JD 4045 External Coolant Loop

[scurvydog_pnw]

Hi we have a John Deere 4045 engine in our boat and is setup to route the engine coolant through an external water heater that has a heat exchanger.

Our existing water heater died this week and I put a replacement one in. The problem I ran into is that the replacement water heater has a heat exchanger marked with inlet / outlet and I am not sure which hose from the engine is the inlet /outlet.

One hose comes off the side of the heat exchanger as seen in the first picture.

The second hose comes off the front of the engine just below the water pump where I assume is the pump gearing to circulate the coolant. That's the second picture. Can someone confirm that the coolant flow direction that I believe is correct on the pictures?

 

[sunchaser]

Maybe it doesn’t matter?? But absent perfect answer:

Simple way - with hoses disconnected from heater start the engine and open the individual valves to see which is suction and which is discharge.

More certain way - Get two buckets and 1/3 fill each one with coolant. Put each hose below the coolant level. Make sure your engine is up to operating temperature and revs at 1000 or so. Then open the valves on each hose. Fluid level increase decrease will tell the tale.

 

[Lepke]

The way most engines supply hot coolant: the supply (from the engine) is taped near the thermostat, probably in the head. You want the hottest water going to the heater. The return should be near the coolant pump suction. Returning near the coolant pump ensures good flow thru the heater.

 

[High Wire]

Generically, either way should work but one way will be more efficient than the other.
With the heater plumbed up, measure the temperature of the inlet and outlet hoses with an infrared thermometer. The correct way (counter flow) will have the heater inlet hose hotter than the outlet hose. The wrong way will have the heater outlet hose hotter than the inlet.

 

[O C Diver]

I have a 4045TFM75 with an external heat loop.

Just to confuse the issue, my John Deere dealer said to draw the water out from the 1/2" pipe thead fitting on the top of the head at the back. The return is your lower picture where the bypass pipe returns coolant to the engine circulating pump.

The top picture is the thermostat housing. The 4045 has a 2 double acting thermostats. In one position they are closed bypassing the heat exchanger. When fully open, they block the bypass channel around the heat exchanger. That port which I believe is 1/4" pipe thread, should give you flow ample for the water heater, but inadequate for cabin heaters.

Ted

 

[NWboater2]

I think OCDiver / Ted knows more than most about, well, lotsa stuff, but JDs specifically.
I have the 6 cyl version and the OUT is in the back of the engine The return/back into the system is forward starboard near the raw water pump. Makes sense if you think about it. Let the engine heat the coolant before it goes on its detour to heat other stuff then put the post-exchanged lukewarm coolant back into the colder end. Like Lepke said, too, I see.

Short answer it’s the opposite of your photos/labels.

Nice clean engine. Good luck!

 

[O C Diver]

I have a 4045TFM75 with an external heat loop.

Just to confuse the issue, my John Deere dealer said to draw the water out from the 1/2" pipe thead fitting on the top of the head at the back.

Below is a picture of my heat loop outlet. It's behind cylinder number 4's injector and the fuel return line to the diesel tank. The port was plugged by a flush 1/2" pipe plug.



Ted

 

[scurvydog_pnw]

Thanks for the input everyone! I appreciate it.