overheating, is it the waterpump?

[HotShot8792]

I have a 98 4.0L Wrangler in which I haven't had any problems from since I have had it. Two days ago I was driving down the interstate with the A/C on, and my check gauges light came on. My temperature gauge is sitting right at the beginning of the red portion of the gauge. I turn the A/C off and it finally shoots down quickly to halfway between the 210 mark and the redline. After making a stop to try to cool it down, I tried to make my way back home. It would go back to halfway between 210 and redline, and then just instantly shoot to the beginning of the redline area, stay there and then shoot back down to where it was. Then after stopping my car one last time on the way home, it ran at normal temperatures until I got close to my house where it started going back up again.

Anyways, the first thing that I did was I replaced the thermostat, drained all the coolant and put new coolant in. The new thermostat works good, and last night I did not have any problems as I didn't make any long trips. I could see where the thermostat was opening up, so thats working fine. However, this morning on my way home, it started warming up again going back to the point halfway between the 210 and the redline, and then just instantly shot up to redline again.

It would seem to me that the waterpump is starting to go bad, but I want to get some other opinions.

[BYuen]

It proly is your waterpump. I would suggest getting an after market one for around 30 bucks, because I've heard that the OEM mopar ones run at a high price or something like that. Install it yourself though, because when I had mine replaced the mechanic charged several hundred... good luck

[jeeptillidie]

In my opinion yes the waterpump is getting weak. If you can tell where the thermostat is opening then its definitely not that. Your water pump is more than likely just getting weak and if that is the case it will eventually go out completely and it probably wont take long.

[dyna]

If its overheating it wouldent make other lights flash etc, and wouldent jump around as you describe, the more you push it the hotter it will stay until cooled down. If your the original owner of an 98 and it still has the plastic/alum radiator its probably seen better days as well as the cap. Did you ever or have any of the "gauge issues " caused by bad connections on the cluster? My cooling system is pretty new and im fine on 100+ degree days towing even,but put the AC on and the guage actually goes down, gotta question how accurate they really are. A/C will add xtra load to the cooling system also from the compressor as well as the condensor up front making heat which transfers back onto the radiator.
As far as a water pump getting weak? either the impeller spun off which I read about here from a autozone replacement or the impeller has actually rusted away which is pretty rare the only other failure it can have is the bearings and seals go and that you`d see in the way of leaking.

[HotShot8792]

i think that maybe all of ya'll are right. Maybe my temp gauge has a glitch in it at that point, and the waterpump is weak. I definitely know i'm overheating from inspecting inside the engine bay after turning the engine off. I just picked up a new pump at o'reilly's for 30 bucks, so i'm going to replace that. Sucks that it is so hot outside though.

[97_tj]

you should also check your fan clutch to make sure it is good

[Rocky.ca]

had that problem... it caused my rad to crack... 50 dollars to get it home and i just replaced the whole cooling setup, water pump, rad, and thermostat... now it runs perfect... a little but under 210.

[BYuen]

Originally Posted by Rocky.ca

had that problem... it caused my rad to crack... 50 dollars to get it home and i just replaced the whole cooling setup, water pump, rad, and thermostat... now it runs perfect... a little but under 210.

Sounds good mine runs b/w a lil below 210 and sometimes a hair above

[PFM]

Might as well replace the water pump and fan clutch while you're messing around with the pump. Not too expensive, and a relatively quick and painless job to do by yourself. The biggest pain in the neck for me was removing a ten year old radiator that didn't want to come out like it should. Nothing like rusty bolts...

[HotShot8792]

Well I replaced the water pump last night and flushed the radiator out with water. The bearings on the old water pump were fine, but the fins were a little rusty. Got rid of a lot of brown crap (don't know how the coolant got so brown originally, guess the previous owners never flushed the coolant before). Drove to work this morning (which is like a 5 minute drive) and the highest the temp gauge got was about 1/3 of the way between the second mark and the 210 (middle) mark. Of course it was very very slowly increasing at that point. I guess I'll find out if things really work today when I make a longer trip. I did notice that I didn't have any heat coming out, but maybe thats because my engine had not completely warmed up yet, or maybe my thermostat is to low of a temp. I believe its the 175 degree thermostat from autozone.

[shadowrider1946]

Mine did the same thing a few weeks back and I changed the thermostat and fan clutch, didn't help. Pulled water pump and found the impeller spinning on the shaft, replaced and all is well.

[dyna]

If you bought a 180 or 160 degree thermostat you better get rid of it and put a 195 back in. Theres numerous posts regarding the need the 4.0 to run at its designed temp which is why it has a 195. You mileage will suffer because it will always run in open loop thinking the engines cold, the xtra fuel will burn out your cay eventually and you`ll have no heater. If the coolant was rusty brown after a few days since the last flush you probably need to at least pull the radiator and have it rodded,a simple flush will not do the trick.

[HotShot8792]

Originally Posted by dyna

If you bought a 180 or 160 degree thermostat you better get rid of it and put a 195 back in. Theres numerous posts regarding the need the 4.0 to run at its designed temp which is why it has a 195. You mileage will suffer because it will always run in open loop thinking the engines cold, the xtra fuel will burn out your cay eventually and you`ll have no heater. If the coolant was rusty brown after a few days since the last flush you probably need to at least pull the radiator and have it rodded,a simple flush will not do the trick.

I didn't flush it last time, i just drained it all out. This time i flushed it. If its still rusty brown, I will do whats next. I will replace the thermostat with the higher temp one next time i get a chance. I just happened to have a 175 degree thermostat for the jeep laying around the house which is why i put it in.

[barefoot352]

This situation pretty much exacty happened to me today. I ran10 miles into town, made a stop and let the engine run idle for about 10 minutes. Then I took off and about 10 miles later, noticed the "check guages" light on...temp was right at the redline. I thought it was weird but maybe got a little hot idling. Then all of a sudden it shot past the redline and pinned all the way to the right. I pulled over immediately and turned her off. I opened the hood expecting to see the radiator boiling over, but nothing. The hood was rather cool and I did not get notice the engien compartment to be overly hot. I sat for about 5 minutes and took off again. It started at the redline then shot up again and I turned off the a/c and kept driving. Within 20 seconds or so the needle shot back below the redline about halfway between 210 and red. Now I started experimenting by turning on the a/c. Nothing for a few seconds than bam back over the redline. Turned off the a/c and drove it to where I was going. I thought maybe a guage problem or maybe the thermostat but who knows. I have been having probs with my a/c controls being that it only works on full blast and crazier still that is when the dial is all the way to the left in the low position. It will not work in any other position and will only work on the recycle air mode. Once in a while the other modes work but only on full blast...kinda frustrating. With the temp needle pinned passed the redline, I would have expected some boiling over when I opened the hood. Oh, and plenty of fluid, I did check that. Kinda brown looking but I didn't dig into it too much. Start with a rad flush and see what happens? I am planning a day trip to Daytona next weekend and need to get her runnin right.