Engine overheating
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Engine overheating
I've got a 351M in a 79 f150 that I picked up cheap which was supposedly rebuilt and set for a about a year without ever being fired up at all not even after it was rebuilt, i put some oil with break in oil additives and water in it and hooked up everything and started it and it took right off surprisingly, the engine ran fine, I ran it without the rad cap on to let any air out, but after about 5 minutes it began to boil out of the neck of the rad and the gage was at the mark before "H". Next I took the thermostat out to see if it was faulty but I had the same results just it took longer for it to overheat. I used a Multimeter with a Fahrenheit water temperature checker or what ever it's called, and sure enough the water was around 230°F. I also made the mistake of shutting the engine off with the cap off and it shot a geyser as high as the hood with hot water. Any thoughts on what this could be?
Postmaster
Joined: Nov 2011
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Normally it should bleed out and run OK in a few minutes... especially with the stat out.
It sounds like water is not circulating. I'd check the radiator first. Look inside the filler neck at the tubes you can see. Are they crusty and blocked? How about the belt... also is the WP turning OK? There are other possibilities but I'd check those first.
It sounds like water is not circulating. I'd check the radiator first. Look inside the filler neck at the tubes you can see. Are they crusty and blocked? How about the belt... also is the WP turning OK? There are other possibilities but I'd check those first.
Cargo Master
Joined: Sep 2005
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With the thermostat out of the engine if you look in the rad cap, the water should be rushing by even at idle. If this is not the case then either the water pump is not pumping or the radiator is clogged.
If it's been sitting don't discount a critter building a nest someplace.
Also make sure it's not running too fast, let it idle while your warming it up.
If you do have good flow past the cap. it could be a fan problem, fan clutch bad?
If it's been sitting don't discount a critter building a nest someplace.
Also make sure it's not running too fast, let it idle while your warming it up.
If you do have good flow past the cap. it could be a fan problem, fan clutch bad?
Postmaster
Joined: Nov 2011
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I would add that the T stat for the 351M/400 is a bit unique with that feature. It was special order at my local AZ. I have seen a few posts where a generic "in stock" T stat was used with bad results. With care by the parts guy/gal "make, model, engine and year" should do it.
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We'll thanks for all the replies, and that is interesting to hear about the thermostats I will definitely give it a shot
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