351/400m overhating problems

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Sep 29, 2010 | 07:26 PM

jonlucille

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351/400m overhating problems

I have a 351/400m that I had re built about 18 yrs. ago. I start and run the engine about every six months. Now I am attempting to drive the vehicle every day but it overheats after about 5 min. i have checked the waterpump ,tstat, installed new rad. and electric fan with shroud. Everything checks out ,but it still over heats????????????? Also I don't know what year the engine is ,how can i tell?

Sep 29, 2010 | 07:33 PM

ctubutis

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From: Denver Metro Area, CO

Are you relying on the factory gauge to tell you it's overheating? Five minutes seems pretty
short but I guess your thermostat could be stuck closed.

In any case, I'd verify the temp....

Sep 29, 2010 | 10:27 PM

jonlucille

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No need to verify temp, water gushes out of radiator after 5 min. ,with or without the tstat

Oct 4, 2010 | 01:03 AM

tbear853

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From: The Shenandoah Valley

Quote:

Originally Posted by jonlucille

No need to verify temp, water gushes out of radiator after 5 min. ,with or without the tstat

What kind of thermostat? 351M / 400s (and maybe the 351C I think) have the bypass cast into the block, it's the hole below the thermostat. With the correct designed thermostat, as the water heats the thermostat opens and while opening, the lower portion starts blocking or restricting the opening into that bypass thus forcing the water to take the path of least resistance .... that being the radiator.

With the wrong thermostat or with no thermostat, there is no restricting action and water flows unrestricted through the bypass right back into the water pump and back through the motor without ever going through a radiator. Only a small portion actually goes through a radiator then.

The ones I use are Robert Shaw Flow Cooler 333-180, though you can get a 160 or 195. If you use the one's intended for a 351W or 289 / 302, etc ... it will overheat.

If I knew I had the correct thermostat with the restrictor plate that starts restricting that opening, then I'ld run a compression test.

I'm thinking head gasket or cracked head maybe.

Links on T-stats for the 351M/400.

https://www.ford-trucks.com/forums/8...ermostats.html

https://www.ford-trucks.com/forums/7...ml#post5793118

Oct 4, 2010 | 11:49 PM

grclark351

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From: chicago burbs

could be pieces of loose scale blocking the front passage at the head gasket, acts the same as if the head gasket is on backwards

Oct 5, 2010 | 08:02 AM

80broncoman

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From: southeren Oh

18 years?? how old is the coolant mixture?? if it is over 3 years I'd flush it with water NO matter how miles are on it. It does turn acidic over time (in a engine, not in the plastic bottle.)