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Discussion Starter · #1 ·
Driving to work this morning about 20 minutes from the house, my check gauges light came on, and I noticed that my engine temp was just at the beginning of the red area - not quite 260, but much hotter than normal. I pulled off the highway and shut the Jeep off to let it cool down. After about 10 minutes, it was back down to 210 so off I went. About 10 more minutes down the road, same thing only I was off the highway at this point. I stopped again and after cooling down made it the rest of the way to work (about 10 more minutes) still running hot. No smoke from the engine bay or tailpipe, and the coolant was not boiling. The interesting thing to me was that the gauge needle was not moving smoothly like it does on a normal day while warming up. I saw it jump from 210 back to the red line the second time, and then again from there to 260. No gradual heating, so maybe something with the thermostat?

Also, just before I got to work, I got a nasty squealing in the left front. Sounded like a suspension squeal, as it was only audible above about 25 mph, and it wasn't constant. It fluctuated louder/softer as the wheels were turning.

So now come the fun parts. Specs: 1999 TJ Sport 4.0L I6, stock everything.

1. Getting home today after work. Is it safe to drive if I can keep it off the highway and stop for a few minutes if it gets too hot, and also will the suspension hold up for the 18ish mile drive?

2. Determining what is causing the overheating. My wife and I went wheeling Saturday, but it ran fine the rest of the weekend. This morning was the first highway driving since Saturday, so perhaps staying on city streets will be less trying on the engine?

3. Determining what is wrong with the left front. My first thoughts were of bearings and bushings. I will run by a carwash today and pressure wash the underside (just hosed the mud off Saturday, maybe something stuck up in the cracks?).

Any help would be greatly appreciated. I am hoping to start with the cheaper end of things and rule them out before I have to dump a bunch of money into it. If that becomes the case, it may just be time for some upgrades (which I may or may not be able to afford right now)!
 

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It's your thermostat

If you take it slow you should be ok, but you need to let it cool down completely of you can before driving.

If it overheats too much you can get the dreaded blown head gasket/ warped head. Quite costly

As far as the squealing goes, get it home and get it on jack stands then start turning your front wheels. Also shake your suspension components, could just be that something needs grease.
 

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That makes for a good start to a day. If I'm not mistaken... The gauges are not linear, meaning they have roughly 3 readings. Cool, normal, and hot. Say if the gauges settings for normal were 160-250 your jeep could be running 249 and read normal but the second it goes over 250 it will skyrocket to hot. Most factory gauges are like this. I would look at the thermostat in hopes that it's just locked in a closed position. Do not drive it while too hot, I have a set of warped heads in the garage from my 370z after a track day when the z started running hot on the last lap at Atlanta motor speedway. That was a big hit to the pockets. Heat is an engine killer.
 

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I had a problem with mine with the guage shooting up like that turned out it was a bad guage. Go to autozone and get the normal off the wall guage and screw it in and check it your temp and if its still over heating return the guage for a flush kit and a therm.
 

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check

Check the coolant level to see that you aren't loosing any. Don't want it to get low. EX-SIL did that when I told him to bring the vehicle down to the house so I could fix radiator. He SAID it never got up to the redline, BUT he let it run low of water. That ended up ruining the engine! And he had water along to keep it full1:firedevil:

When it is hot, check the top radiator hose to see if there is flow. If it is hot, then there is flow, if not, then it is likely the thermostat or water pump. If you have tools, you can take the thermostat out and run without. You can check that at lunch time by warming it up till thermostat should open.

You can run the heater full blast. That will provide some cooling.

When it is cool, open the radiator cap and have someone rev the engine. Even with the thermostat closed there should be a lowering of the liquid in the radiator. If not, then the fins may have let go on the water pump shaft. I have had that happen. Fan tight, bearing good, shaft spins inside impeller. If that is the case, the you really need to break up the drive home because you will get hot spots at the cylinder walls.

If there is flow, then easier to control driving. Check belt tightness to make sure it isn't slipping.

See if it heats up this noon, maybe just idling in the parking lot. If the upper radiator hose is hot, feel the cores of the radiator to see if there is any heat getting to the core. May just be restricted, but not likely if it came on sudden.

While the engine is warming up, rev the engine a little (1200 rpm type) and feel the heater hose. There should be flow through the heater hose all the time. If it isn't getting warm, then there isn't any flow from the water pump.

You need to picture what is happening in the cooling system, then you can use heat differential to diagnose. The water pump sucks water from either the radiator and/or the heater in through its inlets and forces it back into the engine. That pushes the coolant out through either the radiator hose, heater hose, or both. If the thermost is closed there may be a bypass that lets some flow through to relieve pressure on the water pump.

When the thermostat opens, then the water can flow out and through the radiator.

With that in mind, you can feel the hoses, and depending on the temp of the engine you can feel where the water SHOULD be flowing. That lets you feel what is happening and isolate where the trouble is.
 

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Discussion Starter · #7 ·
Thanks, all, for the advice. I think I am going to pick up a new thermostat and a tube of grease on the way home. Anybody have any tips or tricks for the thermostat change?
 

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Discussion Starter · #10 ·
Well, I'll call it a rookie mistake. Got home OK, just took it easy on city streets and it ran a little warm, but not into the red. Popped the hood when I got home to check the coolant level in the resevoir and noticed that almost all, say about 80-90% of the back side of the radiator was still covered in mud :facepalm:. Needless to say, I was torn between embarassment and excitement. I got it cleaned off and am going to see if that helps tomorrow. The coolant resevoir looks a little off color, so I think I will drain and refill the radiator. I will probably check hoses for debris while I have it empty also. Thanks again for all the advice. If this doesn't help (can't imagine it won't), the thermostat will be next.
 
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