XJSurfcaster

On the way home from work today, I noticed that the temperature gauge was not moving, didn't really think much about it since the car was only running for 5 minutes, but it was warm out and I guess I was expecting the car to warm up rather quickly. Gauge went up to about 120 or so and stopped. Then I stopped at a light and the gauge shot up to 210 very quickly, the electric fan kicked on, and the gauge instantly dropped back down to about 120. Got moving again, went to turn into my neighborhood and the same thing happened again. My ride home from the train is only about 2 miles, takes roughly 10-15 minutes depending on traffic. Opened the hood when I got home and everything looked and sounded fine, no leaking fluids or anything (first thing I checked was the head and thermostat). Had the car off for about an hour and I had to run to the store to pick up some stuff, temp gauge never read more than 120 the whole way there. On the way home, same thing happened as before, but this time while driving. I made sure to keep my eye on the temp gauge very closely after I initially spotted this.

I installed a throttle body spacer this weekend, but I ran about 80 miles on the parkway between Saturday and Sunday and another 55 miles last night and didn't notice anything. I distinctly remember last night seeing the temp gauge slightly above 210 consistently (my normal operating temperature) because I have been watching the gauges for problems due to the addition of the throttle body spacer.

Any ideas on what may be causing this issue with the temperature and/or gauge? I appreciate any input guys, I am completely stumped.

kyledye25

Check your coolant temp sensor.

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djb383

Did the efan turn off when the gauge dropped?

XJSurfcaster

Yes the efan turned off when the gauge dropped.

Thanks for the suggestion kyledye25, I will pick up a new sensor when I get home tonight and see if that changes anything.

Dre

I had this problem with an 89. Look at the weep hole on the water pump and all hoses. Visually inspect it. If you find nothing wrong and the hoses aren't spongy, look at the radiator. For almost a year, i was replacing hoses, pump and other things. I checked the thermostat housing and changed it. Until one day, with the right light, I saw antifreeze stains on the radiator. I looked all around it. In a hole on the radiator support, I saw so much antifreeze buildup, I pulled the support off. Just so happened that the seam was corroded! Pays to look it over!

kyledye25

I agree with Dre. Look over everything for sure. I just cleaned my coolant temp sensor. It was working fine but I pulled it out anyways and it was all gummed up and sludge. But I have a new one waiting to be put in. Just haven't gotten to it yet. I'm going to install it when I buy a new radiator. Then everything cooling my XJ will be replaced and in proper working order. Lol I hope so anyways.

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XJSurfcaster

Thanks for the help guys. I wish I would have read this before I left the house last night. I started to smell burning coolant when I was running an errand yesterday so I popped the hood and after some close inspection I found a leak at the thermostat housing. Nothing major, but the coolant levels dropped so after I added water, gauge problem solved. I am going to be putting in a new gasket, new Coolant Temp Sensor and this thermostat: http://www.autozone.com/autozone/par...1_0_1640_93208. Think the increased flow thermostat is a wise choice or should I stick to OEM recommended? The OEM says it opens at 192 degrees and the new one will open at 160 degrees.

Hopefully this fixes the problem. Also going to have to flush the coolant and put in new since I dumped almost a full gallon of water into the system yesterday. Might as well get a new radiator hoses as well while I am at it.

XJSurfcaster

Another question, does anybody think this could have effected the heads at all? I just want to make sure that I fix everything with this coolant issue all at once. I checked the engine oil for coolant and didn't see any in there so I am hoping this is an isolated problem.

Thanks for all the help guys!

1991Jeep_Man

With you living in NY where the heat doesn't become insane, do NOT use a 160* thermo. If the temps don't rise above 80*, I wouldn't use a 180* either. Use factory. Having the coolant flow sooner will keep your engine cooler for longer, screwing with your mileage. Your 4.0 needs to run at its OEM operating temp.

XJSurfcaster

Thanks for the info 1991Jeep Man. I am from Long Island and I run on the beach about 3-4 times a week and everything heats up rather quickly driving on the soft sand so thats why I was thinking about the lower temp thermostat. I will stick to the OEM settings and maybe figure out some other sort of other cooling options for when I am on the beach. I was reading about switch operated efans, maybe that will be the ticket.

Thanks for the advice.

djb383

How did u check the t-stat? How old are cooling system components? If u replace everything at once, u only have to do one coolant drain.

XJSurfcaster

I never actually checked the thermostat to see if it is working. After I added the water, it appears to be working correctly. Gauge is increasing as it warms up and then it stays pretty consistently at about 215-220 or so, which is the temperature that I am normally running at. I just figured that since I am going to replace the gasket, I might as well get a new housing and thermostat along with the coolant temp sensor.

I am debating putting in a new cooling system all at once now, but I am just not sure what I want to do as far as upgrades yet. It appears to be the original cooling system, only had the XJ for 3 years now and all I have done to the cooling system is get the coolant flushed once a year. I don't really have any normal problems with overheating, but the transmission gets pretty hot on the beach so I was thinking of putting in a tranny cooler and getting a new radiator with an oil cooler built in.

I have a get-together on the beach tomorrow night, so I am looking for a quick fix now, while I research and design my build. I am not too sure what the end product is going to be yet, so that's what is making me hesitate on doing the whole cooling system this weekend.

Any input and suggestions for the cooling system is greatly appreciated.

djb383

215-220 is toasty and could easily get out of hand quickly when u least expect or are prepared for it. I think u may be close to a overheat situation. Time for complete cooling system maintenance/replacement. It's a lot easier to do maintence in the driveway when the parts stores are open than on the beach at night when the stores are closed. Hot weather is almost here.

Quickest way to cool off a hot chick is with a overheated Jeep.LOL

XJSurfcaster

That's a great line man.

I figured that the temp was normal because the middle of the gauge is 210. It goes just over and stays there pretty consistently, even on the pavement. Guess I will start to research some new radiators this weekend and tackle a new radiator next weekend. What temps should I normally be running?

1991Jeep_Man

Do you still have all the stock equipment? (water pump, radiator, etc..)