Gunsmoke

1930's flexible brake hose/modern fluids

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Posted (edited)

I'm restoring a 1931 Chrysler CD8 and needed the 3 pieces of 18" flex brake hose, 2 for the front wheels and 1 to go to rear axle union. Found/bought a 3 piece repo set on ebay (Mopar-Direct, Andy B), and also found a pair of NOS hoses on ebay which I also bought (see photo of one of each). I noted that the new set was advertised as "made with modern materials". That got me thinking that there have probably been changes/improvements in materials and brake fluids over the 90 years, and that the older hoses may not stand up to modern fluids. I was advised to use Dot 1 fluid if I was going to use the 2 NOS hoses (they look more original on exposed front wheel locations and I also am using NOS rubber seals I have for the 4 wheel cylinders), and that Dot 2 might also be OK. But not to use modern Dot 3 fluid with these old rubber products (silicone content?). This is a new area of expertise for me, can someone confirm the best practice if I elect to use the NOS hoses? 

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Edited by Gunsmoke (see edit history)

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Posted (edited)

DoT 5 is silicon. No silicon in any other fluid.

 

Just use DoT 4 or 5.1. As the DoT standard evolves, the boiling point increases and the rate at which it absorbs moisture decreases.

 

Based on what I read at https://blog.firestonecompleteautocare.com/brakes/everything-you-need-to-know-about-brake-fluid/

I would keep the NOS hoses as nice, perhaps original, samples and use the new hoses:

"Myth #1: Moisture is the primary problem with old brake fluid.

Today the breakdown of the additive package is the primary problem.

Before the application of modern flexible brake hose manufacturing techniques moisture was an issue. It would permeate through the hoses and into the fluid when the fluid cooled down. Modern hose manufacturing has eliminated this issue."

Edited by Spinneyhill (see edit history)
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Thanks SP for the advice and lead to the article on fluids. Since car will likely never see rain, moisture permeation should not be an issue. However, I may decide to use the modern hoses and save the NOS for someone who wants to be "concours conscious"'! Some of the old wheel cylinder rubber boots looked like they had been badly eroded/eaten by some PO's fluid choice. But I am replacing all seals, lines and boots, and honing the cylinders/master so should be able to get a reliable system. Cheers

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The moisture permeating the hoses would be from humidity as well as wet conditions under the car. Honed cylinders may require oversize cups; I put some in some of my cylinders in the '90s.

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I wouldn't trust old flex hoses. I would expect the rubber to deteriorate over the years even in a sealed package.

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Moisture in brake fluid not a problem? You have to be kidding. Glycol brake fluid (DOT3, 4, 5.1) is hygroscopic. It literally sucks water out of the air. Many if not all of these old systems prior to 1966 or so are open to the atmosphere.

 

I wouldn't trust NOS brake hoses to actually drive with no matter what fluid is in them. As for the wheel cylinders, how special are they? If they take ordinary cups, get some new cups, and just use the original stuff (boots, etc.) for the parts that show.

 

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2 hours ago, Bloo said:

Moisture in brake fluid not a problem? You have to be kidding. Glycol brake fluid (DOT3, 4, 5.1) is hygroscopic. It literally sucks water out of the air. Many if not all of these old systems prior to 1966 or so are open to the atmosphere.

Indeed. The rest of the article talked about a change after about 1996, so that hoses since then are supposed to be far less permeable to moisture than the old ones.

 

No matter what, I change my fluid at 2 + year intervals.

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Reading this thread got me thinking if moisture can permeate hydraulic brake hoses does the reverse happen ie does hydraulic fluid permeate out.  I have never seen any sign of this and would be horrifies if I did but considering the heat and pressure involved am I not checking my hoses enough?  Perhaps someone can explain it to me.

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Maybe not? The molecules are probably a different size. I'm not a chemist....

 

Even if the hoses sealed perfectly, for the master cylinder to work properly, there has to be a way for the level to go up and down in the reservoir. From the late 60s on they generally put a rubber bladder over the fluid that allowed this motion. Before that, there was a vent hole, so the reservoir was open to the air and pulling moisture from it 24-7.

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5 hours ago, Bloo said:

Maybe not? The molecules are probably a different size. I'm not a chemist....

 

Even if the hoses sealed perfectly, for the master cylinder to work properly, there has to be a way for the level to go up and down in the reservoir. From the late 60s on they generally put a rubber bladder over the fluid that allowed this motion. Before that, there was a vent hole, so the reservoir was open to the air and pulling moisture from it 24-7.

 

Thanks Bloo.  Did some internet searches and apparently water molecules are smaller than brake fluid molecules  However, I think there are other areas such as wheel cylinder seals and even the cap seal on the fluid reservoir that would be more problematic in allowing the ingress of moisture than the hoses. Just my opinion.

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If you are going to drive the car on public streets, use new rubber parts. If you are just going to drive it from your trailer to the Concourse, you could probably get away with using the older hoses. You should still flush your system on a regular schedule as the moisture in the fluid can cause damage to the braking system.

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Posted (edited)

Gunsmoke,

Are you sure you don't have "stepped wheel cylinders " ?

If you do, honing will be a challenge.

I did the brakes on my '31  CG, which included a new master, stepped wheel cylinders and 3 new NAPA lines.

I welded up  adapters for where the 3 new rubber lines had to match up to the old hard pipes.

Man those old hard lines are big..........

Flushed the system with about a quart of dot 4, filled her up and never looked back.

Now I can stand on the brakes and not be concerned.

 

Mike in Colorado

 

Edited by FLYER15015 (see edit history)

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Looking at the picture of those brake lines they resemble the lines on my 1928 D B Senior. I bought them on  evil bay as new reproductions. There were some concerns about whether the insurance companies will accept them. Old cast iron cylinders are not the best to hone unless you have precise instruments to measure. They must be 99 percent equal all round  . Then you have to hunt for oversize rubbers which might be difficult to find. Honing cylinder and matching rubber has to be precise. I learned that years ago with my 62 Land rover in spite of warnings from experts.  

The best thing is to sleeve master and wheel cylinders to original with either stainless steel or brass and use new rubbers. I came across an article about that in this  September Issue of Hemmings . I had all my cylinders relined and honed to original .

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Almost all hydraulic brake systems are vented otherwise as your brakes wear, the pedal would sink.  I always assumed this is how moisture gets in.  I switched to silicone brake fluid and silicone high temperature disk brake grease.  I lube all moving parts with the disk brake grease and fill with DOT5 silicone fluid (all military vehicles are required to use DOT5) apparently after Vietnam, they had lots of moisture issues.  Harley Davidson also has been using DOT5 since 1976? (internet search).  I rebuilt my 1929 Graham-Paige (Lockheed Brakes) using all silicone, car sits a lot, brakes are like new every time I drive it, almost 12 years since I have looked at them.  Conventional DOT3 seems to eat my wheel cylinders, about 5 year and I have rust contamination/rubber swelling at the wheel cylinders, and stuck brakes, it is better if you drive it more, I have too many cars.  2X on the new brake lines.

 

PS to be fair my 1928 Graham-Paige has a sealed system, when the pedal gets low you have to unseal the master cylinder and pump up the system (also hydraulic) till the pedal returns to the original height.

 

Permatex 20353 Ultra Disc Brake Caliper Lube, 2 oz.

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I have not ever seen oversize cups in modern times. In any event, you should NOT hone that much.

 

The bore is going to have issues. It just is. Don't try to make it new. Often the pits will not be where the seal normally moves. Even if they are, it is truly amazing how bad of a bore you can get away with and have things seal up just fine, as long as you don't go crazy with the hone, and the rubber is brand new!

 

Use the hone to clean and deglaze the bore and knock down the rust. It doesn't take much. Do NOT try to remove the pits. Even little ones are way too deep. Just scrape down the high spots, wash the bore REALLY clean, assemble the cylinder with a little sil-glyde and call it a day.

 

Resleeving is readily available these days if you need it. It isn't even that expensive, and then you have a brand new bore.

 

 

 

 

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H2O has a very different molecular structure depending on state. In a liquid state it is a macromolecule. The surface tension making it bead up and hang together is a manifestation of that. In a gaseous state, the molecule is extremely small. It is only 2(H2O). Some of you will be familiar with Gore-Tex (TM). It is that property of water which allows the material to be waterproof, while at the same time be water vapor permeable.     -   Carl 

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Thanks for all the excellent advice. I have 8 wheel cylinders and will pick the best 4 (fronts are larger dia than rears). All are decent, and a friend and I honed them very slightly, i.e. de-glazed them. I bought NORS rubber seals/springs and new NORS boots, both in very good rubber (there are some cheapies out there!). I also have a NOS master cylinder but it is slightly oxidized and will need some minor honing, also have a new kit for it. The Master cylinder has the original style vent on top. Hope to get at this job next week, have 1/4" steel lines ready to go, and have thoroughly cleaned all the original special brass fittings. First time I have restored a hydraulic brake system, my '31 Chevrolet was so much easier, just a bunch of rods, cables and clevis pins! I also have 8 sets (16 shoes) of original brake shoes/linings, only 6 shoes are usable as is. The rest suffer from oil absorption, likely from failed wheel cylinders at some point in the past. A friend suggested putting the oily shoes in a camp fire for 2 hours and all the oil product would be burned off? Anyone ever done that? I have read some of the advice on fitting shoes to drums, clearances,  etc. Again, first time for me to do a full brake job, so I expect it will take at least a month to complete.

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IMHO contaminated shoes will never be ok until relined.

 

Some folks think its ok to wash them, but brake material is made to run really hot without gassing off. When they get hot enough to gas off, you can push on the pedal as hard as you want and nothing happens.

 

If there is anything present that will burn at a lower temperature than the brake lining, it will render the brake (on the wheel with the contaminated shoes) inoperable when it gets hot enough, due to gas fade. At lower temperatures there would only be a slight pull due to the contamination, or maybe no symptoms at all.

 

There is a high probability you would never notice until descending some mountain pass, or make a panic stop from high speed, and then the contaminated shoes wouldn't work.

 

I have never heard of the campfire thing. Not on my car, but to each his own.

 

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When I was an ignorant youngster (not much different to now, some say!), I had a Transit van. The rear wheel seals kept failing and it took me a while to work out why - movement of course. The shoes were well oiled with diff. oil. I thought I would be clever and wash them in petrol until it came clean, then burn it in petrol. Yeah, right. The brakes were still lousy. Of course, after fixing the movement ( and replacing the LH thread nut I had split getting it off as a RH thread) and replacing seals plus brake cylinder and shoes, it was MUCH better. Still a pile of rubbish, but the brakes were a lot better.

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Just have your shoes relined. Several places around to do it, probably not where you live, but within shipping distance.😉

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Brake and Clutch (Seattle WA)  and Brake and Equipment (Minneapolis MN) come to mind.

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i think I will take the advice given and get shoes relined. Will look for a local option, have a friend (retired mechanic) who has done it years ago, may try him.

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When it comes to brakes do not fool around. You are playing Russian Roulette. You are taking chances with life and limb. Not only yours but other commuters. Sleeveing cylinders are relative inexpensive. It comes with all the rubbers. Oily lining are dangerous.  If the shoes are made of steel the linings can be bonded. If it is aluminium you have to rivet them . Your local mechanic shop will be able to send It out and have it bonded.

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Make sure you get the right coefficient of friction shoes.  Wrong coefficient and brakes will be almost useless.  Over the years the pressure to the shoes has increased so brake material has gotten harder to last longer.  On the bright side now most of the COF material is available.  I would highly recommend Brake and Equipment (Minneapolis MN).  I had a friend do a set for me, I had to have them redone, never had the heart to tell my friend he used the wrong material.  To give you an idea what you want for stopping power...  my 1929 827 Graham-Paige owners manual (almost 5000lb car) states "occupants will be dislodged from their seat if the brakes are applied suddenly" yes I can lock up all 4 wheels on pavement.

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