I know... I know... another overheating problem! Sorry...
 

Riddle me this...

Why would my 1999 STS overheat at idle, but cool off once the engine is brought up to 2K RPMs? And it doesn't matter if you're driving or standing still!

The fans don't come on, but this is the weird (er?) part...

if you're rolling down hill doing 50 it will still over heat unless you drop down a gear and get the RPMs above 2K.

I've changed the water pump and thermostat. And the coolant cap twice!

The tube that goes from the coolant tank to the engine is clear as well.


What the heck is going on?

I love Caddies (this is my 4th) but the overheating problems (with my last 96 Concourse, as well) are driving me to drink!


HEEEEELLLLLP!!!!!

have u bleed the system air pockets cause funny thing to happen.

do u have a heater core leaking or anything else. should pressure test system

is the waterpump good is the belt actually moving the waterpump.

is your rad & heater core flowing or plugged( have u used seal tablets in system)

for why it cools as the system picks up rpm the waterpump could be pumping more causing a better flow

but the problem needs to be fixed at idle first
so the best way to do this

a) pressure test system and look for leaks

b) check passenger side floor for coolant

c) look at the waterpump and housing including the cross over pipe for leaks

d) check the valve at the back

e) look at hoses and pipes

f)check tail pipe for coolant smell .... white smoke extreme

g) check rad bottle for leaks as well as engine pump heavily back into it

h) check rad bottle for gas smell---- check the headgasket this way there are papers u can buy to test this

forgot to say make sure the fans work as well