Its funny, because other than that, it runs perfectly cool, even carrying close to 20 bales of hay at 40-55mph for probably 15 miles...........Per glove box sticker, its got HD Radiator and Trans cooler, and its a non A/C truck, so it doesnt have much in front of the radiator. Yeah, either way its probably a good time to flush cooling, maybe replace thermo as well, check timing etc........Hadnt even thought about fan and fan clutch, and as everything looks bone stock, and unaltered, and floor mats, seat, dash are all nearly perfect, im thinking this truck may well be low enough miles that a lot of underhood componentry is still original..........Thanks, and i really appreciate the good insights!
Yeah, but after 35 years, the watersides of the radiator will almost certainly be coated with deposits. It doesn't take much of a deposit film to hinder heat transfer. I don't know if you're up for it, but consider the de-scaling procedure detailed below - it would be a shame to scrap an OEM HD brass/copper radiator:
I have used CLR (calcium, lime & rust remover) and Bar Keepers Friend (the BKF needs to be mixed with hot water to get it into solution) to clean radiators several times with no ill effects.
I started doing this because I had a couple of radiators that were original - OEM with brass tanks and copper tubes. They were beautiful - had no leaks and the fins were all there. Looked great from the outside.
But inside was another story, the tube ends (where they are soldered to the tanks) were so fouled that flow was being restricted. The watersides of the tanks were heavily encrusted with deposits as well (so the assumption was that the inner walls of the cross tubes were in similar condition).
There are no more radiator shops around here, so I decided to "boil" them out myself. I figured I had nothing to lose; because otherwise, they would have just been junked.
I have only done this with the radiator out of the truck and lying flat (outside and on a wooden picnic table) with the inlet/outlet nipples open and pointing up. Radiator cap is on and the small connection to the expansion tank is capped.
Pour a whole quart of CLR into the radiator (use either the inlet or outlet nipple - it doesn't matter) and top off with city water. Actually, I use the
ZEP brand - it has a much higher concentration of acid (hydrochloric & sulfamic) than the big name brand. If using Bar Keepers Friend (oxalic acid) mix half a can of powder into warm water and stir until you have a solution that can be poured.
Let it sit for hours. When you want to check the progress, dump the acid/water out (save it in a bucket - it will have plenty of life remaining). Using a garden hose at full flow, flush the waterside out. Go in both directions. Lift and shake a couple of times. When no more deposits are getting flushed out, pour the acid back into the radiator. It helps if you filter the re-used solution through a piece of window screen or similar.
With several applications (dump and flush with clean water between) the deposits will be gone and the copper and brass will be a bright gold color.
When satisfied that you have clean surfaces and will get good heat transfer/coolant flow, do a final long flush to get any remaining acid out. If it makes you feel better, you can use baking soda to neutralize. Reinstall the radiator (maybe flush the rest of the coolant system with Prestone II as well) and run on city water for a while. Dump that city water (it will be filthy) and refill the system with the normal 50/50 mix.
The drop in engine operating temperature will be remarkable.
