Technical Internal Rust on Master Clyinder

I took off my original 1937 Hudson’s cast iron master cylinder to rebuild it as part of the brake restoration. I have a lot of rust on the INSIDE of the reservoir and would love to hear what’s worked for other people to remove rust here?




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You would be surprised what an overnight soak in white vinegar will do.

 

Or feed grade molasses.

 

Feed grade molasses 7parts water, 1part molasses

 

I just pulled a really crusty master cylinder from my ‘47 DeSoto. Just so happen to have a gallon of Evapo-rust from Harb’r Fr8. I’ll soak it til tomorrow and report back.


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Says “ preclean item if it’s oily. Rinse item and completely immerse for 1-12 hours depending on the depth and age of rust. Check progress periodically. Once rust is removed, rinse item with water. “
We’ll see if this is a good option.

 

Go to the hardware store and get a gallon jug of white vinegar. Super cheap. It works well and not that aggressive. Might that 1 to 3 days depending on how rusty it is. On most stuff just a water rinse works when done. If want to be cautious rinse in water and baking soda. And not harmful to dispose.

 

This was done in 25 minutes. Notice to the right where I spilled it. If you're not on a budget this is the fastest way to go. It leaves a zinc phosphate film to inhibit further rusting and promote paint adhesion. This is also good for dumping down welded seems like wheel arches and roof drip rails..

 

What percentage white vinegar do you use? I see it all the way from 5 to 45% and priced accordingly from $3 a gallon to $30

 

All the above will work evaporate rust is the fastest than molasses (7 to 1 with water) the slowest is vinegar(full strength). I like vinegar best, I use white vinegar ( I don’t know percentages) about 3$ a gallon.after the soak( a few days to a week) you need to use a brush in th m/c and the will fall out.

 

There's that thread on using Citric Acid as well.

 

Here you go.

https://www.jalopyjournal.com/forum/posts/13543466/

 

I just buy the 5% white vinegar at the grocery or hardware store and use it straight. About $2.50 a gallon.

 

Careful with the acids....they will attack the machined surfaces on cast iron parts if left to soak too long(days). I ruined a cylinder head that way...

 

Muriatic acid will dissolve things really quick. I'm thinking tomato sauce my wife makes it real shitty tomato sauce a lot of acid. I got try it out.

 

I'm an Evaporust fan. It's not as toxic as some of the other items we use.

 

Good chance the bore is stuffed, if you’ve got rust in the reservoir your going to have pitting in the bore, inspect closely before you spend $$ on it.

 

So what is it? Why is the name crossed out?

 

I cross that out because I didn't want to run an advertisement. I developed this metal prep rust remover because I wanted something fast. I'm from God damn New Jersey and were not known for hanging waiting all day for something to work. There are a couple of good preps like POR 15, Eastwood, and my favorite Master coat.

I don't really care how people get rust off the car, I worry about it coming back.

 

Pulled out of bucket , rinsed with hot water, and dried with blow gun. No real work involved. I am in no way affiliated with this product. I got it to clean up some crusty knick knacks.


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Here is my 2 cents on master and wheel cylinders, unless you can by NOS, buying a replacement from the parts house or repop joints I have been finding lately are junk, the threaded fittings are not made correct and the fittings bottom out before they seal so now you have leaks, the taper is not made correct and they are just shit parts, I've been sending cylinders out and having them stainless sleeved, masters about 100, cylinders about 80 to 90,and Ford step 95, the wheel cylinders you buy today come with metric bleeder screws and the Mopars with the bolt down top have metric bolts that just frys my ass.

 

Brake fluid is hygroscopic and will attract water, so it's a good thing to flush your brake system every so often.

 

I've used vinegar, EvapoRust and electrolysis. Vinegar is the cheapest by far, easier to set up than electrolysis and just as fast as EvapoRust. It's even faster if you take the part out and scrub it with a wire brush every now and then. Usually the part is clean in a few hours or less. Vinegar is environmentally friendly, you can get it at any grocery store and you can use what's left in the bottle for cooking.