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Discussion Starter #1
I finally got my 70 cougar out after a 3 year nap...been starting it on and off in the garage during the big sleep.

Took it out on the road and she roared back to life. Drove for a while and then it started to overheat. 351 Cleveland with automatic - no ac. Replacement 24 inch radiator and original fan shroud and blade.

Checked the following.

Removed thermostat - flow going through radiator.

Flushed out the fluids - Prestone valve in place and ran it for a long time.Water is crystal clear.

Drained radiator through lower valve - clear water running through.

Water pump is nice and quiet - replaced three years ago also.

I could not get the lower block plugs removed so did not get that done.New freeze plugs put in three years ago when block was detailed.

WHAT COULD THIS BE?

WHAT SHOULD I DO NEXT BEFORE TAKING IT THE LOCAL GARAGE.

TRYING TO SAVE A FEW BUCKS WHEREVER I CAN.

YOGI
 

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How is the spring/coil in the lower radiator hose, it may be collapsing under higher RPMs.
 

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As it's happened to me, make sure you've got the 351C thermostat, not the 351W. Autozone and the like will get it wrong every time. Also, what all did you do the motor? Sometimes people make the mistake of putting the head gaskets on backwards.... just food for thought. It is easy to do. If there is no thermostat in it when you're running and it still goes hot, then a water passage has to blocked somehow or the water pump is weak. Good luck man, you'll figure it out on here. MC.net/ Cleveland fanatics lol
 

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Hi all, going to try a new thermostat. Was told to get one for 160 degrees..?? I did switch the original curved water hose inlet to a chrome straight one. Wondering if that could contribute to a thermostat issue. Going to put back on the curved inlet....

Ran without the thermostat and still overheat happened. I did not change the head gaskets. Looks to be original gaskets never opened up...

Water passage block kinda scares me after I did drain out through the lower radiator drain...

Will let you all know.

Thanks, YOGI
 

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192° is what was installed from the factory, but most people run a 180° thermostat in Clevelands.
 

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I run a 192 with stock restrictor plate and mine stays cool, even with the AC on full blast. It does warm up a bit when the outside temp exceeds 100 but it doesn't come close to overheating.
 

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Clevelands have a bad habit of slipping the timing rings on the harmonic balancer! So, you go to set your timing to 6 degrees using the timing light, and in reality, you are somewhere else completely different! How to determine? Pull the #1 plug, and bump the engine over until piston comes up to top. You can hold your thumb over the hole and feel the air coming out...when it starts to draw in....stop and manually turn it back, or bump it around again to TDC. (top dead center) Then check where your timing mark is! If it is in the ballpark of where it should be (zero!), then your problem is not this!

We bought a car way back, 70 4V, that wouldn't pass smog testing due to the fact that the timing couldn't be verified, even though the car was running clean!!! Got a good deal on it as a result! Reset the timing as described and drove it that way until we sold it! Rebuilt motor ran GREAT!!!

Worth a thought anyway!

Clutch fan? Could be slipping....check it at rest cold. If it spins easily with no resistance....it's bad!
Fan shroud installed? (They help!)

Good luck! These problems are a PITA!!!

Steve
 

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Hi
I had the same problem on my 351c. I found some air in the system.
I just let the engine in idle without the raditor cap on, until the thormostat opened.
Maybe it´s only the radiator cap, I have seen that before.

Lars
 
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