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Help me please!

I have a 65 Ford Ranchero 289cid and it continues to overheat.

I have replaced the radiator, water pump, fan, thermostat (180), hoses and added a fan shroud. I had it pressure tested to see if there was leakage at the cylinder head, (there isn’t). I have even taken it in to 3 mechanics to see if I was missing anything and the best they could tell me is “Sometimes they do that” Yipes! Help It was running fine and this problem started suddenly.

Have you replaced the thermostat?
When you replaced the radiator, did you replace the cap too?
Radiator hoses are another possibility on a car this old. The inner liners can collapse.

Have you checked your exhaust system? A plugged exhaust stream can cause too much heat to be retained, however that’ll usually show up as low power also.

Are your spark plugs the right temperature range?
Are there any signs of lean operation?

180 thermostat, new hoses, new cap, proper plugs gapped to spec. I tried advancing and retarding the timing with no difference in either. New exhaust manifold gasket, pipe is in good shape, new muffler, PLENTY of power. I’ll listen to anything else you can come up with though because this problem has me totally frustrated.

Does this vehicle have an automatic transmission? If so, you might want to check if the transmission is running hot. The tranny fluid is cooled by the tranny cooler in the radiator. And if the tranny runs hot, it can cause the engine to overheat.


Thanks! I will check the transmission right away.

When does it overheat? At idle? Low speed driving? Highway driving?

“Sometimes they do that”? Those guys aren’t mechanics.

I couldn’t agree with you more, that’s why I’ve taught myself to work on my own cars.
It overheats the worst after highway speed then slowing down to street speed. If I keep it at 45 mph+ not so much of a problem, never overheats when idling. It doesn’t like stop and go but doesn’t get above 200 which I can live with but if you drive it on the freeway and then exit it will climb to 230+

Check and make sure your fan is turning the right way. I saw a Dodge Caravan that had been in an accident and someone had rewired the fan backwards.It was fine around town because the fan was pushing the air forward thru the rad. and it was fine at high speed because the airflow was overcoming the fan but about 50 the was no airflow thru the rad…

Thanks, I’ll check that

In some cars back then, it was possible (and it happened) to install the thermostat upside down, and that would lead to issues like this. I know it’s a remote possibility but given everything else you’ve done, it might be worth double checking.

Thanks but the thermostat is installed correctly and actually I tried a 160, 180, 192 and no thermostat with very little change. Thanks for the hint though.

I would then second MountainBike’s suggestion about checking the radiator hoses. The inner liners on them have been known to collapse. I don’t recall seeing it often, but it did happen.

I replaced all the hoses and belts.

Does the radiator you installed have an equal or better cooling capacity than the one that Ford shipped the vehicle with? That might be difficult to determine, but undersized radiators can cause this.

Was the cooling system once full of rust and crud, such that some of that material didn’t free up when originally flushed and has since plugged the new radiator?

Another thought.
Although you mentioned the water pump was replaced, make sure you’re getting adequate flow. Sometimes the water pump impeller breaks free from the shaft, causing it to freewheel.

I added a pre filter to the inlet side of the radiator and I keep it cleaned out. The car originally came with a 2 core radiator and I boosted it to a 3 core. I’ll check the water pump, thanks for the feedback.

I added a pre filter to the inlet side of the radiator and I keep it cleaned out.

Can you describe what kind of debris you’re finding in the pre-filter?
Also, what prompted you to get a pre-filter?

Little bits of rust. I added the pre filter because it is a 1965 block and a brand new radiator and I didn’t want it to get clogged with 1965 crap.

Is the pre-filter restricting the flow enough to trigger the overheating?

What happens if you take it out?

Any filter that has openings small enough to catch little bits of rust sounds like it might restrict the heavy flow needed under demanding conditions.

I haven’t tried taking it out, it is a double screen in a holder. I’ll try it and see what happens.