Engine Temp Dropping... Water Pump?

[raptorman3054]

I'm running a 2g with a 420a. Last few weeks, when driving my car's temp will be about 1/2 of what it normally is. The heater still blows air that is just as hot as when the temp is normal. The problem is as the RPM's increase, the temp goes down. however, it only seems to happen at higher speeds. like, in fourth and fifth gear. sometimes in nuetral though.
On a side note, not sure if it's related to this, but when i put my car in gear and start to drive (5-spd) there is a ticking noise. It's hard to hear, and the engine overpowers it by the time the engine is at 2k rpm
Thanks!

Car is completely stock

 

[drewvr4]

thermostat

 

[raptorman3054]

wouldn't be thermostat.
1. just replaced that last dec.
2. engine wouldn't heat up at all

i can visibly watch the needle move. i'll check it, but i'm pretty sure that's not it

 

[Arrow_Runner]

Try replacing your thermostat. It could be stuck open, causing your car to overcool. I have the same thing going on with the Lumina I'm driving. As far as I know, overcooling isn't the best for the car, but it should be fine to drive for awhile.

I don't know about the 420A, but on my 4G63 the thermostat was cake to change. Right out in the open.

On the Lumina it's positioned under the throttle body on the inner side some exhaust piping. PITA.

for GM
for DSM

I don't know about the ticking. It's a DSM so it's bound to make some sort fun noise.

 

[raptorman3054]

yeah, i'm very familiar with "fun noises" from dsm's
this engine started it's life in a '99 neon

like i said, I'll check the thermo.
that'll be tomorrow though, it's already dark here

a friend of mine said it could be the water pump... sounds like he might be right
any second opinions?

 

[Arrow_Runner]

The problem that I have with the water pump theory is that I really don't understand how a failing water pump could over cool your engine. I really don't think it's your pump, plus a thermostat is like $8.

From my understanding, the thermosat opens up when the engine reaches a certain temperature, allowing the cooler coolant from the radiator to flow into the engine. Once the engine has cooled off a little bit, the thermostat closes stopping the coolant flow.

And your engine is cooling off more at the higher RPMs because the water pump is flowing even faster, and if your thermostat is stuck open, that means the coolant never has a chance to sit in the engine and warm up, so the whole thing stays cool, and the faster you drive, the cooler it gets.

I see that exact effect in my Lumina right now. If I drive slow, the engine warms up a little, but on the highway it's way cool.

 

[raptorman3054]

i was giving that very scenario a lot of thought and it makes sense, especially if the thermostat is only stuck partially open. like i said, we'll know tomorrow
thanks!