[Steve91T]

So I've been putting some miles on this engine after it sat for years and I've got a problem that I would like some help with. It's got a new water pump and thermostat, for now the heater hoses are capped off. I'm running a manual fan switch. The water temp gauge is in the drivers should side head.

So everything seems normal except for some reason if I drive down the highway my water temp will drop to about 150 degrees. It acts like the thermostats is stuck open. Yesterday I pulled the t-stat and put it in a pot of water and watched it. It started opening at 180 degrees like it should, then closed when it cooled down.

So why is this happening?

[Blainefab]

No misread - I edited it to clarify as low temperature reading.

When you had the heater removed, did you cap/plug the water pump ports? That would be good and proper. If you tied the 2 ports together with a hose, that would not be proper, and might be the cause of your symptoms.

[Steve91T]

No misread - I edited it to clarify as low temperature reading.

When you had the heater removed, did you cap/plug the water pump ports? That would be good and proper. If you tied the 2 ports together with a hose, that would not be proper, and might be the cause of your symptoms.

Ahh ok. Yeah the two ports were capped, not tied together.

So I installed this engine like 2 years ago and bled the system back then. I've been starting it and putting around the neighborhood every so often. The temps would steadily climb as you would expect. Driving around the neighborhood wasn't enough to keep it cool for long (no fan at the time). Now that the car is almost done, I've been driving it almost daily for the last 200 miles. Running errands and stuff like that. This is the first time I noticed this problem (obviously because I'm able to drive it faster than 20 MPH). It responds exactly the same every time. Running down the road will cool it off to 150 ish. As soon as I come to a stop, it will heat up. Once it hits 200, I flip the fan on and it cools down rather quickly, as it should. This afternoon after a drive, I pulled into the driveway, let the temp get to 190, then flipped the fan on and watched the gauge closely. Temp started to drop and never hesitated or anything. It eventually got to about 170 degree. With a 180 degree t stat, it should drop to 180-185 and not get any lower.



Anyway, just trying to give as much info as possible. Heater core is hooked up and the problem still persists. So idk, I'm stumped.