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Chrysler Sebring 2005 Engine & Cooling System

At idle temperature is above middle. Upper radiator hose, which is connected to the thermostat is hot. Lower radiator hose that feeds back to the engine is cold. Radiator fan will not stop running if the temp guage is at middle to needle above middle. When running the temperature reading is normal at 30 mi/hr (middle to just below middle). Temperature will also go down if at high rpm idle, about 2,500 RPM.

New thermostat replaced last week. Water pump replaced less than one year ago. Upper radiator and lower radiator hoses are pressurized when running and off.

I suspect the thermostat was installed incorrectly. Pressurized hoses mean excess air in the cooling circuit/system. If so, does it mean I have to bleed out the air? How do you bleed out the air on a cooling circuit of a car, I thought the reservoir tank already does that naturally? I think the normal range for the temp guage should be 1/3 of the whole range of the guage, right?

The temperature gauge should be in the middle. Using a scan tool read the engine coolant temperature value, it should be between 195 and 220 degrees at operating temperature.

Which motor?

My Corolla’s dashboard temp gauge reads slightly above mid-way when the engine is fully warmed up. It increases slightly above that during idle until the radiator fan turns on, which causes it to decrease to slightly below midway. But even during idling it only deviates very slightly from the mid-way position, once the engine is warmed up.

Based on what you say, it is possible there’s actually nothing wrong. Why do you think there’s a problem? Have you noticed something about the cooling system has changed recently? Do you notice any coolant loss, enough that you have to top it off once in a while?

You are right that a thermostat installed incorrectly could cause this, and/or air in the cooling system could. But before going on a wild goose chase, good idea to make sure you actually have a problem.

The thermostat is 195 DEG F. The normal range is just under middle of the guage should be between 195-220 as you stated. The question is top is hot, bottom hose is cold, could this be a simple thermostat problem?

With most cooling system designs used in cars, once the engine is warmed up, the top hose should be hot, and the bottom hose should be cool or at most warm. That means the radiator is working.

Is the hot air from your heater nice and toasty?

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Sounds to me like there’s actually no problem

“I think the normal range for the temp guage should be 1/3 of the whole range of the guage, right?”


If that were the case, the engine would fail to reach proper operating temperature. Leading to increased emisssions, decreased fuel economy, and quite possibly a check engine light, due to the engine not reaching proper operating temperature within a specified period of time

my recommendation is to enjoy the car and not lose any sleep over this . . . because what you describe is normal, IMO

Are you rad fans running at higher speeds than 30, if so you do have a problem. All of the Chrysler Corp cars I have owned (many) have kept the temp gauge just below middle.

I think Nevada said to get the actual temperature checked. I may be wrong but I don’t believe the gauges these days are actually reading the temperature anymore or at least accurately. They’ll tell you when its too hot or too cold but other than that don’t rely on it.

Correct, the temperature gauge will read in the center from 180 to 230 degrees. This is the normal temperature range. Cars of the late 80’s and early 90’s would show actual temperature and people would become alarmed while sitting at a traffic light watching the gauge climb before the radiator fans turned on at 220 degrees. Now the instruments are electronic and only display normal and abnormal to please the driver.

And some cars don’t even have a gauge . . . only a warning light when things are too late :fearful:

If the thermostat was stuck closed, the top hose would be cool, not hot. The engine would be hot but the hot coolant would be blocked from getting to the top hose.

In some vehicles, the overflow reservoir will bleed the engine, but not all. If yours doesn’t, then there will be a bleed screw very close to or in the thermostat housing (goose neck). It will probably be a simple bolt that doesn’t hold anything, just screws into the housing.

Personally, I don’t think you have a problem.

I think I may have fixed my own problem. I opened up the thermostat housing again. I poured more coolant fluid down to the engine. I think if there was any trapped air in there, it should be out now. I re-seated the seal and thermostat, then bolted it back down. The generic thermostat that I have doesn’t have a indicator notch like the OEM. Now, the temp guage doesn’t go above the middle range.

You guys were right though, there’s no problem with the system, except perhaps for the thermostat seating, sealing or my suspicion of the trapped air.


Congrats on solving this problem, and thanks for letting us know!

Yes, good job on figuring it out. Whenever I change the coolant in my Corolla or truck the last part of the job is always to turn on the heater to max, then remove the radiator cap and allow the engine to idle until the top radiator hose is hot and water is pouring from the engine into the radiator for 5 minutes or so. That helps rid the system of any trapped air. On some vehicles it works better if you jack the front end of the car up or put the front wheels on ramps so the top of the radiator is the highest point in the cooling system.

The most important part of a cooling system repair is refilling the cooling system, it won’t work without coolant (or some type of fluid).

Overheating returned recently after several repairs. The reservoir keeps filling up, but doesn’t always go
back to its original half fill. I kept the reservoir tank at half full only.

In the mornings, the temp guage on a downhills is low, the temp guage would float very low as if the engine was just starting up. I also don’t put pressure on the gas pedal and just let car drive on momentum. Don’t know if that’s related or TMI.

Replaced the water pump last year.

AC compressor doesn’t run anymore. Didn’t checked that system yet. I don’t know if it’s related here, but warm air through the air vents work.

Another overheating problem I had before this was that the catalytic converter was plugged up. Slowed down to 30 to 40 mi/hr on freeways and uphills. I checked with compression test, no problems. Replaced the cat eventually. New O2 sensors, too. The original problem was “engine misfire,” because of bad sparkplug coil wires. I should’ve replaced the wires quickly, but I tried to drive it home, so the soot clogged up the cat.

Replaced the thermostat sensor last week, because of an error code.
Replaced the thermostat housing (plastic), too, because it warped.
I think I should have replaced the cap, but I haven’t yet.

Before I replaced the above items, the top radiator hose was hot, bottom was less or nearly cold sometimes, but this changed yesterday to both hot. The temperature gauge would also climb past middle at stop signs or at idle. Goes down when I’m running on the freeways. To compensate, I would rev the engine at idle/neutral (2,500 RPM for about 10 to 20 secondcs) to bring the temp back down.

No leaks, except the top cap of the reservoir tank gets wet around the cap.

The fans work when the temperature is at middle or above middle on the temp guage. I don’t know if these should work at one line before the middle.

Relay switch and fuse box under the hood,

I used a DMM. Relay switch (fan lo, #34) is 74.3 across 86 and 85. Meanwhile, an equivalent relay switch on #35 (fan hi) is 73.9 on OHM or resistance test. Sorry, I haven’t done automotive electronics since I took the class years ago, so I’m not so familiar with these anymore. Actual part numbers on the relay switches: 56006709, 50732, and 1714A3.

Off topic: I keep reading about this crankshaft sensor on how it gives you rough idle. I wonder if this contributes to overheating. I’m getting that rough idling too and the engine would even die sometimes at idle/stop. Don’t know if it’s heat or the crankshaft sensor. Car is now 200K+ mi now. I’m discounting the vacuum lines now since I also replaced the check valve and the tubing lines before and after the check valve.

Any ideas would be appreciated. Thanks!

First guess is the replacement thermostat has stopped working. It may be stuck partially open. That would explain under-heating on down-hills, and overheating on up-hills. The radiator fans usually only come on when the temp gauge approached mid-range or higher, so I doubt your fans are the problem.

What I’d do if I had that problem is remove the thermostat, put it in a pan of hot water on the stove, put a thermometer in the water, and check if it opens and closes at the correct temperatures, and to correct full-open dimension.

Rule a faulty thermostat out before considering the other ideas is probably your best bet. In the meantime it’s critical you check the coolant temp gauge at all time and turn off the engine immediately if it starts to over-heat. As it begins to overheat sometimes you can get a little leeway by turning the AC off and turning on the passenger compartment heater to max, heater fan to “high”, that operates like a mini-radiator and will provide some engine cooling. Not a pleasant experience though to turn on the heater when it’s 95 degrees out.

If the thermostat tests ok, probably next step is a cooling system pressure test. You could of course just replace the cap on a flier.

Why haven’t you replaced the radiator cap yet?