Hi, I just bought a 1988 325 automatic with 144k miles which has a
loud howling sound coming from the front end of the car somewhere. I
can't tell which side. It's independent of the engine rpm but
consistent with the road speed. It's noticable above 10mph. It sounds
like a manual transmission which is being wound up too high and should
be shifted into another gear. I would say wheel bearing but it sounds
more like an exhaust note or giant fan motor or something. You can't
really tell anything with the window down. Any ideas? Anyone done this
repair themselves? Thanks for your time.
Well, the car seems to idle smoothly and has adequate power and
reasonable acceleration for it's age but I've never driven it before
today so I don't have anything to compare it to.
The howl isn't present with the car idling, noticeable just over 10mph
or so. I will check the fan tomorrow to see if it's turning when I
start it. Thanks for your response.
Ok, I started the car cold. The radiator fan turns right away. If I
blip the throttle by hand it changes speed with the engine revs. You
are saying this is abnormal? I don't get the impression it's one of
those fans that turns itself on after the engine has been turned off
on hot days. Could this be what's making all that racket?
Also, unrelated to the fan there's a slight tapping sound like lifter
noise from the engine that goes away after it's warmed up. Thanks for
All BMWs have fan clutches. It's the ribbed 8" diameter saucer-like
thing behind the fan. It's filled with a temperature-sensitive oil that
becomes more viscous when hot. You should be able to use a stick
to stop the fan when the engine (and clutch) is cold. This clutch allows
the air rushing through the radiator when the car is moving at speed
to cool things rather than having to use engine power. It also
keeps the noise level down when unnecessary.
I've never heard a fan clutch make noise. I've had a couple of them fail,
but they let the fan spin uselessly on the pulley, and the result is
overheating at idle that is corrected by vehicle speed.
The OP states, at least twice, that the car only makes noise while moving.
The fan clutch on my Z3 went bad resulting in the fan spinning when it
shouldn't. The result was a howling sound whenever I accelerated since the
fan was spinning so fast. Made the car sound like a truck. No more howling
after it was replaced. My brother inlaw has a Mercedes and when his fan
clutch went bad, he had the same symptoms that you describe. That's
probably the more common failure to the fan clutch.
The OP stated that the sound is independent of engine RPM, so it is probably
not the fan clutch. The noise that my car made was only dependent on RPM.
Revving the engine with the car at a stand still caused the howling, as did
high RPMs when the car was moving.
Wrong! When the viscous fan coupling fails it usually locks up and the fan
turns at engine speed making a terrible racket )wind rush) also the engine seems
"heavier" if you get my drift. At high revs the tips of the fan blades will
curl toward the radiator and CAN rip the core out dumping all your coolant etc
The main cause of viscous fan coupling failure - BELIEVE IT - is if the fan
coupling has EVER been removed and laid flat or horizontal the oil seeps past
the seals and the inner workings tend to become clogged with oil in the wrong
places and usually within 2 weeks or 2 months the whole clutch will lock solid.
The units are stored vertical when shipped and vertical on the dealer's shelves
and obviously when fitted they are VERTICAL.
Sir Hugh of Bognor
I used to be an Egotistical Meglomaniac - but now I'm just perfect!
I've never seen a viscous couple fail in a locked condition. I'm certain it
may happen, but in every instance of a failed couple that I've seen, the
couple failed in a mode that it never locked and the result was overheating
at low speeds, or no speed. In one instance, we repaired an overheat
condition by defeating the fan clutch -- we inserted a bolt that was longer
than the others so that the fan would be locked to the waterpump pulley.
Viscous couples are relatively new, and there were many decades of auto
production where there was no couple at all, the fan was simply bolted to
the water pump pulley and that was that. Viscous couples only lock the fan
when there is insufficient cool air to provide for the needs of the
radiator, the common failure mode is that the couple never locks the fan at
low speeds when temps are apt to rise. The default condition of a viscous
coupled fan is that the fan is not fixed to the pulley it is mounted on. the
fan is not connected to the pulley until heat rises sufficiently to cause
the viscous material to expand and lock the plates inside the coupler.
Since the default condition is unlocked, the common failure is that the
clutch never locks, and the result is heat rise.
I agree that the clutch can fail in a locked condition, but I reject your
assertion that this is common. I also submit that the vast majority of the
time, most people would not even notice a fan that was fixed solid to the
drive pulley. The purpose of the couple is to reduce drag on the engine, the
reduction of noise is an unintended consequence -- good consequence to be
sure, but a side benefit not the goal.
You may refute it but since the intro of viscous couplings as opposed to the
earlier BMW use of thermo clutches that do fail in free wheel state I have
replaced about 40 for customers and 3 of my own before I found out the problem
from - believe it or not a Nippon Denso engineer when I complained about the
second fan assembly on my Cedric GT. Since then I have always hung them from
the ceiling or a coat hook until being refitted and have NEVER had cause to
If it's not the cause here then take this as a bit of free advice and knowledge
- it could save you $$$$ in the future.
Sir Hugh of Bognor
I used to be an Egotistical Meglomaniac - but now I'm just perfect!
On Sun, 07 Oct 2007 21:20:41 +0100, firstname.lastname@example.org wrote:
Back 25 years ago, when I was still trying to get into SWMBO's
knickers, she had a Triumph Spitfire. She was on the M5 coming to see
me when the fan clutch let go and sent the whole damned thing
forwards, through the radiator. Naturally, she noticed that all the
nasty noise had stopped, and the only difference now was that a silly
red light in the dash was lit. She drove until the car slowed and
struggled and finally wouldn't go any more. Then she had the AA tow
it to my house.
From the local scrappie, I got a Herald water pump with a fixed fan,
and a radiator. With a hacksaw and a pop rivet gun, I fitted the
radiator. The water pump went straight on and I crossed my fingers
when I cranked the starter. It ran!
A week later, the head gasket went. So, I put a new one in and
persuaded her to sell it. We've been (mostly) happily living together
The ticking is okay. The fan is okay.
You MUST determine that the noise comes from the car moving or not. If the
car must be moving to hear the noise, it is NOT the engine making it. If the
noise does not come from the vehicle moving, then it can be the aux fans
associated with the air conditioner or other system. Your first post has me
dialed in on front brakes or a failed wheel bearing. Of those two, brakes
where my bet is placed.
On Sun, 07 Oct 2007 18:10:06 GMT, "Jeff Strickland"
Ok, maybe it's nothing to do with the engine. It's only when the car
is moving. It starts at 25 and gets louder the faster you drive. I
tried to make a sound recording so you could take a ride with me but
it didn't turn out.
I can make it howl fairly loud at 45mph on level ground about 1500rpm
and shift into neutral; the tach drops to 800 and the noise stays the
same till the car looses speed coasting.
The ABS light came on for about one second when I was backing up
Q: We have a car hoist. How do I check for a bad wheel bearing? It's
definitely the front, probably the drivers side. Thanks again.
Well if it doesn't really start until 25, then I would vote for a failing
front wheel bearing. I had the experience on my 318i.
The 'howl' comes from the fact that the little impulses from the wheel
bearing resonate with the macpherson coil spring and it sings.
I've always described it as more of a moan but I think the best description
is that it sounds 'like snow tires on a pickup truck'.
A wheel bearing can go a long time like this so I would suggest just driving
the car until the symptom becomes more pronounced. If you really want to
find the culprit I would suggest folding up a leather glove and stuffing it
between the spring coils to see if the noise changes. You can't always find
a bad bearing by jacking up the wheel and spinning it because the bad spot
in the bearing is probably on the low point of the inner race and there
won't be any load on it with the car jacked up.
I agree with Jack, except that I think the end has already arrived. The
previous owner already ingored the noise until it grew to a point where it
To the OP
Lift the car and move the wheel from top to bottom and left to right. It
ought to be solid, but it is going to move. Take the wheel off and then
remove the brake and caliper, then take the hub off and replace the
bearing(s). When you get to the brakes, you should see whare the noise is
Start the car. If it makes noise, it's the motor or something related. If it
does not make noise, it's not the motor.
Move the car. If it makes noise, look at the brakes and wheel bearings.
If the transmissioin is the trouble, the noise will come from under the car
where you sit, not from the front or the back.
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