[frank///M5]

last friday i put in a new thermostat and now i have a litle problem whit the coolant level.

i bleed the system and top it to the COLD level the other day.
when the coolant is getting warm it is comming out to the overfill pipe.

can it be air in the system and if so how can i fix it?

temprature is fine now,79-80 and no leaks.

thanks.

 

[nerio02]

you need too fill the radiatorbotlle up to about 2-3cm under the arrow on the side frank. when the coolant is hot it will be right on the marking


for letting air out the circuit, just let the car run and put the heater on full and just wait, check the coolant level after a while, let it cool down and iff needed fill a little up when the air is escaped

 

[AMP]

If the level is at (or near) the COLD mark when the car is cold and you are still getting coolant out of the overflow pipe then there's a good chance that your radiator cap isn't holding pressure anymore. BMW cooling systems run at a very high pressure (2 bar) so even a borderline cap will cause some spillage.

 

[frank///M5]

thanks guys,how can i see if the fill cap is broken?

before the change of thermo it was ok.

 

[Tj Hunter]

You could get the system pressure tested, but you are probably better off just getting a new cap, if it fixes it great, if not you still have a new cap. Caps are CHEAP!

 

[2strokecoldsmoke]

Cap is about $15 - if you think there is a problem, just replace it.
BMW # 17111742231

 

[frank///M5]

it is not that i dont want to buy a new cap,but it was ok before the change of thermostat.

 

[AMP]

it is not that i dont want to buy a new cap,but it was ok before the change of thermostat.

Could be:

1) System wasn't fully pressurizing due to thermostat failure so it never reached the pressure at which the cap was letting go.
2) Removal and replacement of cap during thermostat replacement was the final straw for an already weak cap.
3) The cap just failed and it's a complete coincidence.
4) The cap isn't the problem.

 

[Vector57]

Cap is the likely culprit, but...

Your coolant leak may not be coming from the overflow tube, but rather from the plastic venting elbow that
is located at the top, left (drivers side, US) corner of the radiator. They are prone to cracking at the junction
to the plastic tank and leaks coolant down, right alongside the overflow tube.

Our cooling system is self-venting, by way of this elbow. There is a hose from the elbow to one of the two
nipples located on the neck of the expansion tank where the cap attaches (other nipple is for the overflow
tube) You can easily verify this venting function by letting the engine come to temp with the cap off. There
should be a constant stream of coolant going into the expansion tank from this venting line after thermostat
opens. You must remove the attachment pins for the radiator cover shroud and then tilt it back to view the
venting elbow.

All that being said, the likely probability is the cap itself is not holding the required 30 PSI. The failure, (whether
the cap or cracked elbow) was never evident because the coolant temp was never getting up to normal levels.

Regards,
Alan

 

[Mohammed_A]

i also did a new thermostat and also notice some coolant on the floor, i looked around the thermostat housing for leaks from the o-rings but that is dry, the bulk of coolant lies on the drivers side(rhd) underneath the coolant bottle on the cover under the engine. After reading above about the cap i removed mine and this is what i found? could this be a bad cap? its got some kind of rubber loose piece on it for some reason....

 

[Mohammed_A]

update - changed the cap, leak gone - thanks

 

[68FB]

i also did a new thermostat and also notice some coolant on the floor, i looked around the thermostat housing for leaks from the o-rings but that is dry, the bulk of coolant lies on the drivers side(rhd) underneath the coolant bottle on the cover under the engine. After reading above about the cap i removed mine and this is what i found? could this be a bad cap? its got some kind of rubber loose piece on it for some reason....

If that warped thing is the stock rubber seal ring that seals on tank filler neck, the severe distortion indicates you have some contamination or the wrong type of coolant in your system. The stock rubber seal would never get like that with the stock coolant, IMO.

 

[Mohammed_A]

i have no idea what that piece is, i compared the new cap to the old one and the rubber sealing ring is fine, checked the bottle neck and compared to another bottle and thats fine as well, not sure what the previous owner put onto the cap