Overheating 640

[Doug (OH)]

Hi Everyone, my 640 overheats easily, especially on hot days. I know I've seen discussion/steps to back flush the engine block/cooling system here somewhere. I can't find anything on the subject offhand.
Could someone please direct me to the proper steps? I think I remember something about disconnecting the hoses and using a pressure washer through the drain cock opening on the engine block. I'd
really appreciate any other information you guys might have. Thanks!!

 

[old]

Drain the cooling system including the block drain. Fill with vinegar and run it till hot. Let cool and drain and then rig up a hook up to the block drain and with the cap off let the water flow for an hour or so. Works best if the thermostat is removed

 

[RM-MN]

Start with the cheap and easy. Pressure wash the radiator. They get clogged with fine particles, dust, and fluff from plants. Then replace the fan belt unless it has just been changed. They wear, then slip on the fan which by not moving enough air lets the engine overheat. Check your points and ignition timing. Points wear and that changes the engine timing. Firing late leads to overheating. Once you have tried those 3 items, you can move on to back flushing the engine if necessary.

 

[Doug (OH)]

Thanks, Old. What am I hooking up to the block drain? Will I risk clogging the radiator while it's still hooked up?

 

[old]

Of I remember right the block drain is on the carb side of the engine and is on most a simple pipe plug. No problem with clogging the radiator since your flushing water back wards of normal flow

 

[Doug (OH)]

Thanks for the reply Old. I'm still wondering what I'm supposed to hook up the drain cock hole: a hose, a pressure washer? Let it run with hose hooked up it? Not sure what you mean. Thanks, Doug

 

[old]

Just a simple garden hose. I rigged up a hose hook up and use it when ever I need to flush a cooling system. Short piece of pope and a piece of old garden hose with the female end on it

 

[Doug (OH)]

Perfect. Thanks, Old.

 

[Doug (OH)]

Thanks, RM. Will do. It's been running so well (except for the overheating), I haven't wanted to mess with it!

 

[old]

Pope should have read pipe.

 

[Doug (OH)]

I kinda figured. Anyway, it would be hard to fit the Pope in the engine block and he probably has better things to do...

 

[Tim PloughNman Daley]

Are you overfilling the radiator? Underfilling? Cleaning the chaff out of fins? Keeping the fan belt tension correct? Have the Thermostat installed correctly? All most common suspects for overheating...see here -

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