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Thread: Question about bleeding coolant

  1. #1
    Join Date
    Aug 2005
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    Toronto
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    Default Question about bleeding coolant

    I was trying to get all the air out of my cooling system (got a new rad), following the Bentley instructions, and I noticed coolant coming out of a hose near the firewall, passenger's side, down low.

    Is that a vent hose for coolant, or should it be connected to something? Is it normal for coolant to get vented like that when bleeding the system? Bentley makes no mention of it.

    It was coming out in a small but steady stream, and left about two cups of coolant on the ground in about a minute. I think the flow only started after the engine was up to temp. The HVAC was at full hot, as per the Bentley instructions.

    Thanks in advance for any answers.
    .


    Jay Lebo - Toronto, Canada
    1990 BMW 535i
    5-speed conversion
    Lightened flywheel
    Sachs Suspension Kit
    E.A.T. Chip

  2. #2
    Join Date
    Feb 2006
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    Norway
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    Default

    This doesnt sound right to me.
    Coolant leaked out throug a hose? or through a crack/leak in a hose?

    When the coolant gets hot it is pressure in the cooling system, what would make that hose keep tight?
    Eurospec-12/1988-535iL-M30B35-5speed

  3. #3
    Join Date
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    Default

    That's normal -- at least in the temporary sense when you're bleeding the system. There is an overflow hose on the passenger side of the filler neck. If the coolant lever gets above the neck it will drain thru the hose which runs down the firewall & goes to the ground. There is also an overflow drain hole behind the filler neck. I forget where it drains to, prolly directly down the firewall.

    I have the best luck bleeding the system with the nose of the car elevated on ramps or an inclined driveway. I do it while the engine is cold. I'm assuming you already bled the needle valve on the thermostat housing. You can do that while it's running, but if the coolant is hot, sometimes it will just sputter steam. Make sure you have a stream of coolant out of the "pisser line", the small hose that goes from the top of the radiator to the driver's side of the filler neck. It will barely dribble at idle but if you rev it a little, there should be a pronounced stream, about 1/8" that shoots down into the reservoir from the neck. Giving the hoses a squeeze helps burp more air out of it.

    After it's basically bled, take it for a spin with the heater full blast to circulate the coolant and air out of the heater core, let it cool off a bit, and top off the coolant if necessary. As long as the pisser line has a stream, it bleeds fairly easily, at least mine always does.

    Quote Originally Posted by Jay 535i
    I was trying to get all the air out of my cooling system (got a new rad), following the Bentley instructions, and I noticed coolant coming out of a hose near the firewall, passenger's side, down low.

    Is that a vent hose for coolant, or should it be connected to something? Is it normal for coolant to get vented like that when bleeding the system? Bentley makes no mention of it.

    It was coming out in a small but steady stream, and left about two cups of coolant on the ground in about a minute. I think the flow only started after the engine was up to temp. The HVAC was at full hot, as per the Bentley instructions.

    Thanks in advance for any answers.
    gale
    92 735i 5-spd, turbo project finally underway!


  4. #4
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    Default

    Quote Originally Posted by gale
    That's normal -- at least in the temporary sense when you're bleeding the system. There is an overflow hose on the passenger side of the filler neck. If the coolant lever gets above the neck it will drain thru the hose which runs down the firewall & goes to the ground. There is also an overflow drain hole behind the filler neck. I forget where it drains to, prolly directly down the firewall.
    That's what I'd hoped. Thanks.

    Quote Originally Posted by gale
    I have the best luck bleeding the system with the nose of the car elevated on ramps or an inclined driveway. I do it while the engine is cold. I'm assuming you already bled the needle valve on the thermostat housing. You can do that while it's running, but if the coolant is hot, sometimes it will just sputter steam. Make sure you have a stream of coolant out of the "pisser line", the small hose that goes from the top of the radiator to the driver's side of the filler neck. It will barely dribble at idle but if you rev it a little, there should be a pronounced stream, about 1/8" that shoots down into the reservoir from the neck. Giving the hoses a squeeze helps burp more air out of it.

    After it's basically bled, take it for a spin with the heater full blast to circulate the coolant and air out of the heater core, let it cool off a bit, and top off the coolant if necessary. As long as the pisser line has a stream, it bleeds fairly easily, at least mine always does.
    Thanks for the tips. I'll try them.
    .


    Jay Lebo - Toronto, Canada
    1990 BMW 535i
    5-speed conversion
    Lightened flywheel
    Sachs Suspension Kit
    E.A.T. Chip

  5. #5
    Join Date
    Jan 2004
    Posts
    4,150

    Default The condensate drain for the a/c and heater core is right there also on

    the lower part of the firewall... If you have a leaking heater core you could be seeing it there also , but you would also have the smell of coolant inside the car.



    Quote Originally Posted by Jay 535i
    That's what I'd hoped. Thanks.



    Thanks for the tips. I'll try them.


  6. #6
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    Quote Originally Posted by Bill R.
    the lower part of the firewall... If you have a leaking heater core you could be seeing it there also , but you would also have the smell of coolant inside the car.
    I do have a leaking heater core -- for a couple of years now -- but it's never been a big problem. I seem to lose coolant at a snail's pace.

    I think everything is okay now. The car's running well.
    .


    Jay Lebo - Toronto, Canada
    1990 BMW 535i
    5-speed conversion
    Lightened flywheel
    Sachs Suspension Kit
    E.A.T. Chip

  7. #7
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    Location
    danbury ct
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    Default

    thats normal, its just a vent hose. One trick I learned for bleeding 535s is to fill a two liter soda bottle with coolant(about half way) and invert in the expansion tank. It seals nicely and you can squeeze the upper hose to relieve air into the bottle instead of overflowing the tank and making a mess. This in conjunction with releasing the bleed valve makes a MUCH faster job.

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