coolant flow direction and leak questions

[dmiller]

i have a 351 W, water pump hose is on the driver's side and goes to bottom of radiator, the thermostat hose goes to the top of the radiator.

which direction does the water go? if i had to guess, i'd say the pump outputs to the bottom of the radiator. and the water from the radiator enters the block at the thermostat. is that correct?

i have a small leak. it appears to only leak about a tablespoon a day, and only when the engine is cold. i've replaced the thermostat gasket three times, the water pump gasket once, and then replaced the water pump and gasket once. i've never seen any sign of steam when the engine is hot, and don't smell hot coolant. and the leak will not be observed the day following a drive, it takes about two or three days to appear. i've yet to have to add water to the burp tank due to low level. but the leak is green antifreeze.

allan suggested Barrs radiator treatment, done that twice.

i kinda think it is leaking from the thermostat, maybe so slowly that it evaporates on the hot engine, and takes two or three days to leak enough to spill over where ever it is pooling before hitting the garage floor.

my next step is going to be a new thermo housing, unless some of the forum wits offer a suggestion.

all wet in Louisiana.

thanks

doug

[souzape]

Doug- I have seen this problem, not only on my Cobra but also on a couple of other cars I've owned, caused by aftermarket (usually chrome plated) thermostat housings which were not sufficiently flat to seal against the block. They would leak when they got hot and pressurized and then eventually weep out around the gasket. I would have thought the Barrs would have stopped the problem but I would still suspect the housing is the problem.

Phil Souza

[K.Wilson]

Doug,
Coolant flows from the bottom of the radiator into the water pump (the big tube connection on the waterpump is the suction side, hose manufactures usually put a steel spring looking device in the lower hose so that the pump cannot suck the hose flat and block off flow). The pump pushes the coolant into the block where it flows around the cylinders up into the heads and into the intake where it exits thru the thermostat and into the top of the radiator. This is generally how it works in a V8 except for a 351C, 351 and 400M and some others where the coolant exits the top of the block above the timing cover and does not go into the intake manifold. There are several other exceptions to this with other types of motors but this is how your system 351W works. The flow is designed this way to take advantage of the natural flow of the coolant to rise when heated, and fall when cooled. In the early days cars and tractors had no waterpump the coolant flowed through this natural conductive cycle.
If you take a mirror and look at the bottom of the bearing support in your water pump you will see a small (about 1/4 inch) hole. Next time you run the engine and bring it up to temp. place a scrap of white paper on top of the balancer under this hole (after you shut the engine off). I would guess there is some weepage from the bearing seals during the cool down cycle. Sometimes this is caused by starting the engine without any coolant in the system and the seal gets damaged, sometimes it it caused by the seal not being broken in and sometimes a drop or so is just normal weepage.
If it is the pump shaft seal the Barrs Conditioner will not be effective.
If this is not the problem you can find the leak by placing pieces of white paper in areas you suspect and see if you get a stain on the paper overnight.

[dmiller]

thanks to both, i am using an aftermarket thermo housing, chromed, first susspect now that phil suggest it.

and i will try k.wilson's white paper method. i hope its not the pump, just put a new one on.
thank k.wilson for correcting my thoughts on flow dirction.

doug

[casaleenie]

Thermostat housing.....

I was told that the chromed thermostat housings will leak >>> PERIOD...
They are either warped today or will warp tomorrow.... PERIOD....

AL
2899386

[dmiller]

off to napa tomorrow, thanks guys.

doug

[casaleenie]

Went to NAPA two weeks ago for the part and sure enough they had it.
Now all I have to do is grind off the "made in China" part of the casting and install it... The "made in" will be hidden on the bottom when installed but I want it off there all the same...
$10.00 item

AL
2899386

[KrAzEcJ]

Ford racing has some and might be a better a little better quality http://store.summitracing.com/default.asp?Ref=MFG&N=120+400070.

Unique 4279459