Over Heating Blues

[diggin69]

I hope you guys can help, I got a 80 chev 4x4 you can drive this thing al day long no problem. but if you get on the highway running about 65-70 it startes getting warm real fast....

I have done or replaced.............
flush & fill
thermostate
radiater cap
now can the clutch fan cause this......its about the only thing I havent replaced........
any help.....

[IoWnZa]

The Fan Clutch you mean? that would be a negative. If the Fan Clutch was defective, then it would Overheat very easily in town, but on the Highway it would be fine.

Mine went a few months ago, once I hit the Highway she never went over the normal temp. But in town, it would get warm if I wasn't moving.

[Budweis]

when you replaced the thermostat did you try a 160 thats what i usually use. heres a possible idea my friend had a car we tryed everything on and it turned out was a couple degrees off on the timing and some how caused to overheat, weird. besides that maybe you got a clogged passage somewhere did you have it pressure flushed? have you changed heads on it recently, think back on any changes you made since it started if any and post. how many lb. radiator cap you using? if you removed the heads recently could you have got a wrong set of gaskets? how bad does it overheat if got a temp gauge.

[diggin69]

This truck is all original. I did pressure flush it, the cap is 16lb. I have not had the heads off. I'm the 2nd owner. Its been doing this since I got it. I got rid of the fan clutch last night, this helped but did not solve the problem. I had already blowed out the radiater. I got the front & back clean I thought, I took the top support off the radiater looked down the front is clean but the back WOOO BOOY!!!!! I got all the crap that was in the coils for the air conditioning in the front of the radiater..... I will be taking the radiater out & givin a good cleaning....... ALWAYS THE STUPIDIST THING.........

[714x4lover]

i had that same prob , i changed to 4 core radiator and wa la no more probs, 179 at autozone

[Stocker]

If the lower hose doesn't have a spring inside, it can collapse and block coolant flow.....

[WHSmith]

I had the same problem on my 82 Blazer. I changed the thermostat, installed a 4-core radiator and even bypassed the heater. Turned out that the high volume water pump would suck the lower radiator hose shut at higher RPM and restrict the flow of the coolant. Like was mentioned before, don't ever install a lower hose without the internal spring...

[Destructo]

Yep, make sure the lower hose is not collapsing, at lower rpm it will not suck it closed but when you turn more rpm going down the highway then it will suck more and pull the hose closed if the spring is gone or rusted out.

[diggin69]

Thanks for all the help Guys,

I took the radiater out on tuesday.
I was going to blow all the bugs & stuff out,but soon found that it only had a 2 core. I just happen to have another one out of a 79 that was a 4 core....... Put it in & have not had aproblem since.......So I think you all again for the responses......

Diggin 69