Dot 5 problems

R

Royal Ryser

Well-known member
I have heard of problems with Dot 5 brake fluid, where the stop light switch would leak fluid after a period or use. It appears that seal inside the switch would start to leak and you would lose fluid.
Any of you had that problem?
 
Yep, happened to my stock '40 Ford switch; started leaking and brake lights stopped working. Brake pedal started getting spongy too. Replaced the switch and now back to synthetic DOT 3 fluid - no more problems. For me, silicone fluid wasn't all it was cracked up to be.
 
Been using Dot 5 for over 25 years. Never had a problem with it . I did replace the switch once but not because it was leaking, it burned out because I had halogen taillight bulbs and it put too much current draw on it and eventually burned it out. I bought switches from Ron Francis wiring and Harley Davidson has a good switch also. I put a relay in the brake light circuit so now all the switch does is make and break the ground on the relay.
 
I would venture to say that the HD brake switch was made to function with, or at least tolerate DOT 5 fluid. As far as I know, the current brake light switches available for our old Fords are not as resistant to the ravages of DOT 5 fluid.
 
Everything else aside, DOT-5 is not the way to go. It doesn't work with anti-lock brakes, so it will become more and more difficult (and expensive) to procure in the future. I had it in my '68 Corvette 25 years ago, and once I got it in, it was fine. Getting it in however, was a huge problem, big enough that I vowed never to use it again. It was used mainly by the military, and if they decide against it, good luck in finding any.
 
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I’ve got three 40 Fords with it in there with no problems . Maybe I’m just lucky. I will say that before I put Dot 5 in the brake system, everything has been replaced . Steel lines, hoses , wheel cylinders, master cylinder.
 
I use a switch from Harley Davidson that looks just like the early Ford switch but is supposed to be designed for Dot 5? Can't find the part number. Forgot, the Harley switch's have spade not bullet terminals
 
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The HD switches were Hecho in Mexico last time I purchased one. That was 20 years ago
I'd buy DOT 5 that was a purple color and in 6 months it turns yellow. I quit using it a long time ago. At least DOT 3 is pretty much the same color when I flush the system every two years or so.
 
Got Dot 5 in two cars. never had a problem with it. Have used it on one car for over 20 years (no not the same fluid for 20 years). The other car over 10 years.
 
Go back and read my previous post. The problem with DOT-5 is not that it doesn't work well (given that it is difficult to bleed properly). The problem with it is that it is incompatible with ABS systems and is not used as OEM by any automobile manufacturers.

This means that there will be availability and cost problems down the road. I have decided that I don't want to deal with these.
 
tubman said:
Go back and read my previous post. The problem with DOT-5 is not that it doesn't work well (given that it is difficult to bleed properly). The problem with it is that it is incompatible with ABS systems and is not used as OEM by any automobile manufacturers.

This means that there will be availability and cost problems down the road. I have decided that I don't want to deal with these.
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I understand, but none of my Fords have ABS . So far availability hasn’t been a problem. It’s working for me so far.
 
Years ago I worked in an independent shop in Flagstaff, AZ. Boss had an Austin-Healy (Chevy engine and trans) that he put DOT 5 in. Could not get rid of a spongy pedal. He finally learned that DOT 5 doesn't work at high altitude (I don't recall the theory behind this). anyway, back to DOT 3 and all was well.
 
I had a Harley with dot 5 lose rear brake in the Rockies due to air in the system.
Bled it and it was fine. air must have been entrapped in the system.

I have Dot 3 in my old cars and my newer cars came with it.

John
 
WBrown said:
Anyone out there with DOT 4 experience?
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Interchangeable with DOT-3. It does have a higher boiling point. I always try to use DOT-4 if I can find it, but that is becoming increasingly difficult lately for some reason.:confused:
 
Been using DOT 5 for years with no problems. I always use a mechanical switch.
 
I had problems with mine years ago and changed to one from Ron Francis Wireworks designed for the DOT 5 fluid. No more problems.

Charlie Stephens
 
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