Engine coolant valve and water heater

[PAC3142]

Hi,
I'm going to replace my water heater. The photo shows the engine coolant lines that go to and return from the water heater.
What is the circled valve for (I assume it's a valve), and will it help me when I replace the heater?

Engine is a fresh water cooled Yanmar 3JH2E in a 1994 Hunter 37.5.

Thanks,
Paul

 

[kappykaplan]

It looks like the valve provides a means to stop the flow of engine coolant through the water heater - a bypass if you will.

 

[Stu Jackson]

It looks like the valve provides a means to stop the flow of engine coolant through the water heater - a bypass if you will.

Be VERY VERY careful about making this kind of assumption or suggestion to the OP.
None of us know what the hoses do when they leave the picture.
There is a HUGE difference between a SHUTOFF valve and a BYPASS valve.
As photographed, that valve APPEARS [THAT IT COULD JUST AS WELL] be in line with the flow of the engine coolant to the heater, which then returns to the engine.
If that valve is closed, the engine coolant system WOULD CEASE TO FUNCTION.
That is completely different than a bypass function.

To the OP: It COULD BE that the PO put that there to avoid draining coolant if he had to change the heater. If that was the case, it would haver been wise to put another one on the other line, too. One is supply the other is return, no way to know which from the photo. It COULD ALSO BE that he misunderstood the difference between the concept of shutoff and bypass. It COULD ALSO be part of a bypass system that is not in the photograph.

You asked an honest question. The honest answer is what I've given you. No one can know without more info.

 

[Calif. Ted]

I'm pretty sure that's a bleed valve, screwing in opens and allows flow of coolant or air out. Had one from the factory on the water heater of a boat where it was the high point of coolant lines.

 

[Tally Ho]

I'm pretty sure that's a bleed valve, screwing in opens and allows flow of coolant or air out. Had one from the factory on the water heater of a boat where it was the high point of coolant lines.

I think @Calif. Ted is correct....I believe it is a bleed valve.

Greg

 

[Stu Jackson]

Ted & Greg could also be right. If that IS the purpose, then the valve is actually too low to perform that function, all by itself. It will get 99% of the air out, but not ALL of it, and even 1% air in that line could cause an overheat.
It could work if you cut the zip tie holding the hose to the wall and raise it up when you're filling with coolant.

 

[Tally Ho]

looks like if you cut the cable tie off holding it to the other howe, you could left that valve up to be the highest point.

Greg

 

[Michael Davis]

I agree. It looks more like a standard petcock than any valve I’ve ever seen.

 

[Mechone]

I'm pretty sure that's a bleed valve, screwing in opens and allows flow of coolant or air out. Had one from the factory on the water heater of a boat where it was the high point of coolant lines.

You are 100% right ,it is to bleed air out of the heater hoses going to the hot water tank ,to prevent an air lock most engines that have the ability to heat hot water tank have them. My boat and others I have worked on are a little different ,they use a schrader valve
Just cut the tie, hold the hose higher to bleed ,then retie

 

[weekendrken]

A bleed near the height point of the WH loop to bleed air trapped in that system.

 

[sailme88]

Good opportunity to replace all of your antifreeze and make a winterization manifold for your heater. That is an air bleeder valve. You may want to relocate it HIGHER than it is.

 

[PAC3142]

Thanks all,
I do plan to replace the coolant. I'll take a closer look at this valve while doing that. I'm sure those hoses will just slide right off.

Paul

 

[Scott T-Bird]

Sure is a clean engine!

 

[PAC3142]

Scott,
Thanks, though I can't take much credit. When we first saw the boat 5 years ago it had been sitting in the back of a boatyard for many years under pine trees. The exterior was an absolute mess, but the interior was immaculate. The exterior is now pretty good, and we are doing a reasonable job keeping the interior up.