What DOT type brake fluid are you using?

[Cpt.Fred]

i'm really sorry that i'm flooding the forum with my strange questions at the moment,

but there's a race tomorrow where i want to go to on my own wheel set, and i have to do a lot of work untill then...

so i am not only asking for kicks, but i'm really doing the work and your knowledge won't be wasted, i just fight

different frontiers here at the moment as you can see from my various posts over the last few weeks.

my problem is, that on my brake system everything is new, but 2 days ago

it started the old game again: pressure point dropping, obviously air in the lines.

i am using DOT 4 brake fluid on the car, can that be a problem, is it too agressive?

i can't find a leak though... but i have think about every possibility.

it's funny, this is the most simple brake system i ever worked on, and it keeps on fooling me, i don't get it:confused:

Edited June 24, 2010 by Cpt.Fred

[james curl]

If you have access to the end cap from an original master cylinder you can remove it and use it in place of the filler cap. Install a plug in one outlet and a hose bib in the other, get a small garden sprayer and remove the wand and fasten the hose to the hose bib, now add a quart of brake fluid to the sprayer and pump up to about 20 lbs. Now go and bleed all of the brake cylinders in the sequence as stated in the manual until you have no more bubbles in the fluid. Now you should have a firm pedal. You are still running the original master cylinder in its stock location are you not?

[Cpt.Fred]

yes i am.

i used the system you described on my previos car, too, it worked great.

i inserted an old tire valve into the cap, filled the reservoir and compressed it with a foot pump.

my actual setup is the original master cyl (brand new) and the 4 original wheel cyls (also brand new).

only adition i made you can see on this photo:

a glass reservoir up on the firewall for more comfort and control.

only problem is, i don't know if it's a good idea to put it under pressure...

[p10plymouth]

When I did my 40 Plymouth I put all new master lines and wheel cyl, when I install new parts I just use a hand oil pump fill it with brake fluild,.... Then just fill up each wheel cyl then If nessary (becuase of news lines ) do the same pre fill them up ...

Then I put a hose on each cyl and open the cyl. and have someone slowly pump untill I see fluild only...

I had one guy still had trouble so I told him to lift the frt end up around 1.5 to 2 ft and do this procedure..and his problems where solved (might try that trick)

Any chance you can tell me where you got thatbrake fluild bottle ... I've been wanting one of those item s for my car... or know where I can get a vintage glass one thanks DANiel

[mrspeedyt]

i use dot 3. until lately no problems.... now i guess i have a leak somewhere....

[55 Fargo]

I am using Dot 5 silicone, but I have a completely new brake system, lines hoses mc and wheel cyls.

I am happy with this stuff, especially for long winter storage...........fred

[P-12 Tommy]

Dot 3

Tom

[desoto1939]

Capt,

After you have bleed the brakes and removed the air do you still have a soft brake pedal?

I am assuming that you put on new brake linings. Did you touch the eccentric cams at all. It sounds as if you still need to adjust the shoes again. Even with the use of the Miller tool or the Ammco brake tool to set the arc on the shoes this still causes the system to have a soft pedal.

I have done many brakes jobs on these cars. Now jack up the front end. Perform a minor adjustment onthe brake system. Pull the top cam and lock the wheel. Then backoff the shoe until you have a slight drag on the wheel when you spin it. Then do the rear show onthe same side. You should have a slight drag. Do the other side in the same manner. Depress the brake pedal this is need to set the shoes. The pedal should be firmer. You then should do the rears in the same manner. After this has been done then you should have a very firm pedal. If you played witht he eccentrics then the shoes will not be arched correctly and this will also cause you to have a soft pedal. Please refer to the tech article that I did on the Ammco and the Miller Brake tool, this might help you.

Plese repost your results so we can help solve your issue.

The Dot 4 is not your problem Dot 4 was the stepup from Dot 3 and has a better boiling temp. If you convert to Dot 5 full syntetic then you need to completly flush your system with denatured Alcohol and rebuld the entire rubber parts includingthe lines and cups. DO NOT, DO NOT Mix dot3 or Dot4 with Dot 5. I have DOT 5 in my 39 Desoto for 23 years.

Rich HArtung

Desoto1939@aol.com

[Cpt.Fred]

thanks guys.

i am very, very frustrated at the moment.

i tried to bleed the system four or five times, there was air in there and the

pedal got a little firmer.

but still, after a few minutes i could push the pedal down to the floorboards by hand.

second push: it pumped up, there was pressure, about 2 1/2" from the floor.

when i first did the brakes a few weeks ago, i adjusted the pressure point to be at a very high position,

so that i did not have to push the pedal to far.

this tended to lock the brakes after a few miles, very slowly.

i adjusted the pedal at a lower point and that was it, no problems anymore.

afterwards a few weeks of happy driving.

i pulled the drums on the front and noticed the wheel cyl on the right side (10 weeks, 12 weeks old, brandnew, andy b. reproduction)

had a small leak on the 1 3/8" diameter side. i pulled it, took it apart, changed the seal, bleeded again.

still, i can pump up the pedal.

here's what i will do: i'll pull the rear drums (ooooh, how i longed for that)

and check the wheel cyls (all new as well), then bleed the system with the front lifted, like you told me.

the wear marks on the linings were really good, i was very happy with the braking effect (230pounds on both sides on the test bench).

i did readjust the wheels to have a small drag before and after bleeding.

daniel, i bought the glas from some belgian dealer, it is a reproduction of the brake reservoir of some prewar citroen.

i might find the adress, if you really want, but i can't say much good about the quality. glas is not good, seal is cheap and leaking,

the whole thing was really expensive. next time i'll build one my own out of an old jar.

[p10plymouth]

I forgot to mention .... Make sure you have a little free play on the push rod by the master Cly.

otherwise "if" you get a pedal do the 10 second test pump up the brakes till a good pedal then for ten seconds "hold the pedal down" and lightly pull back and push down .. What you are trying to see if the master "bleeds down " making it show you have a bad master Cly..

Thanks for letting me know about the glass jar ..Something about the French glass jars I saw a used on from the 50's I have my eye on...Thanks again DANiel

[JBNeal]

I replaced all brake lines and sleeved the master & wheel cylinders, so I opted for the DOT 5 in the '48 1/2 ton back in '99...the brakes seem to be holding up with consistent firm pedal. If it weren't for a bad flare on one of my lines, I probably would never need to top off the master cylinder every few months. I repeated this with the '49 1 ton in '04 with similar results.

[Cpt.Fred]

ok, i took everything apart on early friday morning, pulled the rear drums, checked all 4 wheel cyls,

changed another seal on the front driver's side.

bleeded the system.

still no pressure on the pedal.

then i had the idea to do the same thing i did when i assembled everything for the first time:

since the piston in the repro master cyl is different from the original, i had to adjust the lenght of the push rod to get decent pressure.

i did this, and there i was, everything alright, firm pedal, no pumping up.

funny thing (or not funny at all) is, my other old problem now came back, too.

after driving a few miles in city traffic and using the brake a couple of times,

the pressure point starts moving up slowly, ending up with locked brakes after a while!

i have to take out the service lid in the foot panel and readjust the push rod, before i can go on driving.

i realised over the weekend that this is heat related, too. and, after the car sits a while, pressure goes back down again.

i read something on here about this little hole in the bottom of the master cyl,

maybe i should have a look at it...