Temp Spike on freeway

norcalsvt · Jun 23, 2005

Been working on a 67 I picked up 302 w/Automatic & stock radiator. Also has taurus fan w/dc control unit. Temp spikes to 250 on the initial freeway run, then cools down to normal 180 temp after a minute. Can't figure out whats causing this. New thermostat in, coolant changed. Maybe it's the tranny heating up the radiator too fast? I have 3.55 gears & I believe stock converter but not sure. Should I try a tranny cooler. DOes not overheat during traffic or street driving. Just when I first get on the freeway in the morning or anytime engine is cold & I go right to freeway speeds. After it cools down it's fine.

12sec67 · Jun 23, 2005

maybe your belt is slipping.

sometimes the paint on the pully is doesn't let the belt stick under a load.

grego37 · Jun 23, 2005

Sounds like the thermostat is sticking the first time it should open, Id replace it.
did you top off the radiator after the thermostat has opened and starts to flow?

Ronstang · Jun 23, 2005

grego37 said:
Sounds like the thermostat is sticking the first time it should open, Id replace it.
did you top off the radiator after the thermostat has opened and starts to flow?

I would at least boil the thermostat with a candy thermometer to see if this is the problem, but more than likely the thermostat is sticking and a new one would solve the problem. If it is new just take it back and have them give you another. At least if you check it you can tell them it doesn't work for sure.

10secgoal · Jun 23, 2005

I would look at the therm also. If it does it right when getting on the freeway, pull over the second it hit 200-220 jump out to see if the rad is blazing hot. If not, time for a new 5 dollar part.

norcalsvt · Jun 23, 2005

I just replaced the thermostat last night. I did notice that the one I pulled out the button was still in ,so I figured it was stuck, but temp spike happened again this morning. I guess I'll have to test the one I bought, I do notice that if I turn on the heater full blast then I can stop the temp from creeping up so fast.

Roddster67 · Jun 23, 2005

Maybe there is a blockage in the radiator?
Timing set too high?

2nd Mustang · Jun 23, 2005

Does the electric fan cover most of the tubes on the radiator? I've heard of cases where the electric fan has so many blades, and is not running while the engine is cooler, that the blades actually impede the flow of air through the radiator when it is not running.

grego37 · Jun 24, 2005

are you topping off your water/coolant after the therm. opens?
You dont want any Any air in the cooling system

norcalsvt · Jun 24, 2005

Last night I warmed up the engine with the cap off & watched as the temp got to 180 & then the thermostat opened. The fan also kicked on around 185 or so & brought the temp back down to 180 or a little below. What Idid notice was for the next few minutes of idle, the temp got up as high as 190, but I didn't see the coolant swirling in the radiator anymore. Isn't the thermostat suppose to open up again? The fan is able to bring down the temp when it goes up gradually. I'm just beating my brain trying to figure out why the temp gauge reads as high as it does, the coolant in the radiator doesn't seem to be at the same temp. I havn't pulled over right when it spikes , but have around a minute or 2 later & there is no coolant puking at all. Also, doesn't it seem strange that it spikes just the one time & after it gets back down to around 185, it doesn't budge after that. Also, what I am noticing. If I drive on the streets for awhile before getting on the freeway, if the temps reach one 180 & then I get on the freeway, it won't spike.

grego37 · Jun 24, 2005

Can you adjust when your fan comes on? I think it comming on too soon.

If your therm is opening at 180*and the fan comming on at 185* to cool it back down, your therm is opening/closing/opening/closing and so on.
I think when the therm. opens you want it to stay opened.
Id keep the 180* thermostat and adjust the fan to come on at 190-195

or if you cant adjust your fan, change to a 160* thermostat.
check out
http://stewartcomponents.com

Temp Spike on freeway

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