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41 346 "duck call" sound at idle

Started by 41CadJeremy, September 24, 2019, 10:40:06 AM

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41CadJeremy

Wondering if anyone can help me diagnose this:

My 41 is making an awful sound at idle, but when I rev it up it seems to go away.  It sounds like it's coming from the fuel pump, but I haven't ruled out the generator.  I've included a video link below.  There are two videos; in one the pitch of the sound actually changes when the windshield wipers are turn on (discovered by my son "helping" me!)

https://photos.app.goo.gl/s2kjSd7wRoVW4FLM9

Anybody come across this?
Jeremy Masters

41 Cad 62 CCP

Cadillac Jack 82


Your fuel pump/vacuum pump is sucking in air from somewhere.
Tim

CLC Member #30850

1959 Cadillac CDV "Shelley"
1964 Cadillac SDV "Rosalie"
1966 Oldsmobile Toronado "Sienna"

Past Cars

1937 LaSalle Cpe
1940 Chevrolet Cpe
1941 Ford 11Y
1954 Buick 48D
1955 Cadillac CDV
1955 Packard Clipper
1957 Cadillac Series 62
1962 VW Bug
1962 Dodge 880
1966 Mercury Montclair
1967 Buick Wildcat Convertible
1968 Chevy Chevelle SS
1968 Plymouth Barracuda
1977 Lincoln MKV

harry s

Jeremy, Welcome to the club and message forum. Great car and back story. Always nice to keep the tradition going. As to your engine noise I agree with Tim especially given that the sound changes when wipers are turned on. I would confirm by disconnecting the belts. That is one weird sound. Good luck keep us posted.     Harry
Harry Scott 4195
1941 6733
1948 6267X
2011 DTS Platinum

fishnjim

There's gas bubbling in the fuel bowl.  In any event, that's not good, nor safe.   Seems to subside with noise, but not completely.   When engine revs, it flows more gas, so may reduce the relative air flow.   Can't tell but looks like coming in/around the inlet tube.   Could be sucking air through the gasket for the fuel bowl, that's easiest to check.   Remove and replace.   Tighten properly.
The sound is more like some sort of dry bearing noise, so not convinced from a video they are related.
The vacuum or fuel diaphragm might be ruptured and sucking air and that's the noise maker, but I'd not suspect it would lessen at higher rpm unless the pitch becomes inaudible.   Air would transmit up the center rod.   There's some seals/orings on that.
Rebuild the pump and see if it goes away, if the other checks don't pan out..   Could be due to ethanol fuel on old diaphragm, use modern materials.
There's some other diaphragms in the vacuum system for the WWs, so that might be switching off the leaky one.   That's why they got away from vacuum operated/assisting things it's not robust.   
There's diagnostic devices for noise, audible or not, that would aid pin pointing here, but not commonly held in enthusiasts' garage.

41CadJeremy

Thank you all for the replies; very good insight.  I will check the lines into the pump as well as the vacuum lines and gaskets this weekend and go from there.
Jeremy Masters

41 Cad 62 CCP

41CadJeremy

Problem solved...the gasket for the vacuum bowl at the bottom of the pump was pretty well shot and letting in a good amount of air.  The dried up gasket was acting like a clarinet reed and causing the sound.  Got it taken care of,  but still getting bubbling in the fuel bowl.  I think I'll rebuild the pump to be safe, the car was restored in the 70's and hasn't gotten driven much since the mid 90's.  Thanks again for all the advice.
Jeremy Masters

41 Cad 62 CCP

Bob Hoffmann CLC#96

I suggest you do a search on fuel pump bubbling. I feel the final thought was that it was NOT a problem.
Bob
1968 Eldorado slick top ,white/red interior
2015 Holden Ute HSV Maloo red/black interior.
             
Too much fun is more than you can have.

41CadJeremy

Jeremy Masters

41 Cad 62 CCP

harry s

Some bubbling on the pumps is normal or at least present on most I've see to include my three. What a weird circumstance causing the "duck call".   Harry
Harry Scott 4195
1941 6733
1948 6267X
2011 DTS Platinum

Jim Miller

I have some bubbling on my '41 also. Doesn't seem to be an issue at all.
Jim Miller

1941 6219
1949 6237X
1970 CDV
2021 XT6
Past:
1991 SDV
1999 DeElegence
2006 DTS
2013 XTS
2016 SRX

z3skybolt

I have bubbles also with my 40 LaSalle quite often.  They go away if I turn the electric fuel pump  on. Been that way for 8,000 miles and two fuel pump rebuilds.

Bob
1940 LaSalle 5227 Coupe(purchased May 2016)
1985 Lincoln Town Car Signature Series. Bought New.