Brake Fluid Change

[Go Fleiter]

Dot 5 is Silicone class (color must be puple), the others are alcohol classs. Dot 5.2 is NOT silicone too.
You must deciede because the can?t be mixed. Rubber gaskets can be darnaged   with fatal resullts by mixing.
System must be completely washed out when changing fluid to the other class.Old rubber has to be changed than too!
So, whatever is in, take the same (fresh) again!

Maybe old silicone looses its color: it feels "greasy" and will not give results in Your repair shop?s waterabsorption test (for alcohols)

Alcoholes will absorb humidity and have to be changed regularly, when water content gets too high.
Silicone will not take water and stay constant in performance.
On the other hand, when humidity stays unabsorbed, rust may occur at contact places.
Your coast guard and Your tank forces in Germany used silicone due to "put in and forget", even if stored for years.

You find Info at DOT pages!
Greetings from Germany! Go

[1939P8]

Dennis:
You were right - got the drums off and completely rebuilt the brakes on rear.  Planning to replace the brake lines along the rear axle as well.  My next question is based on all of these postings, do you recommend DOT 3 or DOT 5 as I refill the system.  Seems like the majority favor DOT 5.?

[CHS]

JohnRFFain, I could not agree more about DOT5 brake fluid. I used to have to replace my wheel cylinder every few years while I used DOT3 brake fluid. Seems they always started to lead and rust. It has been 3 years since I changed to DOT5 and have never had a problem.

[36 Ply]

Bob Drown's photos (below) and advice and encouragement, helped me get the rear drums off my '36 when the brake pedal was pulsating a while back. It turned out that the bonded lining had come loose from the left rear brake shoe, and was bunched up at the bottom of the drum.

As stated by others, it takes a while, but the drums will eventually come off, and the instructions about the castellated nut are VERY important.

Pat O'Connor

[johnRFain29U]

Herb is right about Dot 5.  I put it in my 29 Plymouth 35 years ago when I installed new brake cylinders.  The car was not used much while I was in the Army.  I overhauled the brakes 5 years ago and just as he mentions, water had settled in the brake cylinders and rusted them.  I had them sleeved in brass by White Post Restorations.  They did an excellent job - and replaced all the parts.  However, I still use Dot 5.  Why?  Because it will not harm paint.

[captbrian41]

Gary, I pulled the rear drums on my '41 Business Coupe 2 years ago and ditto to everything Bob says and don't get disheartened cause it took me days to get mine off. Put the heavy duty puller on and spent days putting a load on the puller, a little bit every day, hitting the tensioner with a small sledge and shooting PBBlaster into the end of the axle. Walked out one morning to hit the tensioner again and lo and behold the drum had popped during the night and was against the castle nut  Set up and did the other side and the same proceedure, all in all close to a week of loading up the puller every day but well worth the effort as I finally rebuilt the rear wheel cyls. and now have brakes that stop the car. Incidently a benefit was draining all the fluid while rebuilding the rears, running some new fluid through the lines and then installing the rebuilt cylinders and bleeding the system. Made a pressure bleeder out of a small garden sprayer and really helped in the bleeding process. Used Dot 3 by the way as the fluid. You will find that the shaft and drum are a tapered fit with a key and that I think is what makes it so hard to come off after having been on for years. Some suggestions were after cleaning the tapers to reinstall the drums dry but I used a thin coat of never seize on them in the hopes of being able to take them off again easily in the future if the need arises. And again caution, leave that castle nut on while tensioning the puller. If it pops off while you're in front of it you will get hurt. The PSI developed by the puller is incredible. I also avoided hitting the end of the puller so as not to damage the shaft or bearings in the pumpkin. Tension just the puller and eventually it will pop. There was a lot of info on here about the whole process and you may be able to look it up.
captbrian41

[RC Drown]

Gary,

You will surely need a drum puller to get the rear drums off, just make sure that you put the castle nut on backward and even with the threads so that you don't ruin the threads, plus when the castle nut is on and the drum does come loose, it doesn't go flying off and hurt you.

You also will need a large hammer, ie, sledge hammer to hit the drum puller with, don't get discouraged as they are darn hard to come off.  You will need a heavy duty drum puller

I have attached a couple of photos, hopefully they will helpl

[1939P8]

Dennis:  which model of P-8 do you have.  I have the 2 door business coupe, and may have some questions for you if you have the same model.  For one, when you lose fluid, do your brakes lock up?  The second question I have is how to get the brake drums off.  Seems like I may have to resort to a puller after trying everything else.  Gary

[Don St Peter]

About 5 years ago I completely rebuilt my 40 Ply. brakes and went to DOT 5. 2 years ago, for reasons I won't go into, I switched to DOT 3 after flushing the system with alcohol. I have had no problems to date. I live in Fl. and drive the car daily.
Don

[Herb]

If you convert to DOT5 you will not be able to go back unless you replace ALL rubber parts in your system.  The silicone impregnates all rubber parts and turns to mud in your system when mixed with all other DOT fluids.  NO it cannot be washed out with alcohol, all that will do is damage the rubber parts leading to premature system failure.  Check with any brake suppler and you will be told you void warranty's using DOT5.   There is NO reason to go to DOT5 unless your car is subjected to weather extremes such as subarctic to aired and back.  Or your using your car in NASCAR style racing.  DOT4 is compatible with DOT3 and will stand up to any type of driving any street or occasional race car will experience.  Brake fluid, like Transmission fluid should be changed every 30.000 miles or so, but they are out of sight and out of mind till problems arise.  By then it's to late!  You will hear stories that DOT5 is a fix all fluid, perpetuated by people trying to justify in their own minds the $$$ they spent in the conversion.  Save your money and completely bleed your system with DOT4.  On other sites people claim just adding DOT5 fixed bad boosters, worn out wheel cylinders, defective master cylinders, rusted brake lines, worn pads & shoes and now their cars stop like a 2011 300C, again in there own minds!  O, Ya, the moisture argument, BS, Yes DOT3/4 absorbs moisture, when you change your fluid it's gone!!  With DOT5 the moisture sinks to the lowest point in your system and cant be bleed out.  That is were you get rusted wheel cylinders & calipers not to mention the moisture turning to steam when subjected to high heat braking.  Just my $0.02 worth from years of using DOT5.  I am sure I will have the DOT5ers screaming foul so all I can say is proceed with caution and think what it might cost you $$ to reverse your actions.

[Go Fleiter]

DOT 5 is silicone and purple,
DOT 5.1 is not Silicone - I  learned it the hard way...
All the lower others are not silicone.

Greetings! Go

[Lew]

The posts are correct; one way to check what fluid you currently have in the system is to test it on a non - visible or old painted surface. I believe the older DOT fluids were Glycol based and will lift the paint. The newer ones ares silicone based as noted.

[JimCno]

I believe there is an issue with mixing the two fluids. I think the proper way to change fluids is to flush out the old fluid, replace all the internal rubber, then put in the new fluid.

It seems like a lot of work for very little results to me.

[Lindsay McConnell]

I'm with TodFitch. Personally, I would stick with DOT3.
Also, WhitePost Restorations, in VA. will tell you to do the same after they re-build the original brake parts.
My two cents worth.

[TodFitch]

The issues I have heard about using DOT5 is in converting a system. Seems like it is safest to flush and refill with what ever is in there. Most likely DOT3. But you probably want to know how to tell. DOT5 is purple and doesn't smell like old fashioned brake fluid.

[DENNIS P NOLAN]

Once again, I need your help. I have a '39 P-8 and I want to change/drain the brake fluid. I don't know what's in there, or how long it's been in there.
I have read previous postings and the best brake fluid is:-______________(your advice inserted here).
I have replaced the master cylinder. I have hoping that I will have some help in this and this is the best time of the year to work out in the garage-as there are no winters here (Phoenix,Az.)
I would appreciate a brief run down to get all of whatever is in those lines - out. This is a great forum-
Thanks ahead of time-
Dennis