temperature gauge fluctuating

[gruntsey]

I looked in a search for "temperature gauge" and "temperature sensor", but couldn't find the answer to my question.

The cooling system temperature gauge in the dash panel is fluctuating between about 150 and 210 degrees F. This just started happening today...I don't want to take it to the mechanic until I have a better idea of what is happening.

What I want to know is, what might cause the gauge to fluctuate while the car is being driven?

Thank you,
Kirstie

oops, it's a 1997 Cherokee Sport 4.0L 4wd automatic transmission

[Po Pilot]

Have you checked your coolant level? A low coolant level will do that - at idle it heats up and when in motion the temp will drop. Anything up to 210 is normal as the I6 runs about 210.

[Saudade]

How quickly does it fluctuate? Are you sure the lower number is around 150?

[fergmonster]

its normal for them to fluctuate some. but once they warm up, they generally don't go all the way down to 150. the top number of 210 is pretty normal though. I replaced my thermostat (with a 180 degree one) and thermostat housing and mine doesn't move at all. sits right on 180-190.

[gruntsey]

Originally Posted by Po Pilot

Have you checked your coolant level? A low coolant level will do that - at idle it heats up and when in motion the temp will drop. Anything up to 210 is normal as the I6 runs about 210.

Yes, the coolant is fine, and yes, it normally runs about 210F.

Yesterday was the first time the gauge has indicated a different temperature, at least since I bought it in July last summer.
I don't know what parts had been replaced on the vehicle before I bought it...so I was concerned it might be the gauge or something more serious than the thermostat, which is now what I think is the problem.

If it isn't the thermostat, it might be that sending unit....I'm going to replace the thermostat first.
I have a friend who can help me with that on Saturday so I don't have to go to the mechanic...yet...
and the thermostat was only $10...that's worth it to me to not have to worry about it this summer.

[gruntsey]

Originally Posted by Saudade

How quickly does it fluctuate? Are you sure the lower number is around 150?

It didn't fluctuate rapidly, but it was noticeable and after a little while, it stopped fluctuating and stayed at 210. Then, today, the temperature gauge never got past the middle mark between 100 and 210....and this is the first time since I bought the vehicle that the temperature gauge has behaved this way. Also, the heater isn't blowing hot air anymore.
I really think it's just the thermostat...I'll find out on Saturday when it gets replaced. : )

Thanks for the replies, everyone!

Kirstie

[gruntsey]

I don't think the previous owner did a lot of maintenance to the vehicle...just whenever something broke on it...that seems to be the case anyway, but before she owned it, it was a state vehicle, so I know it got at least minimal regular service for most of its life. The neutral safety switch has had to be cleaned and the power steering pump went out since I bought it, so it could be that the water pump may be next...time will tell!

[fergmonster]

its very simple to change, where are you located? and have you gotten a quote yet? j

[gruntsey]

Originally Posted by fergmonster

its very simple to change, where are you located? and have you gotten a quote yet? j

Yes, I called PepBoys service dept. (I've had other work done there before at reasonable prices) to see how much they would charge to find the problem, and they want $82 just to look at it....but I can't see paying that kind of money just for a thermostat replacement.....so I called a friend of mine and he said he can help me change the thermostat on his day off Saturday. I'll have to sew a new shirt or something for him, but it will sure beat paying $82! I could probably do the thermostat myself, but it would take me forever and I'd like to have the job completed the same day... .lol

[MidNightBlue]

Don't go to Pep Boys.... Inadequate Tech's & Over Priced.
It sounds exactly as if your thermostat is sticking.
Which is a common issue in the spring.
You're on the right track

[Saudade]

I'm gonna go along with the others and suggest you change the thermostat first. It's relatively a simple job. Sounds like the t-stat may be sticking open and allowing coolant to continually flow through the radiator.

[gruntsey]

Originally Posted by Saudade

I'm gonna go along with the others and suggest you change the thermostat first. It's relatively a simple job. Sounds like the t-stat may be sticking open and allowing coolant to continually flow through the radiator.

Yes, it seems the thermostat was the problem. The gauge now seems to be functioning properly. I won't know for sure until tomorrow afternoon when I give it a real test drive. I think it's going to be fine, but my friend made me promise to let the sealant cure for 24 hrs before I drive it more than what I had to to get it home from across town.

If I had my way, I 'd have this friend who put the thermostat in do ALL my mechanic work, he's knowledgable enough, but unfortunately, he has his own life...so I am glad there is the mechanic at Pep Boys...there is a man in their service dept who knows Jeeps well, he's done other more complicated work for me before, and much cheaper than what the dealer would charge. So I trust this guy for the things that have to be done in a shop. I realize what the other poster was saying about 'generic' service mechanics..but this one mechanic is not your typical generic mechanic. I won't take my car to just anyone to work on...I have to know they know what they are doing before I will even let them touch it... and that comes from lessons learned the hard way. lol

[Saudade]

Glad it works! If you trust your mech then stick with him.