`95 Legacy L with 'whine' & weird smell.

Hello all,

My mom called me from work earlier today regarding an issue that started
happening with her legacy L wagon. On her way to work she first heard what
she described as a high pitch/whine noise coming from the engine
compartment. While she was at work, I took it to the dealership and on my
way there, I could hear a a similiar noise. It reminded me of what happens
when a belt is too tight around a pully and the noise it makes when the belt
is rubbing hard against a pully.

The second issue was that there was a "heavy chemical smell" coming from the
engine compartment blowing back in the window. I too smelled this and the
closest description I can give is that it is a mixture of a burnt belt/hose
smell mixed with that of a chemical nature. I was running things through my
head of what it could be and did a visual inspection but couldn't see any
belts that were tearing/cracked/broken or any hoses that were torn or loose.

When I arrived at the dealership to schedule an appointment and leave it for
them over night to diagnose, the service manager hopped in the car and
revved the engine up to around 3-4k rpm. When he did that with the hood up,
I could once again hear the whine and smell the smell. It seemed to
originate somewhere from the middle to the front/middle of the engine
compartment. Upon closer inspection he and I both could smell that smell
coming from the alternator area. His first reaction was that the alternator
was burnt out.

I do know in recent weeks with my mom's car, that when starting it, I have
to hold the key in the ignition position for an extra 1/4 of a second for
the engine to start. It seems like putting these things together could be
the cause of that. My mom also reported this morning that when she sat in
stoplights the car acted as if it was wanting to 'give out' while idling.
When she said that, I was wondering if it might not be PCV valve related.
The dealership had flushed the carbon out of it last year, rather than
replacing it when it was having idling problems and wanting to idle to idle
to halt.

Anyone here have thoughts/ideas/suggestions?

Brad

 

One potential source of smell is grease or oil leaking on exhaust
system. This happened to me and is easily seen by looking underneath
for burnt spots on exhaust.
Car could have multiple problems.

Frank

 

Shorted alternator diode will cause a whine
and might very well cause the smell.

Typically, a shorted diode will still allow
the alternater to charge the battery marginally,
but at the same time will discharge the battery
quickly if the engine is not running. Have you
had to jump the car lately?

A tech can sort this out pretty quickly. He
needs to disconnect a battery cable and measure
the current with the engine off. I would expect
a reading of 1's to 10's of milliamperes if the
alternater is good and something like 2-3 amperes
if it has a shorted diode.

 

It's definately a bad alternator. The dealership called and are replacing
it for $233 (including labor). The car hadn't needed a jump at all as far
as I know, the only indication was that when it idled at a stop light my mom
said it felt like it wanted to just stop.

 

Did the alternator fix the problem? I've worked on auto electronics for
years, and I've never heard a bad alternator make any noise. They usually
quietly stop working or otherwise go bad and stop charging, drain your
battery when off, etc.

 

I'll find out today. My mom is scheduled to pick it up around noon, I'll
definately let you know.

 

It's a good troubleshooting key. A shorted
alternator diode causes the alternator's
rotor to "cog" since rotation of the shaft
will be much more difficult as the rotor's
magnetic field moves across the winding with
the shorted diode. The cogging is what causes
the whine.

The bad smell was probably from that winding
cooking, since it's full output was being
short-circuited by the diode.

Often, the battery will go dead since the
shorted diode provides a path for battery
current through the winding even when the
engine is stopped. The diode normally functions
as a one-way valve allowing power to charge
the battery, but not to flow back into the
alternator when the engine is off.

You used to be able to replace the diode
pack for about $30 in parts. I haven't
had to deal with the issue for 20 years
so I don't know if you could still buy
one. The job is pretty labor intensive
so I doubt that you'd see many shops doing
it anymore.

 

That was the correct issue, however this happened once to my mom a month ago
but the issue went away. It didn't reappear until yesterday and was
verified as being the issue by the shop. She was billed for $239 for labor
and an entirely new alternator, not just the diode.

 

I'm not 'directly' a mechanic; but I've seen about every version of
alternator failure at work. (I'm a two-way radio tech)

Alternator problems often show up as two way radio problems because many
failures produce "dirty" power that drive microprocessor-controlled
transceivers batshit. Most people don't realize that alternators *do*
have brushes (riding on sliprings) because they don't usually wear out.
"Chattering" brushes can make ungodly audible noises that also produce
massive amounts of electrical noise.

Depending on belt wrap and position; a shorted diode can cause little
"stalls" as the rotor turns that can cause a squeal that's sort of like
a plain old loose belt.

My old Jeep would lose seals in the alternator bearings and squeal like
hell about every two years. (it too spent many hours trying to be a
submarine;}

 

Two Subaru Legacys, three alternators with the whining problem. It
seems that this alternator has a design flaw. (a fourth alternator
broke the usual way: worn-out brushes)

Yes the whining problem is a shorted diode. I opened up one alternator
and found the faulty part. ( Do not try this without having the shop
manuals, there's a trick.) The shorted diode causes one of the three
coils to short circuit. Excessive currents flow through this winding.
It causes the noise by magnetostriction, and it causes the whole
alternator to overheat, eventually making the rest of the components to
fail. With the shorted diode, the Failed battery indicator does not
show in the dash, but the battery will not charge so the car will stop
after a while...

As a test I cut open the diode and reassembled the alternator. No more
noise, no more heat, the battery did recharge. However the remaining
two diode sets were overstressed and second one shorted after a couple
of weeks.

The diodes are press-fitted into plates. Impossible to change one
diode. Changing a plate? Well, the Subaru dealer was asking more for
a single diode plate than it costed to have a rebuilt alt. (not at the
subaru dealer) Alts rebuilt by Delco have a lifetime warranty.

It is easy to find if your alternator charges properly. Get a $!0.
digital multimeter, and measure the voltage at the battery posts. If
the charger works, the voltage will be at around 14.1 volts with the
engine running.

Felix