Mongo

Hey guys, I did a brake fluid flush to cleanse some old ATE Blue brake fluid. Started at the wheels furthest from the master cylinder. I did not bleed the master cylinder. I used a Motive Power Bleeder and pressurized to 7psi.

Pedal feels a little spongy, and bites about fifty percent of the way down. I ran a can and a half of ATE TYP 200 Dot 4 through it with no bubbles so I'm a little baffled as to why I still have a spongy pedal.

Any advice?

Geo55

Only advice I have is to check your pads. Are you power bleeding? Sometimes that constant flow helps, bleed from the furthest to the closest caliper (Of course you probably already know that). Good luck.

Zirconocene

Here's what Stan suggested, in the next to last post on my thread: https://rennlist.com/forums/928-foru...scription.html

I've always had a spongy pedal, so I hope this will fix it, but I only just got back to this today, so we'll see.

Good luck

Mongo

Thanks! Will take Stan's advice.

I'm also going to bleed the master and all wheels again. Need to grab another can of brake fluid

Mrmerlin

If your going to full stroke on a older master cylinder then the pedal is spongy either you ran the fluid low or the seals have been damaged by pushing them
through the corrosion in the bore

Mongo

I assume that the seal damage could have been caused by pressurizing the reservoir by only 7 psi? I've seen others pump up to 15psi to do this job. That's just scary. to me.

Fluid never dropped below half in the MC reservoir during bleeding by the way. I was very careful of this.

Mongo

UPDATE - I bled the master and found some tiny tiny bubbles pushing through the bleeder hose. I pumped up to 9 psi this time. Strangely enough the fluid was not dirty.

I will tackle the bleeders at the wheels tomorrow. Dinner time. I assume if I pressurized the reservoir to bleed the master, more tiny bubbles passed into the lines to the wheels?

Mrmerlin

You can get most of the air back to the MC put a stick on the pedal and to the front of the seat keep the pedal pressed down this will compress the air and it will rise
ope the B nuts one at a time back to front on the MC look for air when it solid fluid close the B nut

GregBBRD

Use the pressure bleeder to keep the system full and eliminate the chance for air to be sucked back into the open bleeder, should the 'pump and hold" timing be slightly off, occassionally.
Then manually bleed the system, with a trained helper pushing on the brake pedal and a trained person opening and closing the bleeders.

FredR

Andy,

You should be OK to use the system at 15 psig- remember the higher the pressure the smaller the bubbles and thus they shoud escape that bit easier. If you cannot use this pressure safely then chances are the reservoir is shot and needs replacing.

I just used my pressure bleeder for the first time and for other reasons have still not had the car running yet. I was surprsied at how much fluid i had to use [best part of two litres] and seemingly had problems getting air out of the system and have yet to prove whether i succeeded [or not].I have a feeling I may have made a "rookie" type error though. The design of the reservoir makes it dificult to pull old fluid out of the reservoir so I deliberately allowed the level to drop in the reservoir by drawing some of the old ATE blue fluid out of the rear bleeder in small steps until the level dropped to the bottom of the main body of the tank. This still left a level in the bottom of the reservoir but as I thought about it after the fact, I was left wondering where the invert levels are for the exit pipe and whether I might have exposed such- this assumes that the bottom of the tank traps a small amount of fluid to ensure any debris does not get sucked into the piping. Whether this is the case I do not know but if anyone happens to know about such your thoughts appreciated.

I was a bit apprehensive about using the pressure bleeder but in the end I think it is a very useful tool if one has no one to assist in the bleeding process- my wife hates doing this! It also left me thinknig it might also be useful for doing the PSD system flush given ti is tricky getting fresh fluid into the reservoir..

Mongo

Thanks for the tips everyone. Fred I did the same thing to empty the reservoir. May have introduced air in the system doing it too. Will try again today and use Greg's method...although I'm going to have to convince the wife to pump the brake pedal while too.

FredR

Do keep us updated how you get on- I have a feeling I may well have the same issue. I am having to refurbish my 3 piece wheels that I did not plan for [but should have] so cannot try the brakes out in any meaningul way. .

Mongo

Well... This came out of the RR wheel. Same on the others, just a little smaller bubbles.

Mongo

After the bleed, I can touch the brake pedal with my big toe and the car stops on a dime. Awesome pedal pressure, not bad for the original master cylinder.

Lessons learned:

1) Bleed the Master Cylinder first!
2) RR, LR, RF, and then LF.
3) If you are using a Power Bleeder, pump to 10-11 psi.
4) Open your bleed screws 1/3 the way, or a little more than 1/4. I had a lot of tiny bubbles come out and one big one at the RR wheel.

Very happy now. Looks like I can take my kids in the car on weekend drives again.

Greg, I didn't have my other half available to pump the pedal. Lucky enough the power bleeder did the job. Funny you mentioned that though since that was the procedure I had to do on my 86 944 track car several years ago. Pain in the **** it was...

FredR

Well done! The entire point of the power bleeder is to get good results with one man operation- sounds as though you have achieved that.

Let's hope mine performed just as well!