How do you clean a 67 brake pressure switch

[Patrick B.]

How far can you disassemble a 67 brake pressure differential switch to clean it. I don't want to risk hurting the internal orings by soaking it in carb cleaner. Are the conical brass inserts that seat the brake lines at the ends removable? Are there any cleaners safe for soaking the valve in?

[Richard M.]

Re: How do you clean a 67 brake pressure switch

Patrick, Once you remove the contactor, you'll see the piston shaft. IIRC I used denatured alcohol to clean it. I used 2 drifts, one on each side, and slowly moved the pistons back and forth to free it up as it was stuck. Once clear, I used some brake fluid to lubricate the inner seals.

Some pics in this recent post.....

https://www.forums.ncrs.org/showthread.php?109723-Brake-Bleeding&p=737104#post737104

Rich

[Patrick B.]

Re: How do you clean a 67 brake pressure switch

Thanks Rich. Alcohol is a good idea. I think I'll put the contactor back in when I move the piston to avoid moving the O-ring out of the bore if it is possible to move the piston that far.

[Richard M.]

Re: How do you clean a 67 brake pressure switch

Yes, the piston will come out and release the internal o-rings. They installed it from one end.

But if they're damaged or worn the piston would have to come out anyway. Hopefully yours are good. I'm not sure if they're "square" edged or "round" edged o-rings.

Rich

[Patrick B.]

Re: How do you clean a 67 brake pressure switch

Yes, the piston will come out and release the internal o-rings. They installed it from one end.

But if they're damaged or worn the piston would have to come out anyway. Hopefully yours are good. I'm not sure if they're "square" edged or "round" edged o-rings.

Rich

I meant just to prevent the O-ring from passing into the hole for the contactor and being partially exposed and possibly pinched or cut. If I knew how to remove the brass insert at one end I would be tempted to remove the whole piston to clean it and replace the O-rings. Do you know how to remove the insert?

[Richard M.]

Re: How do you clean a 67 brake pressure switch

Patrick, I don't have a photo of the ends handy, but if they're like the brass "olives" as I call them as shown on the top, they may only be able to be removed destructively by tapping a appropriate thread in them and using a screw on a puller to remove. Then replacements would need to go back in.

However, maybe a drift on on end may push the other end out via the piston. Then you could get at the o-rings. I have one here that I may rebuild but it won't be for a while.

I'll try to get a few photos of it when I locate it.

Rich

[Larry M.]

[Patrick B.]

Re: How do you clean a 67 brake pressure switch

Thanks for the suggestions. This one worked OK when I took the car apart over 20 years ago. I was tempted to throw it in strong carb cleaner because it looked so dirty, but I'm glad I didn't. I'll try the alcohol and see if the piston moves. If I screw it up, I'll check out Lone Star.

[Patrick B.]

Re: How do you clean a 67 brake pressure switch

Well, soaking it for several days in denatured alcohol worked pretty good to clean it up. I thought the piston was stuck because I couldn't move it with air pressure, but I ground the point off a nail, inserted it thru the brass insert and tapped it with a hammer. To my surprise, the piston moved fine but it was strongly spring centered. I didn't think these were spring centered because I have had to center them by opening a bleeder valve under pedal pressure in the past. However, maybe that experience was with a C3 valve rather than a C2.

[Timothy B.]

Re: How do you clean a 67 brake pressure switch

Pat,

How are you cleaning the outside and what's the original finish supposed to be.

[Patrick B.]

Re: How do you clean a 67 brake pressure switch

I think the original finish is supposed to be as cast steel. I thought mine had black paint under the grime, so I bead blasted it (after carefully plugging the holes). Oddly, some of the black color resisted the glass bead while the areas that were thoroughly cleaned by the bead blast are probably more silver looking now than in the as cast condition. Since I am refinishing the body with base coat/clear coat and using 67 L-89 aluminum heads on my original L-71 block, I am more concerned with preservation than judging. I may just rub a little black paint on it with a rag to give it a moddled appearance, or just shoot it with cast blast.