Stuck Bypass Valve

[Randy W.]

Well, my 1976 75hp is still overheating. After about 10 minutes the tell tale quit delivering water. I have replaced the impeller (twice) and then the thermostat. The water pump housing looked good and then I ran water from a garden hose up the tube to the top of the block and it apppeared unobstructed as it came out. Then I removed the exhaust cover and it appeared like all the channels were clear. Removed the bypass cover (and of course broke one screw) and the spring and valve will not come out--calcified. Would this cause the overheating issue. I also cranked over the motor in a tub of water, but it would not deliver water to the top of the block outlet. Should cranking produce enough vacuum/pressure to bring the water up? Any ideas would be appreciated!

 

[Frank Acampora]

Re: Stuck Bypass Valve

That bypass was a nice touch that relieved pump pressure and bled water back into the leg when the thermostat was closed. A stuck one will not cause overheating. In fact, Late Chrysler engines and Force engine blocks did not have them.

And, since I doubt it corroded in an open position, and since the bleed hole usually corrodes closed, I doubt you are losing water pressure through it.

 

[Randy W.]

Re: Stuck Bypass Valve/Thermostat

Re: Stuck Bypass Valve/Thermostat

Thanks Frank for your reply. Quick question for thermostat experts on a '76 75 HP. Does the thermostat spring always face out (not toward engine) on all three cylinder chrysler motors. Manual says to have spring face out, but parts diagram looks like it faces in??? I have the head design w/o the removable 4 bolt cover. I'm confused....!

 

[Frank Acampora]

Re: Stuck Bypass Valve

As I remember, the the thermostat can only go in spring end out. The hole in the head is not large enough to let the spring end clear and not deep enough either.

 

[Randy W.]

Re: Stuck Bypass Valve--'76, 75hp.

Re: Stuck Bypass Valve--'76, 75hp.

Thanks for the reply Frank. I'm sure you're right, the thermostat can only go in one direction now that I've "toyed" with it.

When I look at the block from the rear prior to putting the head back on, it looks like the water flow enters into the head from the upper left? Then, looking at the head, there's no entry at that point? Once it enters the head at that point there doesn't seem to be an exit into the rest of the head either? I know the water circulation begins in the exhaust area and then enters the head, but I'm having trouble figuring out how it actually gets to the thermostat. The manuals that I have are vague in this area. The bypass value is stuck and I think I'll leave it that way versus opening up another "can of worms". Can anyone clear up my water flow woes for me?