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Heater Control Valve?...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Texan, Dec 10, 2001.

  1. Texan

    Texan 1/2 ton status

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    89' Blazer, stock 350, just about to roll 300K! Won't get above 120* when it's below 40* outside. Because of that the heater sucks. Changed thermostat, all new hoses, radiatior is holding coolant, yada, yada, so I can't figure out what's going on. Auto parts store guy finds a listing for a heater control valve for this truck-I've been under the hood a thousand times and never seen it. Looks like it goes inline on the heater hose between the intake and heater core and appears to be vacuum actuated. I can't find an "extra" vacuum hose dangling from the firewall and my heater hoses are straight in and out so if I ever had one it was removed years ago before I bought the truck. Haynes doesn't cover it in my manual. Anyone know what I'm talking about? Some insight as to where I might find that mystery vacuum hose would be very helpful....

    Thanks,

    <font color=orange>STEVE<font color=orange>[​IMG]
    89 Blazer
    67 Camaro 468
    68 CamaroSS 327
    98 GTP
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    If you have a new thermostat...it ain't working. 40 F is not cold by any stretch and certainly not cold enough to cause overcooling. Any problem with hoses would cause overheating (eg. collapsed lower hose)
    Your 350 is plumbed the same way mine is (according to your description) and with a 192 degree thermostat my Jimmy is quite toasty inside.

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
    <a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>
     
  3. Texan

    Texan 1/2 ton status

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    I can let the thing idle for 10-15 minutes, pull the radiator cap by hand, and never see any water moving. It just isn't getting hot. I know it's alot of miles but surely it should warm up to 180"?....

    <font color=orange>STEVE<font color=orange>[​IMG]
    89 Blazer
    67 Camaro 468
    68 CamaroSS 327
    98 GTP
     
  4. HarryH3

    HarryH3 1 ton status Author

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    K5's didn't come with heater valves. Coolant flows through the heater core all the time. Temp inside is controlled by routing the airflow through or around the heater core. If the engine is running that cold, then water is getting past the thermostat. Even the puny little 4.3 liter V6 in my S-Jimmy can get up close to 200, when it's 18 degrees outside!

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
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  5. Texan

    Texan 1/2 ton status

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    The guy at Autozone found it listed under 89' V10 Full Size Blazer. I've never seen it before either. Can't explain it but he said its suppose to be there. Maybe it's an 89' to 91' thing?

    <font color=orange>STEVE<font color=orange>[​IMG]
    89 Blazer
    67 Camaro 468
    68 CamaroSS 327
    98 GTP
     
  6. HarryH3

    HarryH3 1 ton status Author

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    More likely that his computer is showing the wrong part. [​IMG] I've got a '90 Suburban, which is pretty much identical to a '90 K5 and don't recall seeing a water valve under the hood. In any case, it still woudn't keep the engine from getting warm, it would just keep the heater from getting warm.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     

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