GM Truck Club
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Results 1 to 6 of 6
  1. #1

    Default New memeber with a question about my 99 Suburban heating

    Hello All,

    I am brand new to this's great to see a bunch of Chevy guys and gals helping each other out!!

    Now for my question....I have a 99 1/2 ton Suburban with a 5.7 that I'm having some issues with. I bought it this fall with 130k on it. When I bought it, the intake was leaking (as they all do at one point). The seller claimed to have not noticed this and it appeared to be a small leak off the back of the manifold. I bought it at a reduced price with the knowlege I'd have to fix it. I went ahead and fixed it...replacing all the gaskets in the kit and all ignition parts (cap, rotor, plugs, wires). The only thing I didn't replace was the thermostat.

    Jump ahead to winter months....I noticed the heat wasn't blowing very warm....obviously should have done the thermostat when I had it apart. After replacing, I noticed the front was blowing pretty warm, but the rear was blowing cold. After driving it and checking some more....I noticed that while driving at highway speeds or higher than idle RPM's (about 2500 or so), the front and rear heat were blowing warm, acceptable air temps. As soon as I slowed to an idle, the front temp dropped slightly, but the rear went to cold.

    I talked to some different people and came up with two possible problems....a bad thermostat, or an air pocket somewhere in the system. So....I put in another thermostat and let it idle with the front and rear jacked up high trying to get the air out. None of this worked....I still have the same problem.

    I'm beginning to think the previous owners knew about the leak and filled the radiator with stop leak. Before I go buy a few more gallons of the pink antifreeze and radiator flush.....anyone have a better idea or a similar problem??? Any help would be's been around 0 degrees here (Montana) for the last week!!!


  2. #2

    mfleetwood's Avatar
    Join Date
    Jul 2010
    Denver, CO
    Blog Entries


    Hi JZ, welcome to the Club! Unfortunately, I do not know the answer but I am sure someone here does. If you do not get the response you are looking for here (Member Introductions area) shortly, you should try posting your question in the Tech link below.

    Mike (Denver, CO) - 2008 Sierra 1500 Z71 SLE 5.3L 4WD

    SUSPENSION: Rancho 4" Suspension Lift; Rancho RS9000XL Shocks; Rancho Skid Plates; Rancho MyRide Wireless Shock Controller;
    BFG All Terrain KO 315/70/17
    DRIVE TRAIN: 4.56 Gears; Detroit TrueTrac Differential; True Cool 40k Transmission Cooler
    PERFORMANCE: DiableSport Predator Tuner; Custom Tuned by Diablew; Magnaflow Exhaust; AFE Cold Air Intake
    ELECTRONICS: Kenwood DNX6180 Touchscreen; Subthump box w/10" Kicker; Driver Information Center (DIC); Rear View Camera
    ACCESSORIES: Westin Brush/Grill Gaurd; Westin Nerf Bars; Truxedo Tonneau; 20% Tint; Tow Mirrors w/Heat & Signals

  3. #3

    Red Z71 Max's Avatar
    Join Date
    May 2011
    Myrtle Beach, SC
    Blog Entries


    Welcome to the Club!!! Same answer as Mfleetwood

    (Scott) Myrtle Beach, SC
    January 2012 ROTM WINNER
    2011 GMC Sierra Z71 MAX 6.2 L w/ Trailering Package
    Rough Country, XD Rockstars, Nitto Trail Grapplers, N Fab, Lund Genesis, Putco, Gator Grip,
    Flowmaster 40 series, Diablosport InTune, Banks Ram Air CAI,
    WeatherTech, AVS Aeroskin, Tow Mirrors,

  4. #4


    Thanks for the tip....I got it posted there!

  5. #5


    Welcome to the GM T C !

    2010 Z/71 Colorado C/C
    Black 4X4 w/5.3L V8
    2007 Winnebago Adventurer
    w/8.1L Chevy & Allison 6spd.
    Canyon Lake, Texas

  6. #6



Similar Threads

  1. New Memeber
    By llbaker2 in forum Member Introductions
    Replies: 10
    Last: 11-30-2010, 11:29 AM
  2. another heating question
    By big bopper in forum General Chevy & GM Tech Questions
    Replies: 0
    Last: 06-06-2010, 12:23 PM
  3. new memeber in ct
    By BigWaterJim in forum Member Introductions
    Replies: 7
    Last: 05-10-2010, 08:37 PM
  4. New Memeber
    By hundojoe in forum Member Introductions
    Replies: 10
    Last: 02-21-2010, 08:23 PM
  5. New GMC and memeber.
    By razor1616 in forum Member Introductions
    Replies: 9
    Last: 05-05-2007, 01:26 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts