Needle shows warm, drops, goes back up, drops...

[Psych0matt]

So I noticed today that my car is doing something weird... As I'm driving my temp gauge will get up to around half, maybe a little over, but right where it should be basically, and then will drop decently low. Get warm again, drop again. Rinse. Repeat. I took a couple videos on the way home, same trip, I didn't think the first one took. New 180° thermostat (only because I had it laying around), radiator cap seems to be working just fine, topped off the coolant after the thermostat was put in, and heat seems to be functioning normally. I've just never seen something like this:

 

http://s87.photobucket.com/user/Psych0matt/media/Mobile%20Uploads/IMG_0230.mp4.html

http://s87.photobucket.com/user/Psych0matt/media/Mobile%20Uploads/IMG_0231.mp4.html

 

 

Ignore the low oil light I just added some yesterday, but it seems when it's cold out it thinks it's low when I first start it up

[l67ss]

Id rebleed the cooling lines

So I noticed today that my car is doing something weird... As I'm driving my temp gauge will get up to around half, maybe a little over, but right where it should be basically, and then will drop decently low. Get warm again, drop again. Rinse. Repeat. I took a couple videos on the way home, same trip, I didn't think the first one took. New 180° thermostat (only because I had it laying around), radiator cap seems to be working just fine, topped off the coolant after the thermostat was put in, and heat seems to be functioning normally. I've just never seen something like this:

 

http://s87.photobucket.com/user/Psych0matt/media/Mobile%20Uploads/IMG_0230.mp4.html

http://s87.photobucket.com/user/Psych0matt/media/Mobile%20Uploads/IMG_0231.mp4.html

 

 

Ignore the low oil light I just added some yesterday, but it seems when it's cold out it thinks it's low when I first start it up

[94 olds vert]

Stop going up and down hills

 

Temp sensor. I just had to replace mine in the GTP.

[Psych0matt]

I need to do that and the level sensor then... Hopefully that means I haven't got as hot as I've seen it... At least it otherwise seems to be functioning normally now.

[Psych0matt]

Oh, also no hills. Pretty much flat

[94 olds vert]

Oh I know its flat in MI. Lol

[RobertISaar]

if you had some magical way of checking the guage against what the PCM is seeing, that would be a great diagnostic step....

[Psych0matt]

if you had some magical way of checking the guage against what the PCM is seeing, that would be a great diagnostic step....

 

[RobertISaar]

[tornado_735]

Air in the system, rebleed. Been there a hundred times when my LQ1 leaked water for 6 months.

[Schurkey]

Did you change the temperature that the fan(s) activate at?

 

Kinda silly to have a 180 thermostat if the cooling fan doesn't come on until 210 or somesuch.

 

If bleeding air doesn't fix it, I'd say it's a sticking thermostat.

[Psych0matt]

Did you change the temperature that the fan(s) activate at?

 

Kinda silly to have a 180 thermostat if the cooling fan doesn't come on until 210 or somesuch.

 

I agree, but I'm poor and had this one brand new sitting around, as I said. The old one seemed to be sticking, but this one seems to be working, although I think I have air now.

[19Cutlass94]

My truck does the same thing. Hooked up a scanner, and it never goes above 182* ( 180 themostat ) and only varies about 5-6*. Damn GM gauges.

[dhdolphns]

I know this is an old thread but in case your still looking or like me your on here searching for an answer to a simular problem I thought I would respond-------I dont know what car you have but if its a 92-96 Cutlass there is a TSB on Temp gauge not reading correct temp and cooling fans not working as well due to this issue.. I have a 95 cutlass with the 2 wire coolant temp and the 1 green wire temp gauge sensor..if you have this set up it could be the problem.

 

heres the info I found on it

 

http://www.justanswer.com/chevy/37jd6-95-olds-cutlass-supreme-sl-temp-gauge-gauge-goes-temp-sensor-tsb.html

Edited March 24, 2014 by dhdolphns

[RobertISaar]

1-wire sensor drives only the guage, is in no way connected to the PCM or fans.

[Psych0matt]

It was just a losing coolant and becoming low issue. It happens when it gets too low, but never if I keep it topped off