: Water pump? 1999 STS overheating

01-30-14, 07:30 AM
I have flushed the entire system and replace the thermostat. But still the engine overheats and I lose heat when it does. I bought a water pump I'm bout to put it in, but I am wondering if anybody can confirm my suspicions . Or perhaps another idea

01-30-14, 08:15 AM
Probably is/was not the pump or thermostat.

Water pump drive belt, tensioner, drive pulley OK ? Did you do a purge line check ? - that coolant heated throttlebody or the water crossover holow bolt/nipple sometimes clogs and blocks coolant purge flow, you get air in the system, the water pump cavitates, and the engine overheats.

Perform a cylinder block exhaust gas test to check for the presence of exhaust gas components in the coolant - bad head gasket(s).

All that ^^^ is covered in the sticky posts just above this one, in Cadillac Tech Tips, and in the Cadillac Technical Archive way up ^^^ in the top black bar. Surf through the head gasket sticky just above this post.

The coolant gas test kit can be rented from any large parts store or http://www.sjdiscounttools.com/lis75500.html

01-30-14, 09:25 AM
Unless the WP is leaking, you're wasting your time and money replacing it. Wp's don't cause overheating (if the belt is on and it's spinning).

Its' a '99 and it's overheating. The odds are not in your favor. Follow Sub's advice and do a block test.

01-30-14, 10:55 AM
Another 99..