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Discussion Starter #1
About two weeks ago the temp gauge on my car went to the H about 5 minutes after starting the car and driving through town. I pulled over and let it cool for a bit and started it and it started climbing again but then the thermostat opened and everything seemed fine for the rest of the trip. I assumed the Thermostat was going bad. I get a new fail safe T-stat and installed it. Today the same thing happened with the new thermostat. Any ideas? The gauge was at H and the check engine light blinked on a few times. then I shut it down. The coolant is full and the new thermostat has a small hole in it so there shouldn't be any air trapped. The only other thing I could think of is the radiator cap not releasing. I don't see any milky oil or bubbles in the rad that would indicate a head gasket. I can't imagine a water pump causing this issue either.

Benji
89 Spirit 2.5 turbo auto
 

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Why'd you let it get that hot? Its really not good to let it go much past normal operating temps... thats a good way to blow a head gasket.

I've had thermostats go bad less than a week after buying them. Might be that. Try sticking the thermostat in a pot of water and heating it up and seeing when/if it opens?
 

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Running hot 5 minutes after start up is quick so a few questions. The check engine light is flickering because the CTS is going out of range.Usually overheating that quickly is a sign of head gasket failure and I can tell you from experiance that you may not notice anything else until it fails completly.I was only losing coolant from the overflow bottle every two weeks and then one day BOOM!!!!
Does the cooling fan come on?
Does it continue to run hot while cruising at 40-50 mph?
What condition was/is the coolant in?
Can you see deposit buildup in the radiator core?If so you can bet the water jacket looks the same way.
Remove and inspect the spark plugs,if there is coolant entering a cylinder that plug will be very clean.
Read the "sticky" "Overheating Version 2.0" in the "help" section.I posted Chryslers complete diagnostics for "Running Hot/Overheating" and it has ways to check for combustion gases entering the cooling system.
Also to be absolutly positive all air is out with the engine cold remove the hex plug in the head behind the T-Stat and then fill the rad until the coolant level stays at the top of the opening.
 

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Discussion Starter #5
Pulled the plugs and they all look fine, light brown some carbon build up, normal looking TD plugs. Also when it got hot the first time the upper radiator hose was still cold when I opened the hood, another reason why the thermostat was my first thought. After checking the plugs I took the car for a ride and the needle went up to about 3/4 then dropped to 1/4 and leveled out. I'm still leaning toward the new T-stat being bad, I sprung for the more expensive stant thermostat that the guy behind the counter said was fail safe but I see no mention of it on the box. Do you think they just sold me a premium regular thermostat for 10 bucks? Also the radiator was replaced in 2004 and the coolant replaced then also. Looks and tests good.

Benji
 

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Stant is high quality.If you are not sure about the stat replace it again,new does not mean good. If you can remove the hex plug in the head I recommended doing so to be sure all air is out of the system especially since you are experiancing problems,you want to be sure all steps are taken to ensure that the job is done correctly so that if the problem still exists you can 100% rule that out as a cause.
You may not be able to trust the factory temp gauge as far as accuracy.Backprobe the CTS connector with a digital voltmeter and compare the voltage to the voltage table in the sticky in engine management and then you can see what the actual temp is that the controller is seeing, unless you have a scanner then use that.
 

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Discussion Starter #7
I'm going to keep the scanner in the car to verify temp if/when this happens. I pulled the hex plug and there isn't any air in the system. The new stant thermostat had a hole in it from the factory that I'm assuming is to let any air in the system through to bleed out. Also there are 2 sensors for the coolant one for the gauge and one for the computer right? I'm going to try the car again tomorrow and see if I can get the problem to show up again but I think I'm going to get a replacement T-stat tomorrow just to rule that out.
 

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Yes, there is a single wire sending unit in the front of the block for the gauge and the coolant temp sensor in the head by the t-stat that the controller uses for fuel control and cooling fan control.This is the info you will be reading with your scanner.
 

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Discussion Starter #9
that's what I thought.
 

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Are you sure if the cooling fan is coming on? I hope this wasn't already brought up, but that can make a car get warm pretty fast.
My GLHS had the relay get bad last summer and the car heated up pretty fast. Got really hot too. Sometimes it worked and the fan came on and all was fine. I tapped the relay while the car was getting real hot and the fan came on instantly and cooled everything down. Needless to say, the relay got replaced and all was fine after that.

How about the heater core? I'm not familiar with what type of system your car has. Do you get good heat? If not, maybe it's plugged.:fingersx:
Last year I had a heater core clog up almost over night. The heat got really bad and the temperature went up fast. If your car is one "W/O" the heater control bypass under the hood, this can be a problem. The coolant must go through the core on these types of vehicles and if there is any obstruction, it WILL over heat and do it pretty fast. I flushed my core and the the heat came back and the temperature was fine. If you have the bypass control under the hood, this would not be an issue.
Good Luck. It's always nice when it's not a head gasket. Once in a great while, we get lucky.
 

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I just helped a friend replace a head gasket in a '94 Shadow with the 2.2. The engine was building high cooling system pressure immediately after startup, and pushing the coolant into the resevoir. We removed the head, and the head gasket was in absolutely perfect condition. Not blown at all. Cleaned up the head surface, put a straight edge and feeler guage on it. It had somewhere around .007"-.008" of warpage. Those of you who do the quickie head gasket changes will want to make note of this. The head gasket did not fail, but the head warped from overheating, which simulated a failed head gasket. Cause of overheating was a leaky radiator and neglect.

What causes the engine temperature to go WAAAAY up before the thermostat actually opens is a small leak somewhere in the cooling system. A big pocket of air develops in the thermostat housing, making the thermostat only half submerged in coolant, so it takes a LOT of heat to make it finally open. When it does open, that air pocket is purged instantly and the thermostat regulates engine temperature just fine for the rest of the day. The leak could be anywherej--internal or external. The solution is to drill a very small hole in the thermostat to alleviate thies problem, and your thermostat has that already. Install that hole at the 12:00 position.

Checking for bad head gaskets is quite simple. With a cold engine, start it up, and then take the radiator cap off. If there's pressure, your head gasket is leaking from either a bad gasket, or a warped head. And of course, coolant in the oil is another sign. Other ways of doing it is to use a cooling system pressure tester, pressurize the cooling system and see if it holds pressure. If it leaks, but you see no external leaks, well, it has to be going somewhere.
 

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Another way is to do a simple compression test on a cold engine ... but pay close attention to the values. You might even get lucky and be able to feel/hear the gap between the cylinders.
 

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Discussion Starter #13
Had the scanner in the car this morning and went for a ride. The temp went up to 210 then the t-stat opened and it dropped to 165, then climbed to 205 and dropped to 180 and stayed about there. Now this is suppose to be a 195 T-stat and the old one would keep temps right in that area when cruising on the highway. When the temp starts climbing I have good heat in the car so the heater core is good and as stated before the radiator is newer with a coolant flush. I'm going to pull the t-stat later on once the car cools down and go exchange it at the parts store and give that a whirl.

Benji
 

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I know this sounds crazy,but make sure the T stat is facing the right way. They will go in either way and it will open. They will get hot in under 10 minutes if they are facing the wrong direction.
I have seen this happen to people when changing out a T stat.
Sometimes getting in a hurry it is easy to not pay attention as to how they are pulled out. :bang head
I seen this done on a few cars.
I had a issue like this and it was my heater core. I unhooked a hose off of it and hooked a longer hose on it and tried to blow through it and I bout passed out!
It was plugged up big as day.
Good luck
 

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Discussion Starter #15
Nope, T-stat will only go in one way. Doesn't clear if inserted the wrong way. I got a new T-stat and installed that with the small hole drilled in the top. I haven't had any overheating issues but the car only gets up to 180 on the scanner. The gauge in the car shows about 1/4 or so. After letting the car sit for a while the temp will climb to about 210 and the fan kicks on and brings it down. I'm positive it's a 195 T-stat but am confused that they both only go to 180 before they open. I'm wondering if they had a bad batch or something or if the temperature gauge is off. I'll have to look at it next weekend after I get home from work.
 
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