Cooling fan, hole cover

356 Porsche-related discussions and questions.
Message
Author
Lars Nielsen
356 Fan
Posts: 323
Joined: Fri Nov 25, 2011 7:22 pm
Location: Denmark

Cooling fan, hole cover

#1 Post by Lars Nielsen »

Have anybody used their cars without that cover (#26) in place, and any experince on noise effects?

Is this a Porsche part, or would any VW car have used this part too?
Attachments
image.jpg
1961 356 T5 Coupe

User avatar
DonCichocki
356 Fan
Posts: 521
Joined: Thu Aug 22, 2013 4:29 pm
Location: Lafayette, NJ

Re: Cooling fan, hole cover

#2 Post by DonCichocki »

Lars,
My '65C doesn't have that disc, I don't know if it had one originally but it doesn't have one now. My engine runs perfectly cool without it. Don't know if it would effect the noise level.

User avatar
Vic Skirmants
Registry Hall of Fame
Posts: 9278
Joined: Tue Oct 27, 2009 5:02 pm
Location: SE Michigan
Contact:

Re: Cooling fan, hole cover

#3 Post by Vic Skirmants »

Porsche part.

User avatar
David Baugh
356 Fan
Posts: 673
Joined: Thu Mar 05, 2009 9:29 pm
Location: Daytona Beach, FL

Re: Cooling fan, hole cover

#4 Post by David Baugh »

I've already reported my experience, ad nauseum.

No cooling issues.

From 3200 - 3400 RPM, it emits a piercing whistle. Above that, it quiets back down, then shrieks like a jet engine compressor from 4000 or so on up.

Dave
When in doubt .... Gas it! 
'58 356A Coupe

Lars Nielsen
356 Fan
Posts: 323
Joined: Fri Nov 25, 2011 7:22 pm
Location: Denmark

Re: Cooling fan, hole cover

#5 Post by Lars Nielsen »

I am hunting a loud "ringing" / "screaming" noise, thats only there above 4000rpms.
I have change the fan + mounting plate, and renuild the generator, but this noise is still there.

Reving the car without the belt, no noise.


These noises can be hard to describe I guess, and I am not ro familiar with jet sounds :)
1961 356 T5 Coupe

User avatar
David Baugh
356 Fan
Posts: 673
Joined: Thu Mar 05, 2009 9:29 pm
Location: Daytona Beach, FL

Re: Cooling fan, hole cover

#6 Post by David Baugh »

Lars, you're welcome to read my previous post on this subject. Sorry, I don't know how to cite it for you.

Try running it at 3200 - 3400 RPM to see if you don't also hear it whistling loudly within that range. If so, it's the fan holes, and it should be more noticeable with the heater valve open.

Dave
When in doubt .... Gas it! 
'58 356A Coupe

Lars Nielsen
356 Fan
Posts: 323
Joined: Fri Nov 25, 2011 7:22 pm
Location: Denmark

Re: Cooling fan, hole cover

#7 Post by Lars Nielsen »

Hi David,

Your old post is what got me on to the idea of the missing hole cover.

I do not have the heater tubes connected, but I do hear hear a slight whistle at 3000rpms, not really anything special. The noise above 4000 is quite significant however, its loud and piercing.

When other owners say they run without the plate, and dont notice anything special on the sound, I start thinking it can not be the same thing. This you will notice.
1961 356 T5 Coupe

User avatar
Larry Coreth
356 Fan
Posts: 1930
Joined: Sun Apr 20, 2008 12:48 pm
Location: NE N.CAROLINA

Re: Cooling fan, hole cover

#8 Post by Larry Coreth »

Lars,
If the disc is present now why would you remove it ? The factory obviously put it there for a reason and I having some engineering expertise see potential problems with its absence.
I suggest that since the noise disappears with the fan/generator not running, it is obviously there somewhere. So my first thought do you have the fan shimmed correctly? Is the generator mounting plate (#5) distorted allowing the fan to touch it ?See pg. E 20 of the B/C shop manual. If it touches the fan housing such a screaming noise could be the result. Also the fan could touch the fan housing on the other side if the gasket (P/N 616.106.125.00) is missing.
Larry Coreth
Roanoake Rapids, NC

User avatar
Wil Mittelbach
356 Fan
Posts: 1019
Joined: Sun Apr 13, 2008 8:58 pm
Location: Huntington Beach, CA

Re: Cooling fan, hole cover

#9 Post by Wil Mittelbach »

Lars -
If the disc is there as an original Porsche part with the impeller assembly, why remove it for no apparent advantage or reason??
I re-installed it subsequent to Ni plating my C cab's impeller.

Lars Nielsen
356 Fan
Posts: 323
Joined: Fri Nov 25, 2011 7:22 pm
Location: Denmark

Re: Cooling fan, hole cover

#10 Post by Lars Nielsen »

My car does not have the disc/cover, hence my interest in the effects.

I have replaced the mounting cover, and fan, shimmed to 3mm, nothing touching.
Rebuild the generator. Pulley brand new. But never had a hole cover.
1961 356 T5 Coupe

User avatar
Larry Coreth
356 Fan
Posts: 1930
Joined: Sun Apr 20, 2008 12:48 pm
Location: NE N.CAROLINA

Re: Cooling fan, hole cover

#11 Post by Larry Coreth »

Lars,
It is obvious that if the hole cover is missing then there will be reduction in flow efficiency due to the feedback from the fan housing side (higher pressure). The boys at the factory are pretty smart and they have had much experience and hours of testing available to them, so I would defer to them and find a cover, install it before you chase your tail to long.
If it turns out the problem persists, at least you are confident it is as it came from the factory when it made no such noise which will allow you to search for more obscure causes, such as generator brush noise (clean commutator with alcohol and wipe with light oil).
Larry Coreth
Roanoake Rapids, NC

User avatar
Jan Balder
356 Fan
Posts: 320
Joined: Tue Oct 21, 2008 4:21 pm
Location: Netherlands

Re: Cooling fan, hole cover

#12 Post by Jan Balder »

Lars,
If it is while driving that you hear the screaming noise it may be produced by the gearbox.
Maybe also your belt is slipping and produces a screaming noise, like I hear sometimes while accerating.
Last edited by Jan Balder on Sun May 04, 2014 3:21 pm, edited 1 time in total.
Jan Balder

Lars Nielsen
356 Fan
Posts: 323
Joined: Fri Nov 25, 2011 7:22 pm
Location: Denmark

Re: Cooling fan, hole cover

#13 Post by Lars Nielsen »

Both driving and reving, same noise.
Also tried running the belt both tight and loose.

Found a hole cover that is on its way to me now.
1961 356 T5 Coupe

User avatar
C J Murray
356 Fan
Posts: 9158
Joined: Fri Oct 23, 2009 7:24 pm
Location: 30MI WEST OF PHILA
Contact:

Re: Cooling fan, hole cover

#14 Post by C J Murray »

When I hear a screaming noise it is usually my wife. Most of the time she is justified.
'57 Speedster
'59 Sunroof
'60 Devin D Porsche Race Car
'63 Cabriolet "Norm"
'67 911 S Original Owner
'03 Ferrari 575M
'09 Smart Passion

User avatar
Jerry Henning
356 Fan
Posts: 325
Joined: Wed Mar 26, 2008 10:38 am

Re: Cooling fan, hole cover

#15 Post by Jerry Henning »

I have some limited personal experience with this screaming jet engine sound that one of the OPs is describing. (If you haven't personally heard this phenomenon, it might be hard for you to make blind suggestions to it's possible solution). (…and I'm not married, so the scream wasn't coming from THERE!)
One of my engines is a 1971 616/33-1 industrial engine, converted and upgraded to an auto engine configuration for my VW Type 181 'Thing'. From the first time I fired it up on the engine stand, it would have a 'jet engine scream' starting at the 3500 RPM range, and becoming deafening at the 4000 and up RPM range. The scream or 'whistle' as I refer to it, seemed to not be caused directly by the fan, because the pitch (tone) of the whistle did not change with fan speed, only the intensity of the sound. My reasoning concluded that if the fan or fan cover holes had been acting as a 'siren', the pitch of the whistle would have changed with fan RPM, which this did not. My conclusion was that the fan and air pressure/flow was 'indirectly' causing some other part of the cooling system to 'whistle'. I put up with it for several years, as I seldom ran the industrial engine at these RPMs at my normal cruising speeds.
Last winter, unrelated, a generator bearing started grumbling a bit (a different sound entirely), so I removed the (12v912) generator and fan for replacement. I installed another rebuilt generator, and while I was at it, I replaced the fan itself from my stock of nice Jack Staggs new welded balanced fans. Fan shaft spacers were set as usual to around 2mm gap. I also re-installed the original fan cover plate. When I finished the project, I looked down and noticed that I had forgotten to install a new cardboard fan shroud gasket. I was NOT going back to tear everything down just to install the gasket, and anyway, my pulleys looked to be in good alignment.
So I was pleasantly surprised when I fired up the engine again, and went for a ride, the whistle was gone, and I had a pleasantly (relatively) quiet ride!
I don't have any solutions, but perhaps offer some clues. Since the pitch of the whistle did not change with fan RPM, I assume that the fan and cover plate were not operating in a 'siren' mode. The fan cover plate was installed identically in both cases. The only things really different, were: a new generator (does not make sense that this could do it), a new welded and balanced fan (so was the old one) and the fact that I didn't replace the cardboard shroud gasket this time around. I don't know the reason, but either replacing the fan, or leaving out the cardboard gasket probably quieted things down. Perhaps the missing cardboard gasket moved the new fan closer to the fan inlet volute, and perhaps there was an air leak there before, because of a larger air gap?

I am happy now, but I am not going back to try to recreate the whistle just to satisfy my curiosity. So I offer no answers, but perhaps more information for you to ponder on…
Last edited by Jerry Henning on Sun May 04, 2014 5:05 pm, edited 5 times in total.

Post Reply