View Full Version : Lazy fan clutch?
Hello everyone!
My E34 has recently given me some trouble with its cooling system, and I think I've resolved those issues (such as the radiator failing at the top hose connection). The problem that I am experiencing now is that the fan clutch seems to be late to engage. While on the freeway the engine temperature is shown to be comfortably below the middle mark (about 5mm) which in my opinion is normal. Once in traffic, the engine doesn't overheat, but the temperature needle goes just barely over the 12 o'clock mark. This I am not used to and thus am worried about it. I've noticed that even when the temperature goes up to this point, the engine fan isn't fully engaging. What's even more puzzling is that the fan clutch is brand new. Has anyone received a defective fan clutch before? I'm pretty sure its not an issue with coolant flow since the thermostat is new (actually changed twice to verify that it wasn't it) and so is the radiator. As far as I can tell, as soon as I get moving the temperature drops to or below 12 o'clock.
Recent work done on car:
Changed coolant hoses
Changed radiator and thermostat
Flushed system and refilled w/ BMW Blue
New radiator cap
No noticeable loss of coolant or any signs of problems. Bottom hose on radiator gets hot, so coolant is flowing.
So, what are the chances that I scored a defective fan clutch? The brand is Behr.
winfred
10-31-2007, 04:42 PM
the temp should hit the middle line and pretty much stay with in about a needle width of it, i've gotten bad clutches out of the box but it's very rare with behr, after a run on the road after a few minutes of idling should get it mostly engauged, sometimes you need to turn off the ac to get the clutch to lock up as the electric is keeping the temp just below the fan's engaugenent point, several minutes of idling after a run should get you atleast a short howl when you blip the throttle, if not give it a few more minutes if the temp gauge is not climbing, the gauges are so dampened they are just about as useful as a dummy light
Winfred,
The gauge basically hovers a tick over the middle and when I let the car idle at this temperature for a long time, the fan doesn't engage to the point of being audible. So far I've witnessed it fully engage once, which to me seems abnormal (even if the engine maintains the "just over the middle mark" temperature). Does this sound like a defective clutch to you?
winfred
10-31-2007, 10:26 PM
if it's not needed it won't kick in, double check that the electric isn't kicking on early and floating the mechanical fan, seen it happen a few times and had to unplug the electric to test the clutch
I see you have replaced the t-stat twice , this would have been my first inclination.
The fluctuations are not normal, even if it's not overheating.Your temp needle ought to remain dead center or very close.
I wonder if air is present in system causing the pump to cavitate a bit at slow speed?
I like Winfred's idea about the elec fan coming on, the cruising temp is too low. It's easy enough to unplug and watch the result.
nirvana19
11-01-2007, 08:01 AM
My systems doing the same thing, just replaced fan clutch twice (first WAS defective behr, just last week). I think the new fan clutch is working as before the temperature would start to rise well past the center mark when idling for a long long time. Now the temperature is basically staying at just a little above center, although as I was JUST driving at highway speeds I saw it go BELOW the center line. t-stat for me I guess but our symptoms are EXACTLY the same so I'm wondering.
whiskychaser
11-01-2007, 09:38 AM
Just posted reply to this so if this is a duplicate, sorry. Thought my fan clutch was playing up some time ago. After a lot of searching found a very good test method but cant find the link now. Its 2 pages of pdf so a bit big to post here. Anyone wants it is welcome or you can just tell me where to stick it:-)
@Ross:
The thermostat was first replaced with an 80 degree C unit. Suspecting that the temperature going above the middle mark was a failing fan clutch, I changed the clutch. When the problem continued, I changed to a 71 degree T-stat. I am used to seeing my temperature range between ~5mm below center (at highway speed) and dead in the middle (for traffic). What I see right now is normal highway temperatures, but slightly higher traffic temps. I also think I bled the system pretty thoroughly, but knowing these cars, I'll probably do another round of bleeding. Also, as far as pump cavitation, I noticed today (when I let the car idle for ~15 minutes), the fan did finally engage on and off, and when it was engage the temperature pretty quickly dropped below the middle mark, so I think I'm getting good coolant flow, but lower than desired air flow. It seems that the fan engages at a temperature that is higher than I expect, and effectively disengages once it cools the engine down a bit. So I see this fluctuation of temperature as the fan goes through its cycle.
@Winfred:
Thanks for the heads up on the electric fan. I forgot that there's a temperature switch for it in the radiator (would disconnecting the switch disable the coolant temperature switch only, or both that and the A/C function?)
winfred
11-01-2007, 11:30 AM
if the pisser line into the tank is flowing the system will purge any air on it's own, unplugging the temp switch on the rad will just kill the electric fan's ability to help on engine temp, you should only need to idle 5-10 minutes for the fan to lock up after a drive, you could also just look through the grill and see if the fan is running, id do this test without the ac
if the pisser line into the tank is flowing the system will purge any air on it's own, unplugging the temp switch on the rad will just kill the electric fan's ability to help on engine temp, you should only need to idle 5-10 minutes for the fan to lock up after a drive, you could also just look through the grill and see if the fan is running, id do this test without the ac
This morning, after my commute, the fan seemed to engage (lock) and disengage during a 15 minute period where I just idled the engine. I know my pisser line is clear (new tank too), so it should then purge the air from the radiator if any is present. I checked the auxiliary fan after a drive at the max temperature the engine reaches and it was off. I think I'll grab my IR thermometer and check the temperatures around the thermostat housing, top hose, radiator, bottom hose, and possible fan clutch itself. Perhaps the sensor is going nuts and nothing is wrong?
Scram the 71deg t-stat and replace it with the proper temp.
Scram the 71deg t-stat and replace it with the proper temp.
Ross,
The car has run just fine with a 71 degree t-stat for nearly two years before I replaced it with an 80 degree unit. Because it ran fine with the 71 degree, I went ahead and installed a new 71 degree unit again to see if that was the cause of the issue. I do have an 80 degree t-stat, but will stick with the 71 for now as I don't see it as a source of the problem. What I've found out is that my auxilary fan is indeed turning on BEFORE the main fan engages. Once I disconnected the auxilary fan, the main fan engaged within a minute. I've left the auxilary fan sensor disconnected for now and will see how the the temperature compares. Why would the auxilary fan come on before the main fan? Buggered sensor?
winfred
11-01-2007, 07:37 PM
it's somewhat common on 535s for the aux to kick first then the fan clutch takes over, sorta like the aux is saying "hey ******* wake up" to the fan clutch :D as long as both work i wouldn't worry about it, if it gets warm enough the fan clutch will wake up and get on the ball, it takes about 160* across the radiator sensor to kick the aux into low, sometimes the fan clutch will be a little slow and not be warm enough to close the valve and engage till the aux blows some hot air over it
**** my 633s aux kicked on a couple times while i was testing the gauges, it's a odd temp time of the year, with my aftermarket gauge i can watch the reactions of the cooling system, the aux kicks at 160* on the cold side of the radiator (i boiled the switch with a thermometer) which is right around 210* on the dash, general running temp is 180-195 from interstate to sitting in traffic
Why would the auxilary fan come on before the main fan? Buggered sensor?
it's somewhat common on 535s for the aux to kick first then the fan clutch takes over, sorta like the aux is saying "hey ******* wake up" to the fan clutch :D as long as both work i wouldn't worry about it, if it gets warm enough the fan clutch will wake up and get on the ball, it takes about 160* across the radiator sensor to kick the aux into low, sometimes the fan clutch will be a little slow and not be warm enough to close the valve and engage till the aux blows some hot air over it
**** my 633s aux kicked on a couple times while i was testing the gauges, it's a odd temp time of the year, with my aftermarket gauge i can watch the reactions of the cooling system, the aux kicks at 160* on the cold side of the radiator (i boiled the switch with a thermometer) which is right around 210* on the dash, general running temp is 180-195 from interstate to sitting in traffic
I was always under the impression that the auxilary fan turned on if coolant temperature exceeded some high value like 190F. What I noticed is that with the auxilary fan off, the main fan kicked on and stayed on instead of freewheeling. I would expect the aux fan to improve the main fan response, but this seems to be the opposite effect. I guess I'll see what it does tomorrow with the auxilary fan turned off.
winfred
11-01-2007, 09:43 PM
what's happening is the fan's threshold for engagement and the low speed aux fan are fairly close to one another, with the electric going the clutch will loaf along sorta on sorta off till the temp does something, usually once the clutch gets going the aux fan stays off
Paul in NZ
11-02-2007, 12:53 AM
doesnt the fan clutch RELY on hot air blowing onto it,or can it work with radiated heat from the radiator.I only notice the main fan when i am driving in town,then quite often you hear the WHINE as you acclelerate in first,catch second,the fan disengages....
Sam-Son
11-02-2007, 12:58 AM
Thisa thread has just woken me up to what my problem might be. Just replaced my tstat with an 88c one and the engine still wanders toward the red then comes back down...pretty much the same problem you have...note to self check fan clutch
Just completed my morning drive and didn't notice any substantial difference with the auxilary fan turned off. If looking at the picture below:
http://bmwe34.net/e34main/trouble/Data/gauge_overheat.jpg
My idle temperature while sitting still is a steady 195 Degrees F. I've measured the temperature at the thermostat housing last night and got 197 degrees F there, so it seems that the temperature gauge is at least in the ballpark.
@ Paul:
My understanding is that the fan clutch does need to have some airflow over it in order to react properly to temperature changes. I'd venture to guess that this is why it has so many fins on it. Since the fan spins even when the clutch is disengaged, it moves a bit of air around and should react to a rise in radiator temperature.
So findings so far:
1) Auxilary fan does turn on before the main fan (apparently normal for 535)
2) Main fan does not behave different with the auxilary disabled
3) Temperature rises and stays at 195 degrees in traffic without a fan turning on.
4) Temperature gauge seems to agree with IR temperature measurement at the thermostat.
I'm tempted to blame the fan clutch for not turning on when needed, but is there something else that would do this? The same thing happened with the old radiator before it failed (new fan clutch went in before radiator failure), so I don't think its the radiator. Top and bottom hoses are hot. Thermostat seems to open as it should.
Any ideas?
Haven't you said the temp is running 5mm to the left of center at cruise? what would that temp be, 150?
I still think the 80 deg t-stat will put things back to normal.
BTW I notice your car os Bronzit. How has it held up? I love that color.
Haven't you said the temp is running 5mm to the left of center at cruise? what would that temp be, 150?
I still think the 80 deg t-stat will put things back to normal.
BTW I notice your car os Bronzit. How has it held up? I love that color.
If you look at the picture, the cruising temperature is shown around 153 F. I like that and am used to seeing it there. I've run the car with the 80 degree t-stat, and it does not raise the cruising temperature very much at all. Having a lower temperature t-stat wouldn't cause the engine to run hotter because both the 71 and the 80 degree t-stat should be fully open by the time you reach 190 degrees F.
The Bronzit Beige, when I first got the car, was in pretty bad shape. Had quiet a bit of spider webbing and somewhat faded. I repainted the car almost as soon as I got it and it has been holding up quiet well since then :)
Some pics of the respray: http://zakm.hotbox.ru/BMW/
PS: I think I'm going to go on an intensive bleeding campaign to eliminate air in the system as a possible culprit.
winfred
11-02-2007, 04:53 PM
it has a certain amount of draw with the fan freewheeling but it will kick faster with more heat hitting it faster
doesnt the fan clutch RELY on hot air blowing onto it,or can it work with radiated heat from the radiator.I only notice the main fan when i am driving in town,then quite often you hear the WHINE as you acclelerate in first,catch second,the fan disengages....
Today, after getting home I reconnected the auxilary fan and spent a good 20 minutes observing what the fans acted like with the car idling. The main fan engaged shortly after I opened the hood and blew at full blast for a good 5 minutes. Meanwhile, I went ahead and plugged the auxilary sensor plug back into the sensor. The engine temperature, which was at the 195 mark when I pulled into my driveway dropped to the area between 153 and 182 marks. After about 5 minutes the main fan shut off and the engine temperature began to slowly climb upward again. After disengaging, the fan freewheeled extremely slowly to the point where I could easily stop it with my finger and feel no resistance. In this state there was almost no flow of air from the fan. As the engine temperature climbed, the auxilary fan kicked in, but the main fan continued to just freewheel without even partially engaging. The temperature again climbed to the 195 mark with the auxilary fan running and the main fan not responding. At this point I was still able to stop the fan just as easily as I could at the lower temperature. I spent some time waiting for the fan to maybe kick in again, but it didn't.
I also cracked the bleeder open about this time and saw a steady stream of coolant with not bubbles at all.
At this point I think I'll be contacting Autohausaz and seeing about getting another fan clutch.
whiskychaser
11-02-2007, 06:26 PM
Today, after getting home I reconnected the auxilary fan and spent a good 20 minutes observing what the fans acted like with the car idling. The main fan engaged shortly after I opened the hood and blew at full blast for a good 5 minutes. Meanwhile, I went ahead and plugged the auxilary sensor plug back into the sensor. The engine temperature, which was at the 195 mark when I pulled into my driveway dropped to the area between 153 and 182 marks. After about 5 minutes the main fan shut off and the engine temperature began to slowly climb upward again. After disengaging, the fan freewheeled extremely slowly to the point where I could easily stop it with my finger and feel no resistance. In this state there was almost no flow of air from the fan. As the engine temperature climbed, the auxilary fan kicked in, but the main fan continued to just freewheel without even partially engaging. The temperature again climbed to the 195 mark with the auxilary fan running and the main fan not responding. At this point I was still able to stop the fan just as easily as I could at the lower temperature. I spent some time waiting for the fan to maybe kick in again, but it didn't.
I also cracked the bleeder open about this time and saw a steady stream of coolant with not bubbles at all.
At this point I think I'll be contacting Autohausaz and seeing about getting another fan clutch.
Found link for fan clutch test. Maybe check this out?:
http://www.mwrench.com/Whitepapers/FanClutchtest.pdf
Found link for fan clutch test. Maybe check this out?:
http://www.mwrench.com/Whitepapers/FanClutchtest.pdf
Thank you for tracking that down. The procedure outlined in that document is pretty much what I have done while reviewing the clutch behavior.
Update:
So before going to Autohausaz with my problem, I decided to try something I've read about on bimmer.info. What I did was take the fan clutch off and gently flex the bimetallic strip outward. This didn't noticeably bend the strip, but it did wake the clutch up. It now kicks in as it should in traffic and keeps the engine slightly below the 12 o'clock position on the gauge. The clutch disengages as it should when the car starts moving again. Some may consider this a shadetree repair, but it seems to have worked pretty well (unlike the original post on this board that mentioned the mod being done by a mechanic and effectively locking the clutch at all times). Let's hope the clutch continues to behave itself. :) Thanks for everyone's input!
bmwpower
12-30-2007, 05:19 AM
When you were experiencing this problem, was the lower radiator hose cold? I'm having similar issues and I am trying to troubleshoot.
When you were experiencing this problem, was the lower radiator hose cold? I'm having similar issues and I am trying to troubleshoot.
No, my lower hose was quite warm, which is how I deduced that it wasn't a flow problem through the radiator. If your lower hose remains cold as the car warms up, the fluid isn't flowing through the radiator. I'd look at the thermostat and for any blockage within the radiator.
As for my original issue, the fan is now operating as it should after exercising the bimetallic strip.
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