Hot Rods Any experience using Dot 5 brake fluid?

@milwscruffy I dig that power bleeder and made a makeshift ones years ago but don’t work that good .
I need to upgrade my bleeding procedure as the wife’s leg get sore after a few cylinders .
If you were to buy one today would you get the vacuum pump one or the same one you have?

 

Same one I have, you can control the amount of pressure and pump the system ahead with air (if it's a new system) to check for leaks before fluid goes in.

 

38bill... I am using a pressure pot so there's a learning curve there.. Also, you said "flushed the system"- let's pretend that I want to go back to DOT3..'flush it' with what?

 

Which flare tool did you buy?

 

de-natured alcohol and then some clean Dot 3 brake fluid

 

Press pedal slow even pressure, bring to top of pedal stroke lift foot off pedal slight pause, repeat. When at bottom hold, helper should crack bleeder then close, repeat

 

So, I took the car out to a show Saturday and I still don't have a "firm" pedal, but I have run into something else that might need to be known. The brake pedal linkage is adjusted to very little slack0 actually none. I adjusted all 4 brakes to snug- meaning when I spin the wheel, the tire rolls about 1/2 of a turn and then stops. I wanted all mechanical looseness out of the equation. BUT, when I press the brake pedal, it goes about 1/2 way down before the brakes start to engage. It's as if there was air in the master cylinder itself. But I had put pressure to the system thru the M/C so how could this be? Where else could a big blob of air be hiding?..

 

Been using dot 5 since 1995 in every car I've built since I don't like dot 3/4 paint removal properties. All new brake systems tho. Never a problem.

 

Can we assume the master was bench bled? It matters but I can't really get techy about why.

 

Eighteen years with Dot 5 in my avatar car, drum brakes all around. Like some have already said slow pumps on the pedal when bleeding. I use those Russell bleeders with the check ball in them, eliminates the 2nd person needed. I also flush my system with new fluid every three years. No issues with soft pedal.

Make sure you got no leaks, good hoses and a good master cylinder with no air in it. Good luck.

 

You could assume it- but it would not be true. I did not bench bleed it..

 

Oops, gotta do that.

 

If you don't have a little bit of free play in the pedal you do run the risk of blocking off the ports that allow fluid to return to the reservoir if the master pistons cannot return to their full rest position causing brake lock up.

Not getting the air out of the master cylinder before installing it can very well lead to your problem. Not every time, I have gotten lucky a few times where I could get the air purged without a bench bleed, but I don't recommend it as standard practice

 

I hear what you guys are saying, but I swear to you, I have done countless master cylinder replacements and have never bled them on the bench. Seems to me the fluid would just dribble out the back of it and it would be empty....does it not work that way?

So, can I bleed it while it is in the car or am I gonna have to remove it?

 

I’ve had good luck “bench bleeding” on the car, so you should be able to do it without removing the MC. Use the bleeder kit provided if you still have it, should only have to remove the hard lines. It’s easier off the car and on the bench, but not too hard to do it mounted.

 

Uhhhhhh, no it won’t just “dribble” out of the back…..

 

I don't understand where it would find its way out, you either plug the ports and work the air out into the reservoir through the return orifices or run short lines from the ports back into the reservoir and cycle the fluid until all the bubbles stop.

 

Now this makes sense. I was talking thru my hat, 'cause I have never done one...but running lines back into the reservoir and getting the bubbles to go away makes sense. - Thanks Nick

 

Harley Davidson used Dot 5 for many years. They only switched to Dot 4 because of the boiling point and ABS. I will run Dot 5 in my 32 when finished. Never mix any other brake fluid with Dot 5, it will clot and swell everything that is rubber in your system. We see it all the time in the Service Department.

 

I’ve used DOT 5 in 3 builds where everything was new in the brake system, no issues whatsoever. When I added 4 piston Wilwood calipers to my OT Hot Rod my helper was out of town so I purchased a vacuum bleeder, it worked slick, no pumping the pedal and dispersing air bubbles. When my helper came back he helped me manually bleed the system just to be sure, there was absolutely no air in the system…

 

Not a fan of Dot5. I worked in a specialist brake shop for some years.
Dot5 silicone seemed to cause as many problems as is solved. I well remember the jelly like goo that often came out of cylinders sent in for servicing after running on silicone.
Try to write a very short list of OE manufacturers that use it......very short.
Dot5 is known to be more compressible than conventional, so expect a 'softer' pedal.
For performance applications use Dot5.1 - low compressibility, high temperature rating, and compatible with Dot3 or 4 for top ups if necessary.
I know some have used the stuff for years without problem, but I suspect these guys just got lucky. Not a risk I would take.

 

Be careful pumping the fluid back into the reservoir because DOT5 has a tendency to hold bubbles (think very tiny bubbles) in suspension and you might introduce them right back into the system by recirculating the fluid. It's even important to not shake the DOT5 can or pour it into the MC carelessly because of the same issue. It makes DOT5 sound tedious to use but to me it's worth it. DOT5 in my 2 hot rods and my FED.

Lynn

 

Using DOT 5 on a fresh system presents its challenges. I used stainless lines and did nothing but chase leaks

 

I was ripped a new one when I pumped the pedal at a new shop while bleeding brakes, circa 1975. I have never ever done it since, it was explained to me that it introduces MORE air bubbles. Which I agree on.

Fast forward to around 2018. I replaced a leaky-ish line at the master on the Ford. My buddy that owns a successful repair shop (45 years...) was helping me bleed the fronts. Of course he starts pumping the crap out of the pedal.... I said, please humor me and not do that. He was surprised, but went along with me.

 

I use only DOT 3, go with what ya know . I flush my old car brake system every 4 years or so since it is not a DD.

 

Some food for thought........

 

What exactly is the issue with these failures? Is it leakage, or does the DOT5 destroy the internals of the switches?