No oil pressure

trad016 · #1 08-05-2004, 04:58 AM

My engine had gone to 260+ degrees a few times due to radiator hose leaks and worn water pump. I fixed that, but now I have a problem with oil pressure. When I start the engine cold, I have 40+ psi. It drives normal. If I turn it off at operating temperature, the restart it, I have no pressure, unless I rev over 1000 rpm for a few seconds. Then, it idles at 10 psi. Many times, at hiway speed, it wond go over 20psi. I have changed the oil sending unit, but it didn't change anything. Any ideas?

fredjacksonsan · #2 08-05-2004, 07:46 AM

How many miles? Might need a new oil pump.

trad016 · #3 08-12-2004, 01:18 PM

It has just under 55,000 miles. I called a dealer and they suggested I might have a blown head gasket (over the phone), but I don't see any evidence of leak around the outside and the oil has no antifreeze in it. Oh yeah, the anti-freeze level keeps dropping, too. The oil does, however, have a caramelized oil residue, at least on the dip-stick. If I can avoid a head gasket change, I would definenatly like that. Any more ideas? Thanks.

fredjacksonsan · #4 08-12-2004, 10:36 PM

With the low indication, it could be the guage itself.

BUT... with the dropping coolant level (and no leak) and the residue on the dipstick, your dealer just might be right. It's worth the afternoon spent to replace the head gasket to find out. While you're doing that, you might also want to check/replace the water pump and gasket. Good luck, interested to hear how it comes out.

trad016 · #5 08-16-2004, 01:37 AM

Is it possible that it might be the oil pump and strainer. My suspicion is that the residue is dirt and that may have clogged the strainer. The oil pressure is just fine until it reaches operating temp. I just want to rule out all possibilities before pulling off the head. Thanks for your help.

ron_jon22 · #6 09-03-2004, 11:44 AM

I am having the same problem with my 97. I don't know what to do? Some say to change the oil type but that is not fixing the problem. Anyone have any ideas on what the problem could be?

JDPascal · #7 09-03-2004, 01:47 PM

Quote:

Originally Posted by ron_jon22

I am having the same problem with my 97. I don't know what to do? Some say to change the oil type but that is not fixing the problem. Anyone have any ideas on what the problem could be?

On the jeeps, there is a history of oil pressure sending unit problems.

Either the sender fails or the connector gives problems.

there is also a possibility of a PCM glitch but not that great.

If both of those have been confirmed OK, the next question is - what is your actural oil pressure??? Test with a mechanical gauge with a range of no more than 100 psi if possible.

you don't saywhat engine you have but the spec's for the 4L are 13 psi at idle and 37 to 75 psi above 1600 RPM max of 75 psi

The 2.5L spec's ar 13 at 600RPM, 25-35 at 800 and 37 to 75 at 1600 - max of 75 psi.

Once you know the actual pressure in your engine, you can decide which way you need to go.

What viscosity oil are you using???

JD

trad016 · #8 09-08-2004, 05:28 AM

I did notice that the overheating problem initially started when I had to use 5w-30 rather than 10w-30, but I didn't think the oil temperature rating would affect it.

JDPascal · #9 09-08-2004, 07:53 AM

Quote:

Originally Posted by trad016

It has just under 55,000 miles. I called a dealer and they suggested I might have a blown head gasket (over the phone), but I don't see any evidence of leak around the outside and the oil has no antifreeze in it. Oh yeah, the anti-freeze level keeps dropping, too. The oil does, however, have a caramelized oil residue, at least on the dip-stick. If I can avoid a head gasket change, I would definenatly like that. Any more ideas? Thanks.

If the oil has a lighter color than new, (caramelized oil residue) it probably has coolant in it.

If your cooling system has antifreeze in it, touch a drop of the oil to your tongue and you will probably detect the sweet taste of the antifreeze.

The over heating should not be affected by the 5w30 oil but I would switch back to the 10w30 or even use 10w40 for the hot weather you experience in Florida. (Hope you came through all the storms safely!!!)

Find a shop that you trust and have them check the engine and oil color and also pressure test the cooling system to check for external leaks The pressure test can also detect a headgasket (or a crack in the head) problem if done right.

At the very least, change the oil and filter and monitor the condition of the oil closely for the color change.

As for the clogged pickup tube strainer, if the oil pressure is ok when cold, I would tend to rule that out because the cold oil would find it for difficult to get through any plugging and pressure should be low then too because of less oil getting to the engine.

Usually, confirmed low oil pressure in an older engine when hot is due to engine bearing and pump wear. The overheating may have contributed to some premature wear in the bearings though overheating usually affects the rings more than bearings.

Question- When the engine overheated, did you let it cool down completely before replacing the coolant??? If not, there is a greater chance of a cracked head as well though I'm not familiar with the tendancy to cracking problems in these engines.

JD

sunday420 · #10 04-28-2005, 07:56 PM

Quote:

Originally Posted by trad016

I did notice that the overheating problem initially started when I had to use 5w-30 rather than 10w-30, but I didn't think the oil temperature rating would affect it.

I am having the same problem with my 89 wrangler. Dont know where to hook the guage on the engine to test the pressure. Please help

GreenJeep10 · #11 04-28-2005, 11:44 PM

I would agree with JDPascal. I had a simular problem. After driving for about 20-30 min. my oil pressure dropped to zero but ran fine. I went to a mechanic and talked with him about it and of course he started to quote me prices for a new crate engine. I said can we check out the oil sending unit and make sure and Yatzee! thats what it was. After that the mechanic got all buddy buddy with me I think to try and make me forget about diagnosing a engine failure. I think he didn't even want to mess with me and quoted me this outlandish price to get me to go somewhere else and check it out. Anymore I try to do most of the work on my Jeep myself. I'm not a mechanic and it may take me some time but at least I know what has been done and if its not done right I only have me to blame. Good Luck.

fredjacksonsan · #12 04-29-2005, 08:06 AM

Quote:

Originally Posted by GreenJeep10

Anymore I try to do most of the work on my Jeep myself. I'm not a mechanic and it may take me some time but at least I know what has been done and if its not done right I only have me to blame. Good Luck.

Amen to that, brother. I try to keep people that obviously don't give a .... out of my mechanicals. Of course there are good mechanics out there, but there are just as many butchers that don't have a clue, or try to sell you an engine when you need a sensor.

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