servin

i just replaced my 79 thermostat to 190 deg. also, I gave it new coolant. the engine temp seems to run fine at idle and city driving, but once i get on the freeway the temp starts to climb up to and past 220 deg. is there anything else that might be causing this. front bumper scoop is there but almost falling off. :mad :mad

PatsLs1vette

radiator could be clogged and doing it also especially if its only doing it on highway driving and not at idle.

KENS78SILVERANNIV

Make sure all of your radiator seals are in place. It really does make a difference especially at high speeds. These are seals that go around the radiator shroud and essentially "force" air to go through the radiator core.
You may want to replace your fan clutch too. Flush radiator thoroughly and peek down there to see that you're not clogged up. -Good Luck!

Jvette73

I once had a car that never overheated at idle or around town slow speed driving. As soon as you took it out on the highway and went a steady 60mph+ the engine temp would slowly increase to dangerous levels. I tried almost everything except rodding the rad to correct the problem. Nothing helped. I then had the rad rodded out and it solved the problem. It was clogged up. If you look down into the rad cap and can see that white lookin gunk hangin off the cooling tubes, its a good indication that the rad could be plugged up. If it is plugged up, its not likely that flushing alone will clear it. Fl;ushing is done to prevent clogging. If its clogged already..its clogged...period.


[Modified by Jvette73, 6:59 PM 5/21/2002]

73-454

Check your timming if that is a factory specs. Then remove the rad and take it to a good rad shop they must soaked for at least 2 hours and then test it. That will be the end of your cooling problems.

jlsru

I have this exact same problem with my 75 vette now.I installed a new GM radiator,new hoses,thermostat and I still have the highway heat problem.I have not checked the timing yet.Changing the radiator did help a little but not completely.If you get your over heating problem solved please let me know.

bigvette1

Besides the seals, air dam, rad. seals, hood seals and rad. flow look at the fan clutch. I run a BB and once the outside temps hit 70+ I jerk out the fan clutch and install a flex fan with the spacer to put it into the shroud. I have tried a replacement GM unit, heavy duty Hayden etc and they all do not work as well as the flex fan. Lots of people disagree with me on this, but the temp gauge on the highway says different.

The fan clutch basically engages at idle and low speeds and when you hit higher RPM's on the highway it disengages. If this clutch is the origional they can lose about 100 RPM's per year. Just a thought.

Rockn-Roll

1. Fix the scoop.

2. Pull the thermostat and test it without the Tstat. You can put it back in if you want...but it's worth a check for the $1 gasket before spending $$$ for anything else.

3. Check your timing.

4. Check your wheel bearings and differential lube. I was having an overheating problem until one of my rear spindles broke due to heat damage...there was not enough grease in the bearings to prevent friction. I replaced both spindles and bearings and now I don't overheat on the freeway...even when it's 80 and the A/C is on.

5. Carry a ice chest full of beer (ok...non-alcoholic unless you have a designated driver) so when it gets to about 230 you can pull over and slug down a few cold ones.