Here are the symptoms that I was experiencing on my 2001 Jeep Cherokee Sport, with 60K miles on it: The coolant was disappearing. About every 2 weeks the recovery bottle would be empty. The strange thing was that there were no puddles on the ground and the system was leak tested with no leaks found.  On top of disappearing coolant, my oil pressure gauge was acting up: reading ok until the engine warmed up, then reading 0 psi at idle and light engine load.

After wasting a lot of money on leak tests and replacing the coolant system hoses, i took the vehicle to the Stealership to have it looked at. I tell them the oil pressure is acting up. An hour after dropping the vehicle off, the dealership calls back and asks if I have been losing coolant? I reply "Yes", and they inform me that I have a cracked cylinder head and the leaking coolant is dripping on the oil pressure sender, thereby making it read wrong.  

After some internet research, I see that the 4.0L engine with cylinder head #0331 is notorius for cracking. It seems that when the engine became warm, it allowed the cylinder head crack to open up and start spilling some coolant on the oil pressure sender, causing the readings to be wrong. The whole problem was tied to the engine reaching operating temperature. If you are experiencing both coolant loss and low oil pressure readings I would start by tracing the path of the coolant (looking around the cylinder head, especially cylinders 3 and 4, right around the oil pressure sensor). I hope this helps!  

Have it magnafluxed by your local machine shop!!!!!!!!!!  

I have oil pressure problem on my 2000 jeep Grand Cherokee limited with a inline 6 which i can not figure out.  I figured out the coolat leak.  It was a hole in the radiator near the upper radiator hose.  The radiator has a lot of plastic and the seems are usually where the leak is.  I had the radiator replaced and I have not had to replace the coolant at all.  My oil pressure still drops to zero when warmed and driven for 30 mintutes but only if I turn it off and start it again.  Does anyone know whats wrong.  I took it to a mechanic who worked for jeep and he told me 10 psi is normal and he tested the oil pressure sending unit and said it was the problem and fixed.  But I am still experiencing the same problem with oil pressure. I don't want to damage my engine but I have been told not to rely on the crapping dash gauges because they are wrong most of the time.  Also how expensive is a cooling fan relay for this jeep  

Hi All,

After reading this post I'm begining to wonder if this is a design problem, any way to get jeep to cover this... Here's my story:

I've just bought an '02 TJ , 40,000 miles with a 4.0.

I put 600 miles on it (easy, freeway/town, didn't have a chance to get it off-road).

I was dropping my son of at school, left it idleing while I went around to get him out of the passanger side.  NO indication of any problem... idle was nice, no steam / smoke, no warning lights, nothing.  Sent him off, hopped back in the Jeep, stepped on the gas, blammO.  It started running rough, missing, couldn't keep it going, etc.  So I was stuck.

Fast Forward, it's at the dealer.. they say, no coolant leaks, but the system is loosing pressure.  Also, no compression in #4... they want to pull the head, think it's a gasket.

Fine.  :-(

They get the head off... they say, ummm.. cracked head, you need a new one.

Fine.  :-((  

They call back... ummm... the tappet below the crack in the head is siezed in the block, unrepairable.. you need a block.

That's where I'm at today, and doing some research I came across this thread.

Anyone have any suggestions???

I'm now considering dropping in V8... any suggestions there?

Thanks.  

I own a 1995 grand cherokee @ 175k and a 1999 durango at 217k. Yes. 217,000 miles. I've had my fair share of problems with each.

There are some problems that you just can't help. You think you have everything taken care of and all of a sudden a nasty little surprise pops up. I've heard of a lot of people who have had durangos whose engines failed due to a faulty oil pump at 30k. This resulted in severe engine damage and the dealers told them they would need a new engine, blaming them for not changing the oil enough.

This should fall under a recall, but a lot of times it didn't.

However, there is a grey area which needs to be addressed. Vehicles that aren't under warranty any longer, BUT it's not anywhere near their time to go. If you have a vehicle with, say, 120k on it, and everything seems to be failing, in my opinion, that is too soon. With the way technology has advanced, we're not really applying it to the quality aspects of the vehicle.

We should be constantly rolling vehicles off the line that last over 200,000 miles. It's very sad to see someone with a 2006 at low mileage get a transmission rebuilt, replaced, or even a new engine, not under cover of a warranty.

If anyone finds themself in that situation, I say FIGHT. Don't take the dealer's first service estimate. They might not act like there's anything else they can do, but sometimes they can dig up a recall (you've got to back them into a corner, lol) and get something replaced at no charge to the customer.  

Me too!. Jeep Cherokee 2000 75K miles. Losing coolant for 2 years, replace radiator twice. Now oil drops to zero at idle but increases as revs increases. This started just the yesterday. From reading a lot of posts, it doesnt sound good. You can spend alot of *** and still not resolve this overheating and loss of oil pressure in Jeeps. I think its a defect in Jeep engines. I have a 1991 Saab with 130K miles and runs like a tank. Forget the the Jeep rip off dealership and Im taking it one last time to my Saab mechanic, who I think is a genius. Ive never had him work on the Jeep. Im going to see what he say and let you know. He can tell in minutes whats wrong with my Saab and fix it!
I think I may let go of the Jeep unfortunately if I dont resolve this ongoing issue. Its not worth it. Its almost left me high and dry on the freeway twice and die once 30 mile from home. Its not safe and not a very good feeling.

I will post again with results.

Jon  

http://www.search-autoparts.com/searchautoparts/article/articleDetail.jsp?id=66740

Found the above link on this site. Have a 2000 jeep cherokee with under 70000 miles on it. Water pump went on it. About 2 weeks later my oil pressure problems started. Once it warms up it will red line at a stop sign. If i hit the gas the guage will go up. I wonder if because the water pump went that the cam bearing then went because of the addtitional heat. Went to 10 w 40 with lucas oil addidtive and i dont red line at red lights anymore. I read in a post on this sight on a different make that there is a front and rear plug. If the front plug fails, there is no sign of oil but pressure drops big time. Does a jeep have a similar plug up front hiding in the timing chain cover?  

these plugs are suppose to be in the front and rear of the block that the cam sits in. I dont know much about cars and car terminolgy so it what i said somes alittle funny thats why  

I just bought a 2001 jeep with a 4.0. The person I bought it from said it had a blown head gasket, he said the coolant light was coming on after he drove it. I looked at the radiator, coolant was pretty and green and no signs of oil. Started motor let come up to temp no sign of compression in radiator and no sign of coolant in oil pan. Drove jeep home no coolant light but oil pressure drop to nothing. Motor and jeep look like new only has 108000 miles well maintain. So I figured it had a bad sending unit . Replaced sending unit no change. Replaced oil pump thanking check valve in pump was bad, motor never knocked or rattled oil pressure returned when motor was reved. oil pump did not fix the problem. pulled rod and main caps to look bearings they looked like brand new. So motor never lost total oil volume just oil pressure. So the only thing other than the oil pump that makes pressure in a motor is cam bearing. Tore motor down and found front and rear cam bearing looked good, middle two totally gone. Only question is why. Is coolant leaking on to these bearing and wiping them out.  

I to own a 2000 TJ with approximately 103k miles.  At idle my oil pressure drops to 0 but returns to normal at operating speed.  Concurrently I've noticed the need to refill the coolant bottle frequently as other posters to this thread have mentioned.  To address this issue, I replaced the oil pressure sensor, changed the oil and filter but there was no change to the decreasing pressure at idle.  It sounds as if there is a common problem going on here.  The dealership recommended checking the sender screen as it can clog causing a loss of pressure at low rpm.  Have not pulled the pan yet to see.  

The plugs in the front and rear of the block are for the oil gally.  This is drilled out at the factory, since it cannot be cast in.  They are then tapped and plugged since the oil is not fed from the ends.  The rear will be quite obvious, but the front will just dump the oil back into the motor.

You can call around to a local oil distributor and see if they can do an oil analysis... for a fee I suppose.  This will tell you your wear metals (like bearings and such) and glycol content (antifreeze).  This will help you narrow down your search in what is causing the low oil and disappearing coolant.  If your wear metals are high, this tells that you have bearing issues without pulling apart your motor!!

Hope any of this helps.