thermostat or water pump?

[truepinoy]

When im driving temps reach about 220. when i put it in neutral and rev the engine, temps shoot up to 240 and then down to 160 ish, then slowly climb back up as i drive. i have an electrical fan, aluminum 2 row radiator, 170 thermostat, and im running 50/50 coolant and water mix. any help would be appreciated.

[biggie]

Where are you reading temps, what device and what location is the sensor? Could be almost normal. But first guess is thermo is sticking. Is ele fan stock or aftermarket, how's it wired?

[truepinoy]

the sensor is right next to the old coolant temp sensor, its a mechanical gauge that i tested using boiling water, and the fan is from an oldsmobile and it pulls alot of air. the fan is controlled by a thermo probe switch which is set at the lowest setting( 140F so its pretty much on all the time)

[OutToWinPAHC]

Could also be the fan clutch. seeing that it cool when your moving, not under load and revving. This would tell me the pump is pumping. You don't want to keep driving it, maybe try a T-stat, flush, rad cap, and a fan clutch before pulling the pump. Just make sure its bled properly following the procedures. As for the temp sensors they are cheap as well, but if you do anything you have to bleed it.

[truepinoy]

It's actually an electrical fan, but yes I won't drive it anymore till I do what ya Suggested. Thankyou

[OutToWinPAHC]

Coolant bleeding

Jack the front of the car up
Take off radiator cap
Take a 2 liter pepsi bottle cut it in half and use some black electrical tape and wrap the bottle neck a little, or get a cooling funnel
Flip it around and place the bottle neck were the radiator cap was at.
Now start filling it with coolant about half way
Remove bleeder screw
Close bleed screw after you get a nice even stream of coolant
Squeeze the upper, and lower lined and burp out the air
Add antifreeze until you over fill the rad by a quart
Turn the heat on full blast
Start the engine and let the engine run after 3-10 minutes the thermostat will open and suck in the excess antifreeze (ambient temp affects time)
Fill it again but with about a half of quart.
Let it run until no more bubbles come out. Squeeze hosed time to time.
Replace cap and then shut off the engine

Coolant funnel (best to have)

[truepinoy]

sounds like a plan. my bleeder screw happens to be broken, but i think taking the coolant sensor out should yield the same results. ill get a thermostat and some coolant tomorrow and ill let you know the results. thanks