My f150 has a 3.9 cummins diesel in it. I run wvo. There was a delay in heat getting to the heater core as coolant went thru heated filter, heat exchanger, and heated tank I simply took tee's out and ran it all in series and switched flow direction (I think)! Now the coolant does not flow through core. Is there a check valve in the heater core or perhaps too much pressure with direct flow?

 

flow thru the core is dependent on one side being higher pressure than the other. Original install was one hose toward the suction side of the water pump and one hose toward the pressure side of the water pump........ 30 years ago I worked in a test facility that tested "new design equipment"... we had a few "heaters don't work"... we ended up putting hoses closer to the pump discharge, and closer to the suction side to get a bigger differential between the two hoses........... I might add, these were Cummins construction engines........... you might see if there is a pipe plug closer to the pump to get better DIFF PRESSURE between the hoses.

 

I understand the pressure differential. I rerouted all of my lines with the Tee's in place yesterday. I had heat to my heater core, but none to the Flat plate heat exchanger or heated tank. SOOOOO, tonight I removed the line from the rear of the block and went back to the original in and out locations with all components in series rather than with tees running coolant to my components. NO FLOW AGAIN. I will most likely have to reinstall the setup with the tees in place. I suppose pushing the coolant through the smaller 1/2" hose with fittings doesn't create enough differential pressure. Going back to square one after all these hours of work is not cool. I suppose another option would be an electric circulation pump to boost the flow.

 

Your on the right track... I know with the BIG motor I was working on, they just pulled a couple 3/4 inch pipe plugs on the manifold / block and routed to the heater. No heat but I didn't know why. I put a tygon clear hose on one side so I could see the flow--- NONE. Then noted that both hoses were basically tied to the same part of the system... moved one closer to the pump discharge hose and put the other closer to the radiator bottom hose (suction to the pump).......... electric pump is also an idea.

 

I just re-plumbed it all in the original configuration. I'm getting flow, but not quite enough to get heat to my wvo early enough. I ordered an electric coolant pump I can use in the colder months at start up to get the WVO warm sooner. If heats up quick when running it down the road, so the pump will just facilitate that quicker.