Results 1 to 11 of 11

Thread: Overheating, Radiator Fan running slow

  1. #1
    Join Date
    Jul 2013
    Location
    United Kingdom
    Posts
    2
    My Cars
    316 auto e30 520i e28

    Unhappy Overheating, Radiator Fan running slow

    my 1985 735i E23 auto overheats in traffic if i dont put the heater on full power, i noticed the radiator fan is running slow only even when engine is hot,
    i suspect the fan clutch to be at fault, but what i dont understand is why does this model still have a radiator fan switch if the fan works with a fan clutch? is the fan clutch not a viscous coupling which works by itself if there is too much heat from the radiator coming? what for is the radiator fan switch doing then? BMW wants £30 for the switch which is located at bottom of radiator, but the aftermarket items are from £8.50, but the parts dealers all say they dont fit even the febi website confirms fitment, and the parts dealers themself offer them as compatible with 735i 1985 on ebay, what a confusion.......

  2. #2
    Join Date
    Jun 2010
    Location
    TX
    Posts
    4,487
    My Cars
    1983/84/85 745i

    Thumbs up

    E23 aux fan switches are in the wrong spot to be of much use with their temperature settings. Replace the 'low' switch from its current 91°C to an 82°C unit. And move the original 'low' to the new 'high' at 91°C.

    Install a new Sachs fan clutch, this should fix the can clutch issue. If you have the two row radiator, use a B35 fan with clutch. It moves a pile more air than the little nine bladed B34 unit. If for some reason you have the thicker, three row radiator, use a B34 Sachs clutch and an S38 fan blade.

    Consider finding a 130mm water pump pulley. These are most common on the E32/34 B35 motors, this spins the fan and water pump faster at low speeds for more cooling... but also prevents the lower radiator hose from being chewed up by the pulley.
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    11/1984 735i (10:1-265/6)
    Ford, MB, and GM round out the pack.



  3. #3
    Join Date
    Oct 2013
    Location
    Dubai/UAE
    Posts
    127
    My Cars
    1989 BMW E24
    Quote Originally Posted by Hit Man X View Post
    E23 aux fan switches are in the wrong spot to be of much use with their temperature settings. Replace the 'low' switch from its current 91°C to an 82°C unit. And move the original 'low' to the new 'high' at 91°C.

    Install a new Sachs fan clutch, this should fix the can clutch issue. If you have the two row radiator, use a B35 fan with clutch. It moves a pile more air than the little nine bladed B34 unit. If for some reason you have the thicker, three row radiator, use a B34 Sachs clutch and an S38 fan blade.

    Consider finding a 130mm water pump pulley. These are most common on the E32/34 B35 motors, this spins the fan and water pump faster at low speeds for more cooling... but also prevents the lower radiator hose from being chewed up by the pulley.
    Hi Hit Man, can you please advise the optimal operation of the aux fan in hot climates. I just bought two low temp sensors which plug on the radiator 81Deg-91Deg) Any info how these should work and whether the aux fan should run at full whenever the AC is on. Thx in advance.

  4. #4
    Join Date
    Mar 2007
    Location
    Quadratechtown, PA
    Posts
    741
    My Cars
    5, 7, 4x4
    The BMW cooling system is designed to keep the motor cool in all climates. There are a few parts for Saudi Arabia, but I don't know if that is for the cooling system or not.

    The aux fan must operate with the a/c is on. It switches on low with the a/c. As temps go up it can switch to high as needed based on the connection to the temp sensors on the radiator.

    Keep in mind the thermostat is part of the system and installing a low temp thermostat will not allow the car to get to proper operating temp until the coolant can't be cooled enough to allow the thermostat to regulate the engine temp as it is designed to do. Make the system work together to accomplish proper cooling no matter the climate. Hit Man should have the answers for severe heat use as TX can be hot and humid. Not as hot as Dubai, but much more humid.
    Last edited by 8991XJ; 02-05-2016 at 04:48 PM.

  5. #5
    Join Date
    Jul 2013
    Location
    United Kingdom
    Posts
    2
    My Cars
    316 auto e30 520i e28

    My 735i doesnt have Air conditioning

    Quote Originally Posted by hit man x View Post
    e23 aux fan switches are in the wrong spot to be of much use with their temperature settings. Replace the 'low' switch from its current 91°c to an 82°c unit. And move the original 'low' to the new 'high' at 91°c.

    Install a new sachs fan clutch, this should fix the can clutch issue. If you have the two row radiator, use a b35 fan with clutch. It moves a pile more air than the little nine bladed b34 unit. If for some reason you have the thicker, three row radiator, use a b34 sachs clutch and an s38 fan blade.

    Consider finding a 130mm water pump pulley. These are most common on the e32/34 b35 motors, this spins the fan and water pump faster at low speeds for more cooling... But also prevents the lower radiator hose from being chewed up by the pulley.

    ok thanks, when you are talking about aux fan would that be an additional fan in front of the radiator in addition to the viscous fan behind it?my car doesnt have air conditioning i believe, and i was looking through the front grill i cant see any additional fan fitted.
    How can i test the viscous coupling for the viscous fan ?
    Attached Images Attached Images

  6. #6
    Join Date
    Jul 2017
    Location
    Brooklyn, NY, US
    Posts
    20
    My Cars
    4e31s, e30m3 e23745i
    Hey Guys. This is Dirtboy Nay. I have been experiencing overheating problems. Whether I'm sitting in traffic or not. The temp gauge seems to always creep past the halfway mark. So I took the car to my Mech who is very good. But hasn't seen this car in a great many years. Here is what he discovered the previous owner in the lower radiator line or hose Not the big Lower radiator 859, but a same hose connecting to the radiator was clogged with silicone. this was discovered when he shoot air through the line. Now I don't know what that was doing in there. Any ideas ??? I changed the upper & lower radiator hoses and the fan clutch as it would stop when touched. He also checked the auxiliary fan and it works. I pick the car up let it sat and idle for about 30mins it stay at the halfway mark.
    Once on road I'd say about 30mins into the drive I noticed the temp gauge creeping up when I come to a stop. But then return to the halfway way when I drive. I need to eliminate this problem.
    Hey Hitman, please explain when you say "E23 aux fan switches are in the wrong spot to be of much use with their temperature settings. Replace the 'low' switch from its current 91°C to an 82°C unit. And move the original 'low' to the new 'high' at 91°C." ? Are theses the switches you are referring to ? Genuine BMW Temperature Switch 70Cel - 12631285018, Auxiliary Fan Switch 61311364272/82 ?
    Below are new parts i have just replaced. I've no knowledge just love for 70's, 80's & 90's BMW's so pardon me. Any and All recommendations will be greatly appreciated.


    BMW Engine Cooling Fan Clutch - Behr 376732231
    Last edited by Dirtboy Nay; 03-04-2018 at 07:17 PM. Reason: forgot 80's

  7. #7
    Join Date
    Jul 2017
    Location
    Brooklyn, NY, US
    Posts
    20
    My Cars
    4e31s, e30m3 e23745i
    Hey, Hit Man X. I'm interested to see what your thoughts are concerning temp switch application. You say "E23 aux fan switches are in the wrong spot to be of much use with their temperature settings. Replace the 'low' switch from its current 91°C to an 82°C unit. And move the original 'low' to the new 'high' at 91°C." ? What if you the new 'Low' is Temperature Switch 70°C- 12631285018 & the new high is Auxiliary Fan Switch 82° - 61311364272 ?
    Last edited by Dirtboy Nay; 03-23-2018 at 09:09 AM.

  8. #8
    Join Date
    Mar 2007
    Location
    Quadratechtown, PA
    Posts
    741
    My Cars
    5, 7, 4x4
    One would think that the fan would operate 100% of the time at the low speed since the coolant reaching the radiator would be at 80° and the fan switch is 70°. With a switch located low on the rad, the rad would cool the fluid before it reached the switch. A good rad should cool it enough to prevent the switch from closing. With the switch located high on the rad there is little cooling of the fluid for the switches to sense and the 82° switch might even close at times, but I think that is my E28 with the high mounted switches.

    Forcing overcooling of the motor isn't the best for motor operation. They work best when running at 80°C in normal ambient temps. Running it cool will cause more fuel to be used in a correctly functioning ECU system.

  9. #9
    Join Date
    Jul 2017
    Location
    Brooklyn, NY, US
    Posts
    20
    My Cars
    4e31s, e30m3 e23745i
    8991XJ Thanks for the input. I was looking at the switch used in the National version Saudi Arabia. Am I wrong to think Saudi Arabia version employs the same ECU ? I admit my lack of knowledge in the mechanics lend my to rely on the knowledge of others. Thanks Again.

    Sidebar, can I Assume you have you have a Jag ?

  10. #10
    Join Date
    Mar 2007
    Location
    Quadratechtown, PA
    Posts
    741
    My Cars
    5, 7, 4x4
    8991 XJ is a Jeep Cherokee.

    SA has much higher ambient temps and the rad may not allow enough cooling to get a low temp, necessitating more airflow to get the motor correct. I didn't see a lower temp thermostat so this system would read the temp of the coolant and provide fuel for that.

    It is always best to address the problem, not band-aid a solution but this would work to get the fan to operate. In cooler weather with a good radiator, this would lead to over cooling. Maybe not in stopped traffic in the NYC area, does traffic also go there? Or is the term stop and go traffic a misnomer for parts of NYC? I guess Brooklyn has to be better.

  11. #11
    Join Date
    Aug 2018
    Location
    Chicago, IL, USA
    Posts
    5
    My Cars
    '85 735i, '75 CS
    A late reply on this thread but I've solved my overheating problem and would offer this solution up to you all. After getting everything in my cooling system working and flushing the system 3 days I had marginal improvement. I then decided to use my power washer on the radiator. Much dirt was flushed out. This led me to notice the minimal spacing between the radiator and the HVAC condenser just in front of it. 30 year of dirt and debris had made a home in there. So take out the two mounting bolts of the radiator and let it incline back a bit allowing more space between the two radiators. Then use a power washer and clean thoroughly. Now your cooling system can get the airflow into the radiator as designed.

    After this "fix" my temp gauge is back well below 50% even in 90+F weather. Sitting in traffic is no longer a reason to panic.

Similar Threads

  1. 2002 e46 radiator fan will not stop running
    By gmeyers5 in forum General BMW Mechanical Help sponsored by RM European Auto Parts
    Replies: 15
    Last Post: 08-27-2010, 10:32 AM
  2. Please Help Radiator Fan Blows Too Slow
    By blkg12 in forum 1999 - 2006 (E46)
    Replies: 0
    Last Post: 10-16-2009, 02:52 PM
  3. Replies: 1
    Last Post: 03-19-2009, 12:17 PM
  4. Should the radiator fan run when the engine's cold?
    By Raggadiman in forum 1996 - 2002 Z3 (E36/7, E36/8)
    Replies: 2
    Last Post: 04-18-2008, 07:54 AM
  5. Radiator fan runs constantly?
    By josephb983 in forum 1983 - 1991 (E30)
    Replies: 19
    Last Post: 03-01-2008, 10:36 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •