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Thread: New Development - Luke Warm Heat Until Car is in motion

  1. #1
    Join Date
    Mar 2013
    Location
    So~Cal
    Posts
    1,228
    My Cars
    2003 E46 M3 / E30 Vert

    New Development - Luke Warm Heat Until Car is in motion

    So Ill start out with this.

    Car does not Overheat, Idling, Driving, Drifting, Cruising; Temp stays dead center (more like Dull Center).

    Car has Full Mishimoto Cooling (silicon Hoses, Electric Fan, Radiator, Etc.) New Stock Reservoir, New 88C Thermostat, New T-Stat Housing, New Metal Impeller Water Pump, yada yada. All Cooling was overhauled < 6 Months ago.

    I know for a fact PRE overhaul, The heat would Blast at Idle if the heater was on. it was HOT. Car was Bled properly when overhaul took place, and at time of Final Bleeding, Car had Hot air coming out of Heater at idle.

    I dont really ever use my heater as I reside in Los Angeles, But a few mornings ago we had some lowish temps so I would throw on the heater. All was well, Heater was blowing hot as I was Cruising, But came to a stop light and I Noticed the Air Temp when from HOT, to Luke warm, just a notch above neutral heat. Light went Green, car started moving, heat resumed.

    Few mornings have gone by and I have confirmed that Heat is only being Blown when the car is in motion.

    my concerns:

    1. Heater Core is clogged?
    2. My water Pump is only moving enough water to achieve maximum heat when car is in motion (under load).
    3. My Elec Fan is somehow interfering with my car producing enough heat at idle?

    I could honestly care less about the heat, but the REASON is bugging me. If its #2, should i really be concerned if the car performs well when under normal / hard driving conditions?

    *Note* My electric fan is set up on a temperature relay, i have it eyeballed at about 200F (it kicks on at 200). If elec fan is a considerable variable, is the temp its set at too low / High?

    TIA

  2. #2
    Join Date
    Apr 2016
    Location
    Irvine, CA
    Posts
    664
    My Cars
    99 328is, 03 X5
    I have the same issue. I looked into a heater control valve being the culprit, but will be doing an oil cooler, gauges, and cooling system overhaul again after Bimmerfest to find out for sure.

    I can tell you everything else in my cooling system is less than a year old, so the issue has to be heat specific.

  3. #3
    Join Date
    Dec 2013
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    Chicagoland area
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    4,372
    My Cars
    EXOTICS
    Start at the basics,
    COLD,in the moment before startup for the day,
    what is the coolant level?

  4. #4
    Join Date
    Jun 2010
    Location
    NY
    Posts
    9,079
    My Cars
    1997 328i
    I have to agree to first be sure there is no air in the system. With new hoses, especially silicone the clamps have to be very tight. Consider a UV dye.
    Attn. NEWBIES: Use the search feature, 98% has already been discussed.
    Click the search button, select "search single content type", select the "e36 sub forum" specifically, try the "search titles" then try the "search entire posts".

  5. #5
    Join Date
    Nov 2007
    Location
    Central IL
    Posts
    9,873
    My Cars
    E36
    It's the valve. I'm in the same boat...have been for years. Common issue...never has bothered me enough to go fix it. I read up on it a lot once upon a time.
    BMW CCA Illini Chapter Vice President
    1995 M3
    - My Favorite DIY's and FAQ's



  6. #6
    Join Date
    May 2012
    Location
    Central Wisconsin
    Posts
    640
    My Cars
    '94 325i, '93 325is
    The only time I have had the heat get weak when idling I was low on coolant. Leave the car sit overnight and look at the level BEFORE you open the tank. Sometimes if there is an air bubble because the system is low it will surge the coolant back to the tank when you take the cap off.
    '94 325i Sedan, Arctic Gray: UUC LTW FW, EVO 3 and DSSR, +.020 Maxsil pistons, ASC delete, Eibach shocks/springs, 16" contour reps 238k
    '93 325is Coupe, Schwarz, work beater 299k
    '89 325i Vert, Alpine White: 5spd swapped. Sold
    '04 Toyota Sienna XLE Limited AWD, In progress swapping to M50/G250, http://www.wibimmers.com/board/index...nna-25i-build/
    '05 Volvo V70 R, 6mt, mostly stock, kid hauler 200k Sold
    '85 Toyota LandCruiser: Lifted, gas hog. 205k

  7. #7
    Join Date
    Mar 2013
    Location
    So~Cal
    Posts
    1,228
    My Cars
    2003 E46 M3 / E30 Vert
    Sorry Gents, Level is at KALT.

    I would have loved if it was that Simple, but please know I have done all the prelim checks. Wouldn't have posted this without checking those first mates.

    For further reference, Car has those HPS Hose Clamps with Lock nuts, I Would doubt Air is getting in through there (Although not Impossible).



    Car also has the ECS Aluminum "Light weight" Pulley, so I doubt the Water Pump is struggling to churn at idle.

    Pelican backs up the Heater Valve Theory

    https://www.pelicanparts.com/BMW/tec...e-Cleaning.htm

    If its the heater valve, meh. I dont think ill fix it any time soon, although the DIY Doesnt look too bad. If i get time this weekend Ill try and bleed the car for any air that might have crept into the system and report back. I guess it may be time to replace some of those "Radiator - Back" Coolant hoses to be sure those arent disintegrating.

  8. #8
    Join Date
    May 2012
    Location
    Central Wisconsin
    Posts
    640
    My Cars
    '94 325i, '93 325is
    One test with the heater valve is to unplug it and it should stay wide open.
    '94 325i Sedan, Arctic Gray: UUC LTW FW, EVO 3 and DSSR, +.020 Maxsil pistons, ASC delete, Eibach shocks/springs, 16" contour reps 238k
    '93 325is Coupe, Schwarz, work beater 299k
    '89 325i Vert, Alpine White: 5spd swapped. Sold
    '04 Toyota Sienna XLE Limited AWD, In progress swapping to M50/G250, http://www.wibimmers.com/board/index...nna-25i-build/
    '05 Volvo V70 R, 6mt, mostly stock, kid hauler 200k Sold
    '85 Toyota LandCruiser: Lifted, gas hog. 205k

  9. #9
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    When you're standing still and you rev the engine at like 3000 rpm constantly, does the heat increase then?
    I think heater valve not opening far enough might be the reason.. With relatively low water pump flow at idle there isn't enough water passing through the core to heat the cabin enough, and while driving, the water pump (which pumps more at higher rpm) pumps more water and then there is (just?) enough (at least for California mild morning cold) heat..

    JC43089's tip to remove the plug from the heater valve is a good tip.. If indeed the valve is (mechanically?) unable to open more than a little, then, at idle, the problem should persist. If, on the other hand, the cabin gets hot during idle, then there is another problem, perhaps with the valve or with the electronics/wires driving the valve anywhere between the HVAC console and the valves.
    Last edited by ed323i; 05-19-2018 at 10:22 AM.

  10. #10
    Join Date
    Sep 2005
    Location
    California
    Posts
    15
    My Cars
    1998 M3
    I wouldn't bother fixing the heater valve in CA. But if you want to inspect "https://www.youtube.com/watch?v=SD9FBtSTLv4"

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