why am I leaking coolant at the drain plug

Discussion in 'Chevy Truck Talk & GM News' started by Dtjb, Jan 26, 2012.

  1. Dtjb

    Dtjb New Member

    I'm loosing coolant. The thermostat is working. The water pump is not leaking and the engine stays cool (when it has coolant) but after a good drive 15 mi. or so the radiator is steamy and coolant is pouring out of my drain plug. PPPPPPPPPPPPPPLEASE help.

  2. mfleetwood

    mfleetwood Epic Member 5+ Years ROTM Winner 5000 Posts

    If it's leaking out of your drainplug, could the plug be cross-threaded or somehow not properly sealing, thus when pressure builds fluid escapes through there? Have you checked/replaced your radiator cap or are you sure it has the proper pressure relief? How long has this been happening or did you do any work to your vehicle right before the problem started?
  3. Dtjb

    Dtjb New Member

    Thanks for the reply. The radiator cap was my first move. I replaced the drain plug with one from my local Chevy dealer and took a test drive. Everything seemed fine but one more drive to work resulted in more coolant comming from the drain plug. It must be leaking while I drive. While idling in the driveway, no leak is evident. I'm befuddled. Would the water pump weap while just on the road? It's a 99 C/K 1500 with the 5.7.
  4. Untouchable

    Untouchable Member 2 Years 100 Posts

    Another place you might check for leaks is the cooling lines that connect to the radiator from the transmission.
  5. mfleetwood

    mfleetwood Epic Member 5+ Years ROTM Winner 5000 Posts

    Because of your question regarding it possibly leaking from the water pump, it sounds like you are not 100% positive it is actually coming from your drain plug?

    Water is a funny thing and will follow a trail and many times drip from the trail's lowest point. Untouchable is correct in asking if it could possibly be coming from another source. It could be welds for your radiator hose connects, hose not fully sealed/clamped, cracked/leaking hose, pin hole in radiator. There's a lot of flow and pressure when the RPMs are high, and water is circulating and heating up, thus the leak may not present itself until the tougher circumstances present themselves (more than idling).

    If by close visual inspection, you still cannot find the leak in any of those other areas or in areas in which a water trail could lead to your plug, you might want to try a pressure test. Here is an article that may help you if you get to that point.

    Pressure test to identify any external leaks:
    Pressure testing the cooling system is a simple process to determine where a leak is located. This test is only performed after the cooling system has cooled sufficiently to allow you to safely remove the pressure cap. Once you are sure that the cooling system is full of coolant, a cooling system pressure tester is attached in place of the radiator cap. The tester is than pumped to build up pressure in the system. There is a gauge on the tester indicating how much pressure is being pumped. You should pump it to the pressure indicated on the pressure cap or to manufacturer's specs.

    Once pressure is applied, you can begin to look for leaks. Also watch the gauge on the tester to see if it loses pressure. If the pressure drops more than a couple of pounds in two minutes, there is likely a leak somewhere that may be hidden. It is not always easy to see where a leak is originating from. It is best to have the vehicle up on a lift so you can look over everything with a shop light or flashlight. If the heater core in leaking, it may not be visible since the core is enclosed and not visible without major disassembly, but one sure sign is the unmistakable odor of antifreeze inside the car. You may also notice the windshield steaming up with an oily residue

    One thing that I will add to this article is that if leak is higher than the liquid may be (i.e top of radiator hose weld) then it might not leak fluid when the pressure is applied, but leak air. Double check those types of areas using a vacuum hose and then try listening for the air leak.
    Last edited: Jan 26, 2012
  6. Coach24

    Coach24 Rockstar 3 Years 5000 Posts

    Pressure Test the cooling system. Most auto parts stores will loan you one of these. some will actually walk out nd test your system at the store@no charge
    A a parts store manager we would test cooling, battery and starter at no charge
  7. Dtjb

    Dtjb New Member

    Thanks for the replies and I apologize for taking so long to reply. I have more info for the mechanical minds here. There is no leak evident. However, with the engine running I took off the radiator cap to see if the water pump was actually pulling. The water pump is pulling (not as strongly as I had assumed but pulling) however upon release of the throttle air bubbles came up through the the radiator throat. Am I sucking air somewhere? Could I be leaking at the intake manifold gasket and burning the coolant? Also, the last time i leaked from the drain plug the radiator was full of coolant. I will try the pressure check but it will have to be later. I worked midnights last night and need to crash. Thanks again for your time.

  8. billnorman

    billnorman Rockstar 100 Posts

    Time to investigate for a blown head gasket or mainfold leak.
  9. Dtjb

    Dtjb New Member

    I finally discovered the waterpump weeping Sun morning when I took the radiator cap off (I guess it created a vacuum ). I changed the pump and took a quick test drive. All seemed well till this morning on my way to work the temp got out of range (210 or so). I pulled over and put the old radiator cap back on and it seemed to help ( it was either that or the pressure relief). On the way home this evening the thermostat opened as it should but again got out of range and fluctuated a bit. It eventually leveled out at 165. I'm riding the bike tomorrow and foolin with this this weekend. Still looking for suggestions. Thanks!

  10. JnBama

    JnBama Rockstar 4 Years 500 Posts

    You may have air trapped in your coolant system, others may know or could explain better. Take off your rad.cap and when system gets warm squeeze the radiator hoses till you see and hear no bubbles come through the top. Took my car last year to a shop to have radiator flushed ,while driving it home the water temp jumped way up and started steaming. They towed it back to shop for a whole day and found nothing, ended up doing it myself flushing out brown crud, I also installed a new thermostat and hoses. Reported them to BBB and got a refund and apology from district Mgr

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