How to bleed coolant system? (replacing heater core + radiator)
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    1. #1

      How to bleed coolant system? (replacing heater core + radiator)

      I am going to replace my heater core and radiator tonight, and was curious if there is a special procedure to bleed the coolant system.
      Here is what I will do. Let me know if I should change anything:

      1.) I will drain from the plug in the radiator (open cap on expansion tank first),
      2.) plug drain and fill expansion with plain water, cover expansion cap and run car until thermostat opens and water is pumped throughout the system (allowing it to flush the system).
      3.) wait for it to cool, and drain once more
      4.) remove and replace heater core and radiator
      5.) refill with fresh 50/50 coolant/water mixture

      Does the system automatically burp air bubbles out the expansion tank with the cap on or off? Is there a special valve on the block i need to open to bleed the system, and where?

      Thanks


    2. #2

      Re: How to bleed coolant system? (zpmada)

      Final note, those two hex bolt hoses that appear to run from the transmission, they are filled with coolant, right? When I take them off trans fluid wont come pouring out, will it? It is not an independent coolant circuit that needs to be filled a way other than the expansion tank?
      thanks

    3. #3

      Re: How to bleed coolant system? (zpmada)

      If you mean the trans oil cooler lines on the left side of the radiator, they contain trans fluid!

      There is nothing to do regarding bleeding. There's no heater valve to cause air pockets like older Volvos. Just fill the system via the reservoir, and run the car. Dive it around a bit & let it cool down. The level will have dropped in the reservoir, so just top it off the max fill line (about 1/2 way)


    4. #4

      Re: How to bleed coolant system? (lookforjoe)

      Well, these lines from the trans run to the radiator. My radiator has 4 hose connections (it is for a 99 n/a automatic).

      Finally, how do i remove the drivers side carpet? The plastic footrest appears to be screwed in and I cant "pop" it off to get to the screw (rather, I'm afraid of cracking the plastic foot rest if i pull too hard)


    5. #5
      Senior Member Chilled Man's Avatar
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      bust the foot rest and get a new one there $5
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    6. #6

      Re: How to bleed coolant system? (zpmada)

      When you say 4 connections, I assume you mean the upper & lower radiator hoses, and the two trans cooler lines (which contain trans fluid, not coolant), and you should also have a bleeder hose off the upper rad hose connection that goes to the reservoir/overflow tank.

      NOTE: Do NOT try to undo the "hex" bolt connections by unscrewing them. I assume you are referring to the fittings that protrude from the radiator side tank, these are not intended to be undone, the line simply uncouples from the fitting on the rad.

      The footrest has 'slotted' pegs, so you have to either slide it up or sideways to remove it ( I forget which, probably up, that would make more sense).

      There is no need to remove the carpet, however. Just peel it back from under the center panel, fold out of the way on the floor area, and lay plastic sheeting/garbage bags over the tunnel & floor to catch whatever is left in the core when you withdraw it.


    7. #7

      Re: How to bleed coolant system? (zpmada)

      you also don't need to pull the carpet that far back that would require the removal of the footrest if you are looking to replace just the heater core.

      just pull it along the center console and fold the carpet back diagonally towards itself. place a large trash bag where the floor mat would normally be to catch the coolant.

      1998 S70 T5, 239k '00R 302s/DIY AEM BCS/IPD Stage 1 ECU/IPD 3" Turboback/Comets/OMP brace
      2006 Mini Cooper S, 6-speed, 74k 15% pulley, JCW exhaust/intake/suspension

    8. #8
      So, replacing the radiator requires topping off the trans fluid?

    9. #9

      Re: (zpmada)

      unless you want the tranmission to act as if it was on its last legs(slipping due to low fluid), yes

      this would be a good time to change the transmission fluid while you are at it.

      1998 S70 T5, 239k '00R 302s/DIY AEM BCS/IPD Stage 1 ECU/IPD 3" Turboback/Comets/OMP brace
      2006 Mini Cooper S, 6-speed, 74k 15% pulley, JCW exhaust/intake/suspension

    10. #10

      Re: (zpmada)

      Typically you will lose only a very small amount (whatever is in the cooler lines). What I would suggest is covering the line end with a latex glove to prevent excess fluid dripping out (mainly for cleanliness sake, not much fluid is in the line). If you notice, the lines come UP from the trans cover to get to the rad, there's no pressure in the system when it's not running.

      I wouldn't change the trans fluid unless it is actually needed. Usually what you loose will not even show up on the (trans) dipstick.