GM Truck Club
THE PREMIER CHEVY TRUCK & SUV FORUM
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Results 1 to 8 of 8
  1. #1

    Question 99 suburban coolent usage

    hey guys,this is my first try at this,so here go's I have a 99 suburban with 135k on it. It mysterisly gos through coolent, about a quart every 1200 mi,It had intake gaskets at about 100k,sometimes it will miss at start up,but then clears out and will run fine,also reasently had fuel injectors,cap&rotor,plugs and wires. any ideas? also the cooling system holds pressure

  2. #2
    Master Mechanic Silverado Junkie's Avatar
    Join Date
    Feb 2010
    Location
    Lead Hill, Arkansas
    Posts
    541

    Default

    Quote Originally Posted by jeffrness View Post
    hey guys,this is my first try at this,so here go's I have a 99 suburban with 135k on it. It mysterisly gos through coolent, about a quart every 1200 mi,It had intake gaskets at about 100k,sometimes it will miss at start up,but then clears out and will run fine,also reasently had fuel injectors,cap&rotor,plugs and wires. any ideas? also the cooling system holds pressure
    Well if you keep having to add coolant then its going somehwere. Either you have a leak in a head, head gasket, intake manifold gasket, intake manifold, waterpump, radiator, or a radiator hose. Its leaking somewhere outside to where you could see it by getting under the hood or its leaking in your motor and being burnt off or mixing with your oil. Start by looking all around your motor and look at your oil color. That would help determine where the leak is comong from.
    1995 Silverado,Z71, 3-inch lift,2-inch leveling kit, SkyJacker Suspension, short ram-air intake, throttle body spacer, MSD ignition coil, straight pipes

  3. #3

    Default

    I would probably start by putting a cooling system pressure tester (Autozone and maybe other places lend them out) on it. Many time, you can find the leak if the system is pressured up cold.
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  4. #4
    Jr. Mechanic
    Join Date
    Dec 2008
    Location
    Gettysburg, Pa.
    Posts
    103

    Default coolant leak

    A quart every 1200 miles is probably about a quart every three weeks or so. Correct me if I'm wrong . I have seen a number of these radiators with plastic ends that get hairline cracks where the incoming coolant hits the wall of the radiator (front side by the grill) that leak at about this rate.. It seeps out when the engine is warm and system under pressure. Look for coolant or moisture at the bottom of the radiator in the mounting channel. Its a possibility.

  5. #5
    Master Mechanic bigdaddy77084's Avatar
    Join Date
    Jan 2010
    Location
    Houston, Texas, United States
    Posts
    649

    Default

    No smell of antifreeze in the tail pipe??
    95 tahoe 2dr 4x4 200,000+ miles

  6. #6
    Master Mechanic Big75's Avatar
    Join Date
    Nov 2009
    Location
    Seward, Nebraska, United States
    Posts
    595
    Blog Entries
    1

    Default

    Quote Originally Posted by mrfixdit View Post
    A quart every 1200 miles is probably about a quart every three weeks or so. Correct me if I'm wrong . I have seen a number of these radiators with plastic ends that get hairline cracks where the incoming coolant hits the wall of the radiator (front side by the grill) that leak at about this rate.. It seeps out when the engine is warm and system under pressure. Look for coolant or moisture at the bottom of the radiator in the mounting channel. Its a possibility.

    I agree with this, my 96 has a hairline crack about an inch under the outlet on the plastic side tank. About the same amount of loss. Just happen to hear it one day when I parked it in the garage. Hard to spot as it followed one of the manufacturer lines.
    This post has been rated MA LSV, and is intended for mature audiences. Reader discretion is advised. :fighting0037:
    ghst-_-R3CON83 ----------BATTLEFIELD BAD COMPANY 2----------------------

    (This site won't let me add a real stat generator to my signature)

  7. #7
    Master Mechanic Dr_Zero's Avatar
    Join Date
    Mar 2006
    Location
    Sunny Florida
    Posts
    706

    Default

    I had the tank crack on both my trucks but to fix them cost more than a radiator! Since I was ordering a rad I replaced the old single row with a dual row they use the same brackets and drops right in.

    I got my rad from radiatorclassic off of Ebay and have been very pleased I ordered from them 2 different times.

    Also those pesky intake manifold gaskets will be leaking and you will never find it.
    My trucks!

    1996 GMC Suburban SLT
    1997 GMC Yukon SLT

  8. #8
    Legend

    Join Date
    Feb 2008
    Location
    Red Wing, Minnesota, United States
    Posts
    3,356

    Default

    9 out of 10 times on these vortec 350 its the intake gasket, mine never spewed the tell tale white smoke, if its never been changed on yours then its time, and by the way, do the head gaskets at the same time, it will just save you labor down the road. you got the entire top side ripped off anyway, might as well just take out a few more bolts.
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual
    285/75/16
    ___________________________
    Jason

Similar Threads

  1. overheating/coolent/water temp guage?
    By capt sensible in forum General Chevy & GM Tech Questions
    Replies: 7
    Last Post: 08-22-2010, 09:02 PM
  2. Oil Usage
    By jel1957 in forum GM Powertrain
    Replies: 5
    Last Post: 06-08-2010, 03:12 PM
  3. coolent sensor
    By dodger32 in forum Chevy Silverado Forum (GMC Sierra)
    Replies: 0
    Last Post: 04-21-2010, 01:59 PM
  4. coolant usage
    By mines68 in forum GM Powertrain
    Replies: 10
    Last Post: 01-12-2010, 11:50 PM
  5. Oil Usage?
    By Goldie in forum General Chevy & GM Tech Questions
    Replies: 7
    Last Post: 01-20-2009, 10:12 AM

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
  •