Odd brake issue - fading spongy pedal with hot weather..

[phorty]

All, this issue has recently resurfaced after I originally noticed it last summer. It only seems to be an issue after the engine/brakes are warmed up and the outside temp is 80 degrees or higher.

First off, the braking performance is fine. No noises or issues, no warning lights and I still drive and brake in a spirited manner.

Here is the scenario, car is warmed up and its hot outside, I come to a red light and stop. Applying normal light pressure on the brakes and the car holds as normal while stopped. Then put a bit more pressure on the brakes and the pedal makes a rubbery squeezing noise and I can slowly push the pedal nearly to the floor. I don't lose braking power, the pedal will just go as low as I want if I keep putting pressure on it.

When I first noticed it happening last summer, I pulled the wheels off to make sure no fluid was leaking out anywhere. The whole area around the master cylinder is as clean as a whistle. Then fall hit and I pretty much forgot about it. I bought the car new and it has had a pretty easy 39K miles. I replaced the front rotors and pads 15K miles ago - didn't really need them but I came across some NOS stuff and did it anyway.

Thoughts? Just needs a bleed or is something else at play here? I have a set of brembos that I plan on putting on when I get the chance but wanted to figure this out first. I plan to use my Motive power bleeder at that time. Thanks for the help!

 

[JeremyH]

My car is an 07 with around 40k miles. I just did a full brake fluid flush and put in all new fluid, made a noticeable difference in brake pedal feel and bite. I would suggest that if you haven't done it yet.

 

[WJBertrand]

Sounds like moisture in the brake fluid. When it gets hot, some of the moisture vaporizes, this vapor is of course compressible and makes the pedal feel spongy. Absolutely follow Jeremy's advice and flush/replace the brake fluid.

 

[phorty]

Sounds good, thanks guys. I will do a full bleed when I swap on the Brembos. Just need to get that Motive attachment that fits our cars!

 

[TexasBlownV8]

Yeah I'd do a full fluid replacement and a good blood-letting (I mean, bleed them properly).
Sounds like you have some air in the system, or as mentioned, moisture, so take care of it all and it should be right. If that does not help, I'd suspect a failing master cylinder.

 

[05gtowner]

I just had happen to me exactly what you are describing OP. It would make a speaking noise too. I did a complete fluid exchange and it is completely resolved. Also I have mire initial bite in braking and no more spongy pedal.

 

[thump_rrr]

All, this issue has recently resurfaced after I originally noticed it last summer. It only seems to be an issue after the engine/brakes are warmed up and the outside temp is 80 degrees or higher.

First off, the braking performance is fine. No noises or issues, no warning lights and I still drive and brake in a spirited manner.

Here is the scenario, car is warmed up and its hot outside, I come to a red light and stop. Applying normal light pressure on the brakes and the car holds as normal while stopped. Then put a bit more pressure on the brakes and the pedal makes a rubbery squeezing noise and I can slowly push the pedal nearly to the floor. I don't lose braking power, the pedal will just go as low as I want if I keep putting pressure on it.

When I first noticed it happening last summer, I pulled the wheels off to make sure no fluid was leaking out anywhere. The whole area around the master cylinder is as clean as a whistle. Then fall hit and I pretty much forgot about it. I bought the car new and it has had a pretty easy 39K miles. I replaced the front rotors and pads 15K miles ago - didn't really need them but I came across some NOS stuff and did it anyway.

Thoughts? Just needs a bleed or is something else at play here? I have a set of brembos that I plan on putting on when I get the chance but wanted to figure this out first. I plan to use my Motive power bleeder at that time. Thanks for the help!

Brake fluid is hygroscopic, it draws and retains moisture from the air.
This drastically reduces it's boiling point which is why brake fluid has bot dry and wet boiling points on the bottle.

On a car that is not tracked I would replace the brake fluid every 3 years.
Use a good but not stupidly expensive fluid and flush till perfectly clean.

ATE was selling a brake fluid called Super Blue which was tinted blue.
The DOT prohibits brake fluid from being any color other than clear or amber.
The nice thing with this fluid was that since it is blue you could see the color of it.
I alternate between this ATE Super Blue and ATE typ200 which is amber. This way you could tell when you have completely bled each wheel.

PS: The Motive one man pressurized brake bleeder is the best thing since sliced bread.

 

[thump_rrr]

Sounds good, thanks guys. I will do a full bleed when I swap on the Brembos. Just need to get that Motive attachment that fits our cars!

If you don't want to spend the coin on the motive brake bleeder tool but you have an old insecticide pump sprayer you're not using just buy the Motive 1117 adapter for our cars and jury-rig it.
Better yet get an old master cylinder cap, drill a hole in it and epoxy a fitting to it.

 

[s8v4o]

I use this bleeder and it works GREAT! It's pneumatic and you only need yourself. I used this when after installing my SLP linelock. Traditional bleeding wasn't getting all the air out of the ABS unit. This bleeder worked great.

http://www.harborfreight.com/brake-fluid-bleeder-92924.html

 

[skwerl]

I use this bleeder and it works GREAT! It's pneumatic and you only need yourself. I used this when after installing my SLP linelock. Traditional bleeding wasn't getting all the air out of the ABS unit. This bleeder worked great.

http://www.harborfreight.com/brake-fluid-bleeder-92924.html

I'm going to buy one of those right this minute!

 

[05gtowner]

I use this bleeder and it works GREAT! It's pneumatic and you only need yourself. I used this when after installing my SLP linelock. Traditional bleeding wasn't getting all the air out of the ABS unit. This bleeder worked great.

http://www.harborfreight.com/brake-fluid-bleeder-92924.html

Great link! I think I am going to pick one of these up.

 

[Johnf78]

Me three!

 

[phorty]

I already have the motive bleeder and love the thing, so easy to use. The hardest part is finding plastic tubing that fits over the bleeders!

On the ATE super blue stuff; is that okay on a daily driver? I may even drive it this winter so I want to be sure it's okay for every day street use. Where can you get the stuff?

 

[california gt]

Tire Rack..... Amazon

 

[phorty]

Just learned they discontinued the blue stuff last summer!

 

[joe_momma]

You can find it on eBay still, although it's expensive.