how to tellthe diff between DOT 3 & DOT 5 brake fluid

FWIW. Four piston Corvette calipers ('75 and others) that sit for a period of time (over the winter) unused the pistons will usually stick when put back in use. That's with DOT 3. Going to silicone prevents it. I have silicone in such for 15 yrs and it sits during winter and no problem in spring.
 
Vics Stuff said:
...As mentioned earlier that silicone brake fluid is good for racing applications .
Vic
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It's not even very good for that, due to the very reason you've found. The DOT 5 will entrain air when cycled, which leads to the mushy pedal feel. A mushy pedal that is difficult to modulate is certainly something that is not wanted when racing. The majority of serious racers will used DOT 5.1 due to it's higher boiling points compared to DOT 3/4 and lower compressibility than DOT 5.
 
Over the last 20 or so years I found I wasn't driving my '42 much, and every so often I was finding stuck brakes on one side or the other or a gummed up master cylinder that would need to come out for rework. Lots of fun. I read somewhere that the same thing was happening with army trucks that would sit around for long periods of time and then suddenly would get fired up, until DOT 5 brake fluid was developed for them, which put an end to that (I could be wrong on that). I did the same changeover, and so far have had it in my car for over 2 years with no trouble. But the changeover was a lot of fun though, everything had to be switched, all DOT 3 stuff was thrown away and a Harley Davidson brake sender needed to get put in.
 
When I rebuilt my '40 back in the early 1980s I put dot 5 in a completely new brake system. New cylinders, new lines and hoses, and rebuilt master. I am still waiting for the first problem. Never had any leaks or soft pedal.
 
Jeff/Illinois said:
Best answer yet. How about on my neighbor's loud dumb dog that barks all night? If he croaks in two hours it's DOT 3 if it takes him all day it hasta be DOT 5:p
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I'm sure you're not seriously suggesting the intentional poisoning of a neighbor's dog are you? Even as a joke, that's not funny and has no place on the Fordbarn.
 
Kahuna said:
It's really sad to see so much mis-information here
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I agree that there is mis-information on most any forum at times.

Could you please Carify the mis-information you see on this thread ?










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I agree with Hugh in North Carolina. I completed my '46 convertible in 1990. It had NOS wheel cylinders, new hoses and lines, rebuilt master cyl. Serviced with Dot 5. No problem bleeding system ,never any leaks and always had a hard pedal. I highly recommend its use.
 
Clem, the can tells you, dot 3 comes in a dot 3 can and dot 5 comes in a dot 5 can. I hope this clears things up.Ed
 
epw1949 said:
Clem, the can tells you, dot 3 comes in a dot 3 can and dot 5 comes in a dot 5 can. I hope this clears things up.Ed
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I'm sure Clem is asking how to tell the difference when it's in your brake system
when there is NO Can around anymore. ;)








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If a person purchases a complete, well maintained vehicle, then they can ask the former owner but a lot of the old Fords tend to be kept until us car guys are beyond being able to tell a new owner what's in there. Till death do us part. That makes this a viable question.

My only response can be to recommend flushing the system and putting your own personal favorite stuff in there. That is the only true piece of mind.
 
I was asked to work on a Auburns brakes as the owner complained of leaks in the wheel cylinders he insisted on Dot 5 ,. I replaced all the cups but it still leaked .I found they had re sleeved the cylinders with stainless and the Dot 5 was leaking around the sleeve .If your replacing wheel or M/cylinders strip them down and give them a good inspection as I have found grit and sharp edges were they are drilled from the side .Ted
 
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