Fluctuating water temp

[#1StunnaVic]

ok so i notice that when im on the highway crusing around the temp goes down below half or just at half depending on how fast i go. then when im drivin on local streets it goes back up. also when i start the car and let it warm up it stays below half no matter how long i let it warm up for but when i take it out on the road it goes up a little notch above the half. i was thinking it might be the water pump or maybe clogged up cooling system somewhere? any clues? i searched but didn't really see anything like this.

 

[p5150]

Do you still have a fan attached to your engine?

 

[staticpat]

It could be BHG or as simple as air in the system. I'd burp the system to start out with. Otherwise check for leaks. Give the throttle a few revs when you see it spiking to see if that gives it any change.

 

[a_sesshoumaru]

What about the radiator cap???

 

[bentandbroken]

It could be BHG or as simple as air in the system. I'd burp the system to start out with. Otherwise check for leaks. Give the throttle a few revs when you see it spiking to see if that gives it any change.

I would listen to him. If burping doesn't help, it may be the fan. The worst it could be is a BHG

 

[TheAmazingDave]

Sounds more like the beginning of a failing thermostat. What is your engine's mileage? Thermostats should be changed every so often. I forget the actual mileage, but they are a regular maintenence item.

 

[jdub]

Highly doubt it's the thermostat

Based on the temps increasing at low car speed airflow over the radiator, betcha it's the fan clutch. Read this:

http://www.mkiiitech.com/forums/viewtopic.php?t=1056

 

[#1StunnaVic]

mileage on the car is 174K. i don't think its the head gasket because it was done about 2 months ago from the guy i bought it from. its a stock head gasket though. i'll try burping it though.

 

[TheAmazingDave]

Not saying that you're wrong jdub, but how would a failing fan clutch cause a prolonged warm-up, or temps to fall when driving? In my experience, those have always been symptoms of failing thermostats, and after replacement the issues ceased.

But in all honesty, those were on vehicles equipped with electric fans.

 

[TheAmazingDave]

mileage on the car is 174K.

At that mileage, the thermostat should have been changed a few times already.

Even if it isn't your problem, it's cheap insurance and a quick job.

 

[jdub]

Not saying that you're wrong jdub, but how would a failing fan clutch cause a prolonged warm-up, or temps to fall when driving? In my experience, those have always been symptoms of failing thermostats, and after replacement the issues ceased.

But in all honesty, those were on vehicles equipped with electric fans.

If it was a prolong warm up or a temp spike within a few miles, then I'd be looking at the thermostat myself

From the info given, the temp difference is lower at freeway speed...higher in city driving. Any Supra after start just sitting there, will not even open the thremostat...the coolant in the block has the capacity to absorb the small amount of heat generated.

Easy way to see if the thermo is stuck open is to feel the upper rad hose after a few minutes of run time...it should be cold. If the thermo is stuck shut, the temp will spike after 5 minutes of driving or so.

 

[TheAmazingDave]

If it was a prolong warm up or a temp spike within a few miles, then I'd be looking at the thermostat myself

From the info given, the temp difference is lower at freeway speed...higher in city driving. Any Supra after start just sitting there, will not even open the thremostat...the coolant in the block has the capacity to absorb the small amount of heat generated.

Ahh. Cool, thanks.

 

[#1StunnaVic]

well ill start with the thermostat and see what happens. ill be sure to fill you guys in on it

 

[a_sesshoumaru]

hey check if you have a leaking hose, that hapened to me yesterday and gave me the same symptoms

 

[#1StunnaVic]

thanks ill check it out