Brakes overheating on long descents (1 Viewer)

[69 Pigboy]

My brakes have been overheating on long descents in the mountains the last few days and I’d like some input from some of you non-flatlanders.

After long descents on steep grades over the last couple of days my brakes have started failing. Pads and rotors are new and fluid was recently checked but not replaced. As much as possible I’ve been keeping off them while descending and where possible I’ve shifted down into 2nd. Symptoms are a very soft pedal that goes to the floor before it will engage the brakes. I pulled over to let them cool and checked the reservoir and it was overflowing slightly. Once they’ve had a chance to cool the pedal response improves.

Is it likely that there’s moisture in the fluid or that it has just deteriorated? I’m getting them checked tomorrow but any input would be appreciated.

 

[Squeegee]

Try changing the fluid out to DOT 4

 

[jpoole]

Sounds like moisture in the fluid is a real possibility. I'd flush the brake fluid to remove that as a possible factor. Upgrading to a higher temp rated fluid could also be a good idea but shouldn't be necessary based on my experience which includes towing in the Rockies/Smokies, etc.

Continue to use your transmission to aid in descents. When going faster in the mountains disengage OD to aid in speed management, when going slower downshift as appropriate.

 

[mudgudgeon]

How do you change but not replace fluid?

Certainly sounds like you may have contaminated fluid.

 

[69 Pigboy]

How do you change but not replace fluid?

Certainly sounds like you may have contaminated fluid.

I said checked. There are test strips that will detect degradation in the fluid and when I had some work done recently they tested the fluid in the reservoir.

 

[mudgudgeon]

I said checked. There are test strips that will detect degradation in the fluid and when I had some work done recently they tested the fluid in the reservoir.

Gotcha.

Some days, I swear I'm lysdexic

 

[69 Pigboy]

Thanks for the input guys.

 

[gummycarbs]

I said checked. There are test strips that will detect degradation in the fluid and when I had some work done recently they tested the fluid in the reservoir.

I question how uniformly moisture disperses throughout the braking system. I'm pretty sure I found actually liquid water in my rear calipers the first time I bled them, unfortunately I didn't have any means to test what was in the master cylinder reservoir.

Anyway, you can never go wrong with fresh brake fluid. Castrol Synthetic DOT 4 is my favorite. Don't forget to flush the LSPV.

 

[mudgudgeon]

I question how uniformly moisture disperses throughout the braking system. I'm pretty sure I found actually liquid water in my rear calipers the first time I bled them, unfortunately I didn't have any means to test what was in the master cylinder reservoir.

Anyway, you can never go wrong with fresh brake fluid. Castrol Synthetic DOT 4 is my favorite. Don't forget to flush the LSPV.

Yeah, agreed. With a dead end closed line, your not gonna get a lot of circulation.

 

[-Spike-]

Moisture.

 

[leonard_nemoy]

Change the fluid with fresh and also consider replacing or rebuilding the calipers.

Also check your lines. A soft line might be bulging and causing problems.

 

[jonheld]

Brake fluid should be water clear. The darker the fluid, the more contaminated it is.
Dump the old fluid and replace with new.

 

[musthave]

Brake fluid should be water clear. The darker the fluid, the more contaminated it is.
Dump the old fluid and replace with new.

I've read about this in the past and experienced what the OP stated. I fully agree with your statement, replace with new fluid. Bleed everything.

But, I am always confused when I start to research this and find the following:

""Glycol-ether (DOT 3, 4, and 5.1) brake fluids are hygroscopic (water absorbing), which means they absorb moisture from the atmosphere under normal humidity levels. Non-hygroscopic fluids (silicone e.g. /DOT 5 and mineral oil based formulations), are hydrophobic and can maintain an acceptable boiling point over the fluid's service life.

Silicone based fluid is more compressible than glycol based fluid, leading to brakes with a spongy feeling.""

It would seem like dot five is better. Though, Being silicone based it may lead to a spongy feeling. Spongy feeling, but less degradation seems better. What am I missing?

 

[jpoole]

There are reasons that the engineers chose hygroscopic fluids for use in brake systems.

As I understand it the general idea is to keep the moisture that enters the system in suspension vs. allowing it to pool. If the water were to pool it would likely be heavier than the brake fluid and so pool in the low points of the system (calipers/wheel cylinders typically). In those locations where more heat is seen there would also be less resistance to high temps/boiling. Where the water pooled there would also be a lower freeze point and more risk of corrosion damage.

If the water is in solution in the brake fluid the overall system boiling point / temp resistance is higher, freeze point is higher and corrosion threat is lower. I suspect that it's also easier to get the water out of the brake system if it's in solution in the fluid vs. pooled in a low point. Water would likely be heavier than most brake fluids used and since bleeders are typically at high points to remove air water could sit below the flow of fluid and remain trapped in the system.

 

[69 Pigboy]

So it turns out that there was moisture in the system but additionally, two of the calipers were in dire need of replacement. Rotors and pads were ok except for one set that had been impacted by a bad caliper. I’m in the middle of a long trip that will take me across multiple mountain ranges so I’m glad I was able to get it taken care of. Wierd thing is that a shop that I trust didn’t catch anything when they installed new pads and rotors on the rear a few months ago. It’s possible that the problems developed since then but it makes me wonder.

Im here to tell you that nothing makes your butt pucker up like squishy brakes on a steep mountain descent.

Thanks for everything guys.

 

[ozarkmud]

New pads and rotors in the rear, but the calipers seemed fine? Are you sure you actually burned through those rotors? I'm a little suspicious here.

 

[musthave]

So it turns out that there was moisture in the system but additionally, two of the calipers were in dire need of replacement. Rotors and pads were ok except for one set that had been impacted by a bad caliper. I’m in the middle of a long trip that will take me across multiple mountain ranges so I’m glad I was able to get it taken care of. Wierd thing is that a shop that I trust didn’t catch anything when they installed new pads and rotors on the rear a few months ago. It’s possible that the problems developed since then but it makes me wonder.

Im here to tell you that nothing makes your butt pucker up like squishy brakes on a steep mountain descent.

Thanks for everything guys.

I once came down from Guanella Pass into Georgetown Colorado. They got really squishy near the bottom, and where the first stop sign was, I had no brakes at all. Bled the brakes with new fluid, no further issues. Also, as others stated, shift down a bit, and let the cruiser do some of the work for you.

Glad that you were able to get it sorted out.

 

[69 Pigboy]

New pads and rotors in the rear, but the calipers seemed fine? Are you sure you actually burned through those rotors? I'm a little suspicious here.

The pads that got eaten up were in the front. The pads in the rear that were installed recently with the new rotors were fine. When I said “one set” I was only referring to the pads. I wasn’t very clear…. The rear caliper that needed replacing just had a piston that was not functioning properly. The seal around that piston was chewed up.

 

[jpoole]

I had this happen when working as a camp counselor descending a steep road with 10 to 15 kids riding along. It was an old, poorly maintained camp van and the brakes went away with a lot of descending ahead. Aggressive downshifting saved the day and while I didn't tell any of the passengers what was going on none of them complained when I pulled over at the first possible place to take a short walk and a few deep breaths. That van went straight to the maintenance man on our return to camp.

That experience combined with fixing too many neglected brake systems over the years means that I now gladly perform and enjoy the regular brake fluid flushes that I do on my own autos. Regular flushes are so much easier than all the other drama that can come up with crusty brake systems.

 

[69 Pigboy]

I had this happen when working as a camp counselor descending a steep road with 10 to 15 kids riding along. It was an old, poorly maintained camp van and the brakes went away with a lot of descending ahead. Aggressive downshifting saved the day and while I didn't tell any of the passengers what was going on none of them complained when I pulled over at the first possible place to take a short walk and a few deep breaths. That van went straight to the maintenance man on our return to camp.

That experience combined with fixing too many neglected brake systems over the years means that I now gladly perform and enjoy the regular brake fluid flushes that I do on my own autos. Regular flushes are so much easier than all the other drama that can come up with crusty brake systems.

New fluids are cheap insurance.