If anyone wants to tell you POR-15 is...

[DocsMachine]

... Immune to brake fluid, I'm here to tell ya it ain't.

I put that MC on back in 2015, and the paint had badly curdled by the end of that summer. I've been working on the brakes again, and while I had the cylinder off, I peeled almost everything off the entire back third of the casting, in big flakes.

The stuff's holding up great on my suspension components, and it probably lasted longer against the brake fluid than rattlecan would have, but it sure as hell isn't immune to the stuff.

Doc.

 

[isb cornbinder]

I will never use that product.

 

[RWorth]

I don't think any paint can survive brake fluid.

 

[Bad Eye Bill]

I don't think any paint can survive brake fluid.

About ten years ago I was replacing a torn up fender on a neighbour's Ford tractor. The one he brought me had several coats of hard used and abused Tremclad paint on it and needed to be stripped. I thought I'd try peeling it off with brake fluid. I painted the whole fender with brake fluid and let it sit for a month or so while doing some other work on the tractor. Reapplied brake fluid several times, no dice, never so much as produced a bubble.

I've spilled brake fluid on paint before and if unnoticed a disaster is soon encountered. Why wouldn't it lift Tremclad?

 

[BillK]

Looks to me like the POR15 was put on over the original paint and did not stick to the actual metal.

 

[driftpin]

I used it on a rusty pair of trailer wheels years-ago & they still look good. I did remove as-much as I could of the rust.

 

[DocsMachine]

Looks to me like the POR15 was put on over the original paint and did not stick to the actual metal.

-No. I bought the master cylinder brand-new and completely unpainted. I degreased it and painted it with the POR before the thing had ever seen a drop of brake fluid.

But, I was running low at the time, so the first coat was black, and the second the last of the grey I had.

I will never use that product.

-As I said, it's holding up very well on my suspension components, and this is not a car only driven on dry, sunny days. (If it was, I'd only be able to drive it like, twice a year. )

It's good paint, for what it is, it's just that they advertise it as being resistant to "most major underhood chemicals"- but clearly brake fluid is not one of them.

Doc.

 

[K13]

About ten years ago I was replacing a torn up fender on a neighbour's Ford tractor. The one he brought me had several coats of hard used and abused Tremclad paint on it and needed to be stripped. I thought I'd try peeling it off with brake fluid. I painted the whole fender with brake fluid and let it sit for a month or so while doing some other work on the tractor. Reapplied brake fluid several times, no dice, never so much as produced a bubble.

I've spilled brake fluid on paint before and if unnoticed a disaster is soon encountered. Why wouldn't it lift Tremclad?

It was synthetic brake fluid was it?

 

[Randy in Maine]

Usually on clean metal you have to use some sort of phosphoric acid etching compound (they call theirs "Metal Ready" or something) all give the POR 15 something to bite into, like a little rust. Then it is pretty tough to get off.

Brake fluid seems to remove about any finish from anything though.

 

[ebonyswan]

No. I bought the master cylinder brand-new and completely unpainted. I degreased it and painted it with the POR before the thing had ever seen a drop of brake fluid.

That's why. POR does not do well in that scenario at all. It wants a rougher surface, some surface rust or an etched surface. It does ******-all on smooth metal.

 

[DocsMachine]

I'd hardly call cast iron "smooth metal", but I do get what you're saying.

In this case, however, I very much doubt whether it mattered how rough, smooth or etched the surface was- the brake fluid clearly softened and swelled it.

Doc.

 

[Bad Eye Bill]

It was synthetic brake fluid was it?

Nope, good old fashioned everyday brake fluid.

 

[miragesmack]

Por-15 is all about the prep. About 99% of failures are due to poor prep. Need to acid etch before using on non rusty surfaces. It shouldn’t be used in that area anyway because sunlight experience over will affect it, and a master cylinder sees sunlight.

 

[n20junkie]

I didn't put silicone based fluid in my car because I didn’t think POR reacted to it. **** if I wasn’t wrong!

Lesson learned.

But I sill love POR, and use it in a lot of places. My drag car has just sheetmetal floors and with the POR it looks great even after years of getting in and out with rocks stuck to my feet.

 

[paranoid56]

Por-15 is all about the prep. About 99% of failures are due to poor prep. Need to acid etch before using on non rusty surfaces. It shouldn’t be used in that area anyway because sunlight experience over will affect it, and a master cylinder sees sunlight.

it doesnt see enough sunlight to effect it. lol

 

[66Caprice]

It don't help that it's not fully encapsulated with the Por15. The edge under the cap is going to give the fluid a place to creep under the Por15.

 

[tcianci]

Por-15 is all about the prep. About 99% of failures are due to poor prep. Need to acid etch before using on non rusty surfaces. It shouldn’t be used in that area anyway because sunlight experience over will affect it, and a master cylinder sees sunlight.

POR-15 is susceptible to UV from sunlight but as a guy who has been using the stuff for nearly 20 years, I can tell you first hand, they mean direct sunlight and if you read their web site, they tell you that although the finish will degrade in color, it's rust protective qualities are not diminished.

I usually defend the product because 99% of the time your average POR 15 thread is rife with misinformation and sad stories about guys who didn't follow the instructions and got unsatisfactory results. As far as taking sunlight, the bottoms of my running boards see a lot more light than a master cylinder and they are shiny and black after about 12 years of being coated. Same with my trolley beam in my garage, coated maybe 15 years ago, still black , shiny and intact despite steel wheels running on the beam flange all the time.

Read anything you want about that stuff, then go to the manufacturers website and read the straight skinny on how to prep and apply the stuff.

It's not magic, it's just a well characterized moisture cured urethane that has a lot of engineering behind it and does a pretty darn good job for what it is intended to do.

 

[joe_padavano]

I'm not aware of any claims that POR is impervious to brake fluid. I've been using this product with good results.

 

[fsae0607]

I'm not aware of any claims that POR is impervious to brake fluid. I've been using this product with good results.

I'm using this stuff on my '61 GMC truck when I replace the MC.

 

[GMCGarage]

Por-15 is all about the prep. About 99% of failures are due to poor prep. Need to acid etch before using on non rusty surfaces. It shouldn’t be used in that area anyway because sunlight experience over will affect it, and a master cylinder sees sunlight.

This is why I alway put my master cylinders under the hood.

 

[mikec35]

I used POR-15 on my engine, just as long as I don't spill any brake fluid on it I think I should be ok. Brake fluid has done a number on a couple of spots on my epoxy floor though.

 

[Racer_X]

I don't think any paint can survive brake fluid.

Imron can.

 

[DougMN]

Por-15 is all about the prep. About 99% of failures are due to poor prep. Need to acid etch before using on non rusty surfaces. It shouldn’t be used in that area anyway because sunlight experience over will affect it, and a master cylinder sees sunlight.

Prep? It's paint over rust. POR

 

[DocsMachine]

I've been using this product with good results. [Eastwood brake cylinder paint]

-I wasn't aware such a thing even existed. I wonder what it is, then?

And how "resistant" is resistant? Long enough for the spill to be wiped up? Only bubbles up after a couple of months of contact?

Doc.

 

[joe_padavano]

And how "resistant" is resistant?

Good question and obviously there's a reason why they call it "resistant" and not "impervious". So far the small amount of brake fluid that tends to seep out between the cap and the top of the M/C hasn't caused an lifting. I wouldn't expect it to survive INSIDE the M/C reservoir, for example.

 

[Two Speed]

Prep? It's paint over rust. POR

True for aged metal, a new MC would be oily. The metal prep is to remove any oils etc before applying the POR.
incidently, if you use laquer thinner to clean something before POR15, it will also peel.

 

[Paco Pena]

POR 15 sticks well to rusted metal not nice smooth unrusted metal in my experience.

Paco

 

[bczygan]

I haven't had any problems with my POR-15 for many years.






























It's still in the can!

Bill

 

[CN Spots]

Proper prep for clean metal is to toss it in a pond for few months.

 

[lbhsbz]

-No. I bought the master cylinder brand-new and completely unpainted. I degreased it and painted it with the POR before the thing had ever seen a drop of brake fluid.

But, I was running low at the time, so the first coat was black, and the second the last of the grey I had.



-As I said, it's holding up very well on my suspension components, and this is not a car only driven on dry, sunny days. (If it was, I'd only be able to drive it like, twice a year. )

It's good paint, for what it is, it's just that they advertise it as being resistant to "most major underhood chemicals"- but clearly brake fluid is not one of them.

Doc.

New castings like that are coating with a packing oil that is almost impossible to properly remove without heat to cook it all out of the porous iron.