2002 Jeep Wrangler low oil pressure and disappearing coolan

Tiny
JOHNGALT12
  • MEMBER
  • 2002 JEEP WRANGLER
  • 6 CYL
  • 4WD
  • MANUAL
  • 70,000 MILES
Hope someone can answer this definitively as I know these problems are commonplace with the Jeep 4.0 enging and systems:

I have a 2002 Wrangler Sahara and here's my story:

1. For two years, I have been losing coolant. First over the course of months, then full to empty overflow reservoir in one month. No visible leaks ever. I have had the following maintenance donde:
(i) Replaced water pump; (ii) Coolant system flushed; (iii) thermostat replaced; (iv) temperature sending unit replaced. The engine oil does not look like a chocolate milkshake, and there isn't any visible white smoke coming from the tailpipe.

2. Last 3 months, I have zero to low oil pressure upon startup, but the dipstick reads full (oil has always been changed every 3K - 6K miles). Oil pressuer goes to normal as RPMS go up, but never at the typical 40 - 55 lbs it used to be at. Doubt this is a guage problem, but I don't know. There is no engine knock.

I had the engine pressuer tested all day, and the tester never registered any leak. As I said, I have found no visible leaks of any kind in any system on this Jeep after a close inspection.

Is this likely a head/gasket issue? I am at a total loss and would like any ideas before spending the dough to have the engine taken apart only to come to the conclusion that the entire engine is going to go and will need to replaced shortly. I've heard this is a common issue with the 4.0 but I can't seem to find anyone with a definitive answer.

Any ideas?
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Sunday, January 4th, 2009 AT 6:39 PM

6 Replies

Tiny
AIRSOFTSOLDRECN9
  • MEMBER
Remove the electrical oil pressure potentiometer (switch) from the engine block and use a mechanical guage to test pressure at startup. This is a definative test and will verify the pressure of the oil passing through the crankshaft, rod and main bearings. Have you verified that the engine is not leaking coolant on the ground anywhere? If so how much and over what period of time? More than likely you have a cracked cylinder head gasket. There are leak detection devices available at your local auto parts store. The device will test for traces of exhaust gases in the cooling system.
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Monday, January 5th, 2009 AT 10:43 PM
Tiny
SUNSPIDY
  • MEMBER
Johngalt12,

Were you able to fix your coolant problem? I have same problem with my 2002 Sahara (automatic transmission). I repalced thermostat, water pump, radiator cap, couple of hoses and now still running with same problem.

I see no traces of coolant leaks nor engine oli is milky. Its wired problem. I have been trying to fix this almost 6 months now, but still at ground zero.

Any help on this is appreciated.

Thanks Sunny
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Monday, April 20th, 2009 AT 5:03 PM
Tiny
DAVERDAVE
  • MEMBER
I too lose coolent and oil pressure. I have a 2000 Wrangler with 168k. I only take it out in snow and beautiful days, but I'm afraid I'm doing real damage to the engine. And it doesn't help with the gas milage when I have to keep my foot on the gas to keep the oil pressure up in traffic.

If anyone has answers I sure could use them!

-Daver
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Thursday, May 21st, 2009 AT 6:11 PM
Tiny
TUBES420
  • MEMBER
I have the exact same problem. I drive a 2002 Jeep 4.0L Sport.
It works almost great with high revs but as soon as I go to idle oil pressure drops and then it starts to overheat. Towards the end I was going through a bottle of coolant a week at least but then I just started to get the chocolate milk oil & coolant mix. I stopped driving it about a year ago or so I could build up some repair money. Just opened her up a couple weeks ago to start working on her. Removed the head, sent it to the machine shop to get it looked at & resurfaced. Just got a call back today. I have a cracked head! So good luck to everyone else who has this same problem. Anyone know of a good place to get a Jeep head from?
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Tuesday, June 9th, 2009 AT 1:14 PM
Tiny
DAVERDAVE
  • MEMBER
What do you mean "head" like the valve cover? The actual cylender head? I'm confused.
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Tuesday, June 9th, 2009 AT 2:19 PM
Tiny
TUBES420
  • MEMBER
Not the valve cover. They said I had a 4-5 inch crack in the cylinder head. It makes a lot of sense with all of the problems I was having but, I was just hoping it was a gasket (muchhh cheaper). It sucks but I did see that Quadratec has a new cylinder head replacement w/ valvetrain for $570. I think that might be my best bet. If anyone has a better idea let me know.
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Tuesday, June 9th, 2009 AT 2:29 PM

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