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SOLVED A/C box vacuum pots, rejuvenate rubber innards

Posted By: Michael Ecks

SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/01/20 01:17 AM

Since I managed to do this I thought I would share the fix.


"Currently working through "restoring" the a/c heater box in my e body and found that a couple of the vacuum pots (actuators - whatever you want to call them) weren't well... actuating when I applied vacuum. Sticky doors are probably part of it, which I'll be cleaning up of course.

But is there a way to rejuvenate the rubber parts, or some kind of conditioner for them so that I am not tearing this thing apart again in 5 years?

I was able to get the push-pull ones to at least move back and forth after removing them from their doors by cleaning the little shafts up with fine sandpaper and putting some silicone grease on them. Just wondering if there is a good product out there to treat the rubber itself."

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Posted By: Michael Ecks

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/10/20 12:47 AM

All of the pull offs were working, but the push out parts not so much. One not working at all, and the other working but not holding vacuum. You can see the problem in the graphic that the seal was not sealing against the rod. You can also see fine cracks in the seals on my actual vacuum pots, and the rubber had expanded away from the rod as well, leaving a gap.

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Posted By: Michael Ecks

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/10/20 12:55 AM

The best way to rejuvenate old rubber seems to be methyl salicylate or synthetic oil of wintergreen. This guy did a good somewhat scientific comparison of varies methods of softening rubber and methyl salicylate 25% in alcohol came out best. https://www.youtube.com/watch?v=EnGsllKvheQ

I also got recommended a product called rubber renue, which comes from a well known company in the electronics field. It is primarily used to restore rubber pinch rollers in old reel to reel and cassette equipment. I checked the MSDS and it turns out to be 15% methyl salicylate in a bunch of nasty solvents.

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Posted By: Michael Ecks

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/10/20 12:57 AM

So I found methyl salicylate on amazon and mixed it with strongest rubbing alcohol I could find to make a 25% solution. Then I used fine typed syringes to fill the vacuum pods through the tube. The monoject ones fit perfect, and you can also use the action of the diaphram to pull the fluid in.

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Posted By: Michael Ecks

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/10/20 01:00 AM

Since you have to turn it over to get good flooding of the vacuum pod, I did one side at a time (about 4 syringes in the large pods and three on the smaller ones) I let them soak for about 12 hours on each side and then emptied (save the fluid) and flushed with straight alcohol.

Just doing this was enough to get both vacuum pods to seal against the rods once I got to the point of soaking that part.

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Posted By: Michael Ecks

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/10/20 01:03 AM

To help deal with the expansion of the seal I measured the OD of the seal and used slightly smaller o-rings around it to act like a tension spring used in axle seals and engine front seals.

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Posted By: Michael Ecks

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/10/20 01:09 AM

Finally, I put a fine layer of silicon lubricant on the shaft and then painted the o-rings and the top of the seal with ultra-black rtv. This was to protect the o-rings and also to create a new sealing surface around the top of the seal where it had expanded out. Coating the shaft with silcone lubricant ( I used Sil-Glyde ) prevented the rtv from atatching the rod, leaving a nice clean new round seal around it.

I haven't got everything back up and running in the car yet. But testing the restored A/C box with a vacuum pump, all of the actuators work both ways now and hold vacuum once they reach the end of their travel.

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Posted By: Michael Ecks

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/10/20 01:17 AM

This was all for my 1971 Challenger A/C/heater box that blew out the heater core about 4 years ago. I used Duplicolor Vinyl and Carpet Specialty Coating on the housing and Seymour Stainless Steel Paint on the doors after I bead blasted them. All new gaskets throughout from Detroit Muscle Technologies. All great products.


Can't wait to get it back on the road with heat and defrost again. Depending on how much I get back in taxes I am hoping to put A/C back in the car later this year. (I flushed the evaporator while I had it all apart).

Hope this post helps someone out.

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Posted By: A727Tflite

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/10/20 01:49 AM

Pure genius - thanks.

Going to try this on my son’s Toronado - his one headlight won’t open. Guessing it might be the same issue as this.
Posted By: Lee446

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/10/20 02:54 PM

Well done! Thanks for posting this for the rest of us!
Posted By: moparx

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/10/20 04:48 PM

ingenious fix ! up bow
now if i can only remember it if and when i need it !
beer
Posted By: EV2RTSE

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/10/20 11:32 PM

Very cool stuff! Will have to tackle this project myself soon.
Posted By: Mattax

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/18/20 04:26 PM

Thanks for sharing!
What did you see as the advantage of using alcohol instead of xylene and ethylbenzene for the carrier?
Posted By: BcudaChris

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/18/20 07:00 PM

Thank you for adding to the tech base on Moparts. Please update us from time to time.

I did not get farther than cleaning my vac pots and conditioning the exposed rubber, then using small zip ties in the way you used O-rings. Mine is all in and up and running and performs admirably. Your efforts look like a longer term solution than mine.
Posted By: mopars4ever

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/18/20 09:16 PM

Yes, I would be curious on how long it lasts. luck
Posted By: Michael Ecks

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/20/20 01:26 AM

Originally Posted by Mattax
Thanks for sharing!
What did you see as the advantage of using alcohol instead of xylene and ethylbenzene for the carrier?


Mostly I was trying to keep it simple and cheap as possible. Purchasing the pre made rubber renue would have been about 4 times the cost for the same amount, and I didn't want to go buy containers of the xylene etc. Rubbering alcohol, is cheap and has other uses around the house for me.

Ethylbenzene is also toxic when inhaled, but if all you are doing is using a cotton swab to clean pinch rollers in audio equipment probably not a concern. I figure the stronger solvents are probably used in the rubber renue to clean guck off of audio equipment rather quickly while the oil of wintergreen takes care of the softening part of the job.
Posted By: Michael Ecks

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/08/23 07:26 PM

Originally Posted by mopars4ever
Yes, I would be curious on how long it lasts. luck


Had to track this post down for someone else to reference so thought I would give an update. Still working great 3 years later !!! luck
Posted By: mopars4ever

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/08/23 07:52 PM

very cool!
Posted By: moparx

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/08/23 08:31 PM

this repair almost needs to be a "sticky" somewhere here.
i scrolled to my original reply, and yes, i DID forget about it !
thanks for bringing this back up with real world results. bow
beer
Posted By: TJP

Re: SOLVED A/C box vacuum pots, rejuvenate rubber innards - 02/09/23 02:03 AM

Originally Posted by moparx
this repair almost needs to be a "sticky" somewhere here.
i scrolled to my original reply, and yes, i DID forget about it !
thanks for bringing this back up with real world results. bow
beer
iagree
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