Technical brake fluid, rebuild kits, m/c woes anew?

Ok, once you say to yourself you fucked up. Twice you scratch a raw spot in your head wondering if you did it again. 3 times? Who else is having master cylinders leak out without notice or reason just from sitting? Used to be if you had silicone fluid long term storage did cause shit to leak out sometimes. No, not an invitation to discuss silicone vs regular. Having stomped on old shit for a lifetime that still held fluid after nearly a decade that doesn't seem to be the case. I notice all fluids now say "synthetic" regardless if it's house brand or some premium company. I rebuilt 2 in a row with good ol Raybestos parts, got perfect results, couldn't be happier. Weeks later, that really loud "WTF!" y'all heard from the midwest was me. Upon disassembly I find nothing wrong. The inner finish is probably 400, and no I didn't do a scientific RMS test, it's nice and smooth and clean. I'm of the mind that something has changed. Part of the fluid retention was how it kept the rubbers swollen just enough to work right but not fail.

I still have more to learn about "synthetic" brake fluid vs the good old destructive shit from days gone by. What woes have any of you experienced? Is the material in the soft parts now different to work with newer fluid? I'd hate to have to drain my brakes when I park the car for the winter That doesn't seem right. As to my level of sanity, I'm currently the caretaker of 47 Caddy conv (for sale BTW ) and it has the same old fluid in it from over can't-remember-how-long and I serviced this car off and on for over 25 years. No issues. Spill it (no pun intended), who's having brake fluid/master cylinder issues? What changed? Did I use the wrong finger to scratch my ass?

Signed,

frustrated in Michigan

 

My guess would be the quality of the rubber parts, which very likely don't come from here. Years ago, I started buying $1 wheel & master cylinder kits at yard sales & swap meets. As long as they're name brand, they're still good.

 

I haven't noticed it. But then I also didn't notice that Dot 3 fluid is now synthetic.

I've only had one mystery leaking brake system recently, and the car was a total mess, and so I just added fluid every day on my trip and it was fine. I don't know where it went. I doubt it had anything to do with the fluid, more likely the m/c was leaking. No sinking pedal symptom, either.

 

When I put my 40 coupe together I used a new remote fill mc from Speedway. After setting with little use while I slowly got it driveable I noticed it leaking. Since it was a couple of years old at that point I bought another new one just like it. After awhile it started leaking. I was discussing it with a friend who has a repair shop and he said that he has better luck with rebuilt mc’s over new. So I went to a local parts store and bought a rebuilt, been on there many years, no leaks.

 

The way I heard it, brake fluid has always been synthetic but it sounds good from a marketing standpoint, so that's what gets put on the label now.

See also: "Organic".

 

I new a bloke that used to drink brake fluid. We begged him to give it up. He said he did not have a problem and could stop anytime he wanted.

Happy new year.

 

Dot 4 is what we use at work. Seems to last and not leak.

 

I’m with Truck64, I don’t believe that the actual fluid has changed, I think the marketing rocket scientists just added that expensive, magic word “synthetic”. People who don’t know any better, get all warm and fuzzy with car fluids that are “synthetic”.
We have had the same problem at work with two particular trucks. These are medium duties with hydraulic drum rear brakes with discs in the front. (Those of you who are in the know of medium duties know who built these trucks, not bashing any manufacturers .) The system is made by Lucas Girling. These systems have been known for leaks, but in the last 6 weeks, these two trucks have each received 3 sets of wheel cylinders and expanders. All under warranty. We finally switched venders and are trying Meritor brand reman cylinders. I’ve worked on these systems for 25 years, done a few hundred and never had these issues. Ether the brake parts we are now getting have really shitty rubber inside or the cores are worn out after so many rebuilds. I really don’t know, but feel your pain. Please let us know how this plays out. Thanks,
Andy


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Wonder if going to the expense of having the cylinders sleeved would be worth it ?

 

check all the threads about speedway's sleeved cylinders leaking

 

The kick in the dick was that we stomped on this thing regularly just to check. Probably got stepped on a hundred times if it got once. Just accepted it was all good. Few weeks later, leaked out. The kit was a Raybestos and it actually looked a few years old. Not the kool antique old but enough to create that sense of (now false) security. And yes, if I solve this case Nick Charles and I will present the facts. Only the really old guys know who that is...

 

Yep...always rebuilt mine with old NOS kits cause no one had repair kits for a Studebaker. Also wonder if Raybestos newer kits are made somewhere besides the states ?

 

I don't know what the problem is, I've rebuilt cylinders and masters for years, no problems, just the last 3 to 5 yrs I've had leakers, same thing as the posts above, nothing looked to be wrong, other than a little rust on the cylinders past the cups, and if I bought new cylinders or masters most of the time they leaked as soon as I put them on, I've found on several masters from NAPA that the threads are not cut correctly and the tube nut runs right to the hex for the wrench, I bought a master from an army vender and right off the bat the threaded fitting leaked, he sent me another and it also leaked, he got a little upset with me when I told him they were shitty china junk.
The fix I've been doing is send orginals out and have them stainless sleeved, I just did one on a Model A that had been converted to 39 Ford with step cylinders, those and a master were 600 $, been one there for a year and no problem.
Another case in point, I didn't want to wait for a 2 week turn around on a couple Dodge wheel cylinders, the ones I had were pitted, got two from NAPA one from china one from mexico I installed the right side then the left side and hooked the return spring and the right side was already leaking from what fluid was in the cross over line tuns out there was a big scar in the bottom of the mexican cylinder, I sent the other two out to get sleeved.

 

So isn't all brake fluid synthetic I don't think there is a brake fluid tree or plant. I understand synthetic oil because it is not made from petroleum.

 

Just keep that damn dog quiet.... LOL

 

Sure it is.

 

at work
The last 3-4 years have had terrible issues with aftermarket brake parts leaking prematurely ( wheel cylinders, masters , etc )
I think the rubber quality has gone down on new stuff or the machines parts have shittier tolerances . Even buying oem can be a crap
Shoot.

Raymond reach trucks used girling master cylinders from oem about 3 years ago there was such an issue with them leaking as girling “ changed manufacturing plants” that you could not buy a master aftermarket or oem for about 4 months !!!
I don’t recall off the top of my head who’s making them now, but quality is better.

maybe it’s like what @31Vicky with a hemi said the fluid is getting “smart “

 

As I look fwd to a better 12 months my thoughts drift into solving these nearly "never before" gigs. Sleeving shouldn't be the problem or issue. No rust or pits, good finish. So, the finish. Smoother? Rougher to create a seal like piston rings? My overall WTF tends to drift into the soft parts used. Seems the only logical change that might increase manufacturing profits but in the end will kill the product because it just doesn't work now. Like newer piston rings which break in right away, should I damn near polish the bore? Or, should I finish to just what the stone makes which has been the standard over the history of the job? While I resent the need to reinvent a basic task I may have to experiment. Asta will help...

 

There's a Thin Man marathon today on the Movies Channel


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"Song Of The Thin Man" gets into the hep cat lingo, and it's scary how much I knew. I thought of our HAMB cats n kittens, go figure.

 

I stand corrected Back in the day I had a customer looking for a high temp grease because the machine ran at 530 degrees. The suppliers engineer said you will need to go with a synthetic one without petroleum because the boiling point of petroleum is less than 400 degrees. So is any oil with additives a synthetic or at what point does it qualify as a synthetic.

 

I've seen some problems with very premature leaks in new master cylinders. Brand name stuff, Raybestos, NAPA branded products all made offshore now. Price point seems way more important than quality by the looks of the end results.

I had to buy 3 master cylinders before I found one I was confident enough to install on a customers car (mid 60's GM with single pot M/C). Other than a tied up car and a concerned owner, the part I found most interesting was the labeling of the offending master cylinder(s). What very much appeared to be the same part in the same box through 2 different suppliers, only real change was the label on the box. Both companies used their own brand name on the label, and one company just put their label over the existing label on the box. You could clearly read the label underneath and the country of origin changed from one label to another ??

With new wheel cylinders I now take them apart and inspect assembly and part quality. It's yet to be a problem but if / when it is I plan on catching it before I install it.

 

This would be a good time for that oil guy here to weigh in.

Synthetics are derived from conventional oil base stocks. They gotta start with somethin'. Some kind of magic mumbo jumbo jiggery-pokery chemical treatment that changes the molecular structure in to longer chains or shorter chains, and I don't know what all.

Then, a miracle happens. Wala! Synthetic Oil. They package it, ship it, and charge about 6 bucks a quart probably. It is good stuff, it flows like water below zero, and provides good engine protection when regular motor oil would be charred cinders. I've never needed that.

 

thread drift, but i noticed on my last trip for oil ALL the valvolene says "synthetic blend". there was no real oil. is that the future?

 

I bought a new wheel cylinder a while ago. 3 days after the install, it started to leak. The parts store didn't have a replacement in stock and it was suppose to be a week out before one came in. Out of frustration, I pulled it apart. The inside bore felt like a set of railroad tracks inside. I honed it out to smooth with my wheel cylinder hone and reassembled it using the same parts. No more leaks.

The machining on this new stuff isn't anywhere as good as it used to be. I don't believe the quality of the rubber available today is anywhere near as good as it was even 5 years ago either. The two combined don't add up to happy.

If I was smart, I'd probably pull apart all the "new" stuff and look inside before I installed it, but unfortunately, I'm not that smart, or I'm too lazy, or a bit of both. I have reached a point that if I get a leak in anything that is "new" in a brake system, I will pull it apart and have a look inside before I'm going to install a replacement part. The saddest part of the whole deal is, many of these old housings are getting in such bad shape that even a poorly machined new housing that can be fixed, is better then rebuilding the old part.

Just another thing that falls under the category of "New no longer means its good." Gene

 

Gene, NEW= Never Ever Worked


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Today I plan to rehone the inner bore to as smooth a finish as can reasonbly be done. After assembly I'll "break in" the moving parts with fluid as the lube for several strokes, perhaps even over a hundred. Then a bench bleed, plug it, then let it sit for a week or more in a position that would encourage a bore leak. If it stays, ok install it. If not listen toward the midwest again for a nuke level "WTF!!" Film @ 11:00...

 

are you using dot 5 fluid and having leaks?
as I think dot 5 is silicone based fluid
dot 3 -glycol
dot 4 glycol with someting in it to do with boiling point - probably to do with
motor industyry time line 1970's front discs being fitted
dot 5.1 - glycol based 'even' more shmoo for boiling point
I would hazard a real WIDE guess, ideal in 4 wheel disc brakes

/\ just a guess, but begs the question - why would you change

So to re cap and ask a 3 quaestions
1. do you use dot 3 brake fluid in an all drum set up
2. do you use dot 4 fluid in a disc drum set up
3. do you run dot 5.1 glycol based fluid in all round discs

4.9 - do you run dot 5 silicon based brake fluid in any brake system that was intended to use glycol based fluid, does the silicon eat the rubber parts of for example a 1956 wheel cylinder,
5.7 I there anything in the compounds of hydraulic rubber -
FOR EXAMPLE the simply O-ring on a power steering box HAS to be a something other than a simple rubber o-ring from a multi-pack, something about butyl ether or sometyjing, maybe the all are already

 

I use Dot 3 in everything, because I'm a cheap bum. All of my stuff is front disc/rear drum.

As I understood the differences back in the day were the amount of moisture the brake fluid would absorb (less is better) and the boiling point of the fluid (higher is better).

I live is a pretty small town (25,000) out here in the sticks with gently rolling hills. We (the wife and I) don't tend to use our brakes very hard, so the higher boiling point isn't much of a requirement.

As far as the rubber and "O" rings are concerned, I suspect there are a few applications with specially material specifications, and I'm also sure there are probably some specific "O" ring diameter and shape specifications. I'm sure there are several locations where a generic "O" ring assortment "O" ring simply will not work. Gene

 

Used a proper kit made for this cylinder (41 Packard 160) and no 'generic' seals or universal assortment parts. Fluid is DOT 3 according to the bottle. No silicone, I don't like it for many reasons.