Heater control valve for my Ultima

[2001ultima]

All, I have been reading about the heater ports on an LS engine and there is a lot of debate as to whether the ports can be blocked off or not. The theory is that the coolant should be always flowing which passes over the thermostat. If the flow is blocked there could be issues with the thermostat working properly. Some report no issue with the ports blocked and others do. I seem to have the issue as my ports are currently blocked as to keep the heat down in the cabin. I bought a heater control valve from a 95-00 Chevy pickup truck. It is a 4 port valve, when closed works as a by-pass and the coolant will flow back to the engine and when open will flow though the cabin to the heater core. I am going to install it in the engine bay to prevent the heat from getting to the side pod (in the summer the heat radiates). The valve has 5/8 and 3/4 inch ports. I will need a longer pull cable to turn the flow on and off. The only mod is to unscrew and remove the vacuum switch and fabricate a plate to attach the cable end. Attached is a photo of the part from (AC Delco 15-5533) and a photo of a similar valve with a plate for a cable. The other item needed is a 3/4 to 5/8 hose reducer as the heater core hoses in and out are 5/8 and the LS engine out is 3/4.

[2001ultima]

F.C., Nice setup. I saw this 4 port electronic valve as well. See page 20 of http://www.oldairproducts.com/pdf/2013_oldairprodu...

I want to stay with the old school mechanical valve. There seems to more and more nice stuff available.

[2001ultima]

mt308 said:

I like the old school valve too, but seem to get heat in the heater even when should be off. Anyone else suffer this issue. I have had a play recently but not been out in the car since so not sure if I gave cured it. Surely a basic valve should be just as effective as an electronic one and air should not be heated at all when fully closed?

Mark, Do you have a bypass? without a by bypass the pressure will push the coolant through any crack. I hope with the 4 port valve that the bypass will prevent the coolant from working it's way to the heater core.

[2001ultima]

Some photos of the 4 valve heater by pass install. It work out nice and keeps the cabin free of radiant heat.







Part purchased from: http://www.oldairproducts.com/pdf/flipbooks/2013_f...
Page 16.

heater hoses used from engine to valve: http://www.summitracing.com/parts/dac-70001

You will likely need a reducer for the larger heater port (engine port) to the valve (I believe 3/4 to 5/8 if I remember). I originally had AN fittings in the engine heater ports and the ports blocked which was not the right thing to do as the coolant needs to be constantly flowing past the thermostat for the thermostat to work properly.