Re: [Chrysler300] Leaky Vacuum Actuators-1964 300K
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Re: [Chrysler300] Leaky Vacuum Actuators-1964 300K

One thing I did that helps is to put silicone grease on the rod where it passes through the grommet . Sometimes the rubber Dries  out adds friction and seal there is poor . It does not fix it in the perfection sense but it makes it work . It is tolerant of small leaks . Plenty more vacuum to fil what leaks out! Weatherstrip cement would seem right with a toothpick for od of it. Especially if To can turn grommet to get it in . 
On bad diaphragm I doubt a patch would work due to pretty aggressive flex and travel . Nothing to lose by opening a bad one . And looking ? Maybe inner tube piece ? A little similar to vacuum advance can ? 

Sent from my iPhone

On Apr 24, 2017, at 12:52 AM, 'Rich Barber' c300@xxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

I need a little experienced advice on servicing vacuum actuators as installed on ’60-’65 Chryslers.  So far, I have the heater bypass actuator out and determined to have a leak across the diaphragm and the damper/main actuator and deflector actuator leaking around the OD of the grommets that seal the rods to the cans.  The main and deflector actuators do not leak across the diaphragm.  All three actuators still work but present constant vacuum leaks that I hope to correct.



  1. Is it feasible to disassemble the metal can, access the diaphragm, patch it and reseal it?  I viewed a video on line by a guy that did that for an old T-Bird.  He patched the leaky diaphragm with a tire patch!
  2. Does anyone rebuild these commercially?
  3. Does anyone have a used and functional heater bypass actuator they would part with (this is the actuator mounted under the hood)?
  4. Is the grommet just that or is it part of the internal diaphragm?
  5. Are new grommets available?
  6. If available, can leaky grommets be replaced without disassembling the can?
  7. What would be a good material to use to seal the OD of the existing grommet?  JB-Weld?  Windshield gasket sealer?  Other?  All the cans have light surface rust and cleaning around the edge did not stop the leak.
  8. I had to pop off two little snap rivet connectors on a plastic shield covering the main rod end connection in order to remove the damper actuator.  Anyone know if the tiny plates just snap back on to the rivets?  Very difficult to access the end connection without popping off the little plastic cover.


BTW, the ’65 Service Manual has better pictures of and instructions for this heater-A/C unit and the ’65 Parts Catalog has better descriptions and nomenclature for each of the four actuators.  The ’62, ’63, ’64 & ’65 Parts Catalogs all show the same part numbers for these four actuators.


Back to the garage tomorrow to check out the fourth actuator.   I’m learning more than I want to know about the plumbing, linkage and wiring behind the 1964 300K dashboard.


Rich Barber

Brentwood, CA


Posted by: John Grady <jkg@xxxxxxxxxxxxxxxxx>

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