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  1. #1

    Default First Suburban ~ Have Some Underhood Questions on my '99

    I recently picked up a 99 Suburban, 197K miles, barely broken in...I have a couple underhood questions:
    There is what appears to be a factory installed secondary battery tray, and there are two positvie leads off of the battery. what is puprpose of this second tray?

    Also on my radiator, just below the filler neck, there is a roughly half inch nipple that is capped off, any idea of the purpose of this additional fitting?

  2. #2


    I've got a 1998 with the same spare tray. Someone correct me if I'm wrong, but I believe that was a heavy duty option to have 2 batteries run in parallel (double your capacity). Just below the filler neck on the radiator there should be an overflow back to the overflow holding tank. Is your hose that connects from the radiator to the holding resevoir not there??

    - - - Updated - - -

    Oh, congrats on your purchase. You'll come to love it very soon

  3. #3


    Already love the truck. The radiator overflow tube runs back to the bottom of the resevoir. This is an additional outlet. I will post a photo of the outlet later today or tomorrow.

  4. #4


    Yeah, they used to call that the camper/trailer package where it allows you to have two batteries, that's my first exposure to one of these actually. However, if you've got a winch or some type of non-PTO system than you need the most battery capacity that you can get.

    This video does a very good job of explaining the basic concepts of how to run two batteries together in parallel to make a double-capacity 12-volt system.

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  5. #5


    Welcome aboard!

    On mine, one battery lead goes to the starter, the second crosses the fan shroud and feeds the fuse block and trailer posts by the master cylinder.

    I too have the empty aux. battery tray, which I hope to fill soon. I think there was a diesel option at one time (anytime GM!), where the second battery would have been needed. If you're planning on accessories, wire that sucker in.

    Where you describe a capped nipple, I have a tranny coolant line. Is your Burb 1/2t or 3/4t, and what engine?

    Good luck, and lets see those pics,

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  6. #6

    Default Pics of radiator outlet

    This is the outlet on my radiator I am not sure of. Also, my truck is a 1/2 ton, with a 5.7L .
    Attached Thumbnails Attached Thumbnails WP_000128.jpg   WP_000127.jpg  

  7. #7


    Hmmm, interesting. Maybe an aftermarket/replacement radiator?? Mine is stock (1998) and doesn't have the capped off nipple so I'm not sure...

  8. #8


    I'm reasonably sure (my Suburban is out and about right now) that the unattached fitting is for an optional engine oil cooler. Replacement radiators tend to have both engine and transmission oil coolers (don't need to stock as many radiators). So, as noted, the radiator has been replaced at some time, and the engine oil cooler was not used.
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  9. #9


    its an aftermarket radiator that was produced to fit more than one style of vehicle so that extra nipple was for a vehicle that would have used it. its a place to watch for coolant leaks, i have seen the rubber cap crack and then burst after time and you loose a bunch of coolant.

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