90 accord brake pedal to floor on hot days.

[01emb]

Does anyone know why when im stuck in traffic or on the brake pedal for longer than usual the pedal goes to the floor. Very spongy when in traffic and especially on hot days. Anyone know what the problem could be?

[somick]

I would start with bleeding brakes.
Considering the age of your vehicle fluid replacement would not hurt either.

Sam

[jeffcoslacker]

Originally Posted by 01emb

Does anyone know why when im stuck in traffic or on the brake pedal for longer than usual the pedal goes to the floor. Very spongy when in traffic and especially on hot days. Anyone know what the problem could be?

Classic fluid failure, moisture contamination in the fluid boils, under heat and prolonged use, then the lines are vapor locked, and the pedal behaves as if there's air in the lines....

Purge and refill with DOT4 synthetic. Will never happen again. DO NOT use DOT 5, unless you are up to all the conditions and limitations of it...

My motorcycle has a hydraulic clutch, works the same as a master cylinder for brakes...if the fluid gets old and contaminated, the clutch will do the same thing in heat and stop and go...lever gets low, and clutch stops working...DOT 4 fluid change solved this aggravation also...

[jeffcoslacker]

If you have any doubt, take it to one of the chain brake and muffler stores, and ask them to chemstrip your fluid...(should be free or nearly)...they just dip a chemical treated paper strip into the master cylinder that changes color propotionate to the amount of contamination in the fluid...my guess is it will show it to be completely torched...

If not, after verifying no external leaks (I'm assuming not, as you mentioned no fluid loss), it's master cylinder time for you...the seals are breaking down in the heat...but it's much more common for bad seals to show themselves after a good cold snap...the cold compromises the seals' ability to conform to the bore of the cylinder, fluid bypasses them, pedal drops..

[jeffcoslacker]

Speaking of clutches...you have a hydro clutch if not an automatic...if the M/C fluid is shot, the clutch fluid is no doubt bad also, and your clutch will start the same nonsense before too long...

[AccordCodger]

How come no one mentioned the master cyl? That's a well-known symptom you have right there. Get it replaced.

That said, you HAVE been getting the brake fluid replaced according to the schedule, right?

[jeffcoslacker]

Originally Posted by AccordCodger

How come no one mentioned the master cyl? That's a well-known symptom you have right there. Get it replaced.

That said, you HAVE been getting the brake fluid replaced according to the schedule, right?

post #4 Codger (mine)

"If not, after verifying no external leaks (I'm assuming not, as you mentioned no fluid loss), it's master cylinder time for you...the seals are breaking down in the heat...but it's much more common for bad seals to show themselves after a good cold snap...the cold compromises the seals' ability to conform to the bore of the cylinder, fluid bypasses them, pedal drops.."

[AccordCodger]

Yup. You're right. (Though my experience of master cyl failure doesn't follow that pattern. Florida. Hot weather. Sometimes the pedal went to the floor). While I'd still like to hear if the questioner ever flushed the brake fluid (in 17 years!) I stand by my recommendation - replace the master cyl.

[ProMan]

That is correct!

Air in the brake line will not floor the padel. The symptom is totally different.

It's the master cylinder. The cups are old and leaking. Replace it will solve your problem.

[jeffcoslacker]

Originally Posted by ProMan

That is correct!

Air in the brake line will not floor the padel. .

and this would be on what planet?

Go open a bleeder on your car, pump the pedal a few times, and close it. Go for a ride. Report back after the accident...

[jeffcoslacker]

not talking about just a localized air pocket here...talking about moisture contaminated, overheated fluid. The moisture content within the ENTIRE brake system vaporizes above a certain temp, and fills the whole system with zillions of tiny bubbles of vapor as the moisture boils out of solution...vapor is compressible...liquid is not.

Result, entire syetm behaves as if there is air in ALL the lines (because basically, there is now)...and the pedal hits the floor as all that vapor simply compresses with little or no action at the business end when the pedal is depressed...I've had a brake seize and overheat crappy old fluid, and lost the pedal entirely...drift to the side of the road, and there was so much residual pressure from the vaporization that the cap blew off when I loosened it, and fluid shot out...the system was essentially vapor locked...more extreme than the typical contaminated fluid scenario, but same principle...

[AccordCodger]

I guess 01em has lost interest with all this bickering.

[starynight]

Originally Posted by jeffcoslacker

and this would be on what planet?

Go open a bleeder on your car, pump the pedal a few times, and close it. Go for a ride. Report back after the accident...

Originally Posted by jeffcoslacker

not talking about just a localized air pocket here...talking about moisture contaminated, overheated fluid. The moisture content within the ENTIRE brake system vaporizes above a certain temp, and fills the whole system with zillions of tiny bubbles of vapor as the moisture boils out of solution...vapor is compressible...liquid is not.

Not sure what you are talking about. Open the bleeder will only let the air in. Then you say it's not the air but the moisture. It's like you slap your own face by denying what you just said.

Think over and decide what you want to say. And report back.

[somick]

Originally Posted by starynight

Not sure what you are talking about. Open the bleeder will only let the air in. Then you say it's not the air but the moisture. It's like you slap your own face by denying what you just said.

Think over and decide what you want to say. And report back.

I will try to explain it to you.
ProMan said that air in the system will not floor your pedal down. So jeffcoslacker offered him to experiment with it. Let the air into his brake system and try it himself.
I personally would not recomend it - too dangerous!!!

Sam

[jeffcoslacker]

Originally Posted by starynight

Not sure what you are talking about. Open the bleeder will only let the air in. Then you say it's not the air but the moisture. It's like you slap your own face by denying what you just said.

Think over and decide what you want to say. And report back.

I realize it's VERY hard to keep two whole related ideas going in your head at the same time.

You posted the answer to your own innane BS in the quotes you supplied. Reading comprehension's a bitch, ain't it?

Moisture contamination boils under heat stress. Boiling fluid releases vapor. For the purposes of hydraulics, vapor and air are synonymous. Therefore, Air (or vapor) in the lines at boiling point produces the symptom, but the underlying cause is moisture contamination of the fluid.

I was merely making a comparison between the two.

Try reading before flaming next time, moron....