A funny thing happened on the way thru an oil change

I was changing the oil in my car, and while waiting for the dripping to
stop, I looked around at all of the stuff there is to look at under a car,
and wondered what all of the plastic parts were that were laying around near
the bottom of the radiator. It hit me that the fan was gone. The plastic
parts were the remants of the fan blades. The fan was completely gone.

I had no idea from the guages or anything else that the fan wasn't with me
anymore. Indeed, I have been wondering if the motor runs too cold in the
morning because I have seen the guage take forever to reach the mid point of
the scale, then over the course of a mile or so on the freeway, the needle
will drop to the blue and slowly rise back to the mid point again. I was
guessing that the tstat might be stuck open, but I had no idea that the fan
wasn't there. I would expect the engine to get very hot, at least is slow
moving traffic on a hot day, if the fan was not working, but there was no
indication whatsoever.

The fan is very easy to replace, one reverse-threaded nut on the fan clutch
and three small allen screws. That's it.

I just wanted to share ...

Jeff Strickland wrote:
> I was changing the oil in my car, and while waiting for the dripping to
> stop, I looked around at all of the stuff there is to look at under a car,
> and wondered what all of the plastic parts were that were laying around near
> the bottom of the radiator. It hit me that the fan was gone. The plastic
> parts were the remants of the fan blades. The fan was completely gone.
>
> I had no idea from the guages or anything else that the fan wasn't with me
> anymore. Indeed, I have been wondering if the motor runs too cold in the
> morning because I have seen the guage take forever to reach the mid point of
> the scale, then over the course of a mile or so on the freeway, the needle
> will drop to the blue and slowly rise back to the mid point again. I was
> guessing that the tstat might be stuck open, but I had no idea that the fan
> wasn't there. I would expect the engine to get very hot, at least is slow
> moving traffic on a hot day, if the fan was not working, but there was no
> indication whatsoever.
>
> The fan is very easy to replace, one reverse-threaded nut on the fan clutch
> and three small allen screws. That's it.
>
> I just wanted to share ...
>
>

That is a funny one, Jeff. But I suppose one would never notice their
lack of a fan unless, or until, they get stuck in traffic and need to
stand stationary for a while.

Which brings me to another thought... why do we need fans that run
directly off the engine, increasing and decreasing with engine speed,
when in all reality, the biggest need for additional air flow thru the
radiator will be at the lowest engine speed, and the least need for the
fan will be at higher rpm when we are making good speed?

Seems like an intelligently controlled electric fan would be a better
design, no?

-Fred W

"Malt_Hound" > wrote in message
...
> Jeff Strickland wrote:
>> I was changing the oil in my car, and while waiting for the dripping to
>> stop, I looked around at all of the stuff there is to look at under a
>> car,
>> and wondered what all of the plastic parts were that were laying around
>> near
>> the bottom of the radiator. It hit me that the fan was gone. The plastic
>> parts were the remants of the fan blades. The fan was completely gone.
>>
>> I had no idea from the guages or anything else that the fan wasn't with
>> me
>> anymore. Indeed, I have been wondering if the motor runs too cold in the
>> morning because I have seen the guage take forever to reach the mid point
>> of
>> the scale, then over the course of a mile or so on the freeway, the
>> needle
>> will drop to the blue and slowly rise back to the mid point again. I was
>> guessing that the tstat might be stuck open, but I had no idea that the
>> fan
>> wasn't there. I would expect the engine to get very hot, at least is slow
>> moving traffic on a hot day, if the fan was not working, but there was no
>> indication whatsoever.
>>
>> The fan is very easy to replace, one reverse-threaded nut on the fan
>> clutch
>> and three small allen screws. That's it.
>>
>> I just wanted to share ...
>>
>>
>
> That is a funny one, Jeff. But I suppose one would never notice their
> lack of a fan unless, or until, they get stuck in traffic and need to
> stand stationary for a while.
>
> Which brings me to another thought... why do we need fans that run
> directly off the engine, increasing and decreasing with engine speed, when
> in all reality, the biggest need for additional air flow thru the radiator
> will be at the lowest engine speed, and the least need for the fan will be
> at higher rpm when we are making good speed?
>
> Seems like an intelligently controlled electric fan would be a better
> design, no?

Years ago, I had a 1971 Ford truck. the fan was bolted straight to the water
pump. It didn't matter much since the engine didn't go much past 4000 RPM
anyways.. However, in the newer cars. they have a fluid clutch, so when its
cooler, the fan almost completely slips. As it gets hotter, the clutch will
engage more and more until its fully locked.
This has worked for many years, but just as you say, its not the most
efficient way of doing it. The fan usually robs about 15-20 HP. So removing
the mechanical fan and putting in an electric one with a thermostat is
better, but also costs a fraction more. This is most common on front steel
drive cars with the transverse mounted engines.

"Malt_Hound" > wrote in message
...
> Jeff Strickland wrote:
> > I was changing the oil in my car, and while waiting for the dripping to
> > stop, I looked around at all of the stuff there is to look at under a
car,
> > and wondered what all of the plastic parts were that were laying around
near
> > the bottom of the radiator. It hit me that the fan was gone. The plastic
> > parts were the remants of the fan blades. The fan was completely gone.
> >
> > I had no idea from the guages or anything else that the fan wasn't with
me
> > anymore. Indeed, I have been wondering if the motor runs too cold in the
> > morning because I have seen the guage take forever to reach the mid
point of
> > the scale, then over the course of a mile or so on the freeway, the
needle
> > will drop to the blue and slowly rise back to the mid point again. I was
> > guessing that the tstat might be stuck open, but I had no idea that the
fan
> > wasn't there. I would expect the engine to get very hot, at least is
slow
> > moving traffic on a hot day, if the fan was not working, but there was
no
> > indication whatsoever.
> >
> > The fan is very easy to replace, one reverse-threaded nut on the fan
clutch
> > and three small allen screws. That's it.
> >
> > I just wanted to share ...
> >
> >
>
> That is a funny one, Jeff. But I suppose one would never notice their
> lack of a fan unless, or until, they get stuck in traffic and need to
> stand stationary for a while.
>

That's what I woulda thunk too. But, I'm in Southern California and we have
already been well into the 90s and I've been stopped in traffic with the A/C
on high.



> Which brings me to another thought... why do we need fans that run
> directly off the engine, increasing and decreasing with engine speed,
> when in all reality, the biggest need for additional air flow thru the
> radiator will be at the lowest engine speed, and the least need for the
> fan will be at higher rpm when we are making good speed?
>
> Seems like an intelligently controlled electric fan would be a better
> design, no?

Anything that won't break would be an improvement.

It isn't the engine speed that dictates the air flow, it's the ground speed.
If the car is moving, there is air flow through the radiator, and if the A/C
is on, there is an electric fan that kicks in, maybe this fan is enough ...
Hmmm,

Strictly speaking, no. It's the air speed only. However, we won't quibble
for a motor car... :-)

For an aircraft it really matters whether there is a headwind or tailwind.
The difference between ground speed and air speed can easily reach 50 mph or
more.

DAS

For direct contact replace nospam with schmetterling
---

"Jeff Strickland" > wrote in message
...
[...]
>
> It isn't the engine speed that dictates the air flow, it's the ground
> speed.
[...]

----- Original Message -----
From: "Malt_Hound" >
Newsgroups: alt.autos.bmw
Sent: Wednesday, July 06, 2005 2:16 AM
Subject: A funny thing happened on the way thru an oil change


snip

> Which brings me to another thought... why do we need fans that run
> directly off the engine, increasing and decreasing with engine speed, when
> in all reality, the biggest need for additional air flow thru the radiator
> will be at the lowest engine speed, and the least need for the fan will be
> at higher rpm when we are making good speed?
>
> Seems like an intelligently controlled electric fan would be a better
> design, no?
>
> -Fred W

BMW fans are viscously coupled - engine cold - fan slips ; engine hot fan
spins.

Electric fan should cut in if engine get too hot (e.g. in traffic), but
represent a potentially disastrous failure mode if relied on completely.

I should try and find out why the fan blades broke - any sign of the remains
of the neighbour's cat that hid under the bonnet.

"R. Mark Clayton" > wrote in message
...
> ----- Original Message -----
> From: "Malt_Hound" >
> Newsgroups: alt.autos.bmw
> Sent: Wednesday, July 06, 2005 2:16 AM
> Subject: A funny thing happened on the way thru an oil change
>
>
> snip
>
> > Which brings me to another thought... why do we need fans that run
> > directly off the engine, increasing and decreasing with engine speed,
when
> > in all reality, the biggest need for additional air flow thru the
radiator
> > will be at the lowest engine speed, and the least need for the fan will
be
> > at higher rpm when we are making good speed?
> >
> > Seems like an intelligently controlled electric fan would be a better
> > design, no?
> >
> > -Fred W
>
> BMW fans are viscously coupled - engine cold - fan slips ; engine hot fan
> spins.
>
> Electric fan should cut in if engine get too hot (e.g. in traffic), but
> represent a potentially disastrous failure mode if relied on completely.
>
> I should try and find out why the fan blades broke - any sign of the
remains
> of the neighbour's cat that hid under the bonnet.
>

No signs of the cat. Well, there wasn't any fur on the plastic parts that I
found. I did have some service recently, and I found that the fan shroud
wasn't fully clipped into place. I don't know that it came unclipped as a
result of the fan coming apart, or caused the fan to come apart. The shroud
is in good shape considering the other distruction in the area.

R. Mark Clayton wrote:
> ----- Original Message -----
> From: "Malt_Hound" >
> Newsgroups: alt.autos.bmw
> Sent: Wednesday, July 06, 2005 2:16 AM
> Subject: A funny thing happened on the way thru an oil change
>
>
> snip
>
>
>>Which brings me to another thought... why do we need fans that run
>>directly off the engine, increasing and decreasing with engine speed, when
>>in all reality, the biggest need for additional air flow thru the radiator
>>will be at the lowest engine speed, and the least need for the fan will be
>>at higher rpm when we are making good speed?
>>
>>Seems like an intelligently controlled electric fan would be a better
>>design, no?
>>
>>-Fred W
>
>
> BMW fans are viscously coupled - engine cold - fan slips ; engine hot fan
> spins.
>
> Electric fan should cut in if engine get too hot (e.g. in traffic), but
> represent a potentially disastrous failure mode if relied on completely.
>
> I should try and find out why the fan blades broke - any sign of the remains
> of the neighbour's cat that hid under the bonnet.

Yeah, but my SAABs with 4 cylinder transverse engines all had electric
fans, and they were pretty darn reliable. They worked simply on the
thermostatic switch that measured the coolant temp in the radiator. So
long as the coolant in there was OK then the cooling system should be
able to regulate properly via the regular coolant thermostat.

The nice thing about that design is that when you are traveling at a
decent speed (45mph+) the forced airflow through the radiator is more
than the little fan can create so it does not need to run.

OTOH, there is a 2 speed control on the SAAB fan so that with the AC on,
or if the temp gets above a secondary threshold the fan goes into warp
drive.

This really seems to be a more intelligent design to me...

-Fred W

In article >,
Malt_Hound > wrote:
> Yeah, but my SAABs with 4 cylinder transverse engines all had electric
> fans, and they were pretty darn reliable.

With a transverse engine and a front mounted rad it would be difficult to
have an engine driven fan...

--
*If at first you don't succeed, redefine success.

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" > wrote in message
...
> In article >,
> Malt_Hound > wrote:
> > Yeah, but my SAABs with 4 cylinder transverse engines all had electric
> > fans, and they were pretty darn reliable.
>
> With a transverse engine and a front mounted rad it would be difficult to
> have an engine driven fan...

It would be difficult to have an engine driven fan that was between the
engine and the radiator. If one didn't care where the fan was relative to
where the radiator was, then it would be a relatively simple matter to have
an engine driven fan. It wouldn't be a very useful fan though.