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Robertson 06-07-2013 09:14 PM

Engine Overheating and Fuel System(I Think)
It's a '98 Cherokee, 4.0L, nothing fancy about it.
I've got 2 problems.

1. Overheating. I recently had to remove the AC compressor/pulley and replaced it with a bypass pulley, as well as a new serpentine belt. Drove with no overheating issues for about 3 days. One morning it overheats out of nowhere, I park immediately, pop the hood, and steam and a little smoke is rolling from the engine. I noticed some coolant around the radiator cap, which makes me believe the cap is working properly. The Radiator is new, so I dont think it is the problem either. There is no loss of coolant, no leaking anywhere that I can see, aside from the bit that came out of the cap when it overheated..I'm really not sure what I should be looking for or into next. Possibly the water pump? I don't know a thing about Jeeps, so i'm not sure if this is a common problem.

2. I had a problem with the fuel pump not running. I replaced the relay for it, and it still wouldnt work, so I put in a new fuel pump, and it ran right away with no problem. . This was about 2 months ago, Now I've noticed the Jeep shuddering alot when i'm just idling, and it even died once while at a stop light. I've noticed that when i'm having problems, I can tap on the PDC and the problem will not be as bad, and even goes away sometimes, temporarily. There is also a light film of clear grease on the relay tips when I pull them out, is that supposed to be there?

I'm at a complete loss here. I really dont want to get rid of this jeep, but I'm getting tired of putting money into it. I could really use some help. Thanks.

Paradise XJ 06-08-2013 09:28 AM

1. There should not be any coolant escaping from the cap, filler neck or overflow tube (it's not a Model T). The cap is faulty or there is a crack in the filler neck. Replace the cap with a 16# cap. The guy at the auto parts store will tell you it takes a 13# cap, trust me, get the 16# one. When that's all sealed up, check the filler neck. Quite often the neck can get bent and/or cracked during shipping. Anything that let's coolant escape also lets pressure escape, which lowers the boiling point and renders the cooling system less effective

2. The clear grease on the relay connector is a good thing. There are other reasons than a faulty fuel pump that the Jeep is "shuddering" at idle. If it's running OK down the road then the fuel pump is working. Check all the electrical connections to the PDC, especially the grounds. If tapping it solves the rough idle issue temporarily, it may just be a loose connection. You could also remove and clean the throttle body, the Idle Air Control (IAC). Be careful cleaning the IAC, don't pull on the plunger, just spray it down with some throttle body cleaner.

Here's the "how to"

Courtesy of TJWalker:

The Idle Air Control (IAC) is mounted on the back of the throttle body. The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled.

3. You have a 15 year old Jeep, expect to spend some time and money on it to keep it going for another 10 yrs.

Robertson 06-08-2013 04:04 PM


1. I went ahead and bought a new thermostat and new #16 cap, and installed them. After about 10-15 minutes of running it, it overheated again. This time, I did not have any coolant coming from the cap, but, I did notice right about the time it overheated, there was alot of steam coming from directly under the cap..where the cap seal would meet the top of the filler tube.

2. I cannot thank you enough on your help with the idling issue. I took the throttle body apart, as well as the IAC, cleaned them both(There was a ton of carbon build-up), put it back together, and now it idles like a champ. There's still a very slight hesitation when I go from idling to applying pressure on the gas, but it's only a split second, so I don't plan on stressing over it. But yes, the idling issue seems to be fixed.

tjwalker 06-08-2013 05:07 PM

*Is it overheating at idle, on the highway, or both? Overheating at idle only can be caused the the fan clutch. Overheating at speed is usually radiator or water pump related.

*Is your fan shroud intact? Fan shrouds are important!

*I'd seriously consider getting a new water pump installed. I generally install a new one when I replace the radiator unless I know the history of when it has been last replaced. They are inexpensive and not that hard to install.

And while you're replacing that water pump and have the system drained down, install all new hoses if they look like originals. Original hoses on a 98 are a recipe for disaster. The money you spend on your cooling system is possibly the best money you can spend. If overheating continues, you'll blow your head gasket, crack your head or possibly worse. Gotta get this resolved. Borrow a vehicle until it is.

Robertson 06-08-2013 05:54 PM

It overheated itself at Idle this time. I didnt actually put it on the road. And actually, now that you mention it, Part of the fan shroud is missing. I accidently Broke it off when I was changing the serpentine belt. I will order a new fan shroud for it, and I will replace the water pump as well. The hoses actually look like they are in very good condition. I don't know if a previous owner had bought new ones, but they look fairly new.

Robertson 06-09-2013 10:21 AM

There was also a slight whistling noise for about 1 minute..then it went away, not entirely sure where it is coming from, but it sounds like it's from the water pump.

Robertson 06-09-2013 05:04 PM

Replaced the water Pump. Problem is gone, no more overheating. Thank you, thank you both, very much for the help!

tjwalker 06-09-2013 05:25 PM

Thanks for the update; many do not report back. Glad we could help! :)

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