The 81 I recently picked up has a tendency to run hot in general (about 3/4-4/5 toward the red-zone) and it creeps even higher when I pull a hill. It's worse on hot days. The funny thing about it is that temp changes are slow both going up and going down. One would think that if it were a water flow problem the heat would climb fast and drop slowly. Also, it tends to run hotter at higher speeds, and cool down at idle....somewhat counter intuitive since at speed more air would be flowing over the radiator. Running the heater slows the climb, but doesn't negate it.

I've already replaced/tightened the fan belt, and replaced the thermostat and coolant, and fiddled with the timing but none of those had a noticeable effect. Water flow SEEMS to be adequate.

I've heard that a plugged cat can cause overheating, but I already have plans to redo my exhaust (I love being a welder! ), so to me that's a non-issue ATM.

Are there any other things I can look at trying before I resort to replacing the radiator and/or water pump? Pumps are cheap but a pain to swap, radiators are easy, but more expensive.

 

Recoring the radiator with a thicker core and replacing the water pump worked for me.

You might want to pull the hoses and check for mineral buildup. The PO might have run tap water and cheap antifreeze.

Brand-new radiators are $150.

Replace the water pump and hoses while you're at it, and only use Peak anti-freeze (specially formulated to fight aluminum corrosion).

 

On my '85. overheating in hot weather and/or under high loads was due to a partly clogged radiator. In coll temps, the rad could shed enough heat to keep the engine cool, but above about 75F, or on grades over 4% or so, the engine temp would creep up. I put in a 3-row radiator and it has run cool for the last 10 years.

 

I also vote for plugged radiator. those aftermarket radiators tend to get plugged easy, especailly if the owner doesn't change the coolant every year like they are supposed to.

Feel the radiator while its hot. If there is a cold zone, you have a problem.

 

i am in the same boat on my 83. new rad, hoses, thermostat, coolant 50/50 mix and i can not figure it out...its seems ok till I turn on the ACand it gets hotter on the freeway. Any one else had this issue....

Did not mean to jack your thread

 

sooo... if it stops burning your hand you have a problem?

Al

 

Whats the best way to unplug the radiator?

 

A radiator shop can hot tank it and then rod out the core. Usually costs about as much as a new radiator, though, depending on your local labor rates.