View Post
    i think part of the problem they are having pinning it down is that it only seems to happen when the engine is hot and even the its not consistent.. happens more when the AC is on though..
    Well, keep in mind that oil pressure will be directly impacted by two things, engine RPM and oil temp. Hot oil is thinner than cold oil, so you would expect to see lower oil pressure when the oil is hot. Similarly, the oil pump is geared to engine RPM, so the faster the engine turns, the higher the oil pressure. The converse is also true, which is the slower the engine turns, the lower the oil pressure. Engaging the A/C will drop the engine RPM a little at idle, which then lowers oil pressure, and also make the engine run a little hotter. Combine A/C and hot oil, and you may have a problem. By the way, new oil is usually a little thinner than the old oil that's drained out due to the gunk that thickens it up, so if you've recently changed the oil the problem will be worse. Also, if you have a shop change your oil (particularly one of the rapid oil change chains), it's entirely possible that they put in the wrong weight of oil or not enough oil.

    I have to say again, rather than wringing your hands and writing emails, get an oil pressure gauge connected to the motor and understand exactly what's going on. If you really do have low oil pressure, the engine is probably not long for this world.

  11. #10
    carnut is offline Cadillac Owners Master
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    Re: repost: Oil pressure light

    The oil leak and oil light could be the same problem. If the oil pressure switch is leaking then the oil light and leak are one and the same.

  12. #11
    walk3rb0h is offline Cadillac Owners Member
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    Re: repost: Oil pressure light

    So like have one mounted in cab someplace.. i think i can arrange that.. could my idle being a little low by a cause or a symptom of this issue?

  13. #12
    walk3rb0h is offline Cadillac Owners Member
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    Re: repost: Oil pressure light

    ok well i told the people i took my car too they where morons after they quoted me 2k to replace my fuel filter.. took my car to another place and described the issue with oil pressure and loss of power and they said.. has anyone checked the cat? and im like no but hey good idea.. and they checked it and whala all kinds of nastieness.. so I get my baby back later today and ill let you all know if that solved the issue.. also is the fuel filter something i can do easily myself or should I have a mechanic do it?

  14. #13
    joe_padavano is offline Cadillac Owners Member
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    Re: repost: Oil pressure light

    Quote Originally Posted by walk3rb0h View Post
    ok well i told the people i took my car too they where morons after they quoted me 2k to replace my fuel filter.. took my car to another place and described the issue with oil pressure and loss of power and they said.. has anyone checked the cat? and im like no but hey good idea.. and they checked it and whala all kinds of nastieness.. so I get my baby back later today and ill let you all know if that solved the issue.. also is the fuel filter something i can do easily myself or should I have a mechanic do it?
    A plugged cat will definitely cause a loss of power. It might cause the oil pressure problem due to overheating and low idle, but that's only a possibility.

    The fuel filter is easy to change, BUT it is also very easy to strip the threads that hold the filter housing in the cheesy pot metal carb body. If you're comfortable taking that risk, have at it. If not, make the shop responsible for stripping the threads. (Mayby the $2K included "insurance" for replacing the carb...) Actually, you can get oversized self-tapping fittings in the event the carb threads do strip, since this is a common problem.

  15. #14
    walk3rb0h is offline Cadillac Owners Member
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    Re: repost: Oil pressure light

    Ok well replaceing the Cat and the oil pressure sending unit has definatly made the car run better howerver it has not solved the issue so the car is headed back to the shop soon.

  16. #15
    walk3rb0h is offline Cadillac Owners Member
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    Re: repost: Oil pressure light

    Ok so this is not good.. I have a bad engine.. Mechanic says i have atleast 2 loose rods and any other work i do to this engine is a complete waist of time. So 3.5k replacement or get rid of the car.. tough choices..

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