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Need some help with overheating 400 sb - part 2

 
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TonyD
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Joined: 26 May 2006
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PostPosted: Sun Jun 18, 2006 7:58 pm    Post subject: Need some help with overheating 400 sb - part 2 Reply with quote

after idling 5 mins, the temp goes up to 230+. this is the factory temp guage hooked up, the aftermarket guage read the same way (even if it appeared to be sitting on the header, but it wasnt.

i replaced the upper and lower hose, new 180 thermostat and radiator cap. still overheats fast.

the upper hose never gets hot to the touch. and the hose going to the heater from the water pump, right by the water pump doesnt get hot either. but both hoses near the heater core are hot. the heater isnt blowing hot air.

could it be a clogged heater core? or bad water pump? what do you all think?? TIA

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jeep_406
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PostPosted: Sun Jun 18, 2006 8:39 pm    Post subject: Reply with quote

With the radiator cap off do you see any coolant flow in the radiator? What's the chance that you have a faulty stat or could it be in backwards?
Are you sure the block and radiator are full?
Could someone have put stopleak in the radiator and clogged it up?
When the engine is hot are there cold spots in the radiator core?
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TonyD
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PostPosted: Sun Jun 18, 2006 8:49 pm    Post subject: Reply with quote

not really seeing any coolant flow in the radior with the cap of.
the stat should be in correct, - faulty, i dont know? the water neck and very base of the top hose gets hot, but the rest isnt hot at all.
havent felt the radiator for cold spots either?

the radiator is full but i dont think the block is? not sure, doesnt seem like the coolant is circulating so im guessing its the water pump - but there are no leaks from the weep holes.

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Paul P
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PostPosted: Sun Jun 18, 2006 9:15 pm    Post subject: Reply with quote

Does this have a serpentine belt driven water pump? If Yes did you install a reverse rotation pump? I have to ask this because of your last answer.
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10sec.et
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PostPosted: Sun Jun 18, 2006 10:14 pm    Post subject: Reply with quote

you could have an air pocket. i usually drill a 1/8 in hole in the t-stat to vent any trapped air. Paul made a good point. if it has a reverse flow pump on it , it will overheat no matter what you do. have the heads been off recently? seems i remember something about steam holes causing an over heating problem if you used the wrong gaskets.
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jeep_406
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PostPosted: Sun Jun 18, 2006 10:20 pm    Post subject: Reply with quote

I was going to suggest drilling a small hole in the stat as 10 sec.et did. I do that on everything I do to remove the chance of an air pocket at the stat.
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Big Dave
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PostPosted: Mon Jun 19, 2006 7:42 am    Post subject: Reply with quote

It also helps to initially fill system with engine at an extreme angle (front end jacked up) to alleviate any air being trapped in block. Factory block 400's have to have at least the three lower 1/4" steam holes drilled in the heads with 1014 FelPro gaskets, with "Little M" Dart blocks you don't have to (not sure about World products).


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TonyD
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PostPosted: Mon Jun 19, 2006 8:11 am    Post subject: Reply with quote

here's my plan,
its not a serp setup, but im going to replace the water pump anyway, since i dont know anything about it. also, im going to drill 1/8 hole in the stat. and will refill the coolant with the front end raised.

its a factory 400 block. i dont know if the steam holes were drilled or correct head gaskets. so if phase 1 doesnt work, ill have to look there. but would lack of steam holes cause coolant not to circulate like it is?

thanks for the help so far.

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Big Dave
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PostPosted: Mon Jun 19, 2006 11:55 pm    Post subject: Reply with quote

Steam pockets once they form are difficult to collapse, without a means to vent them. The steam pocket expands with overheating, and contributes to the problem by isolating the cylinder wall from the coolant which gets hotter, and perpetuates the problem. Steam doesn't conduct heat nearly as well as the coolant does.

Race cars or any car that spends 75% of it's time above 2500 RPM and very little if any below 1500 RPM doesn't need steam holes as the velocity of the coolant prevents the formation of a pocket of steam in the block (this assumes no voids or air pockets trapped in the block to start with). Conversely a car that lives in traffic needs all six steam holes, and a big high efficiency radiator.


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