Overheating Problems

[Steven_in_SC]

Ive got a 74 with a 200. Heres the problem. Whenever i start off and it gets warmed up the temperature gauge jumps up to 220 or 230. Then the temperature falls back down to about 170 or less. It will stay at 170 to 190 from idle up to 45mph even in 100 degree weather. Whenever i go 55mph or more the temperature shoots up to 230 and i have to stop and let it cool down. Ive never had it overheat because i keep stopping to cool down. Any sugggestions as to what might be wrong. Is it my gauge broken or something else.

 

[Sharkman]

Have you replaced your thremostat. It may be sticking. Just a quick guess and a place to start.

 

[BoltBuster]

Does it have a clutch type fan, in other words if you turn the fan when the engine is off does it spin freely or is it secure?

If its free its more likely a clutch type fan.

If it is a clutch fan it may be on its way out to being replaced because it no longer is able to keep up with the speed(RPMs) of the engine.





Do the cheap stuff first.

Like Radiator Flushes and Cap and Thermostat replacement-

 

[BwoncoHowie]

This happened to me on 2 different occasions, which was exactly what you are describing.

The first time it was the radiator, 2/3 of the tubes were plugged, so I got it recored at a radiator shop

The second time it happened the thermostat was stuck in the 1/2 open position.

Both times the coolant flow was restricted, which caused it to run HOT at high RPMs, of course when I would slow down but keep moving the temp would cool off.

I'd say do the cheapest thing first and install a new thermostat, then see what happens.

If you have a lot of deposits or debris in the radiator, it may be time for a new one of those as well.

BH

 

[astro-mike]

Do you have the "spring" in the lower radiator hose? It may be Collapsing at higher rpm's.

 

[Steven_in_SC]

Ive replaced the thermostat with a 190, changed my radiator cap, flushed the radiator and its still doing it. I even added some Redline Water Wetter and still no luck. Any other suggestions i dont think that i have the clutch style fan. My heater does not work either now. Could it be my heater core??

 

[BwoncoHowie]

[quote author=Steven_in_SC link=board=5;threadid=16384;start=0#msg125054 date=1050464482]
Ive replaced the thermostat with a 190, changed my radiator cap, flushed the radiator and its still doing it. I even added some Redline Water Wetter and still no luck. Any other suggestions i dont think that i have the clutch style fan. My heater does not work either now. Could it be my heater core??
[/quote]

Whatever has plugged your heater core is probably the same chunks of rust and debris that is clogging your radiator. if you used a chemical flush you may have dislodged a bunch of scale from the water jackets, and that will plug and restrict everything. BH