Blows Hot Air When Off?

[Mango]

Installed a Shut off valve on heater hose going to the heater core stops the hot air in the cab! But i get a serous coolant leak? Too much pressure in the system ??

 

[MarineOne]

For it to work you need 3 claves and a cross over tube to allow normal flow or you'll get hot spots in head if it's still feeding from head. T both heater core hoses with shutoff in and out of heater core along with a shutoff in the cross over

When heat is used the 2 heater core valves open and crossover closed.

When heat not used crossover valve open and heater core valves closed

 

[Rusty Nail]

Pix?

 

[Craig 85]

There are some adjustments to the top of the heater box that close off the air flow from the heater core. I had this issue when I finally got the A/C hooked back up in my truck.

I grabbed this off the internet. I believe in my case I needed to adjust the solid rod, just left of the circle.

You must be registered for see images attach

 

[Rusty Nail]

Awesome pix!

 

[Mango]

Thanks for the replies, i will and try adjusting the flapper door
Marine One is that a valve i can purchase or is it all custom work? This is what I Have now Vacuum hose runs off the back heater switch to close the valve. No longer use it. Back heater and AC all gone

 

[Mango]

Removed the Valve no more coolant leak
Checked all Flapper doors working correct
Still blowing hot air with everything off ?
I Quit mat be time to get the AC rebuilt!

 

[RecklessWOT]

Just bypass the heater core alltogether. Instead of using some fancy shutoff valve and stuff, just get a loop of hose and connect it to the inlet and outlet before the coolant ever reaches the heater core, now there's no way for it to get in there. Then when it starts to get cold again (in Jackson that's probably the end of next month or so) just hook it back up and constant hot air shouldn't be an issue. If there's a more mild fall day and it gets a little warm in the truck, roll the windows down.

That'll buy you some time until you can rebuild the A/C

 

[Mango]

Sounds like a Plan Thanks Originally from MAINE miss the East, Kind Of

 

[75gmck25]

Based on my experience, it’s hard to get relatively cool fresh air. It just seems to pick up heat regardless of what you try to fix.

I tried a vacuum-operated heater bypass valve - stopped water flow and helped cool it down a little, but water in heater core was still warm.

Also remove the glove box and take off the plastic plenum panel behind it so you can see into the heater box. There is supposed to be foam insulation so that the inside doors seal better, but it has usually fallen apart. It’s also very common for something to fall down the defroster vent and then block full travel of the doors. Pens, small bolts, match books, etc. will cause problems. The heat control door is cable operated (like the picture in previous posts), but there is also a vacuum operated door that changes air flow.

 

[SquareRoot]

I gutted the factory 40 year old technology. Sticky cables, rotted hoses, cheesy vacuum lines.....all of it in the dumpster! Vintage Air. Plug and play. Yesterday I drove 30 miles home from work, the temp gauge in the mirror said 115. Inside...nice frosty air pouring out them vents. Carry on.

 

[gmbellew]

on just the vent setting, the air comes in hotter than ambient on my 1990 suburban, even on the highway cruising. usually it is about 8-10 degrees warmer. I attribute it to old tech inefficiencies and old door seals on the climate control system. but I don't have a lot if air flow coming in if the system is set to off....