spacecoast66

I bought an '86 pick-up a few months ago. (2wd, carb, 4-speed, 22r). My problem is that around town, it runs normal as far as coolant temperature. When I take it out on the interstate, the temperature gauge starts to climb slowly but steadily. It gets all the way to past the normal range and into the hot area. I don't smell any antifreeze and I never lose a drop of coolant. Before I start swapping out parts, I would like to get an idea of what's going on. Is my radiator blocked up? Fan clutch going bad. When it comes to diagnosing a problem, "I'm not mister mechanic". When I know the problem, I'm good to go. Any advice what this might be? Thanks in advance.

skypilot

iTrader: (1)

Fan clutch is irrelevant above 30mph, just make sure it turns and does not wobble. Sounds like you have a bad lower radiator hose and its collapsing at highway speeds when the water pump is running fast and pulling hard on that hose.

Change both radiator hoses even though its the bottom thats no good. Also I would run a radiator flush with distilled water ( let it work for 30 minutes and get it hot by driving it on errands) then flush again with distilled and refill with Zerex "red" for toyotas.

22repower

iTrader: (1)

What's the point of the red coolant?

Hilux808

Try the simple stuff first, how's your coolant level? It could also be improper belt tension. At highway speeds if your water pump is not spinning as fast as it should you will have a rise in temperature. Check your belt tension. Check your hoses too, if they are old and really soft and spongy feeling they could be collapsing under load like skypilot said. I recently had to change my radiator out cause it was plugged. This caused the same symptoms you are experiencing. I could tell it was my radiator cause when I drained it the coolant came out a lot slower then it should have, plus verything else in my cooling system was working properly. Got a new radiator and it solved my overheating on the highway.

bigwavedv

X2 With Skypilot.

My 87 did had the same symptoms. (don't keep allowing it to heat up...head gasket may start leaking). I had minor heating, new fan clutch, another new fan clutch (couldnt hear it roar at higher rpms when obviously should be- still couldn't hear it), new everything else- water pump, thermostat, coolant, hoses. Engine in great condition. Began to heat more and more. In the end...radiator. Flushing did not matter and upon tear down the center of the radiator that was the same size area as where the fan pulled air was so coated (internally) with 300,000 miles of use (even with good antifreeze maintenance) that it was not dissipating heat, the clutch never got "hot" air pulled onto it and never engaged (yes it is necessary on the highway as well especially on hills or with loads...if you don't hear it on a warm day something is wrong). The day I changed the radiator, no more heating and instantly the clutch would cycle on and off on long pulls on hills or acceleration. I love the Toyota "red" coolant, but only necessary in newer rigs- these never had it so as it won't hurt, it is not necessary IMO. Hope thins helps.

spacecoast66

Thanks guys. I was kind of leaning towards the radiator. I will change it out and change the hoses. Upper, lower, and there is one in between. I'll let you know how it works out.