Low Oil Pressure Guesses
 

Wife's '97 TJ, 2.5eng., 77,000 miles.

Never been under water, or overheated.

Oil always changed at 3500mile intervals.

Problem: It has low oil pressure after warm up.

Cold (ambient, 65deg.) pressure is 45psi. After warm up, it cruises around
25-30psi then it idles down to "0", and all the check gauges lights all come
on. Pressure confirmed within a psi or two with a "live" gauge.
Tapping the throttle obviously raises the pressure slightly, and lights go
off. Running the A/C helps increase the idle slightly, increasing pressure
slightly.

Hoping but not really believing it would work, I changed the oil pump, which
made no difference whatsoever. I switched to straight 30W oil, which has a
higher cold start pressure, but makes no difference after warm up.

I don't really want to change the engine, but it would be easier than
putting in new main, rod, and cam bearings.

Any other ideas, or is there something about these 2.5's I've missed?

Spdloader

Re: Low Oil Pressure Guesses
 

On Tue, 1 May 2007 13:33:22 -0400, "Spdloader"
<askforit@nospam.triad.rr.com> wrote:

>I don't really want to change the engine, but it would be easier than
>putting in new main, rod, and cam bearings.
>
>Any other ideas, or is there something about these 2.5's I've missed?


Sounds like worn bearings. You might try 15w40 (not 10w40) as this can
boost pressure in a worn engine. Sometimes a can of STP or motor honey
can help here too but a real fix would be new bearings and you should
be able to replace them in car easier than a engine change. The 2.5 is
a sturdy mill and not trouble prone in this area. You did not mention
if you bought it new or the mileage on it. Also that engine tends to
work pretty hard at times and 3K miles is a better change interval for
it. I have one in my wifes 2000 Cherokee 5sp (we had a very hard time
finding one with a 2.5 too) and it has been trouble free since we
bought it new and it has over 80K on it now. Never regreted getting it
with 2.5 either as it is mostly a commuter and it gets around 20 or so
in town consistantly and around 23 to 25 MPG on the road with A/C on
longer runs to kids college. It has gotten as high as 27. Motor has
good torque for its size.
-----------------
TheSnoMan.com

Re: Low Oil Pressure Guesses
 

On Tue, 1 May 2007 13:33:22 -0400, "Spdloader"
<askforit@nospam.triad.rr.com> wrote:

>I don't really want to change the engine, but it would be easier than
>putting in new main, rod, and cam bearings.
>
>Any other ideas, or is there something about these 2.5's I've missed?


Sounds like worn bearings. You might try 15w40 (not 10w40) as this can
boost pressure in a worn engine. Sometimes a can of STP or motor honey
can help here too but a real fix would be new bearings and you should
be able to replace them in car easier than a engine change. The 2.5 is
a sturdy mill and not trouble prone in this area. You did not mention
if you bought it new or the mileage on it. Also that engine tends to
work pretty hard at times and 3K miles is a better change interval for
it. I have one in my wifes 2000 Cherokee 5sp (we had a very hard time
finding one with a 2.5 too) and it has been trouble free since we
bought it new and it has over 80K on it now. Never regreted getting it
with 2.5 either as it is mostly a commuter and it gets around 20 or so
in town consistantly and around 23 to 25 MPG on the road with A/C on
longer runs to kids college. It has gotten as high as 27. Motor has
good torque for its size.
-----------------
TheSnoMan.com

Re: Low Oil Pressure Guesses
 

On Tue, 1 May 2007 13:33:22 -0400, "Spdloader"
<askforit@nospam.triad.rr.com> wrote:

>I don't really want to change the engine, but it would be easier than
>putting in new main, rod, and cam bearings.
>
>Any other ideas, or is there something about these 2.5's I've missed?


Sounds like worn bearings. You might try 15w40 (not 10w40) as this can
boost pressure in a worn engine. Sometimes a can of STP or motor honey
can help here too but a real fix would be new bearings and you should
be able to replace them in car easier than a engine change. The 2.5 is
a sturdy mill and not trouble prone in this area. You did not mention
if you bought it new or the mileage on it. Also that engine tends to
work pretty hard at times and 3K miles is a better change interval for
it. I have one in my wifes 2000 Cherokee 5sp (we had a very hard time
finding one with a 2.5 too) and it has been trouble free since we
bought it new and it has over 80K on it now. Never regreted getting it
with 2.5 either as it is mostly a commuter and it gets around 20 or so
in town consistantly and around 23 to 25 MPG on the road with A/C on
longer runs to kids college. It has gotten as high as 27. Motor has
good torque for its size.
-----------------
TheSnoMan.com

Re: Low Oil Pressure Guesses
 

On Tue, 1 May 2007 13:33:22 -0400, "Spdloader"
<askforit@nospam.triad.rr.com> wrote:

>I don't really want to change the engine, but it would be easier than
>putting in new main, rod, and cam bearings.
>
>Any other ideas, or is there something about these 2.5's I've missed?


Sounds like worn bearings. You might try 15w40 (not 10w40) as this can
boost pressure in a worn engine. Sometimes a can of STP or motor honey
can help here too but a real fix would be new bearings and you should
be able to replace them in car easier than a engine change. The 2.5 is
a sturdy mill and not trouble prone in this area. You did not mention
if you bought it new or the mileage on it. Also that engine tends to
work pretty hard at times and 3K miles is a better change interval for
it. I have one in my wifes 2000 Cherokee 5sp (we had a very hard time
finding one with a 2.5 too) and it has been trouble free since we
bought it new and it has over 80K on it now. Never regreted getting it
with 2.5 either as it is mostly a commuter and it gets around 20 or so
in town consistantly and around 23 to 25 MPG on the road with A/C on
longer runs to kids college. It has gotten as high as 27. Motor has
good torque for its size.
-----------------
TheSnoMan.com

Re: Low Oil Pressure Guesses
 

Spdloader writes:

> Hoping but not really believing it would work, I changed the oil pump,
> which made no difference whatsoever.

Dunno about your 2.5, but on the 4.0, there's a press-fit tube that has to
be changed with the oil pump to get a good fit. Was that part of your pump
changeout?

Re: Low Oil Pressure Guesses
 

Spdloader writes:

> Hoping but not really believing it would work, I changed the oil pump,
> which made no difference whatsoever.

Dunno about your 2.5, but on the 4.0, there's a press-fit tube that has to
be changed with the oil pump to get a good fit. Was that part of your pump
changeout?

Re: Low Oil Pressure Guesses
 

Spdloader writes:

> Hoping but not really believing it would work, I changed the oil pump,
> which made no difference whatsoever.

Dunno about your 2.5, but on the 4.0, there's a press-fit tube that has to
be changed with the oil pump to get a good fit. Was that part of your pump
changeout?

Re: Low Oil Pressure Guesses
 

Spdloader writes:

> Hoping but not really believing it would work, I changed the oil pump,
> which made no difference whatsoever.

Dunno about your 2.5, but on the 4.0, there's a press-fit tube that has to
be changed with the oil pump to get a good fit. Was that part of your pump
changeout?

Re: Low Oil Pressure Guesses
 

You did not mention
> if you bought it new or the mileage on it.


Um, I did buy it new, and I did mention that the mileage was 77,000.

Spdloader