How the heck does this work?

TimWafer · Nov 25, 2012

I had this posted over on the Farmall board but never got a real answer. This is the bypass hose on a 656 with a D282 diesel engine.

It appears to connect from the radiator side of the thermostat to the water pump. I assumed flow was toward the pump. How would this circulate water through the engine when the thermostat is closed? Isn’t that the purpose of a bypass?
I was told it’s really a pressure line from the pump but that makes no sense to me either.
Tim

notjustair · Nov 25, 2012

Never pondered it. My Ford 370 and GMC 270 engines (in trucks) both have them just the same places. Those are both elbow shaped hoses and I am convinced that it is impossible to replace them without bloodying at least two knuckles.

Janicholson · Nov 25, 2012

THe hose enters the area of the block near the T stat, but does circulate coolant between the Water pump (sucking out of the block) and the head, keeping things from having hot spots. Jim

Bob Bancroft · Nov 25, 2012

I agree. It does appear that the bypass hose goes to the radiator side of the thermostat. But without opening it up, I wouldn't know for sure.
Many older engines had no bypass, and I never knew of it causing a problem. I've seen newer applications where there are all sorts of little bypass hoses, I suppose to avoid air locks.
I know of one application in a combine where a diesel engine rebuild was ruined because of an air lock.

TimWafer · Nov 25, 2012

(quoted from post at 22:14:23 11/25/12) THe hose enters the area of the block near the T stat, but does circulate coolant between the Water pump (sucking out of the block) and the head, keeping things from having hot spots. Jim

I always thought the water flows from the lower radiator hose to the pump, into the block, up through the head and if the thermostat is open through the upper radiator hose back to the radiator. If the thermostat is closed it can circulate from just before the thermostat back to the waterpump through the bybass hose to eliminate hot spots in the engine. On this engine it appears the bypass hooks in above the thermostat.
Are you saying this pump sucks out of the block and the bypass is indeed a pressure line?? Then what about the lower radiator hose? Just doesn’t make any sense to me.

Janicholson · Nov 25, 2012

What I described works that way. some pump out of the block, some hav inlets into the block (this one probably) Jim

Fritz Maurer · Nov 25, 2012

You did too get an answer on the Farmall forum!!You asked how to plumb the heater and two people told you how to do it!

37chief · Nov 25, 2012

To me it looks like it just courulates the water in the block until the thermostat is heated until it opens. Then to the top of the radiator. Stan

guido · Nov 25, 2012

Hello TimWafer,
Water pump takes coolant from the bottom of the radiator usually, there are exceptions,and through the bypass hose goes into top hose of the radiator, regardeless of the thermostat state of opening.In other words it bypasses through the themostat housing and goes right into the radiator'top feeding hose.
When the thermostat is open coolant from the block flows together with the rest of the bypass water, againg into the top of the radiator.
Guido.

rustred · Nov 25, 2012

yes, this one has inlet into block behind pump.

TimWafer · Nov 25, 2012

(quoted from post at 00:49:09 11/26/12) You did too get an answer on the Farmall forum!!You asked how to plumb the heater and two people told you how to do it!

Sorry if I offended you. What I really wanted to know is how this bypass system works. I just cant make sense of it in my own mind. Im confused as to the directions of flows I guess.
If I understand whats being said, the bypass circulates water through the radiator and not the block & head.
What good does this do and how would it eliminate hot spots in the engine? I dont understand the theory of this system and I like to understand whats actually happening.

TimWafer · Nov 25, 2012

Hello TimWafer,
Water pump takes coolant from the bottom of the radiator usually, there are exceptions,and through the bypass hose goes into top hose of the radiator, regardeless of the thermostat state of opening.In other words it bypasses through the themostat housing and goes right into the radiator'top feeding hose.
When the thermostat is open coolant from the block flows together with the rest of the bypass water, againg into the top of the radiator.
Guido.

What is the purpose of circulating through the radiator rather than the block when the thermostats closed? I cant see any flow through the block in any direction with this system when the therm is closed.

37chief · Nov 25, 2012

You will see it when you need to replace the pump. That's a strange one to me. Stan

BushogPapa · Nov 25, 2012

Circulates coolant IN Block, while Thermostat is Closed, for even temps and less stressful warm-up..

I think you will find, the Thermostat is actually above the top bypass connection..

Nothing else would make any sense..

Ron..

LAA · Nov 25, 2012

The flow is from the thermostat housing through the water pump, the by-pass allows a small amount of hot return water to mix with the cooler water that the pump is drawing from the bottom of the radiator, as this water circulates it keeps the entire engine block at a more even temperature which increases efficiency, in other words, keeps the block and the heads at an even temperature instead of block cooler -- heads hotter. The reason the water will divert is because an engine water pump is not a positive displacement pump.

gbs · Nov 26, 2012

in your case it looks like it's set up for heater hoses the connection on the thermostat housing appears to be above the thermostat, as for a bypass most of the time they are to prevent air locking of the pump or thermostat,Detroit had petcocks on the thermostat housing never had to open one until one night we blew a radiator pipe coupling hose on an 8V71 in a bus it had two separate radiators, two water pumps, one filler cap couldn't get it to take water on the closed side it would try to get hot idling, after myself and the field mechanic had ran out of things to try the man that hauled fuel for us walked by an opened one of the petcocks it swallowed the water and we were able to fill the system one of the pumps was air locked never had that before ,but the radiators were mounted above the engine one on each side

TimWafer · Nov 27, 2012

Those of you who said the bypass is connected to the block side of the thermostat even though, from the outside it hooks into the upper thermostat housing were correct.
You can see how in the included photo.

So it does function as a normal system like I’m used to. The bypass hose is a suction hose, NOT a pressure hose and flow is toward the pump. The oil cooler line however is a pressure line from the pump and flow is toward the oil cooler, returning to the lower radiator hose. I verified these both before I removed the upper thermostat housing by temporally putting a piece of clear hose in line to visually see the flow.
Thanks to everyone for their help!
Tim

How the heck does this work?

TimWafer

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notjustair

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Janicholson

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Bob Bancroft

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TimWafer

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Janicholson

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Fritz Maurer

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37chief

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guido

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rustred

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TimWafer

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TimWafer

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37chief

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BushogPapa

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LAA

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gbs

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TimWafer

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