Engine "Woo Woo" Noise
 

My distributor is back together and engine is running great (thanks wwest, timmy2, tirwin, and the rest of the PP ignition geniuses).

However there is an odd noise that has been emanating from the engine throughout the adventure, and has not dissipated along with the arcing fix. It is a hollow "woo woo woo" noise, similar to the sound of blowing across the top of a glass soda bottle. It only appears once the engine has warmed up. Sometimes it stops, but soon returns. With the engine lid closed, you cannot hear it very well unless you are listening for it.

Maybe a vacuum leak of some kind?

<iframe width="560" height="315" src="https://www.youtube.com/embed/8vEMytRoQOI" frameborder="0" allowfullscreen></iframe>

Sounds like a resonance to me. See if the fan blades are rubbing on the housing.

Did you re-build your dizzy?

I took apart everything except taking the weights and springs. Cleaned the metal parts with carb cleaner, cleaned the plastic parts with electrical contact cleaner. Killed three toothbrushes and many paper towels.
Got rid of lots of metal filings and grime. Removed a partially disintegrated bronze washer in the bottom of the housing. Replaced that giant washer with a new one. Oiled everything and reassembled it with new pins and proper shims to negate any up-down play. I was planning to replace the top bushing but there was no side-to-side play at all, so I left that for now.
I'm not sure if that qualifies as a "rebuild" since I didn't replace springs or soda blast and such. But it is all smoothly spinning and clean, no slop, and seems to be working fine.

Ok, I'll carefully inspect the inner surface of the housing. I've seen pictures of what this can lead to, and it's not cheap!

Did you replace the Bronze Thrust washer with another Bronze one or metal?

I presume you are referring to the one that rides between the top bushing in the housing and the bottom weights' disk on the rotor shaft? I replaced it with another bronze one that came with my shim kit.

It was the big one on the right:
[IMG]https://www.************.com/images/Product/medium/1196.jpg[/IMG]

I had that same sound at one point, but never quite figured it out.

It was either my alternator bearings, or my engine compartment blower fan.

I had the alternator rebuilt, and I replaced the blower fan. I do not have that noise anymore.

Perfect, Yes, that is the thrust washer. I think this is normal for the rebuild because if you recall and looked at the housing and below the weight assembly, it was damaged/grooved due to the disintegrated steel shims. Mine also makes a slight "woo woo" sound after recent rebuild. I will give it a month for the bronze to seat in and will re-inspect the thrust washer. If need be, I will revert back to OEM setup of Steel/Fiber/Steel shims for the upper and lower assembly.

I will also call PK to see if this is normal.

I know there should be 0.10MM up/down play after rebuild.

Mine was something close to that. Little enough I didn't have any reasonable way to measure it even with my micrometer. But enough that I could feel it move when I pulled.

Good, I am waiting for a call back from Kurt at PK.

Which one sounds like yours?

A:
<iframe width="640" height="360" src="https://www.youtube.com/embed/m5jVuOIC8VY?feature=player_detailpage" frameborder="0" allowfullscreen></iframe>

B:
<iframe width="640" height="360" src="https://www.youtube.com/embed/kuz6H7L9T1s?feature=player_detailpage" frameborder="0" allowfullscreen></iframe>

Neither A or B sound like mine. Mine has a more hollow tone. What I hear in A and B is more like a bee hive.

I used a stethoscope and I could not hear any discernible abnormal noise emanating from the dizzy. please check yours.

Mine was O2S connected and disconnected after checking with the stethoscope. Hmmm?

I used headphones to listen to your "wha wha wha" noise. I hear it more clearly now. It does sound resonate. See if you can isolate with stethoscope or remove belt and see if it can be heard without the belt.

Brother Oso, I have some bad news.

Just spoke to Kurt, this is classic "record player syndrome", once the housing and weight assembly is gooved the new shims/thrust will work but the side affects is the resonant "woo woo" or "wha wha" sound.

We can leave this alone but it will soon wear out the kit we put in.

His rebuild process is to rebuild the assemblies and machine the surfaces so they will out last OEM specs with his shim set.

Okay I am done, I am sending my dizzy in for a rebuild and balance.

I think we can prove this by borrowing a known good dizzy to see if the noise goes away.

Doh! $9.89 fix, yeah right, not on these cars :-(

Jim

I have a friend with an '80 SC. I'll compare with him next time we meet up. Fortunately, it is a fast swap and check - the worst part is getting to TDC.

I hear yeah brother! I am going to borrow a 75K Mile dizzy from my buddy.

Still heard it last night after putting some more miles on the new distributor washer. I'll see if I can distributor-swap this weekend.

After some more listening, I think it is actually coming from inside the fan housing. I am not sure of the best way to check the source. Maybe it is time to use a hose to do a fake stethoscope with some hose?

Can you disconnect your fan belt and run - just for a moment - to eliminate the fan and alternator?

Franny

Remove the fan belt and check. Do not run for a long time, just enough for a listen.

I have my buddy's Good Dizzy, will be checking against my rebuild. His is tight and 0.10MM play only and the proper drag upon spinning.

MY VW made that sound when it sucked a piece of paper into the fan. If the sound goes away with the fan belt removed, look for something that may have gotten sucked up by the fan and is under the shroud.
Bob B

I'll try the fan belt when I get home tonight (unless raining).

Sounds like "wooo wooo"?

Might it be this?

<iframe width="420" height="315" src="https://www.youtube.com/embed/JZD-ADArwXo" frameborder="0" allowfullscreen></iframe>

Hey, OsoMoore,

Did the dizzy fix your arcing?

I must've missed the update.

Long shot, Belt tension?

Yes tirwin, some combination of my dizzy cleanup, green wire fix, and new coil. Details here! http://forums.pelicanparts.com/porsche-911-technical-forum/856863-bouncing-tach-when-cold-zap-noises-7.html#post8595884
I really appreciate the input from all y'all on that challenge. (Drat, too much time spent in Texas.)


So I was going to pull the belt last night, but the wife wanted to go for a drive and a movie, and who am I to say no? Hopefully Saturday morning I will have time to wash the car and check this too. I think I also need to up the idle a little bit. She's at about 700 and sometimes coughs because of it.

My 86 makes the sam sound and always wondered what it was. I will try removing the belt and report with my findinds.

Damn, you beat me to it!!!

Another vote for the fan belt too tight here. Or a faulty alternator bearing.
Last time I installed my alternator I had the belt a bit too tight and there was a Woo Woo sound like yours.
Jose

Playing forward..

There does seem to be a failing bearing noise in he audio background..

I'm with CCM911, could be alternator related, bearings and even the diodes working (or not) can make similar noises.

Run the engine with the fan belt removed to see if the noise goes away. Also with the engine off, spin the fan with one hand and your other on the housing to feel for a rough bearing.

Whilst awaiting a CDI swap, I have taken out the alternator. Spinning on a table, there are no bad noises and things seem OK. I'm planning to put it back in and adjust the belt when I get the new CDI box.

Change of heart! Took apart the alternator partly. Removed the long bolts but haven't gotten the rest off yet (going shopping with the wife for her birthday now).

One of the brushes is significantly shorter. I'll post a picture. Does anyone sell an alternator rebuild kit, or a new brush kit? Doesn't seem that hard to work on seeing as it is just a clean-refresh effort and nothing is actually broken.

I used these guys to source all the parts for my alternator rebuild

- Alternator & Starter Parts Wholesale

I think the hard part is soldering/welding the brushes on with hot enough soldering tool.

You can purchase slip ring brush/holder assembly, no soldering required.

But given the HEAT level of the pulley you noted earlier I would be very suspicious of the front bearing. Where you able to find the # of years/miles your alternator has been in service?

Complete rebuild kits, new slip rings, brushes, regulator, bearings, are available for under $40.

And be sure and look closely, examine, the stator wiring support/insulators.

Ok, I'll see if I can nab such a kit. Would you happen to have a link? I'll start looking around. Right now I ran into an annoying issue during dis-assembly. I can't quite get a wrench onto this stupid bolt:
http://forums.pelicanparts.com/uploa...1432645644.jpg

Also, here is a picture of the current length of my brushes. The long one is 1/4 inch, the short one is 1/8 of an inch.
http://forums.pelicanparts.com/uploa...1432645682.jpg

I can check my records when i get home. It is a Valero alternator that has somewhere between 40 and 60K on it, assuming it at least replaced during the rebuild 15 years ago. I'll have to pull out the Big Book to be sure.

I see lots of kits here: Bosch - Alternator & Starter Parts Wholesale
But I don't know which one is right.