1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

Water pump replaced - hoses collapse

Discussion in 'Early CJ5 and CJ6 Tech' started by DKillam, Jun 8, 2008.

  1. Jun 8, 2008
    DKillam

    DKillam Sponsor

    San Angelo, Texas
    Joined:
    Oct 31, 2005
    Messages:
    228
    F-134. New problem. I replaced the water pump due to a leak, thermostat housing, thermostat (180), upper and lower radiator hoses, fuel pump, oil filter inlet and outlet hoses yesterday. No leaks, however first time starting, temp went up higher than normal, then dropped off some. Shut the engine down to let cool off and later came back to find upper and lower hoses sucked in (almost flat) and a vacuum on the cooling system. The radiator cap had to be pulled open and then the hoses opened back up. I thought the problem was not enough coolant (all was drained for the water pump replacement) so I added enough to get within 1" of filler neck and tried again. Same story - temp goes up above normal, although never out of operating range, back down to average (middle of gauge) runs fine, but when cooling off - hoses collapse again. Whats wrong - defective t-stat, upside down, wrong temp t-stat, not enough coolant still??? BTW - I checked the direction of T-stat before installing upper hose - pointy thing was up. :rofl: Any suggestions?

    :cry:
     
    DKillam, Jun 8, 2008
    #1
  2. Jun 8, 2008
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Well, the thermostat can't cause it since both sides of it are connected through the radiator. I'd be more suspicious of the radiator cap. Not sure about the function of the cap, but I expect it should allow air in when the engine cools and the vapor pressure of the coolant lowers. Cooling of the coolant would cause the pressure inside the system to lower, sucking in the hoses. It might be that your system was leaky enough before your repairs that the reduced pressure was leaked away, and you never saw collapsed hoses.

    BTW shouldn't the lower hose have a spring in it to prevent collapse?
     
    timgr, Jun 8, 2008
    #2
  3. Jun 8, 2008
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
    Joined:
    Nov 6, 2002
    Messages:
    4,275
    A common modification is to drill a 1/8" hole in the disc in the T-Stat, this solves two problems:

    First: Many folks have had issues with overheating after changing the T-stat out due to air being trapped in the system. Drilling that vent hole will allow the air to bleed out of the system before it overheats.

    Second: The problem you describe. If there is air trapped in the system it will cause a vacuum in the cooling system and when it cools off it will suck the hoses flat like you describe.

    HTH. ;)

    <edit>

    Tim is correct, a preformed hose should have a spring in side it to keep it from sucking flat.
     
    w3srl, Jun 8, 2008
    #3
  4. Jun 8, 2008
    DKillam

    DKillam Sponsor

    San Angelo, Texas
    Joined:
    Oct 31, 2005
    Messages:
    228
    Both hoses I took off had a spring in them, but neither of the new ones do. :rofl:
    w3srl - you may be on to something - there may still be air trapped that hasn't worked it's way out. I just got back from a short trip (6 mi) and so far no collapse. I'll check after it cools off more. My neighbor thinks that the t-stat may not be closing off completely during cool down cycle causing the collapsed hoses. I just read in the service manual to test the t-stat at 10 degrees below and 25 degrees above the rating. If either fails the test, replace.
    May have to try the hole in the stat if all else fails.
    timgr - leaky may be an understatement :oops:
    I'll keep you posted!

    Thanks,
     
    DKillam, Jun 8, 2008
    #4
New Posts