Erratic Temps

[BHiggins]

Just replaced the radiator in my '92 yesterday due to a pin-hole and a leaking fin, now the temp gauge is surging. The temp goes about halfway up the gauge, then back down to around 1/4, then back to 1/2 and then back down to 1/4. It does this "cycle" every couple of minutes or so. I'm fairly certain it's not the thermostat, when they go bad they usually stick open or closed and this thing is back and forth. I'm thinking I have an air pocket somewhere, but I can't find one... Any ideas??

 

[JGrefenstette]

my gauge moves a good bit also. in 30 degrees or lower, at highway speeds it will go from strait up and down to in between the left third window. it varies with speeds for all seasons. if i hold it at 55mph, it fluctuats more. if i keep it a 65-70, it holds solid on the right end tick of the left 1/3 window (if that makes sence) norm operating temp.



just somthing else to think about... my temp gauges is remotly affected by the volmeter. if i put up both windows and the voltmeter jumps around, the temp needle will move up to a 1/4inch to the right.

 

[BHiggins]

Mine only started doing it when I replaced the radiator. Up until then the gauge would go up until the thermostat opened then it would go down slightly only to level off and remain steady. Even towing a trailer up long hills, my temps were steady. Now it's up and down constantly.

 

[JGrefenstette]

hows your fluid level in the resivoir? is it at the MIN line when cold, and MAX line when hot?

 

[BHiggins]

I filled it to the max line after doing the radiator, haven't checked it after that. Why do you ask, do you have an idea of what might be causing the fluctuation in temp?

 

[JLEONARD]

Air is in there someplace I would think from what you described.



Let it idle for a while with the cap off so air can escape.

When I replaced my radiator it also surged as you are describing, but I was very careful during the fill and let it idle a while with the cap off... hence it surged only 2 times then never again.

Jay

 

[BHiggins]

Thanks Jay, I'll try that in the morning.

 

[JGrefenstette]

i was just wondering if your fluid level was too low and there wasnt enough circulating to keep the temps at a constant... i think Jay's got it covered though.



Jay - do you start the motor cold. with the cap on, then imidatly remove it? how long to you run it for?

 

[JLEONARD]

do you start the motor cold. with the cap on, then imidatly remove it? how long to you run it for

I start it with the cap off and run it until it burps some coolant out. . maybe 15 minutes?? Then I top it off, put the cap on and take it around the block. . it will cycle a couple of times. Then after it cools I pull the cap and top off as needed.

 

[JGrefenstette]

ill give this a try. maybe it will help steady out my thermostat

 

[Greenleaf]

I fill the system with the cyl head plug removed. Then I top it off and operate the engine a few min with the cap off.



I also have removed one of the coolant hoses to the heater and fill till it spills out there then top off and operate a few with the cap off.



Still surges hot to cold/back and forth, over and over again. I have replaced the thermo a couple times with different types and still no luck, however it will stop surging with this new NAPA thermo if I can drive steady for maybe two hours non stop.



Good luck with that. You may want to throw in the towel and just drive it.

 

[BHiggins]

Yeah, I've tried everything I can think of at this point... I'm just gonna drive it.