Heater control valve

[wildwilly4x4]

Has anyone added a cable or vacuum controlled heater conttol valve to their truck? I believe the heater core is the root cause of my truck slowly getting hot at idle with the A/C on. Running an 8.1, stock aux. fan plus second aux. fan. Heater is plumbed like stock, which dumps heater core return to cold side of radiator. Truck has factory high cap. radiator (same size as diesel rad.)

[tucsonjwt]

I installed a 3/4" PEX valve (with barbed fitting ends) I got at Home Depot in the supply side heater hose before the firewall. I keep this valve closed in the summer and open in the winter. I think it does improve the A/C performance in the 100+ HotZona desert weather. Just remember to open it back up when the cold winter weather returns.

I know that some use cable operated valves but I like things simple. I have even heard of thermostatically actuated valves being used, but I think that is even more complicated.

[wildwilly4x4]

I like simple things too, but this is a pretty high quality built truck that i want fully functioning for when my wife drives it. Also we live in the TX panhandle and there are many days during the year that we may use the A/C and heater within a few hours of each other. Im hoping to find a valve that i can either T into a vacuum control line or maybe use cable operation by linking into the blend door cable. Just trying to see if anyone has tried to make it feel as "stock" as possible from an operational standpoint.

[hatzie]

You can do it automatically when the AC is on or with a switch or even both.

Four Seasons 74858 5/8" inline vacuum heater valve.https://www.amazon.com/Four-Seasons-.../dp/B000C2Q8OS
2 port 12v Normally Closed Vacuum Solenoid https://www.amazon.com/Universal-Con.../dp/B003R43J2C

The Vacuum valve in the heater hose is the part that will look most out of place. The Vacuum Solenoid looks similar to GM emissions parts.
Tee into AC Clutch + wire or use a switch inside the cab or both.
Tee into AC Vacuum between the accumulator can and the dash control head. The rest of the vacuum routing is self explanatory.

[wildwilly4x4]

That sounds like some good info! I have looked into those valves, and although the elec. looks to be the easiest, the reading I was doing on it seemed to show that it only had a duty cycle of 4-6 hours. Its not common for me to go 4-6 hours, but long trips that we go on (this is our family vehicle) could get into that time frame easily, with only stops for fuel. I kinda wonder if those short breaks would be long enough for the solenoid style to cool off and then be good for another 4-6 hours? As much as I hate vacuum stuff, that may be to most durable way to go. Thanks for the input.

[hatzie]

Originally Posted by wildwilly4x4

That sounds like some good info! I have looked into those valves, and although the elec. looks to be the easiest, the reading I was doing on it seemed to show that it only had a duty cycle of 4-6 hours. Its not common for me to go 4-6 hours, but long trips that we go on (this is our family vehicle) could get into that time frame easily, with only stops for fuel. I kinda wonder if those short breaks would be long enough for the solenoid style to cool off and then be good for another 4-6 hours? As much as I hate vacuum stuff, that may be to most durable way to go. Thanks for the input.

Never considered the vacuum solenoid duty cycle. The engine compartment heat may not do it any favors either.
If there's room... maybe you could mount the little monster inside the evaporator housing to cool it. Cut a biscuit out of the housing and mount the solenoid valve on a gasketed metal plate like the blower resistors. Pass the wires and vacuum lines through the mounting plate.

The other option is to use the AC vacuum line off the control head.

The AC control vacuum hoses are Nylon with soft ends. You can get nylon vacuum line on the HELP rack and any decent auto parts store will be able to get Tee, Straight, and 90° soft ends to slide over nylon vacuum hose.

The vacuum line diagrams are in the service manual.

[wildwilly4x4]

Sounds like a plan. I may order up some parts tonight for some experimentation! I'll keep up with the thread to show progress. I know idling with a/c in traffic makes this 8.1 get up in the 220+ temps fairly quick. Then it doesnt want to run good until i can either get the rpm up above 1500, or back at cruising speed. The heads must heat soak pretty bad on it, as you can feel it spark knock. The old stock 454 acted the same way. Mech fan just doesnt move enough air at idle. Even with two elec. fans it doesnt keep up. The full flow of hot h2o to the cold side of radiator is the only culprit i can come up with. All cooling system is in perfect condition, fan clutch, 4 row diesel sized radiator, fan shroud intact and hood shape.

[hatzie]

Wonder if it's possible to reverse flow the cooling system so the heads cool first like the mid 90's LT1... Now back to reality...

You may want to look at whether the fan is sucking hot air from the engine bay through the radiator. Running shrouds from the radiator sides right up to the radiator support to block air from the engine bay from being re-cycled back through the radiator might help.

[wildwilly4x4]

Yeah I sealed all of the gaps in the cores and whatnot when I swapped in the parallel flow condenser and motor swap. Don't ever have any problems with it running warm unless Im also running AC. Pulling my rock rigs through the mountains, AC on etc. the engine is moving the water through the rad. enough that I don't have any problems. But at idle, when water flow is slowest the heater core is still running full bore hot water into the cold pump suction side of the radiator. I haven't pinched off the line to verify this, but it makes sense, and you can actually hear the water flow through the heater core when sitting at a stop light. In the winter the heater in this thing will literally have you burning it gets so warm. Even just a restrictor plate in the coolant return line may help it out.