Brake freeze?
 

Odd problem that may have been a one off. Washed car yesterday and drove for some time after. Also had it in my garage which has yet to get below freezing. Then today I am on the highway and I notice my economy needle is pegged straight down. The cruise control was even a little jerky. I figured a vacuum leak even though all my engine vacuum tubes and rubber are new. So i pull over and briefly notice a burning/foundry smell. Thinking belt I pop the hood and everything is fine. Also no vacuum hiss or smoke. Engine seems fine. I let the car idle for a while then get back onto the highway and all is well, needle never gets more than a quarter inch from left.

So my thoughts are that residual water in the brakes caused them to freeze up? And sitting allowed the ambient heat to melt the ice. I did go from garage to highway before the car engine even warmed up. Possibility? Or is this a common issues with the brake design?

Ever flushed the brake fluid? It is hygroscopic and needs to be flushed at a max of every few years. Why? When it freezes it is like a box of knives stabbing the o-rings in the master cyl. Not what you want...

SO you could have a failing MC as it is sticking internally or a dying caliper. Both are easy to replace, just a pain in the ass.

I had this happen to my SDL just recently. Pull a wheel and check the pad material, if it is melted (as mine was) you have found your problem.

I have not flushed it yet. Been thinking of it. The MC looks brand new. The OP replaced it, but it could have been a couple years ago. Guess it cant hurt since brake fluid is pretty cheap.

Anything specific that I should use for a fluid?

Anything which has DOT4 on the bottle will be fine.

-Jason

Unless DOT 3 is recommended, which is usually the case. Dot 3 absorbs moisture at a slower rate than DOT 4.
But frozen brake fluid isn't the OP problem; frozen water between the caliper and the brake pad is what he believes to be the problem and that is a reasonable conclusion.

Gen2 W126s use DOT4, older benzes probably do as well. The manual calls for a brake fluid change every spring.

-Jasno

Well since I have green coolant, there is no telling whats in there. And with ABS there may not be a practical way to flush whatever is in there and clean it out 100%. So is DOT3 and DOT4 mixable? I forget. I have a case of DOT 3 on hand already anyway.

But yes, I still think that is may just be a frozen water issues right now. And maybe it will not happen again. I sure hope not. But bringing up the fluid does remind me that I do now know when it was changed, so I will also do that.

It just flushes right on through, no big deal. Scoop up a Motive Power Bleeder to make life easy.

Your car calls for DOT 4, use it

could be a stuck caliper. Which tire got hot? And it is unlikey that the brake froze with water, as braking produces heat, which would melt any ice buildup in the caliper.

A check valve, some clear hose and a plastic spice container make a one man bleeder. If you want to do an entire line use a bigger jar, but the jar has to hold vacuum.

An internally swollen or collapsed rubber line can cause similar symptoms.

Or just fill the jar with brake fluid until the hose is well under the fluid level

Which brings up a good point: The flexible lines are 20 years old. Replace them.

-J

Ever used the pressure bleeder? For $50 it is a 'must have' along with a Mity Vac.

2x on the power bleeder. Way better then vacuum bleeding.. you don't get air sucked in around the bleed screw giving you false bubbles.

-J