We have a '77 with a 302 auto. Bought her 5 yrs ago.
Have replaced the thermostat already.
Ran her 4.5 hrs during the heat of the day Thursday and she ran pretty hot so ran the heat, which cooled back to norm during the trip.
Had to do the same coming home on Sunday.
This truck sat for a few yrs, b4 I bought it from an older fellow.
The service record shows the 88k miles are original!
I'm wondering if the "sitting" made debris settle/solidify to the bottom and NOW that its run a few times a week it has decided to wash/loosen silt and clog the fins?

Y'all think I should replace the radiator?
Could the water pump be failing?

Thanx

ole John

 

Running the heater as a supplemental radiator indicates that there is some restriction in the cooling system. Most likely you have scale & maybe loosened "silt" that is clogging part of the radiator. Remove the thermostat & drain system. Refill & add a flush additive. Drive around with the heater ON. 10 miles should do it. Drain the flush solution, it should look quite dirty. Refill with fresh water, With rad. cap off & motor running, see if the water is flowing in the radiator. This will confirm water pump operation. Drain, reinstall thermostat & refill with coolant.

>>I'm wondering if the "sitting" made debris settle/solidify to the bottom<<
You're right about this. Sitting for a long time will cause problems.

 

I would drain the radiator then flush it with a garden hose for a few minutes with the lower hose off as well as what tiresmoke said. I had that problem on an old 73 with the 5.0 that sat for a while. These old trucks have dirt/debri and rust from inside the engine that builds up over the years. It can restrict the cooling system more than people think. A good flush and cleaning will help out greatly.

 

I agree 100% with what has been said. Old radiators get scales and crap built up inside.

I have a 69 chevy notorious for hard to cool. Replaced fan with electric hi flow, properly repair shrouding, changed thermostat, hoses, etc.

Final answer? Replaced radiator. Fixed ALL overheating issues.

Even went back to stock clutched fan and original shroud.
Good luck!

Scott

 

[QUOTE=tiresmoke;3597196]. Refill & add a flush additive. QUOTE]

Refill with water or coolant?

 

[QUOTE=oldster;3616672]When using flush (Drano for your engine), just use water. When done flushing, rinse out the flush well before filling with coolant.

 

I would replace the rad the core is more then likely plugged with calcium. Then I would remove DRAIN plugs at the block and run the hose through it. The casting will rust and build up in the block. By just opening drain plug and sticking a garden hose will do nothing.

 

If doing total flush, is it best to by that kit where you add a port to hook up a garden hose? (towards the rear of the engine-like on a heater hose???)

 

I would do the simple flush first. That may be all it needs. If that doesn't do the trick, then you may have to remove the rad. & have it re-cored. I have seen cases where the passage between the head & block have become restricted with crusty build up. I hope you don't have that. If you end up pulling the radiator, pull the water pump too. In fact if the wp is old, it wouldn't hurt to just replace it while you have everything apart.

 

If I were you I would remove the plugs in the block and flush the block.
Frost plugs don't rust from the out side, they rust from the inside out.
If I were you I would pull the block plugs, Change the water pump and rad.
If your truck if running hot this is a restriction in the rad or very poor flow.
Don't save a dime to cost you a dollar. Personally I would I joy my truck a lot more if I wasn't constantly looking at my temp gauge. When the water pump is out and the plugs use a garden hose and flush it out. You will be shocked what comes out the plugs