Oil Pressure is scaring me!

[tkjeeper]

agghhh! Hate this stupid metric system up here! I have the idiot KPA instead of good ol' psi, mine reads just under 4 KPA? what the hell does that mean? have to find a conversion calculator i guess, same with cool temp, pisses me off about our gauges.

 

[tkjeeper]

Oh I see, 360 kpa is approx 55 psi, I guess I'm ok, drops to 300 at idle which is ok too.

 

[RichP]

You might want to reconsider the switch to synthetic. I tried just 2 quarts of synthtic in mine and my jeep went from 3000 miles with almost no oil consumption (<1/2 quart in 3000 miles, with 245,000 miles on the odometer) to using 1 quart every 100 miles. I went from 20W50 Dynao to 20W50 synthetic.

I had already replaced the valve cover gasket and oil pan gasket, rear and front seals and the distributor gasket and the CCV lines. I had no leaks. Then it started leaking at the oil filter adapter a few days after using the synthetic. I fixed the oil filter adapter leak 2 weeks ago and now the oil consumption is down to 1 quart every 200 miles. The synthetic seems be very good at getting through tight spots like new bearings, which makes it great in a new engine, but not so good in a used engine.

I am still puzzling over the current oil loss rate. Fixing to post it in a new thread.

I would suggest you look behind the harmoic balancer, I had a 1qt loss between changes that I could never find. Then when I was doing a water pump on my 98XJ and had the front all out I noticed it was wet and shiny back there. All the bolts had backed out and the only thing keeping them in there was the balancer. Tightened them back up and the 1qt mystery was solved. Three months later #3 injector stuck open and took out my #3 cylinder on the PA turnpike but it still got me the 90miles home. Probably could have saved the engine if I had had my acctron scanner, would have pulled the spark plug and unplugged the injector and turned it into an audi...

 

[Ecomike]

No leaks there either.

Sorry to hear about your woodbe audi.

My mystery black hole that was sucking oil into another dimension seems to have stopped, or slowed down considerably. I did add one quart of Lucas to replace the last quart that evaporated into the Ether but I also replaced the 3 mm CCV orifice I was using with a 2 mm orifice which slowed the ventilation rate on the valve cover / crankase.

Not sure at this point if one of those changes or maybe both together solved the oil problem in mine. So far 140 miles and no oil is missing, yet.

If it stays that way for the next 500 miles I will try the 3 mm orifice again out of curiousity.

 

[88xjlover]

No leaks there either.

Sorry to hear about your woodbe audi.

My mystery black hole that was sucking oil into another dimension seems to have stopped, or slowed down considerably. I did add one quart of Lucas to replace the last quart that evaporated into the Ether but I also replaced the 3 mm CCV orifice I was using with a 2 mm orifice which slowed the ventilation rate on the valve cover / crankase.

Not sure at this point if one of those changes or maybe both together solved the oil problem in mine. So far 140 miles and no oil is missing, yet.

If it stays that way for the next 500 miles I will try the 3 mm orifice again out of curiousity.

Have you checked your air filter for oil? You could have a clogged line caused by a stuck cvp? (spelling). What are those things called again?:cheers:

 

[DaveKerwin]

I just bought my 1998 jeep cherokee classic 2 days ago. It runs awsome, no motor noise and 78k miles. However, after it gets warm, at idle the oil pressure will drop to 8-10psi. Is this ok at idle ? While driving it's at 40-45psi. My 95 XJ that I had never dropped below 30psi. I was told to put a thicker oil in there to bump the pressure up but wanted some other opinions on it.

I have an 01 XJ, and I have the exact same symptoms. 79k miles, and 10-11 at hot itle, 45 on acceleration. Manual says that as low as 14 is acceptable at hot idle, but mine is under that, which has me concerned. Mine also had a the bad head, which was replaced, but I am starting to wonder if it caused any permanant damage.

I changed oil and upgraded to the K&N filter, no change at all. So I am thinking I am gonna try cleaning the oil pressure sender, and see what that does. I also have a engine flush no my mind to see if that does anything.

If none of that works, I am considering changing some bearings and a high flow oil pump. I don't know really, and I am praying that I just have a bad signal from the sender. I better get a mechanical guauge on it before spending any real money on this thing.

 

[Ecomike]

I have an 01 XJ, and I have the exact same symptoms. 79k miles, and 10-11 at hot itle, 45 on acceleration. Manual says that as low as 14 is acceptable at hot idle, but mine is under that, which has me concerned. Mine also had a the bad head, which was replaced, but I am starting to wonder if it caused any permanant damage.

I changed oil and upgraded to the K&N filter, no change at all. So I am thinking I am gonna try cleaning the oil pressure sender, and see what that does. I also have a engine flush no my mind to see if that does anything.

If none of that works, I am considering changing some bearings and a high flow oil pump. I don't know really, and I am praying that I just have a bad signal from the sender. I better get a mechanical guauge on it before spending any real money on this thing.

I seriously doubt if flushing it will help any in your case, unless it is sludged up. The oil pressures you reported does not sound like a sludge problem.

Replacing a quart of oil with a higher viscosity oil or additive like Lucas oil will help bring up the hot idle pressure from about 10 to about 20 psi.

What brand oil and viscosity are you using currently?

What went wrong with the head you replaced???

Do check the sender electrical connections, but if it is reading 45 PSI until it gets hot and then drops, it is probably working OK.

The first signs of some bearing wear seems to be a lower pressure at hot idle, than at cruising and cold start conditions.

 

[DaveKerwin]

I seriously doubt if flushing it will help any in your case, unless it is sludged up. The oil pressures you reported does not sound like a sludge problem.

Replacing a quart of oil with a higher viscosity oil or additive like Lucas oil will help bring up the hot idle pressure from about 10 to about 20 psi.

What brand oil and viscosity are you using currently?

What went wrong with the head you replaced???

Do check the sender electrical connections, but if it is reading 45 PSI until it gets hot and then drops, it is probably working OK.

The first signs of some bearing wear seems to be a lower pressure at hot idle, than at cruising and cold start conditions.

the head problem was the cracked 0331. previous owner had it replaced 10k miles ago. I am wondering if he sold it because of the problem that I am now noticing (bought the jeep almost 2 months ago).

I have 10w30 I think, just had it the oil change shop change it with regular oil, not synthetic. Is there only one kind of Lucas oil, or is there a certain kind I want?

I am going to check the connection on the sender for good measure. And if I can, get a mechanical guage on it for exact numbers. But oil additives and high flow oil pumps seems to be a bandaid in my situation? I also hear what I am calling piston slap (not terribly loud, but noticable, but not every day, on occasion). I talked to a guy who rebuilds jeep motors, and he says that the wrist pins are failing and that I am gonna blow up my motor, but he is motivated by dollars, so not sure what to think.

 

[Ecomike]

the head problem was the cracked 0331. previous owner had it replaced 10k miles ago. I am wondering if he sold it because of the problem that I am now noticing (bought the jeep almost 2 months ago).

I have 10w30 I think, just had it the oil change shop change it with regular oil, not synthetic. Is there only one kind of Lucas oil, or is there a certain kind I want?

I am going to check the connection on the sender for good measure. And if I can, get a mechanical guage on it for exact numbers. But oil additives and high flow oil pumps seems to be a bandaid in my situation? I also hear what I am calling piston slap (not terribly loud, but noticable, but not every day, on occasion). I talked to a guy who rebuilds jeep motors, and he says that the wrist pins are failing and that I am gonna blow up my motor, but he is motivated by dollars, so not sure what to think.

Duct tape is a bandaid, and a Real good one at that! Changing to thicker oil is routine for older engines as they wear. If you are still using 10W30 and getting 45/10 psi then all you probably need to do is go to 10w40 or even better 20w50 oil.

Until you get around to changing your oil you can just add the quart of Lucas to get the pressure up at hot idle. There is regular and synthetic Lucas. Just use the regular Lucas.

On the noise part, many of us have noisy jeep engines that would scare most engine mechanics to death, and they just keep running. Many of them with 200,000 to 300,000 miles on them and still going. Mine sounds like a cross breed between an industrial sewing machine and Diesel Freightliner, and it has 246,000 miles on it. And it doesn't even burn oil yet. Uses about 1/2 quart every 3,000 miles. It just has that weird low oil pressure at hot idle, that goes away with a higher viscosity oil (20W50) or a single quart of Lucas added to the crankcase.

 

[DaveKerwin]

I appreciate the information, thank you!

one question though, if the oil is having trouble being moved around, and we use a heavier oil, wouldn't it seem that it would be even more of a problem? I realize it is not, but just trying to understand the dynamics involved.

for me it is kind of depressing buying a lower mileage truck and paying the extra money to have to do the same type of work involved than if I bought the truck that was older and more miles, for half the price. I knew i shoudl have never violated the laws of cheapness!

I am gonna try lucas and see what happens.

 

[Ecomike]

I appreciate the information, thank you!

one question though, if the oil is having trouble being moved around, and we use a heavier oil, wouldn't it seem that it would be even more of a problem? I realize it is not, but just trying to understand the dynamics involved.

for me it is kind of depressing buying a lower mileage truck and paying the extra money to have to do the same type of work involved than if I bought the truck that was older and more miles, for half the price. I knew i shoudl have never violated the laws of cheapness!

I am gonna try lucas and see what happens.

I does not work that way. You are thinking of it backwards. If the pressure loss is due to larger increased bearing clearances the oil flow rate through the engine increases and the oil pressure drops as a result. If the pressure drop is due to the oil getting hotter and thining out then the oil flow rate through the engine increases and the back pressure drops. Either way the oil flow rate increases as the pressure drops if the filter, pump and intake screen are OK.

The concern is that as that happens tighter bearings may get starved for oil by the looser bearings who are passing too much oil, if the pressure gets too low.

Increasing the viscosity and getting the pressure back up to 20 to 30 psi just re-normalizes things so that all the bearing surfaces get adequite oil flow.

 

[DaveKerwin]

UPDATE, with pics:

I wanted to post some results. I removed a quart of oil (I am running regular 5w30) and put in a quart of lucas oil in its place.
I took pics of the oil pressure before, and then after, both at highway speeds and hot idle.

I gained 5lbs of pressure at idle, and nearly 10 on acceleration, by doing this alone.
Pics: http://picasaweb.google.com/DaveKerwin/OilPressureChanges

 

[Ecomike]

UPDATE, with pics:

I wanted to post some results. I removed a quart of oil (I am running regular 5w30) and put in a quart of lucas oil in its place.
I took pics of the oil pressure before, and then after, both at highway speeds and hot idle.

I gained 5lbs of pressure at idle, and nearly 10 on acceleration, by doing this alone.
Pics: http://picasaweb.google.com/DaveKerwin/OilPressureChanges

Impressive, most Impressive, Obi-Wan has taught you well!

Now try 10W40 plus a quart of Lucas on your next oil change, and cry all the way to the bank....and Keep on Jeepin!