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99 suburban coolent usage

Discussion in 'General Chevy & GM Tech Questions' started by jeffrness, May 13, 2010.

  1. jeffrness

    jeffrness New Member

    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. Silverado Junkie

    Silverado Junkie Rockstar 4 Years 500 Posts

    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.
  3. MrShorty

    MrShorty Epic Member Staff Member 5+ Years 1000 Posts

    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.
  4. mrfixdit

    mrfixdit Rockstar 100 Posts

    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. bigdaddy77084

    bigdaddy77084 Rockstar 4 Years 500 Posts

    No smell of antifreeze in the tail pipe??
  6. Big75

    Big75 Rockstar 4 Years 500 Posts


    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.
  7. Dr_Zero

    Dr_Zero Epic Member 5+ Years 500 Posts

    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.
  8. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    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.

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