Heat at idle

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BonBon
Joined: Tue 08 Jan, 2008 21:10
Posts: 1195

  Z3 roadster 1.9

Heat at idle

Post by BonBon » Sun 09 Dec, 2018 09:27

Has anyone observed that the heat from the hot air blower when idling (eg red light) is not boiling as when driving? I know my valve is clean. If it's not like that for all - the only thing I suspect is a partially blocked core.
Any insights?

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colb
Joined: Sat 05 May, 2012 23:46
Posts: 647

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: Heat at idle

Post by colb » Sun 09 Dec, 2018 13:09

Air lock that requires bleeding, bad thermostat or failing water pump would be my guess given what you are experiencing.
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

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BonBon
Joined: Tue 08 Jan, 2008 21:10
Posts: 1195

  Z3 roadster 1.9

Re: Heat at idle

Post by BonBon » Sun 09 Dec, 2018 13:43

Colb - all the 3 items you listed have been checked. The air is not cold - it's quite warm but noticeably cooler that the really hot air when raising the revs. (My first thought was a partially blocked heater core valve - but checked that as well)

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colb
Joined: Sat 05 May, 2012 23:46
Posts: 647

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: Heat at idle

Post by colb » Sun 09 Dec, 2018 14:41

If you suspect the heater matrix core best way to check is to disconnect the heater hoses in the engine bay and run a hose pipe through it in both directions (backflush) and note the strength of flow it makes. If it runs as a full steady flow that will prove you have no blockages and rule the matrix out as being at fault. If it gets ruled out best check the thermostat out again, how long after a cold start till the temp guage hits the 12 o'clock position on the temp guage? If it takes an age then I would suspect a failed thermostat in the open position. You say you bled the system are you sure you got all the air out? Z's are nortorious for air locks particulaly in the heater matrix and a pain to bleed. You need to get the front of the car as high as you can get it to get it to bleed all the air out it gets trapped in the heater matrix.
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

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BonBon
Joined: Tue 08 Jan, 2008 21:10
Posts: 1195

  Z3 roadster 1.9

Re: Heat at idle

Post by BonBon » Sun 09 Dec, 2018 17:35

Will look at a backflush (as thermostat is fine)

LaRy
Joined: Mon 12 Nov, 2018 17:47
Posts: 9

  Z3 roadster 2.8

Re: Heat at idle

Post by LaRy » Mon 10 Dec, 2018 19:43

I have a 2.8 l with exactly the same problem. Checked everything and it was ok, even the water pump is new.
I started to read forums and comment from all over the world. Summary, this is normal, Z3 has a poor heating system. Of course, roof should be down, who cares about heat. More important that the AC is working.
If you compare to some other solutions used in other cars, it is common that you have a termostate in combination with the heat adjustment valve, to make the temperature more even att different engine/water speed, not Z3. It is rather well known that the heating in BMW from these years are not to good. Some of the other BMW models from the sane time have a pump in combination with the electrical heat valve (that you most probably have found), just to get better water flow at idling. This solution is actually used in the Z3 M series with the 321 hp engine.

As an engineer, I wanted to improve my heating. So I went to a junk yard and found a similar valve/pump as used in some other BMW models to solve the problem and tried to install it, but the space was to small, had to make a lot of extensions with pipes and got leakage problems. I also had to add some electric relays to start the pump when the solenoid is open, too much problems for me to just get heat at idling speed. So today, I just accept facts.
Maybe you have not noticed yet, but if you are driving and have like 50% heat on, the heat is OK in your foot well, but in the passenger foot well, it is cold. This is Z3, nice, not perfect, but just a roadster, a pure care. Love it as it is!

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BonBon
Joined: Tue 08 Jan, 2008 21:10
Posts: 1195

  Z3 roadster 1.9

Re: Heat at idle

Post by BonBon » Mon 10 Dec, 2018 19:53

So in the UK the driver footwell is cooler than ours?? :sunny

LaRy
Joined: Mon 12 Nov, 2018 17:47
Posts: 9

  Z3 roadster 2.8

Re: Heat at idle

Post by LaRy » Mon 10 Dec, 2018 21:05

Probably it is like you say, in the UK.

This link is showing what I tried to install, normally used in the 3 series and in the Z3 M.
https://www.ebay.com/itm/00-05-BMW-M3-3 ... 1016099131

As you can see, it has two cylinders, one is the electric water valve and the other is the pump motor. It must be a reason why BMW was manufacturing this……..
Unfortunately, the valve need no power to be open at the same time as the motor need power to work. And when valve has power to close, the pump should stop. German engineering!

It is no chance to install this unit at the same place as the Z3 has its electric valve, not even nearby.

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BonBon
Joined: Tue 08 Jan, 2008 21:10
Posts: 1195

  Z3 roadster 1.9

Re: Heat at idle

Post by BonBon » Mon 10 Dec, 2018 21:26

Indeed it’s quite tight there - but “douze points” for trying.

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Robert T
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Joined: Mon 12 Jun, 2006 11:35
Posts: 10053

  Z3 roadster 1.9
Location: Cheshire

Re: Heat at idle

Post by Robert T » Mon 10 Dec, 2018 22:46

The heater in the Z3 is an air-blender, so on anything but full heat it will blow colder when the water flow through the heater matrix decreases at idle.

To solve this, I believe BMW fitted a second, electric, water pump. This makes up for the comparative lack of water flow at idle.

More modern BMWs have climate control which tries to regulate the temperature by altering either the water-flow or air-blend.

Cheers R.

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Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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