Adding hydronic cabin heat from a AQ140A engine

[Braebyrn]

It didn't look like we could access any coolant ports on the water pump with the AQ140A engine. We found some plugs that go into various places on the block and the head. We didn't find any diagrams or photos online with others doing this modification.
The plan was to run some heater hose up to the cabin area and install a heater core with fans and ducting. If we have to add a electric water pump inline that is easy to do too.

 

[Braebyrn]

It didn't look like we could access any coolant ports on the water pump with the AQ140A engine. We found some plugs that go into various places on the block and the head. We didn't find any diagrams or photos online with others doing this modification.
The plan was to run some heater hose up to the cabin area and install a heater core with fans and ducting. If we have to add a electric water pump inline that is easy to do too.

 

[Bondo]

Ayuh,..... Does this motor have a heat exchanger,..??

If this was a Chevy, you'd pull water from the manifold, just before the t-stat, 'n return it to the water pump housing,....

You need 2 different pressure points, from a slightly higher pressure, to a slightly lower pressure, so the water will circulate,.....

 

[Braebyrn]

Ayuh,..... Does this motor have a heat exchanger,..??

If this was a Chevy, you'd pull water from the manifold, just before the t-stat, 'n return it to the water pump housing,....

You need 2 different pressure points, from a slightly higher pressure, to a slightly lower pressure, so the water will circulate,.....

There is a heat exchanger but it's attached over the water pump housing and there's no ports on the water pump. That's why I was looking at the block or head.
If someone doesn't chime in that they've done it before, we just might have to do an experiment on the donor block.

We could install a pressure gauge at each port individually and hook up a drill to the engine block coolant water pump and see what pressures they show.

Following Bondo's advice then pick lowest and highest.

 

[Scott Danforth]

factory manual would be where you would have to look to see if there is a port.

 

[QBhoy]

Danger of it running too cool, perhaps. Be a larger heat exchange than the usual hot water tank might have

 

[dingbat]

Danger of it running too cool, perhaps. Be a larger heat exchange than the usual hot water tank might have

The danger is overheating….

Short cycling of the thermostat would keep the motor running border line over temp all the time

 

[Braebyrn]

factory manual would be where you would have to look to see if there is a port.

I looked at the factory manual again today and there is not a description for such a port.

 

[Braebyrn]

Danger of it running too cool, perhaps. Be a larger heat exchange than the usual hot water tank might have

There is a functioning water temperature gauge also on the instrument cluster. Maybe a 12v solenoid valve inline with the proposed cabin heater hoses would make it so the operator could control the heat output and also for the summer months when cabin heat is not needed.

 

[Grub54891]

There is a functioning water temperature gauge also on the instrument cluster. Maybe a 12v solenoid valve inline with the proposed cabin heater hoses would make it so the operator could control the heat output and also for the summer months when cabin heat is not needed.

A simple ball valve would do that nicely.

 

[Braebyrn]

Today we hooked up a pressure gauge to the coolant port on the rear of the block where it is the lowest part of the block and where the drain tube is hooked to.
After removing the thermostat and turning the water pump with a drill, there was no pressure indicated on the gauge. Maybe I shouldn't see any since it is a circulation pump and wouldn't build pressure, right!
I removed the heat exchanger and can see right into the water pump now. We will get a clear tube that will go in place of the heat exchanger to see if there is movement and what direction. I would assume that the hot engine coolant goes into the bottom of the exchanger and comes out the top. The cold seawater line goes into the top of the heat exchanger and out the bottom of the tank it looks like.
Maybe the car enthusiast side of these engines would have a engine cut away to see the coolant passages and which ports would be best to connect to. Or we can remove the fluid and all of the ports, put a water hose on the coolant tank and see where the water comes out first and last.

 

[Braebyrn]

 

[Bondo]

Today we hooked up a pressure gauge to the coolant port on the rear of the block where it is the lowest part of the block and where the drain tube is hooked to.
After removing the thermostat and turning the water pump with a drill, there was no pressure indicated on the gauge. Maybe I shouldn't see any since it is a circulation pump and wouldn't build pressure, right!
I removed the heat exchanger and can see right into the water pump now. We will get a clear tube that will go in place of the heat exchanger to see if there is movement and what direction. I would assume that the hot engine coolant goes into the bottom of the exchanger and comes out the top. The cold seawater line goes into the top of the heat exchanger and out the bottom of the tank it looks like.
Maybe the car enthusiast side of these engines would have a engine cut away to see the coolant passages and which ports would be best to connect to. Or we can remove the fluid and all of the ports, put a water hose on the coolant tank and see where the water comes out first and last.

Ayuh,..... 1st off, I don't know yer motor very well,.... But,....
The circulating pump don't build pressure, per say, but the t-stat holds back the flow of the pump,....
When the t-stat opens, it allows flows from the pump, to the heat exchanger,....

Reviewing yer pictures,....
It appears that in yer very 1st picture, the pipe plug center forward, just above, 'n forward of the oil pressure sender in yer 4th picture, Not the one in the exhaust riser, Should be a water port, which will be the hottest water in yer system, which could feed yer cabin heater,....
That is, if it's a water port, 'n not an oil port,....

For a return port, again in yer 1st picture, the most forward port, appears to be in the bottom of the H/E, nearest the in-coming port of the circulating water pump, which will be the lower pressure, return from the cabin heater port,....

 

[Braebyrn]

Ayuh,..... 1st off, I don't know yer motor very well,.... But,....
The circulating pump don't build pressure, per say, but the t-stat holds back the flow of the pump,....
When the t-stat opens, it allows flows from the pump, to the heat exchanger,....

Reviewing yer pictures,....
It appears that in yer very 1st picture, the pipe plug center forward, just above, 'n forward of the oil pressure sender in yer 4th picture, Not the one in the exhaust riser, Should be a water port, which will be the hottest water in yer system, which could feed yer cabin heater,....
That is, if it's a water port, 'n not an oil port,....

For a return port, again in yer 1st picture, the most forward port, appears to be in the bottom of the H/E, nearest the in-coming port of the circulating water pump, which will be the lower pressure, return from the cabin heater port,....

Bondo, I appreciate the encouragement with your answers.

I made a loop with a clear plastic tubing and two 3/8" barb fittings. This helps me to simulate the proposed hydronic heater line.

With one in the bottom coolant port of the heat exchanger and the other 3/8" port in the
block near the oil pressure sender. There are two ports there, but one is very small and from the oil galley and the other 3/8" size is for a coolant port.

Because of the clear tubing, and when I spin the water pump in the clockwise direction, I can see the water flowing from the heat exchanger to the block. In this configuration the water would be coming out of the heat exchanger already cooled from the seawater. Not going into the exchanger.

With this discovery, I tried other port configurations and it appears that the rearward lower "drain" port and the port on the rear of the head underneath the intake also flow well.

Unless I am mistaken, there would be sufficient heat built up already at that rear lower drain port that I can pull from to heat the cabin with and return it back via the port at the intake.

 

[Scott Danforth]

As you add system volume, you may run out of expansion volume in the heat exchanger tank

 

[Braebyrn]

As you add system volume, you may run out of expansion volume in the heat exchanger tank

Scott,
Do tell. I will also do some research on that.

 

[Scott Danforth]

Scott,
Do tell. I will also do some research on that.

Factory expansion tank volume is designed for 6-8% expansion (from temp change) and 6% draw down

 

[Braebyrn]

Scott,
Do tell. I will also do some research on that.

My donor hydronic heater core has 1/2" and 5/8" lines. I read that the larger line would help to always keep the pressure lower on the outlet side.

But that doesn't have to do with the expansion volume. Hmmm

 

[Scott Danforth]

Add the internal volume and see if the extra 8% will be a problem

 

[dingbat]

My donor hydronic heater core has 1/2" and 5/8" lines.

Best plumbing practice to reduce back pressure
1/2” is intake
5/8” is exhaust