Does my 1987 Jimmy not have a heater control valve?

[Edpoe]

My 5.7L 1987 doesn't seem to have a heater core control valve? Is this correct? I see the part listed at the auto parts store, but I don't seem to have one nor do I have a vacuum line that is not connected. Does the temp control just work by mixing outside air? New to K5s so sorry about asking all these stupid questions.

 

[Fastereddie]

The temperature is regulated with a blend door that mixes the air. No valve just a cable from dash lever to door.

 

[Edpoe]

The temperature is regulated with a blend door that mixes the air. No valve just a cable from dash lever to door.

Thanks, that's what i thought. Wasnt sure.

 

[sweetk30]

I can tell you adding a valve for summer time to stop the flow cuts down a LOT of unwanted heat . I noticed a big change in my truck .

 

[Fastereddie]

I can tell you adding a valve for summer time to stop the flow cuts down a LOT of unwanted heat . I noticed a big change in my truck .

I know some vehicles come factory like that. I’ve always wanted to try it to see if it helps in the summertime, but I don’t know if I should put it in the feed line to the core or the return side back to radiator. And then will it cause an air pocket? Make a hot spot? Or should I completely disconnect and make a bypass loop. The bypass loop seems better in my head, but what if I go up to the mountains and need my defroster? Then I’ve jacked myself haha

 

[diesel4me]

Mostly only A/C equipped vehicles got the vacuum operated heater control valve,to stop hot coolant from getting in the heater/evaporator core "box" and make the A/C work more efficiently..you could add one,or a manual ball valve to block flow to the heater core in summer..

 

[frankin5]

The only square to get heater shut off was the rear heater equipped Suburbans.

 

[sweetk30]

I know some vehicles come factory like that. I’ve always wanted to try it to see if it helps in the summertime, but I don’t know if I should put it in the feed line to the core or the return side back to radiator. And then will it cause an air pocket? Make a hot spot? Or should I completely disconnect and make a bypass loop. The bypass loop seems better in my head, but what if I go up to the mountains and need my defroster? Then I’ve jacked myself haha

i am a bit ocd so when i did mine it got 3 valves . 1 mid T-crossover for heat season shut off . then 2 on core to stop 100% flow both lines .

reason i did T-line is the L31 vortec flows a little different and i needed to keep bypass flow more than full block off like older sbc engines . but i have since figured out the problem and now i dont need it but i am leaving it in there .