Engine running cool / Thermostat replacement

[Maim Menu]

I noticed some time ago when going downhill on the highway and releasing the gas that my temp gauge was going down between middle and C (a quarter basically). The coolant tank is slightly above the FULL mark, could that be why?

I'd also like to change the thermostat cause it seems like a pretty easy job to do but do you absolutely have to flush out the coolant and refill or you can just replace the thermostat and top off the tank/radiator afterwards?

[ag6286]

Well it will go down slightly on the hill but not really that noticable, i would place a safe bet its a faulty thermostat, its not outputing the right voltage probably

[hilux5084]

"I noticed some time ago when going downhill on the highway and releasing the gas that my temp gauge was going down between middle and C (a quarter basically). The coolant tank is slightly above the FULL mark, could that be why?"

The coolant overflow tank slightly over full wont affect cooling I would think it is normal your going down hill no engine load lots of cold air the temp will go down.


"I'd also like to change the thermostat cause it seems like a pretty easy job to do but do you absolutely have to flush out the coolant and refill or you can just replace the thermostat and top off the tank/radiator afterwards?"

You don have to flush the system, only flush if it been in for more than two years since the last flush.

Joe

[T.YORK]

sure, it`s a normal situation for a car

[Maim Menu]

I know it's not an alarming situation, but it didn't do that before so...

Thanks a lot for the info

[Mike Gerber]

Main Menu,

Your thermostat is probably stuck in the open position. Change it out and refill or top off the system with a 50/50 mix of coolant and water. Then bleed the system thoroughly. It's an easy thing to do. You don't have to drain all the coolant out, but it will be a lot less messy of a job to do if you at least drain the radiator first. This is due to the location of the thermostat on the 5SFE 4 cylinder engine you have. If you want to reuse the coolant that is in there you can do that. Just put a piece of tubing on the outlet of the radiator directing the flow in to a clean drain pain and then unsrew the plastic wingnut at the bottom of the radiator. You will still have to top off some of the coolant in the system since you will still loose some coolant from the block.


"Well it will go down slightly on the hill but not really that noticable, i would place a safe bet its a faulty thermostat, its not outputing the right voltage probably"

ag6286,

A thermostat is a mechanical device. There is no voltage coming in or out of it. The heat of the coolant just opens the spring, allowing the coolant from the engine block to flow to the radiator to be cooled. You must be thinking of the ECT sensor or the old style Cold Start Time Switches used on older Toyota engines.

Mike

[RningOnFumes]

Do what Mike Gerber says.

Here are some visuals:

http://toyotanation.com/forum/t112582.html

[Maim Menu]

Woah, thanks.