Engine New Heater Core, Now Overheating!!

Discussion in 'Fox 5.0 Mustang Tech' started by MikeUrban, Nov 11, 2013.

  1. Hey guys, I'm back with another problem. First off, I had been driving my project car around for a while and it would stay right at 190 no matter what. But one day it started leaking from the heater core, pretty sure it's because I don't have a flow restrictor. But I finally decided to change it, and when I went to see if it would leak a new problem came up. It's overheating...BAD.

    I turned it on with the cap off the radiator, so that I could burp it of air. The coolant level only dropped on the initial start up, so I thought that was a good thing. It sat there at 150 for a little while and I didnt see it bubble or gurgle any so I couldn't add any coolant. But then it just started chucking coolant, and I mean DUMPING. The whole time I had my eye on the gauge and it jumped from like 160 to 210 right as it started puking. So I shut it off before it did any damage. There is no way I can see being able to burp it without it overheating. Could I have lost a thermostat or water pump (both of which are brand new)? I'm at a loss here.
    Thanks in advance

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  2. I believe that the system needs to be pressurized (meaning cap on) for the cooling system to work properly. I usually fill as much as it will take, cap it and run it for a bit. Then I turn it off and check coolant level and add as needed. Then I run it again etc. Maybe give that a try.

  3. You probably have a huge air bubble in the system.- due to the loss of coolant and sucking in air at the leak.
    I would do this.

    1. bypass the heater core for nowuntil you get a new one using a U shaped piece of heater hose. You can get that any any part store For the new heater core, you can either use a restrictor or a small 3/8 drive 1/2" socket.
    2. Fill the system using a lisle 24680 funnel- It is the best $25 you will spend. It will allow you to burp all of the air out of the system. No need to jack the car up. I've used it for years on several cars and it has paid for itself many times.
    3. when the car begins to warm up. check your temp gauge and see if the upper hose begins to get hot and you can feel the coolant . You will see the coolant level drop in the funnel but keep it somewhat filled. The gauge should go up and then back down once the stat opens.

    You can run the car for some time with the cap off but once it reaches operating temp put the cap back on. It should not puke out coolant doing this method unless the stat is stuck or the H20 pump isnt working properly. ALso with the car off, check the fan and clutch to make sure they are in good working order.
  4. That coolant looks pretty dirty.

    IMO, start over, add a new 180 mr gasket t stat, and flush the hell out of the system. It's going to be a PITA and it's going to take some time, once the coolant gets brown like that, just changing it isn't enough.

    Then you have to fill it and let run until all air is out.

    Water pumps usually leak, not break, so that's unlikely the issue.

    I'd bet you just have air in there now.
  5. +1 on the air. did you have the heater on high when you were filling the system?
  6. Wouldn't a cracked head cause this?
  7. While a cracked head or head gasket could cause this, he said it was fine before the heater core swap.
    And unless he has aluminum heads, ford iron heads rarely crack unless you really really screw something up.