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Thermostat stuck open?

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Joined: 22 Jan 2008

PostPosted: Mon Feb 25, 2008 8:17 am    Post subject: Thermostat stuck open? Reply with quote

I have a 1999 JGC and after going through a million diagnostics, am still having issues with lack of heat in my car.

I have a 6 month old cooling system, almost completely restored - including the thermostat.

I don't think it is the heater core, the blend doors or anything else like that.

Now, one thing that has struck me is that, while pretty new, the thermostat could have gone bad prematurely, and that is at least an EASY FIX.

My temp gauge (which, BTW SUCKS insofar as gauging temperatures) come up fairly short of the halfway mark, and takes a while to get there.

If the thermostat was stuck open, would it even get that high?

Can someone explain the symptoms of a thermostat that is stuck open?

Help! (please?)
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swamp boy
Cherokee Muderator
Cherokee Muderator

Joined: 01 Jan 2004
Location: New Orleans LA.

PostPosted: Mon Feb 25, 2008 9:25 pm    Post subject: Reply with quote

Where are you >IE what state??

If its very cold there and you put a 180* thermostat.. it may be keeping your engine to cool..

Your thermostat should be 210 .. But assuming it is a 210* stat.. It very well could be stuck open.. Your temp will rise up to normal and then drop down and stay there.. It should climb and drop once in a while if its operating normally....

You can do like alot of people who live in cold weather areas and put cardboard between your grill and radiator.. That should get your temp up..
Then keep and eye on your temp and see if it gets around 200... The fan and thermostat should keep your engine from over heating even without outside air blowing across it..

When I lived in Michigan I did it.. It was the only way to get any heat out of the little 4 banger I was driving...
Unless you include the sawzall work..

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Joined: 22 Jan 2008

PostPosted: Tue Feb 26, 2008 7:10 am    Post subject: Reply with quote

Thanks for the response.

I live on Long Island in New York. While it is not Florida by any means, average daily temps are in the 30's and low 40's sometimes and we can dip into the teens at night where I live.

The previous owner (my bro-in-law) had a major cooling system repair, including the tstat back in September of last year. I ASSUME they replaced it with the stock temp of 195. I wouldn't know what it is unless I opened her up and replaced or checked it.

Thinking about it, and judging by some of the symptoms I read, I am still not convinced it is the tstat.

The temp gauge on my instrument cluster is useless - its broken down by evenly spaced hash marks yet the increments are impossible to be spaced like that. Anyway, it SEEMS as if, when fully warmed, the needle sits around what I can only estimate is indeed 195. Should it be closer to the 210 mark?

From what I gather, if a tstat is stuck open, your guage wouldn't even come close to the level of the 195 temp (assuming that is the temp level I have in there), is that correct?
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