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Thread: cooling problems, oveheating

  1. #1
    Join Date
    Jun 2009
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    CA
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    cooling problems, oveheating

    I've finally got the truck driving around ok for most of the time. But it seems to overheat at almost random times. For instance I drove it 100 miles one day in city and freeway and the temp stayed consistent in the expected range. Then a couple days later I drove it about 5 miles into town, was idling in a parking lot for 5 minutes and everything was fine. Then went the gas station and filled up, when I went to get back on the freeway the truck never cooled off from sitting at the gas station and slowly got hotter. Also a couple other times this would happen when I started from being hot. And it happen once when I was just driving down the freeway and going up a light grade. Once it starts to overheat, it usually happens very quickly and I've had the stop on the side of the road, let it cool, then It will usually drive fine for a while after that staying cool. Overall it drives fine 90% of the time.

    I've replaced the thermostat twice and now have a 187deg stat from the dealer so I don't think that is the problem. I'm using a newer 34" radiator, and didn't put the cap on till the engine was warmed up and coolant filled. I'm using 50/50 dexcool/water. The steam lines from the front of the heads bypass the throttle body and run into the very top of my radiator near the cap. This is where one of the old heater lines was connected when the old engine was in. The water pump makes no strange noises and no coolant is leaking anywhere.

    I know on the newer truck radiators the steam lines go into the radiator side tank about half way down. And there is a hose running from the fitting right next to the cap on the top(where my setup's steam lines go in) to the top of the expansion tank. My system is a little different than this but I don't understand why that would cause any problem.

    Any ideas???
    1995 K2500 with '05 6.0L, XR265HR cam, 918 springs, PCM by Nelson Performance.

  2. #2
    Join Date
    Nov 2003
    Location
    Denton Texas
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    20,540
    have you removed the steam hose at the head and see if there is air there? Park with the front uphill and pull the hose and leave it off until pure coolant/no air runs out of it. If thats not the highest point in the system, remove it from the highest point possible on the steam line.
    See my truck data in the "My Garage" section here... http://www.ls1truck.com/forums/my-ga...tml#post191709

  3. #3
    Join Date
    Jun 2009
    Location
    CA
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    I took one of the stem lines off of the passenger head with the front parked up on some tree roots, and coolant poored out. The steam lines go to the fitting where the heater line went on the 95 radiator. Still having the problem. What else could it be?
    1995 K2500 with '05 6.0L, XR265HR cam, 918 springs, PCM by Nelson Performance.

  4. #4
    Join Date
    Nov 2003
    Location
    Denton Texas
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    If you replaced the head gaskets you may have one one backwards.
    See my truck data in the "My Garage" section here... http://www.ls1truck.com/forums/my-ga...tml#post191709

  5. #5
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    CA
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    I didn't replace the head gaskets and there is no water in the oil or oil in the water. . .

    Thanks,
    Danny
    1995 K2500 with '05 6.0L, XR265HR cam, 918 springs, PCM by Nelson Performance.

  6. #6
    Join Date
    Dec 2006
    Posts
    4,033
    try taking your belt off and see if you have drag on the pulley? from the bearings..

  7. #7
    Join Date
    Jun 2009
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    CA
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    Could it be that the headgasket is leaking intermittently into the cooling system? I never see bubbles in the coolant when the radiator cap is off and engine running, but I never have the cap off during a time of when it started overheating.
    1995 K2500 with '05 6.0L, XR265HR cam, 918 springs, PCM by Nelson Performance.

  8. #8
    Join Date
    Jun 2009
    Location
    CA
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    And the waterpump pulley seems to turn fine. I don't think it's the water pump since it runs fine for most of the time. It seems like if the water pump was broken it would be an all or nothing type of failure.
    1995 K2500 with '05 6.0L, XR265HR cam, 918 springs, PCM by Nelson Performance.

  9. #9
    Join Date
    Sep 2005
    Location
    Austin Tx.
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    13,138
    BRINGING THIS BACK FROM THE DEAD!

    Was this ever figured out? WHile driving 5+ miles this evening, with my fans on, at idle the coolant temp would get up to at 230-233, and then driving it would quickly go back to like 195-205. Did this at almost every light idiling. Any idears?

    These temps are confirmed with the normal cluster gauge and the interceptor gauge. Not sure how accurate either of those are, but I dont have a thermometer to put up my trucks ass.
    1951 3100
    1984 C10

  10. #10
    Join Date
    Feb 2007
    Location
    Spring, Texas
    Posts
    1,739
    Quote Originally Posted by ducky View Post
    BRINGING THIS BACK FROM THE DEAD!

    Was this ever figured out? WHile driving 5+ miles this evening, with my fans on, at idle the coolant temp would get up to at 230-233, and then driving it would quickly go back to like 195-205. Did this at almost every light idiling. Any idears?

    These temps are confirmed with the normal cluster gauge and the interceptor gauge. Not sure how accurate either of those are, but I dont have a thermometer to put up my trucks ass.
    Check the thermostat. Mine just did the same thing and the stat wasn't opening up. Keep us posted!

    2004 Silverado Crew Cab, forged iron 5.7, STS w/MP turbo, 10+ psi, FMIC, Tial 50mm BOV, Vic Jr, Snow performance meth, MTI Stealth cam .220/.220 .581/.581 115lsa, Comp chromoly pushrods, Yank TT3000 stall, LS1 Efans, 160 tstat, Trucool 40k trans cooler, 60# injectors, Walbro fuel pump, Patriot springs, Built 4l65E w/billet input & output shafts, Eaton posi, SD tuned...all installed by Klein North Automotive

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