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Hi folks,

I'm thinking of switching to DOT 5 (silicone) brake fluid in the 1953 Cavalier. If I did this, I from what I understand I would need to replace the three hoses, the slave cylinders, install a rebuilt Treadle-Vac, and a new stop-light switch.

I would also take this opportunity to replace the hard lines at the rear axle. But I recently had to replace the hard lines going to the rear and the ones up front, don't want to replace those again. I have read mention of the need for flushing the brake lines with denatured alcohol - but how does one do this?

Do you fill the old brake system with the alcohol, bleed it till the alcohol comes through? Or some other method? What do you do after you have the lines full of alcohol?

Thanks in advance

Not even sure replacing the brake switch and starting fresh would be long lasting with the move to silicone fluid. No matter which switch type or brand, based on comments here and on other forums the silicone seems to make a shorter life of all of them if they are directly exposed to the fluid as is the case with hydraulic operated switches.

If it were my car, with silicone fluid I would seriously consider going to a mechanical switch working off the pedal arm to operate the brake lights. It may not be as simple as screwing in a new switch but it is long lasting and reliable.

Here is the mechanical conversion several have done with dimensions for the 56 arm bracket. This switch is shown for the TL system but for regular suspension you would just use the 2 terminals nearest the plunger instead of the 4 or get a 2 terminal switch. The other change would be to fabricate the bracket that would work with the narrower arm located on the opposite side of the column. I have not tried but the dimensions for the 56 version may work with the 55 and earlier arms and bracket would just need to be rotated to the other side. This bracket had the clamp welded on but easier would be to allow for tabs and bend them up as shown in the drawing. Use a screw type hose clamp covered with black heat shrink or vinyl tape to disguise and to protect the column. Place the clamp over the tabs and tighten to hold the bracket to the column.

After bracket is done you would make a small two wire loom for the extra length needed to reach the old switch location. Connect to the switch and use .156 bullet connectors at the other end to reach and plug in to the existing connectors at the old location.

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  Mech Brake Switch.jpg (79.44 KB)

I use silicone in all my cars (synthetic oils too) and have had no adverse affects but was surprised to see that the Treadle-vac kit came with a warning that silicone was not recommended. I’m not sure if there is a supplier of kits that support silicone but it’s something to ask before buying!

As for flushing, I’ve read those things too but I generally pressure bleed the system repeatedly at each wheel which seems sufficient. However, I also always blow out the lines with filtered (no moisture) air to remove any residuals or dirt, this can be taken a step farther by putting one end of the line into a container with the alcohol and use a hand vacuum bleeder at the other to pull the alcohol through the lines.

What benefits are U hoping to see from such a change? Much ado about nothing, methinks.
There's more data from DOT 3,4 use, than DOT 5 and converted systems.

The flushing issue revolves around some incompatibility between the traditional glycol based fluids and DOT5 silicone oils that can cause potential braking failures. I have not seen any data on that just what the DOT and manufacturers say. I suspect it was tested that's why not approved for back compatible. I haven't seen any specifications for conversion cleanliness. That's the only one I'm aware of without back compatibilization.
DOT3,4 requires flushing and fluid change as normal maintenance.
Dept of Transportation controls brake fluid and components.
law.cornell.edu/cfr/text/49/571.116

For a vehicle that sees regular use, I can't see the benefit to using DOT 5. Great for a car being prepared for museum life. I never had an issue with DOT 4 fluid use.

It sounds like a lot of work for maybe not a lot of benefit. I don't know a lot about the DOT 3/4 vs DOT 5 debate, but DOT 3/4 seems to be working well for me right now. Is DOT 5 better for long-term storage?

If someone were to ask me if I wanted to do all that work to switch over to DOT 5, my answer would be a firm "no".

-Kevin

Because of a combination of:

A) I don't have a hub/drum puller

B) I bent my largest C-clamp trying to take off the U-Joint to replace the rear differential pinion seal (which is leaking)

I'm taking it to a shop I trust to replace the rear brake cylinders and the differential pinion seal (and I'm trying to talk them into the steering gear seal as well) - but they aren't comfortable with DOT 5, so I'm just going to go with DOT 4 for now, with regular flushing.

But my reasoning was generated by the recommendation from Kanter (below) as well as a few others, and based on previous experience with crystallization in my BTV before I rebuilt it, which gives me pause. Perhaps at a future date when I have obtained a hub puller I will do the job myself.

Thread on Treadle-Vacs, DOT 5

The message you quoted was from James who works with Kanter but it was not an official message from Kanter itself as far as I know. James is not even in the Packard department of Kanter but works on Packards personally. Point is, be careful referencing a company without knowing that the company actually said it.

In any event, I use nothing higher than DOT 4 and the main reason is that it is considerably less expensive the synthetic DOT 3 for some reason. DOT 5 was cheaper yet in bulk but seems more in keeping with race cars and that sort of thing with high heat characteristics.

From what I understand, switching to DOT 5 is what requires all the flushing, etc. because of the incompatibility between glycol fluids (DOT 3, 4, and 5.1) and the silicone-based DOT 5.

In any case, the message as I understand it was the result of a study by Kanter itself

Kanter Study

The main reason to switch to DOT 5, from what I understand, is that the systems in these cars are vented to the atmosphere, not sealed with little bladders/diaphragms like in modern cars, so they absorb more water than present day vehicles, especially in areas with significant humidity, and DOT 5 does not absorb water, unlike the glycol-based DOT 3/4/5.1. I guess until/unless I do the change I'll just flush the brake system regularly.

My car sat for over 20 years.

I sent my tv to ross. The cleanest one he ever worked on



If it had dot 3. It would of been toast.