up and down temp.

[dans99]

I replaced the radiator and t-stat today. Now the temp.is going up and down. it goes to the line before the 210 mark then back down to the normal spot. it will do this while driving and just ideling. I thought I bought a crappy t-stat so I got another one different brand (failsafe one). I bled the hell out of the system. Let it burp with the radiator cap off with the heater on high. I have done radiator swaps before but never had a problem. Any suggestions??

 

[07Burb]

This actually seems normal to me. I did this same thing in a 95 I had and it'd go between a high of 200(or slightly higher) and back down to 180(or slightly lower) after the radiator and tstat change.

 

[dans99]

would the temp. keep going up and down all the time like that?....Before the swap my temp. would go up till the t-stat would open then come back down and stay at the normal mark and never move from it.

 

[96ProCompTahoe]

mine stays around 180-190 all the time once the t-stat opens. new rad. hoses, t-stat, water pump, no bouncing here.

 

[TahoeJim]

Moving up and down continually is not normal.

Is your overflow/reserve tank filled to the line and that hose attached to the radiator? How old is the radiator cap? Replace that with a Stant for $11.00 if it's more than a few years old, make sure the radiator is holding pressure.

With the cap off, squeeze the top hose slowly and see if you can burp anything when it's cold. Put the cap back and leave it on there, don't remove it again. Drive it for short trips, just to get the t-stat to open. Park the truck and let it cool down. Check that overflow tank and make sure it's at the line for hot or cold.

 

[retorq]

I did a Vortec swap and have been chasing down a cooling issue ... the temp up and down is definetly NOT normal. My thermostat bypass is kinda screwey, I drilled a few hols in the lip of mine and that helped a little. Still gets hot enough to kick the fans on but registers 180ish to the computer.

 

[2K6TBSS]

I am experiencing the same problem with my 99 Denali. I replaced the intake manifold gasket, and since everything was already out (or very easy to access) I did a coolant system refresh. After bleeding the system, I noticed the gauge was going from about 210 to under 175ish.

I hooked up my scanner and looked at the coolant temp live data and it was sitting right at about 185, even when the gauge was reading 210.

Is this "normal" probably not, but I know that in my instance the vehicle is not running with drastic temp changes, even though the gauge is telling me different.

 

[SunlitComet]

What condition is your fan clutch in as well?

 

[Sweet_N_Low]

Temperature sending unit?

 

[NorCalBryan]

Temperature sending unit?

Wouldn't the ECU get the temperature from the same place, though?

---------- Post added at 12:49 AM ---------- Previous post was at 12:48 AM ----------

...nevermind, I was reading 2K6TBSS response.