Hi all!

Not sure if this is the right forum, but I had a quick and dirty problem with my brakes the other day and I'm trying to diagnose it.

HOT day... misjudged a corner, hit brakes hard, no problem... a few miles later (in city traffic) I thought brakes started to feel a little spongy... a few miles later, I KNEW they felt spongy... less than a mile and I had to hit the floor at a stop light... and this after pumping the brakes to build pressure (didn't work)... but I did stop! only had a quarter mile to go, so I prayed and went for it... had no pedal, but did stop when pedal hit floor...

no fluid leaks at wheels, fluid level full, couldn't jack up the van but rocking wheels didn't show a bearing problem... all this, and after a few hours of sitting, brakes were back, no sponginess, and no signs of it returning. Oh, rubber hoses look old and may be slightly worn, but no cracks or such found... And I tested the staying power of the pedal... I could stand on it and it would hold (although it did seem to push ever so slightly further to the ground after a few minutes).

So, what do you think?

Thanks! Jeanne

 

How old is your brake fluid? I'm no expert but offhand I'd say it sounds like your brake fluid might have boiled, which would result in excessive pedal travel and little or no braking power. If the fluid is old, there might be some water in the system which would cause the fluid to boil at a lower temperature.

Isaac

 

Check for leaks to.Try bleeding them.Put new fluid in like IJRoorda said.You never know what some one might of put in it before you.Faulty ABS can do that to.Ive seen a guy at the gas station putting in 15/40 motor oil into his power steering.I told him he will blow his power steering pump.He jumps in his car not saying anything,and bolts away.

 

Jeanne ,

That is my sister's name !! I think I would install a new mastercylinder and also the fluid as suggested . I would not trust that master cyl now .

jlrdds ( Jamie )

 

Thanks everybody!

I installed the new master cylinder today. Boy was that old fluid ugly!!! I guess even if it was just the fluid boiling, I'll not have to worry for quite some time about the master cylinder going out. This has been a learning experience for me... I've done a lot of my own mechanic work, but this is a first for the master cylinder. I'm wondering the best way to get all the old fluid out. I could just keep bleeding the wheels until I see clearer fluid coming out... any better ways?

Thanks! Jeanne

 

Hi Jeanne ,

I would guess you were surprised at how easy it was to replace the master cylinder and I am glad you did that . I have never purged a system of brake fluid so am not sure what the pros do ? Somebody else can probably advise you better than can I .
I would think that bleeding the brakes as you are doing would be sufficient . I hope you have some help for that .

Jamie

 

Yeah your master cylinder probably popped a big leak around its seal and just decided to seal again.

You must bleed all 4 wheels. This cleans out the whole line system and if done properly there will be no air in the lines. Simply getting the old fluid out is only part of the job, getting in the new fluid without introducing air is the other.

 

Keep bleeding until new fluid comes through each line. Very cheap insurance.

 

N_fini_T,

I think your problem may be elsewhere. Replacing the master cylinder won't hurt, but it may not keep it from happening again.

It could be that one of your front brake calipers stuck during the hard stop. The drive home caused it to heat up and boil the fluid. The caliper being stuck and the hot fluid would cause the low soft pedal. Mine did the same thing about a month ago, except that the next brake application caused it to release.

Several things can cause a caliper to stick. Old brake line hoses, corrosion caused by old fluid in the system, external crud in the calipers and their mounting system and plastic caliper pistons. I had a Ranger many years ago with the plastic pistons that would lock up after hard braking. You can rebuild them with steel pistons or exchange them for rebuilt calipers that has steel pistons in them if that is the problem. The hoses deteriorate on the inside and can develop a lose flap of rubber on the inside of the hose that will act like a check valve, allowing the fluid to go one way through it but not the other. If they are old it?s best to replace them. That deterioration along with other rubber parts breaking down also contributes to the dark fluid that you found.

You didn't say how old your van is or how many miles it has but it may be time for a thorough going over of the brake system.

Gene

 

Gene,

Thanks for the info... I am planning to change the brake lines because they look old enough to cause a problem. My vehicle information is in my signature... I keep forgetting that they don't show in the post, and that you have to click on my signature to see it... it's a 1991 E250. I'll also check the calipers to see if they show anything.

As for now, I've bled all the brake lines and new fluid is running through them, and the brakes work like a charm... no more sponge and good hard brakes!

Thanks for all your inputs! Jeanne