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Hi evryone,got in my car today and after 20 mins and engine up to temp noticed that heater was blowing cold with temp set at 26 degrees,then it went hot again for 5 min then cold and so on and so on,does anybody have any clues as to what would be causing this as i'v had no problems before.Many thanks for any replys
 

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Try the following procedure first and see how you go :thumbsup

How to bleed the cooling system.
1.Jack the front of the vehicle up onto stands as high as possible,
2.Turn the ignition on to Aux 2, Engine OFF, heater on fan setting 1 and temperature fully hot,
3.Remove the rad cap/expansion cap,remove the bleed screw from the radiator and IF you have them the bleed screw(s) from the thermostat housing/top hose, return pipe or EGR thermostat.
4.Fill the radiator/expansion tank up and keep pouring till there are no more air bubbles coming out from the bleeds, using a funnel that fits tight in the expansion tank neck and filling it full of water will help push any troublesome air out, when good you can then install the bleeds and tighten down(don't snap them),ensure the rubber O-rings/seals are still on the screws/on the bleed holes.
5.Suck some water out so it's not full to the brim, start the car up and check coolant shoots out of the small hole on the inside of the expansion tank neck when the revs are held up, if it does then replace the cap and then run the car up and check for heat from the vents when the car is warm, then carry on and check if over heating still persists. You may have to bleed troublesome cars again afterwards.(but very rare).
6.If all is good then check the water level again in the morning when cool.

or

Ignition on, heater set to hot, bleed screw out.
Pull the top hose off the radiator. Pour coolant SLOWLY down the rad hose a litre at a time. When the coolant is building up in the hose, hold it above the level of the rad hose stub and keep adding it. When coolant starts to dribble from the rad, refit the hose. You may find that coolant starts to overflow from the rad cap orifice - if it does, just screw the cap back on. Once you've done that, the engine and radiator are full of coolant - the little air pockets that might be left will come through the bleed screw.
 

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Im having this exact same problem on my E36 328 but bleeding has not rectified the problem.

Any ideas?

Thanks
I have already tried the bleeding but the problem is still not resolved?
You've got to stop hijacking threads and create your own for your model :thumbsup. In your case, have a look at the heater valve.
 

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Discussion Starter #6
Hi thanks for the tips. Have bled it the exact way you have said but still no joy.The temp gauge is sitting at 12 as it should which is a relief and have noticed that it blows cold when the car is idle (stationary at lights) then blows hot once I'v set off again which still makes me think it needs bleeding again but a friend has said it could be somthing stuck open not sure what...any ideas anyone
 

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Hi thanks for the tips. Have bled it the exact way you have said but still no joy.The temp gauge is sitting at 12 as it should which is a relief and have noticed that it blows cold when the car is idle (stationary at lights) then blows hot once I'v set off again which still makes me think it needs bleeding again but a friend has said it could be somthing stuck open not sure what...any ideas anyone
From WDS
****************
In order to ensure adequate water throughput at low engine speeds, an electrical auxiliary water pump is installed dependent on the engine variant and installation of a latent heat accumulator. This water pump ensures virtually constant speed-independent water flow through the heat exchanger.

The auxiliary water pump is switched on at:
•Control variable Y for driver or passenger > 5%
or
•maximum heating set
or
•latent heat accumulator switched on
and
iignition lock position 2
and
•control unit OK
******************
The "Y" value mentioned is a calculation done by the HVAC control of the difference bewteen cabin temp and the set point temp, i.e. how fast should it be trying to heat (or cool if on A/C). The heat exchange mentioned is the heater core inside the cabin that heats to air going to the vents.
If the auxillary pump isn't operating one might expect loss of cabin heating while the engine is idling in traffic.
On my 2003 530I, the pump is located at the bottom of the radiator, attached to the fan shroud. I looked in WDS for your year but unfortunately my version of WDS doesn't have a locator diagram for this pump in your model year. Perhaps you can work it out from realoem.com parts diagrams when you specify your precise model.

Good luck

RDL
 
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