DOT 5 Brake Fluid

[Champ51]

Both of my SCCA showroom stock race cars were switched to DOT5 and never had mushy pedals, and back then, I wasn't particularly careful about getting all the DOT3 out first, but we were positive to get ALL the air out. On subsequent antique cars, I've learned to flush well or end up with rust in the odd places where some of the old brake fluid remained.

DOT 5 means one less maintenance task per year.

[bsrosell]

I am just nearing the brake-replacement (ALL new components and lines and Turner M/C); but my brake switch (57 Golden Hawk) is NOS.
So from what I'm hearing that old rubber won't hold up with DOT 5? It will not get driven that much (Minnesota winters :-( ) so I want the most rust protection for the cylinders as possible (have Cunifer lines, so no issue there)

Is the Harley brake switch an exact swap out? Are they all the same (just stop at a Harley dealer, conveniently across the street from work) and ask for a brake switch?

Sad not to use the NOS one, I get a kick out as much original Stude hardware as I can get for her.. but, a small sacrifice for better longevity and not having to hassle under the floor "cleaning up" before removing the Turner M/C cover to refill or check on fluid. That is sure one improvement since '57, having the brake reservoir on the fire-wall. Considered Bob Johnstone's conversion to run a tube up there for it, but think I'll go DOT 5 and minimize opening the sealed system instead.

[sweetolbob]

I've continued to wonder as I read posts about Dot 5 why that fluid would cause brake switch failure when Silicone fluids are generally thought of as some of the least aggressive and solvent neutral available. I also know that Dot 3/4 will do an excellent job of removing paint from a firewall if left in contact with paint for any length of time.

Here's some reading on a couple of possible reasons. I won't argue that folks have failure of switches with Dot 5 but It's difficult for me to understand based on swelling of the rubber. I've used Dot 5 since back in the 80's or so because I had access to it in the Dow Corning employees store and have never found a failed switch nor swollen component in any of my vehicles. The oldest was a 39 Ford Coupe.

http://www.britcycle.com/Manuals/DOT5.htm

http://www.sw-em.com/hydraulic%20brake%20light%20switches%20notes.htm

Happy reading, Bob

[jclary]

I've continued to wonder as I read posts about Dot 5 why that fluid would cause brake switch failure when Silicone fluids are generally thought of as some of the least aggressive and solvent neutral available. I also know that Dot 3/4 will do an excellent job of removing paint from a firewall if left in contact with paint for any length of time.

Here's some reading on a couple of possible reasons. I won't argue that folks have failure of switches with Dot 5 but It's difficult for me to understand based on swelling of the rubber. I've used Dot 5 since back in the 80's or so because I had access to it in the Dow Corning employees store and have never found a failed switch nor swollen component in any of my vehicles. The oldest was a 39 Ford Coupe.

http://www.britcycle.com/Manuals/DOT5.htm

http://www.sw-em.com/hydraulic%20brake%20light%20switches%20notes.htm

Happy reading, Bob

Here is a link to a thread I posted on November, 2015, on the subject.

http://forum.studebakerdriversclub.com/showthread.php?92221-Investigating-the-failure-of-brake-switch-with-DOT-5-brake-fluid-(silicone)&highlight=brake+light+switch

In this thread, I cut a failed switch open to find corroded contacts. Otherwise, the switch showed no sign of leakage. In fact, the "dry" side of the switch was dry, and the only problem was a tiny amount of non-conductive corrosion had formed at the contacts.

[JoeHall]

Over the years, I've had two Studes, prior owners had converted to DOT 5. The brake light switch was a problem on both, and a Harley switch was not the answer. Biggest difference between a Harley switch and a FLAPS' switch is price, with Harley costing about five times more. Even on the 1986 Harley I've owned for 10-12 years now, with DOT 5, the switch still needs changing every 1-2 years. I used to buy them from Harley, but now just buy them from FLAPS.

On one car, the guy I sold it to inadvertently put DOT 3 in it. So I later helped him convert it back to DOT 3. The other car, I lost track of, but no problems other than the brake light switch while i had it.

Not sure DOT 5 is a cure for anything, but it can bring on headaches, with the switch, or if mixed with DOT 3 or 4. As for changing brake fluid, only when a brake problem occurs, when I usually wind up rotating the fluid in the course of the repair. Never had a problem due to worn out fluid.

[karterfred88]

Something Mike just noted struck a nerve with me. Although it's not Studebaker related my daily driver is a 2004 with a hydraulic clutch. Tuesday, while waiting for the light to turn green I tried to put it into first & it wouldn't let me. I shut the engine off & put it in gear but when I tried to start it, it moved forward like the clutch was still slightly engaged, so I was towed home. The next day I tried it & everything worked perfectly. Perhaps the fluid is old & heat effected it to do that?

2004 what? How many miles? More likely it's a sign the slave is getting ready to fail. If it's part of the TO bearing assembly, as most are, be prepared to buy a new clutch, since the trans/transaxle will need to be removed to replace it. My 2005 PT cruiser started doing that at 75,000, nursed it to 85,000 before it needed to be pumped up like a bad master to get the clutch to disengage. If it happens once, best to get ready to replace it.

[Stan.Gundry]

Of all the people who have responded, I apparently have the longest history with DOT 5 in a completely new system--34 years. I have never flushed it, though I did have to add some when I switched to the Turner disc system years ago (I was one of the earliest to switch) and again when I installed a dual M/C. I was careful not to not shake the fluid (it takes forever for the bubbles to rise the top) and I bench bled the M/C. In 34 years I have had no leaks, no rust, no spongy pedal. However, the pressure switches failed every 6-8 months, even the Dick Francis one and the H-D ones. So I finally switched to a mechanical one. With a new system, DOT 5 and a mechanical switch are the only way to go

[2moredoors]

I put DOT 5 in my '55. No problems except for the hill holder. Did not clean it out and the rubber deteriorated. I have since rebuilt and ready to reinstall. I have replaced the brake light once since I changed over in 2008-09. I also put it in my '37 Olds and again did not clean up the master cylinder. Same thing with the rubber and then I rebuilt the m/c. I have also changed the brake light sender in this car. In each case I put in new wheel cylinders and in the '55 new M/C. My error for not going through the system completely. For my other two studes I use dot 3 and make sure it stays clean.

[jts359]

WE put silicone fluid in our 64 Daytona 30 years ago when I did a total resto on it ., I decided to go thru the entire system this week , The only odd thing I found was the wheel cylinder pistons had some black sticky residue on them , It cleaned right off with brake cleaner. I do have problems with the switches but if you put regular brake fluid in the switch before installing it they last longer ,, The reason for going thru the brakes , Bad rear axle seals and 30 years is a long time Ed

[bsrosell]

OK, the last few posts make me think "go ahead and use the NOS Stude brake switch", as none of them seem to last forever.

Now, this being my first Stude (and first brake switch of this type, unless my '63 Chev had one in college and I never knew 'cause it never failed", HOW do they fail and how do you know? My guess is they start to weep a bit, and increases the longer you don't take action?

WITH DOT5, I would also assume it is easier to get those three brake lines off, since there should be no corrosion? (my originals will NOT come apart, I'd break 'em if I kept trying, but replacing whole thing so stopped trying; just leaving them in place as a pattern for the new lines before I rip them out and sandblast and paint the chassis.)

I'd rather swap out one switch than four wheel cylinders and a master cylinder, or worse yet have a failure. Mine WILL sit a lot, and through Minnesota's cycle of -30F to 100F, so water condensation is almost a certainty over time.

I can't remember, it's been so long since I took off the front end and fenders; how bad is it getting AT that brake switch? Can you reach it from the top over the fender, or is it a messy 'laying under the car with brake fluid in your face' job?

What is the mechanical switch replacement? How does that work and where does it mount? I'm really surprised DOT 5 would make these switches fail within a year (at least NEW switches). The older rubber in my NOS switch, ok, I can understand that might not hold up to modern automotive chemicals..... Strange.

[2moredoors]

In my case the there is no leakage at the switch. It just fails so the brake light does not illuminate. This has happened on both cars I have equipped with DOT5. As suggested the type used by Harley may be the answer.

[jclary]

It has been my experience, that when my standard old style brake switches failed, there was zero leakage. They just simply stopped working. The very first one that ever failed for me, was back in about 1964. I was a teenager. The way I found out it had quit working, was when a patrolman pulled me over and told me. He wrote me a warning ticket, told me to get it fixed, and sent me on my way. The car was either a Buick or Pontiac.

I've had them to fail on a Studebaker. Of course, it is no fault of Studebaker, because the switches were not made by them. However, I have Studebaker vehicles I have owned for decades. Over that much time, corrosion will happen and the switch will fail.


The corrosion that failed, on this switch, took years to form. When I cut it open, the side that is supposed to be dry, was dry. There was no leakage, but, you can see the corrosion. The switch came out of a car with DOT 5 fluid. I have had them fail with the old style fluid too. Although, for some reason, they seem to fail sooner with DOT 5. I do believe, that if you convert to DOT 5, you will likely have less trouble with your system. Converting to a durable, dependable, electric brake switch would be a bonus with the change over to DOT 5. (I'm still using the old style switches) If someone will post a good switch, easy to install, I might give it a serious look. I'm still not convinced that the current failures are the fault of the brake fluids, or due to cheaper construction.

[bsrosell]

thanks John, never seen one apart before, the corrosion for electrical performance makes sense; I'm focused on leaking fluid as I starting collecting my tubing and fittings. :-)

[JLB]

I've had Dot 5 in my Studebaker for 25+ years and there have been no issues, other than the brake light switch that has been discussed here. I converted to a mechanical brake light switch about 15 years ago, and eliminated that problem. I also have a '33 Ford 3 Window Coupe that has this same switch. Converting it to a mechanical switch is not in the cards, due to its location. It has failed many times in the past and I've tried all of the switches previously described in this thread. I've not found one that is better than the other. What I have done that has greatly increased the life of the switch, is to wire it through a relay. I have not changed the switch since changing the wiring through a relay several years ago. Your results may be different, but for the minor cost of a relay, it might be worth giving it a try.
John

[jclary]

I've had Dot 5 in my Studebaker for 25+ years and there have been no issues, other than the brake light switch that has been discussed here. I converted to a mechanical brake light switch about 15 years ago, and eliminated that problem. I also have a '33 Ford 3 Window Coupe that has this same switch. Converting it to a mechanical switch is not in the cards, due to its location. It has failed many times in the past and I've tried all of the switches previously described in this thread. I've not found one that is better than the other. What I have done that has greatly increased the life of the switch, is to wire it through a relay. I have not changed the switch since changing the wiring through a relay several years ago. Your results may be different, but for the minor cost of a relay, it might be worth giving it a try.
John

I had not given the "relay" option a thought. Since the current don't seem as big a deal as it would with a big draw like a horn or headlight circuit. However, if you think about the brake light switch, and the closeness of the contacts, being a constant "live" hot wire so close to the ground wire...the potential for corrosion is always there. With a relay, the corrosion potential for the brake light switch to corrode is much reduced. Perhaps the rest of us should consider this.