Question about bleeding coolant

[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.

[Espen]

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?

[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.

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.


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 535i]

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.


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.

[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.




That's what I'd hoped. Thanks.



Thanks for the tips. I'll try them.

[Jay 535i]

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.

[will2002tii]

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.