Apart from my shut off valve being opposite to as it appears it should. What could make the water flow reverse ?.

 

Depending which heater you have, reverse flow thru the heater wouldn't affect it's perfomance. Flow is normally from the lower connection to the heater core, to push any air out . The box style heaters have a horizontal core so there is no low side.

There is always more pressure at the head connection than at the water pump, so flow will always be from head to pump.

I'd guess you'll have no problem taking the valve off the pump to work on it, if it's stuck closed.

 

Perhaps I misspoke. The water obviously can't flow in reverse. It's designed to flow in one direction, but many people have a misunderstanding of the direction of flow, and I did a crummy job of explaining. My apologies.

The first thing to check, imo, is to see if your valve at the water pump is open. My guess is that it's closed or at least not open enough, and the little bit of hot water you're getting is from percolation effect, just enough to give you some heat, but not enough to get real warm since the water isn't actually circulating. That's my take on your description of the hoses being hot near the engine, but cold at the heater. Having the shut off valve at the wrong end will also let this same effect happen in the summer, when you really don't want any hot water going to the heater. If it were me, I'd pull the valve from the water pump and replace it with a standard nipple, and put new, or at least a known good working valve at the head, then test the core and hoses for flow.

The thermostat is there to regulate the minimum engine temperature. If your 140F temp is accurate, I would put in hotter thermostats.

 

Just a quickie, my stats are 160f .Tested and working properly. I agree with all. I will drain the system again and try to remove the valve at water pump to to test it. Maybe I could quickly pull the hose from that junction and see if anything pours from the water pump before draining the whole system.

 

Just to double check...you are talking of purging air from the hoses at the heater inside the cab ?.

 

Update... I have eventually managed to free up the tap on the water pump outlet. Took a while with the help of some WD40 and grease, but now the heater is working fine. Thanks to all for their help with this issue.

Suffolkman

 

Yes, where the hoses connect to the heater core.
When I installed the heater in my COE it had an air pocket....this was the only way I could get it to work as the heater is way higher than the engine.

 

Can you post a picture of your heater? Once the valve has been addressed, I'd be surprised if you need to purge the heater. If you have a MagicAire you might have to.

 

Yes ...will do that over the weekend.

Suffolkman

 

Finally managed to take a photo of the heater in my truck. I guess someone has dressed it with the checker plate to enhance the appearance. It does run a 3 speed fan, which is quite noisy.

Suffolkman