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  1. #1

    Question 98 K2500 Sub. - 454 - Coolant leak at intake

    All,

    It's a K2500 Suburban with 7.4L vortec. It has 140k on it. There is a small coolant leak where the intake manifold meets the block. It is right where the oil fill tube goes in. I check overflow bottle and it was empty...took rad cap off and filled with the 50/50 dexcool quick fill stuff. Then added to the overflow until it was at cold full level.

    Talked to my brother-in-law and he said to put stop leak in it. He said there is a risk in pulling the intake manifold with that high of mileage as debris can fall into the engine and cause other problems.

    Is this a common source of leaks with the 454? Any other suggestions? It is my father-in-law that owns the truck....I think he has an exhaust leak as well. He has the typical ticking sound under load and when we started it with the hood open strong exhaust smell.

    Thanks in advance for the help.

  2. #2
    Jr. Mechanic
    Join Date
    Dec 2008
    Location
    Gettysburg, Pa.
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    103

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    Don't let the thought of doing this job intimidate you it really isn't as bad as it looks. Mileage has no effect on whether debris will fall into the engine anything that would fall already has fallen while the engine was running. Just wash the exterior before you start then once you have the intake carefully removed lay a towel down to catch anything while you scrape the gasket surfaces. Also have a manual such as a Hayes manual to refer to and a warm place to do it so the sealants can cure properly. Good luck to you and I hope you decide to do it.

  3. #3
    Jr. Mechanic
    Join Date
    Sep 2007
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    Los Angeles, CA
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    116

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    Before you condemn the intake manifold. Double check where the leak is, it might be your thermostat housing. If it's that, it'll be an easy replacement. With that many miles, just change the housing, thermostat and gasket. If it is indeed your intake manifold, mrfixdit is right, it's not as big of a job as it may seem. If you have a basic set of tools, a manual and some patience, you should have no trouble getting it all done in one day. Just remember to be methodical, clean, and your torque wrench is your best friend.
    '88 Jimmy 4X4
    5.3l L59/ 4L60E Tuned by Tad
    4" Lift 33" BFG. Custom Brush Guard, KCs, outside spare, Oil pan guard etc.

  4. #4
    Master Mechanic
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    Oct 2008
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    Washing the engine before repair good idea, but have someone steam clean it, do not wash it persay, unless you have done it before with the over-the-counter cleaner. Be careful to not damage the sensors, any of them. To test for the leak, have a garage or yourself if you have the tool to pressurize the system. This will put the system to the 16lb max pressure(if thats whats rating is) and if there are any leaks you will see coolant and where its coming from. News flash, you have dirt always being brought into your engine, its micro particles, airborn contaminants, but dirt just the same. Like its stated when the intakes removed, cover the valley to keep the debrie out when working in the area....

    Jeff
    JMoney02

  5. #5
    Jr. Mechanic
    Join Date
    Dec 2008
    Location
    Gettysburg, Pa.
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    103

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    I forgot to mention that stop-leak is bad stuff of bygone days, not a good idea, it may stop the leak but that is only "trimming the branches" not getting to the "root" of the problem. If that gasket is bad stop leak will seal it at that point and the leak will bust out at another point like maybe into your block and you wont know it til its too late also there is a small pinhole in the diaphram of your thermostat that helps keep excessive pressure from building up while the engine is cold and the thermostat is closed. Stop-leak could seal that hole too and cause problems.

  6. #6
    Legend

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    Feb 2008
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    Dont be too worried ALL older Vortec (5.7 & 7.4) motors were notorious for intake gasket failure, usually it was aroun the 75-100k mark, mine did at 75k, this is a common problem. Just make sure if you do it yourself you get the correct gasket as they never recalled but you can get an improved gasket over the original one.
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual
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  7. #7

    Default

    This is an awesome forum! Thank you guys for all the responses. I will pass this info along. I think he has a Chilton or Haynes for it already. It is his tow rig and he is trying to get at least another year of service out of it. On top of all this he just had both his power steering hoses blow out on him within about 3 months of each other.

    What about rear main seals guys? I replaced his drain plug for the oil leak, but it looked like the oil was coming from higher up. I used engine degreaser both under the hood and under the vehicle to clean things up, so we will see if the oil returns. I also gave it a fresh oil change with some full synthetic Valvoline.

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