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Thread: No heat at idle

  1. #1
    Join Date
    Dec 2006
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    Homer Glen, Il
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    33
    My Cars
    1999 M Roadster

    No heat at idle

    It has been -11 here yesterday. Heat work great, blows hot, then I stop for a red light and almost instantly the bolwer is blowing cold air. If I rev the engine upto 1500 rpms hot air comes back. I have searched the forum and the best I can reason is it is a common problem to some and others don't have this problem. There must be an answer why this happens. Is the water not circulating fast enough, is there a valve or something else. This can not be right, how could a car be designed that if you start it and go back in the house to let it warm up it just blows cold air at idle. I watched the temperature gauge and it remains straight up showing the engine is hot and that the thermostat is not stuck open, and I checked the antifreeze and its full. Does anyone know how this is suppose to work?

  2. #2
    Join Date
    Jun 2003
    Location
    South of the Border
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    1,050
    My Cars
    99 911 ... gone now
    Water pump failing.

  3. #3
    Join Date
    Dec 2006
    Location
    Homer Glen, Il
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    33
    My Cars
    1999 M Roadster
    I ordered a new pump. I should get it this Thursday, will install Saturday. Hope this solves the no heat at idle problem.

  4. #4
    Join Date
    Feb 2005
    Location
    Baltimore, MD
    Posts
    1,396
    My Cars
    2000 Z3 2.3
    Exactly what I was going to say. At least your engine stays warm. When I move, mine drops to the first white line. It warms up only when sitting still or charging up hills.

    Stupid really, really, really cold weather.
    Tires are Evil. They MUST be destroyed.


  5. #5
    Join Date
    Dec 2006
    Location
    Batavia, IL
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    4,399
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    00 M Coupe, 08 335xi
    Hey Joe PM me if the water pump fixes it. I have the exact same issue. Did you go stock on the pump or get an aftermarket one?

  6. #6
    Join Date
    Dec 2006
    Location
    Homer Glen, Il
    Posts
    33
    My Cars
    1999 M Roadster
    Changed the water pump today. This is on a 99 M Roadster. The original water pump had a light gauge stamped metal impeller. There was nothing wrong with it but I changed it out anyway because I already took it out and had the new one. I installed one with a cast metal impeller not OEM, cost $59.00. This did not fix my problem with the no heat at idle. I checked the hoses on the heater valve thats on the drivers side. I found the hose from the block to the heater core to be very hot and the out put hose from the heater core to the heat valve to be cool. I took off the hose on the input of the heater valve with the engine running and there was no flow of water. I then took off the hose on the output of the heater valve and again there was no flow of water but when I raced the engine to 1500 rpms I got a flow of hot water. I expected the water to be with pressure from the water pump but it was just a nice flow. This would explain why I get no heat at an idle and at 1500 rpms I do get heat. Back in the day I use to bleed the air out of a heater core by taking the hose off with the engine running, but it was for an air bound heater core that you got no heat out of at any rpm. With my taking the hose off and at the higher rpms getting a flow and at the lower rpms not getting any flow I am thinking the heater core is blocked. The input hose to the heater core from the block is hot and hard and the output of the heater core is cool. Is it possible that the heater core is just air bound or is it common for the heater cores to get blocked. There are 72,000 miles on the car.

  7. #7
    Join Date
    Dec 2006
    Location
    Homer Glen, Il
    Posts
    33
    My Cars
    1999 M Roadster
    Test drove the car, 99 M Roadster, to verify the heater still has same problem that the water pump didn't fix. Heres what I have, at idle heater blows very cold air, at about 2000 rpms while driving the heater blows very hot air, at 3000 rpms the heater blows extremely hot air, stop for a red light and within 10 seconds the heater is blowing extremely cold air. I can't see how the heater core could be blocked with it blowing such hot air at 3000 rpms. What am I missing?

  8. #8
    Join Date
    Jun 2002
    Location
    Austin, TX
    Posts
    225
    My Cars
    Farbissina
    Did you fully bleed the cooling system? Sounds like there is air in the system still.

    2000 MCoupe - Cosmos | Kyalami

    ECIS CAI | Conforti | Remus Exhaust | UUC UDPs | Fan Delete | M50 Intake Manifold
    Ecsta MX | Strong-Strut CL | Camber Shims | Bushing Stuffers | H&R+Bilstein

  9. #9
    Join Date
    Dec 2006
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    Homer Glen, Il
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    33
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    1999 M Roadster
    I ran the car at 2000 rpms for over 5 minuits with the bleeder cap off watched till there were no bubbles, capped it. What bothers me is that with the engine running removing the heater core hose no water came out at low rpms and at 2000 rpms a steady stream but not with any force. Could this be a pressure related issue, is there a pressure release valve that is going bad and not letting the pressure build up?

  10. #10
    Join Date
    May 2002
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    SW Florida
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    99-01 M Cpe & Rdts, X5M
    For whatever reason, that's just the way the heater valve works.

    Firts time I was going to flush my own cooling system, the BMW tech told me to run it up to 2000 RPM so that the heater valve would open.

    Sorry I didn't catch this thread before you went through the trouble of changing the waterpump...

  11. #11
    Join Date
    Dec 2006
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    Homer Glen, Il
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    33
    My Cars
    1999 M Roadster
    Randy thanks for the info. So when it's -11 degrees outside starting the car to warm it up will heat up the engine but the heater in the car will not heat the car or defrost/de-ice the windsheild. That just doesn't seem right to me, thats a poor design. Also I did take the hose off both sides of the heater valve and at an idle no water came out so its more like not so much the valve isn't opening but more like the water dosen't circulate till about 1500/2000 rpms. Do you know if the hose on the valve is on the input or output of the heater core, it seems to me to be on the output which makes it seem as though the heater core is blocked or air bound. I didn't take the other hose off because it was very hot and the valves side hose was cold indicating to me to be the output side and the side to bleed.

  12. #12
    Join Date
    Jun 2003
    Location
    South of the Border
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    1,050
    My Cars
    99 911 ... gone now
    Isn't there a bleed valve on the block as well as the radiator?

  13. #13
    Join Date
    Dec 2006
    Location
    ALbuquerque, NM
    Posts
    45
    My Cars
    1999 Z3M, 2003 Jeep Rubicon, 2006 Acura TL
    My '99M blows heated air at idle.

    Dan

  14. #14
    Join Date
    Oct 2006
    Location
    Edmonton, Alberta, Canada
    Posts
    202
    My Cars
    E90 335i
    my 2000 only blows warm air at idle...

  15. #15
    Join Date
    May 2006
    Location
    Cincinnati, OH
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    1,172
    My Cars
    '13 BMW 335i Convertible
    I have the same problem. I start my car, the engine warms up, but it's still blowing cold air. This morning I actually used my wipers to clear my windshield and bits of snow started coming out of my vents. After 100 yards or so of driving, it starts to blow warm air.

    Did anyone ever get resolution to this?

  16. #16
    Join Date
    Dec 2006
    Location
    Batavia, IL
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    00 M Coupe, 08 335xi
    Found a post on Bimmerfest that suggests that it's air in the system.

    Though I would have thought that that would have cause poor/no heat all the time. The other suggestion is the water control valve.

    "This sounds like the classic symptoms of trapped air in the cooling system. I would start first by bleeding the system. It's free and easy. I was experiencing the same thing last week and here is what I did: Turn key to "On" position (don't start) and set heater knob to red zone (hottest temp). Open small bleed screw next to overflow tank cap. Remove overflow tank cap and pour in antifreeze until it flows out of the bleed hole. Grab hold of the upper and lower radiator hoses with each hand and slowly squeeze about 20 times. Top off with antifreeze if needed. By keeping topped off you are squeezing air out but not letting any air in."

  17. #17
    Join Date
    Dec 2006
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    Batavia, IL
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    00 M Coupe, 08 335xi
    This problem has now been fixed for me. It was air in the system.

    The heater has worked fine at idle since I had a coolant flush completed at the local indy BMW shop last week.

    The heater control also is a little more gradual now rather than the "on/off" that it was before.

  18. #18
    Join Date
    Jan 2008
    Location
    Vilnius, Lithuania
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    1
    My Cars
    Z3 Coupe 2.8
    I know this is an old thread, but I believe I can contribute....

    I have the same issue with 98' 2.8 Coupe. I went to BMW Official center and after thorough tests, the BMW technicians explained to me that this is a poor design of BMW.... At idle the the pump is not suffiecient to provide the water to the heater.

    THEY HAVE SHOWED ME 1998'S TECHNICAL PAPERS, where BMW informs all technical centers about this issue. In 1999 they have upgraded the system with an additional electric motor which turns on, depending on two parameters - heating system temperature and the engine temerature. This motor is installed between the heater and the engine and simply circulates the water...

    I asked if my car can be upgraded, but they said that besides the electric motor there is the motors management, which is connected to the heating system and the engine sensor. So they would not do the upgrade.

    However, I believe that with some thought one can easily put an electric motor to provide the same functionality. And the only parameter that needs to be known to turn the motor on, to my understanding, is rpms, which is 2000..

    I will try to find some more info about that and try to solve the problem. If I succeed, I will definitely post here...

  19. #19
    Join Date
    Sep 2006
    Location
    Tyrone, Ga USA
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    9,847
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    2010 135i M Sport 6MT
    that is interesting and explains the electric motor sound in my car when it is cold out and i want the heater to work while at idle.

  20. #20
    Join Date
    May 2002
    Location
    SW Florida
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    12,323
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    99-01 M Cpe & Rdts, X5M
    A few years ago, I replaced every rubber hose in my cooling/heating system, and I didn't find any connected to a circulating pump (motor).

    Unless it's contained in this (which looks like just the valve to me)...




  21. #21
    Join Date
    Jan 2008
    Location
    Basking Ridge, NJ
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    104
    My Cars
    2001 BMW Z3 2.5i
    Old thread or not I noticed the same thing on my '98. Poor heat at idle but quite hot with revs. Will try a careful flush and bleed.
    It's not the years in your life that counts, it the life in your years...

  22. #22
    Join Date
    Feb 2007
    Location
    Corvallis, Oregon
    Posts
    152
    My Cars
    99 M Roadster, 2015 328i
    I have pretty much the same issue. On my car, it didn't show up until I replaced my water pump. I thought I had bled the system adequately, but maybe not. The heater valve was fairly progressive before, but it would put out some pretty decent heat at idle after fully warm.

    Of course living in the central valley in California, I can heat the inside of the car on most days with a BIC. ;-)

    I'll try to bleed more thoroughly and see what happens.

    Bob S.
    Bob S
    Davis, CA

  23. #23
    Join Date
    Nov 2006
    Location
    St. Petersburg, FL
    Posts
    374
    My Cars
    02 M Coupe
    Same issue with my S54. The S52 (2000) worked fine.
    Bill
    2002 M Coupe. Steel Gray/Black.

  24. #24
    Join Date
    Feb 2007
    Location
    Corvallis, Oregon
    Posts
    152
    My Cars
    99 M Roadster, 2015 328i
    Randy,
    The Bentley manual shows the valve in your photo for the models up to 2000 and and a similar one for later except for two cylindrical towers, the valve and the pump motor I would guess.
    Bob S.
    Bob S
    Davis, CA

  25. #25
    Join Date
    Jul 2003
    Location
    Dexter, MI
    Posts
    2,244
    My Cars
    2002 M roadster
    Look at your gray car, it's slightly different. P/N 64.11.8.369.807, "WATER VALVE WITH ADDITIONAL WATER PUMP".

    Quote Originally Posted by Randy Forbes View Post
    A few years ago, I replaced every rubber hose in my cooling/heating system, and I didn't find any connected to a circulating pump (motor).

    Unless it's contained in this (which looks like just the valve to me)...



    Daniel
    2002 M roadster
    persistently obsolete mod list

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