nicklouse10

HI,

I'm in a bit of a panic...
booked into a track-day tomorrow and just got around to flushing out all the old brake fluid and replacing it with new stuff. I'd cooked the brakes on the past track-day and assumed I'd boiled the old fluid, and that replacing it would cure the problem

the brake pads are all new and the lines are braided and in good condition

I've bled them properly but it hasn't cured the spongy pedal... the pedal travel is huge and the brakes don't feel very good. could I have damaged something else that's giving me excessive pedal travel?

any suggestions would be most welcome?

nicklouse10

sorry... it's a 1983 944 with everything original equipment apart from the braided lines...

Potomac-Greg

So it was spongy before, and after the flush it is the same? I guess I'd start by trying to bleed it again (since that's the cheapest-easiest solution and the only one that will sold it in a day). You could have air further up in the system. After that, I think you need to be worried about a leak or some other more significant problem that is not likely to get resolved in a day. Good luck.

Chads996

How did you bleed? Pressure or with a friend? If you used the pressure bleeder, trying continuing to bled/flush with a friend helping you. Sounds like you may still have a little air in there.

C.

Jfrahm

If your brake pedal went to the floor a few times you might have damaged the seals in the master cylinder. Over time, the MC piston gets pretty nasty in the areas that do not generally get swept by the seals and when the pedal gets soft and the pedal goes all the way down, this gunk is forced through the seals and can ruin them.

-Joel.

DarylJ

Exactly. Happened to me. Then I bought a Motive. Never again.

Potomac-Greg

Interesting analysis. If you bleed brakes using the two-person pump technique, then you're repeatedly pumping way down the piston stroke. I feel like maybe I dodged a bullet (this time). I have a Motive now, and this is another reason to get one.

GaryM05

On my 1983 944, I find that I have to bleed the rears an extra time, after bleeding all 4 wheels, to make the pedal firm up. So I do RR, LR, RF, LF, RR, LR. If I don’t do the rears this second time at the end, the pedal feels soft, but bleeding the rears one more time seems to work wonders. So, that might be something to try.

Also, I use the old-fashioned manual method with a helper pushing the pedal while I open the bleeder screw. Good luck, but don’t take the chance of going to the track if you’re not 100% confident in your brakes (not that you don’t know that already…just giving a little extra reinforcement!)

nicklouse10

thanks for the advice
I used a pressure bleeder (pump by hand type). I couldn't see any air int he fluid coming through, but I could have been mistaken.
I'll get out there in the morning and have another go with a pal the two person pump way.
very interesting about the damaged seals in the MC. This sounds highly plausible... will investigate and post back
thanks
Nick

DarylJ

I doubt its the reason your pedal doesn't firm up without re-bleeding the backs, but you probably want to do LR, RR, RF, LF, not the order you mentioned. The rear brake lines come down the passenger's side, making LR to longest line, as it has to cross over in front, and then again in the back.

Jfrahm

Yes, you can prevent seal damage by bleeding with a pressure bleeder, you can also put a block under the brake pedal when pumping it to try to limit pedal travel too.

However if you overheat the brake fluid at the track you can get pedal overtravel there too. Honestly with your problem, given that you have replaced so many other components I'd be inclined to bin the old MC regardless. $40 from Rockauto before discount. I have been known to stretch a dollar or two but not for a brake MC on a 25 year old car.

-Joel.

Spidey944

Wow Joel, besides myself, this is the only time I have heard anyone saying what you said above. Nicely done!!

nicklouse10

just re-bled them and it's made no difference... looks like I won't be going out on track today.
on the last few laps of the last track day, the pedal was almost to the floor, so I think you guys are dead right with the over-extended-damaged-seals diagnosis.

$40 seems too good to be true for a new MC! the cheapest one I can find in the UK is £90
however, with the express shipping I'll need (booked another track day for 3 weeks time) and all the myriad taxes that I'll get stung for, it works out about the same price getting it from the UK.

I gotta get out of Scotland and over to the states for a few years I reckon

nicklouse10

today I ordered a new master cylinder and a couple of front brake calliper seal kits for good measure.

I've removed a couple of MC's from 944's before, but it was a long time ago and that was from cars I was breaking up for spare parts to sell online, so I did it the quick way... undo any mounting bolts and hacksaw though the hard lines

I've never fitted a new one so any tips or hints would be most welcome

Cheers
Nick

DarylJ

Hit the bolts and hard line nuts with penetrating oil ASAP, and hit them every moning/evening until the parts come in. Then just go slow with a proper line wrench and you'll be fine.

If the MC comes with or you happen to have a bench bleeding kit, use it. If not, installing a MC dry is no big deal as long as you have a pressure bleeder.

One more thing, your MC probably won't come with a reservoir. It should come with gaskets. Take off the reservoir before you remove the MC from the car so you can get some force on it. Wiggle it back and forth and pull with steady even pressure and you should get it off without a problem.

As always, clean everything that's going back on very well, with brake fluid. And make sure you cover the fender you're working over. Brake fluid makes great paint remover.