Author Topic: neutral safety switch hiss  (Read 1054 times)

Offline David Greenburg

  • CLC #3830
  • Posts: 1997
  • CLC Number: 3830
  • Name: David Greenburg
neutral safety switch hiss
« on: February 10, 2013, 02:59:44 AM »
The auto. parking brake release on my '60 was not working when I acquired it, so I got a used, but supposedly tested neutral safety switch.  Now the release works correctly, but when I shut the car off there is a about a 10 second vacuum hiss that appears to be coming from the switch.  Is this normal, or does it indicate that there is a leak in the switch?   
David Greenburg
'60 Eldorado Seville
'61 Fleetwood Sixty Special

Offline The Tassie Devil(le)

  • Administrator
  • Posts: 12421
  • CLC Number: 18992
  • Name: Bruce Reynolds
Re: neutral safety switch hiss
« Reply #1 on: February 10, 2013, 03:24:16 AM »
Sorry, but you have a leaking switch.

You could try dropping a very small amount of oil inside the vacuum connection, to soften up the membrane that is supposed to be creating the seal, but if it has shrunk too much, it will never seal.

The 10 seconds of hissing is the depletion of all the vacuum in the reservoir and lines.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Offline TJ Hopland

  • Posts: 10193
Re: neutral safety switch hiss
« Reply #2 on: February 10, 2013, 08:05:44 AM »
Something like silicone or vegatable oil would likely be safer than a petroleum based oil.  Are you sure its not a hose issue?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Offline Scot Minesinger

  • Posts: 6004
Re: neutral safety switch hiss
« Reply #3 on: February 10, 2013, 09:29:52 AM »
The hiss is usually form the neutral safety switch, happens on Cadillacs up through 1970 (maybe later years too).  These switches also hiss if not adjusted exactly correct.  The shop manual explains how to adjust them and it is pretty simple.

If you are in doubt of any vacuum hoses they should replaced.  This is an easy and inexpensive repair and it produces smoother idle, stops pining under heavy acceleration, better mileage, and the like.  Whenever someone complains about their Cadillac not running and operating correctly, that is the first thing I check after looking at their receipts because no one ever replaces them.  To replace the engine through fire wall and into dash hoses, attach a coupling to the hose to be replaced inside the engine bay to a new coil of hose and pull it through.  Then it will be exactly routed as it left the factory if it was original.  Don't know if there is a vacuum line to trans like on 64 and up, but if so check that as it is often never replaced.

Good luck,

Scot
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Offline David Greenburg

  • CLC #3830
  • Posts: 1997
  • CLC Number: 3830
  • Name: David Greenburg
Re: neutral safety switch hiss
« Reply #4 on: February 11, 2013, 01:45:02 AM »
I'll try adjusting it, although I didn't realize that the adjustment process affected the vacuum release; I just thought the adjustment was for making sure the car only starts in park/neutral. I  must admit I ddin't try adjusting it when I installed it; I put in on and the car started in park and released the brake, so I though I was done.  I don't think I'm going to try oiling it.  Seems like a temporary fix, and I paid good money for a used, but tested switch from one of the larger vendors, who I have dealt with before, so if an adjustment doesn't do it, I'm going to send it back.

I don't think its a hose issue; hose feels ok, and when I got the car, the hose was disconnected from the switch and plugged.  I do agree with Scot that lots of problems are caused by rotten vacuum hoses.  When I get an older car, I routinely replace all the vaccum hoses that  don't feel nice and soft.   
David Greenburg
'60 Eldorado Seville
'61 Fleetwood Sixty Special

Offline 66Deville

  • Posts: 5
  • Name: J.Boddaert
Re: neutral safety switch hiss
« Reply #5 on: February 11, 2013, 06:13:16 AM »
Never use petroleum based oil on rubber seals. It will destroy them.
I had the same problem on my '66, just had to re-align the switch according
to the shop manual procedure and it was fixed.

Offline Scot Minesinger

  • Posts: 6004
Re: neutral safety switch hiss
« Reply #6 on: February 13, 2013, 07:25:15 PM »
David,

There are so many times when I have gone to replace an item on my Cadillac if I had done so without reading the shop manual, it would have been not good for me.  Even changing the most elementary item I always read first.  The shop manual will explain how to adjust the N-S switch and it is not difficult.

Frankly the most difficult issue I used to suffer is mechanics not reading.  Before I was forced into doing anything myself possible as a result of poor mechanical work, I would photo copy the manual sections and highlight the items that were possible to mess up if instructions were not followed, then I would go over it with them - still they would fail to follow instructions.  Guess they get so used to doing things themselves without reading they get over confident?

Enjoy your Cadillac,

Scot
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

 

Sitemap 1 2 3 4 5 6 7 8 9 10 11 12 13