ok this is puzzling me, brand new BR built motor in my car. this motor has 200 miles or so on it.

driving the car today in 85 degree weather home from the gym the temp was bouncing all over the place. idle/cruising it would jump up then drop back down. its bugging the **** out of me, doing pulls the temp will rise and drop back down as well.

headgasket and water pump are brand new. i did a 1st and 2nd gear pull right before i parked it and the overflow isn't filling up, nothing is mixing. not losing any coolant, heat blows hot.

i also tried bleeding my coolant system, i will try again tomorrow and see what happens.

however i did notice while bleeding the coolant the ground on the front of the thermostat housing is loose, would that have any affect on the reading its giving me on the inside of the car?

 

It sounds like Air in the system to me.

 

Air in system or a crap thermostat...$.02

 

No clue, but good luck.

Hope you figure it out so you have no issues in the future.

 

you either have air in the system or the thermostat is sticking.

 

+1 to air on the system or the thermostat took a crap!!!

1st thing you can do is bleed the system again, if that doesnt work run the the car without the thermostat.

 

Could be a bad thermostat. A bad connection to the coolant temp sensor can also cause erratic readings. When you say it "bounces all over the place" does the gauge fall to below operating temperature, or does it jump up and then down to operating temp? If the needle is dropping below operating temp, you've got a bad sensor or a bad connection.

 

it jumps up and down then goes back to operating temp. i was thinking about that last night because while david was tuning the car the sensor through a code, i cleared it when i got home and it has never come back on though.

ill bleed it again today and see what happens!

 

i think your ground was prob the issue. if gauge bounces around prob getting false resistance signal.

 

Could be a grounding issue as well. We had a customer bring his car in for "overheating" issues and it ended up being a grounding issue. The temp gauge was also all over the place. When the car would "overheat," we hit the radiator with the laser temp gun and it was the same temp at operating temperature. We also noticed when we hit the rear defrost button, it would "overheat," and as soon as we turned the defrost off, it would go back to operating temp. That's how we knew it was a grounding issue. Put a grounding kit on and problem solved.

Check the thermostat and bleed the system first. If that doesn't solve the issue, I'd lean towards a grounding problem.

-Josh

 

How olds the thermostat? Mine started to crap at around 90K..replaced it no "overheating" issue.. it was just sticking. Like the rest have said either air in the sytem, grounding or thermostat bad.

 

if the ground from the intake manifold to the firewall is missing this can happen for sure-

cb

 

Common thing that is forgot when people are putting motors back together. just a simple ground will make the motor overheat.

Also check for air in the coolant. If those two things are good then try a themostat.

Mikey

 

thanks fellas, thats a good point. i never did put that ground back on the car when i put it back together!

thermostat only has 44k on it

 

^ Then that is your problem

Let me know if it fixes your car and I'll close this thread! Thanks

Mikey