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post #1 of 17 (permalink) Old 05-30-05, 10:09 AM Thread Starter
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Irratic Oil Pressure Problem in CV

My 1993 Crown Vic (4.6L, 84k miles) starts and runs well with a minor (2-3 drops a day) oil leak. When I first start up, the oil pressure stays steady at the "o" in Normal on the gauge. After 5-15 minutes of idling the oil pressure begins to dance up and down, and after a minute of this it drops to zero and stays. At this point you can hear the tapping sound of an engine idling with little oil. I first thought this indicated the need for a new oil pump, but I don't see how a non-working oil pump could have pressure at first and then have none. I have flushed the oil 3 times adding new filters and oil each time, but the problem remains. The oil level is fine. What could this be and how might I go about fixing it, or more thouroughly determine the cause? Thanks.

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'93 CV w/84k
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post #2 of 17 (permalink) Old 06-02-05, 02:31 PM Thread Starter
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Re: Irratic Oil Pressure Problem in CV

Information I received from another site says I might have a bad oil pump, or a bad sending unit, or a blocked intake tube. Which of these (or other problem) would other Crown Vic owner's say I most likely have, creating my erratic oil pressure problem? Maybe I should repost the questions and add a poll!? Thanks.

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post #3 of 17 (permalink) Old 06-04-05, 01:14 PM Thread Starter
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Re: Irratic Oil Pressure Problem in CV

If I do need to repair or replace the Pressure Relief Valve on this car where is it? I can't find any info on this in my Haynes manual!

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post #4 of 17 (permalink) Old 06-07-05, 12:05 PM Thread Starter
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Re: Irratic Oil Pressure Problem in CV

Maybe my problem is PCV valve related. It may not be the problem with the low oil pressure now, but a faulty PCV valve may have been a contributing factor to my problem in the past.

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post #5 of 17 (permalink) Old 06-07-05, 06:00 PM
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Re: Irratic Oil Pressure Problem in CV

Sorry but the 4.6 is a mistery to me. The only thing I ever did on them was a tune up. I'm going to take a stab in the dark and say perhaps your oil gauge is bad. I had a sunpro oil gauge that a inner spring snaped after age and a lead foot. At a start up it should hover around 40-45psi. Then at a idle when warm should be 15-20psi (about 750-850rpm). Then when you accelerate you should have 35-40psi. Make sure its 10w-30 SAE. On more thing is maybe therea a kink or melted point in the line thats caused it too act strang. Thats the only things I can come up with.

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post #6 of 17 (permalink) Old 06-08-05, 07:04 AM Thread Starter
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Re: Irratic Oil Pressure Problem in CV

Thanks for the reply and PSI info, Blue Steel. The oil gauge on this car is electronic, not a true mechanical pressure gauge. And I really am experiencing low oil pressure due to the engine tapping appearing in-sync with the oil gauge drop. I can't imagine what could make the oil pressure run fine for the first 5-15 minutes and then drop to zero. Sounds like maybe a pressure relief valve, but I can't find any info about this on the car. I'm going to try giving it another good engine flushing, and hope this can dislodge/dissolve some crud in it that maybe be blocking a passageway. That's all I can imagine for now.

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post #7 of 17 (permalink) Old 06-08-05, 10:22 AM
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Re: Irratic Oil Pressure Problem in CV

I have a 4.6L in the backyard. I'll start tearing into it the next couple of days and see I can figure any thing out for ya. Its very possible that one of your lifters or more have collapsed and get bad when it warms up. I don't have a clue what runs the oil pump on those things.

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post #8 of 17 (permalink) Old 06-09-05, 12:00 AM
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Re: Irratic Oil Pressure Problem in CV

Quote:
Originally Posted by SciFiArtMan
My 1993 Crown Vic (4.6L, 84k miles) starts and runs well with a minor (2-3 drops a day) oil leak. When I first start up, the oil pressure stays steady at the "o" in Normal on the gauge. After 5-15 minutes of idling the oil pressure begins to dance up and down, and after a minute of this it drops to zero and stays. At this point you can hear the tapping sound of an engine idling with little oil. I first thought this indicated the need for a new oil pump, but I don't see how a non-working oil pump could have pressure at first and then have none. I have flushed the oil 3 times adding new filters and oil each time, but the problem remains. The oil level is fine. What could this be and how might I go about fixing it, or more thouroughly determine the cause? Thanks.

SciFiArtMan
'93 CV w/84k
Hey Man,
Your problem is that your oil return passages are clogged up. This causes the tapping. And the gauge is not registering right because the sending unit is what reads the pressure and its not getting the oil because of the clog.Remove the valve covers and clean the return holes with a long brush or piece of coat hanger, then drain the oil pan and flush the holes with some type of solvent, change the filter and refill with a quality oil. This should fix the problem.I have a 92 CV that did the same thing exactly.
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post #9 of 17 (permalink) Old 06-12-05, 07:48 PM Thread Starter
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Re: Irratic Oil Pressure Problem in CV

Well, I still haven't gotten that oil gauge yet, a friend promised to bring his over this weekend, but he could find it. So looks like I'll need to buy one.

In the mean time my local experts (read: half-drunk moterheads with more big stories than actual knowledge) came over and convinced me to drop some SeaFoam into the crankcase. I did and it started right up like it always does, with the oil pressure reading at the "o" in Normal. After 5 minutes the gauge dropped, all the same as before. Someone suggested I drive it around a bit. Which I wasn't too keen on with the engine tapping and the OP gauge at zero. But I did drive it around a little, nothing too strenuous. The point is, I noticed that when I rev'ed it up, the pressure reading came back up to Normal.

Back in the driveway, I rev'ed the engine up pretty good and goosed it several times. The oil pressure stayed high as long as I had the RPMs up. And the engine sounded fine, no tapping or so little I couldn't hear it over the engine sound. When I returned the RPMs back to idle the gauge dropped and the tapping returned.

I don't know what this means but it must say something to you true experts.

Now should I leave this SeaFoam in the system overnight, or should I follow the directions and drain it as directed (I've seen both ideas explored elsewhere). Thanks for your help!

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post #10 of 17 (permalink) Old 06-12-05, 08:59 PM
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Re: Irratic Oil Pressure Problem in CV

Are you possitive you have the right amount of oil in it? I don't know if theres a differnce, but in my 74' rancheros 460 it had a 78 lincoln dip stick in it, the lincoln had a diffent oil pan and used differnt levels, I found that out cause it was 1 court over the dip stick thats suppose to be in the 460. The oil gauge jogged around when it warmed and went to normal when I reved it. I then got the right dip stick and the oil gauge work right after that. Another possible thing is the sending unit is no good, I'm still tearing into that 4.6 in the back yard, the heads are real clean.

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