How to adjust brake master cylinder pushrod. 986 MY02

[abbiy]

Hi to all,

I just fitted a new brake master cylinder in my Boxster MY02. I need to adjust the brake master cylinder push rod. I can see a rubber boot beside the battery in between the brake booster and firewall, do i need to take this boot off/push back to reveal the pushrod inside?. I cannot see any adjustments below where the pedal rod that goes into the fire wall.

Can anyone please provide directions to the adjust the push rod.

Thank you for your help.

Abbiy. ;)

[1schoir]

Hi to all,

I just fitted a new brake master cylinder in my Boxster MY02. I need to adjust the brake master cylinder push rod. I can see a rubber boot beside the battery in between the brake booster and firewall, do i need to take this boot off/push back to reveal the pushrod inside?. I cannot see any adjustments below where the pedal rod that goes into the fire wall.

Can anyone please provide directions to the adjust the push rod.

Thank you for your help.

Abbiy. ;)

Abbiy:

Go to this link: http://www.renntech.org/forums/index.php?s...ic=15633&hl , and take a look at the third photo in post #10.

Does that help?

Regards, Maurice.

[pk2]

I don't think master cylinder is adjustable. If it is, it's a first for me in screwing with cars (lots of German) for 20 odd years. The fluid pressure is supposed pick up the slack.

Regards, pk

[abbiy]

[Go to this link: http://www.renntech.org/forums/index.php?s...ic=15633&hl , and take a look at the third photo in post #10.

Does that help?

Regards, Maurice.

Hi Maurice,

Thats it !. That looks like adjuster i am sure. My problem started when i suspected my MC sinking to the first stage of the MC. I replaced the MC which i purchased form the US through Pelican. After installation i bleed the system with Motive Power bleeder, again purchased form the US thorugh Pelican. I have two problems now!. If i stomp hard on the pedal and hold, it sinks very very slowly (air in the system) but if push very lightly, the pedal sinks rapidly to first stage, so last night i loosen the two long bolts just to get the booster and MC away slightly and problem seems to improve!. The rapid sinking does not happen when light pressure is put to the pedal. That's when i figured i need to adjust the push rod. Sounds fair.

Abbiy.

[abbiy]

I don't think master cylinder is adjustable. If it is, it's a first for me in screwing with cars (lots of German) for 20 odd years. The fluid pressure is supposed pick up the slack.

Regards, pk

Hi PK,

That link mentioned by Maurice looks like it can be done. what you think?. This brake problem is pissing me off!. I can stiil drive the Boxster and the pedal is fine as long as i stomp on it. But if i ease into it with light pressure it sinks half way to normal. I am sick of trying to bleed the system and may liters of brake fluid. Now i just connect a 3 m clear tube form the nipples direct to the MC reservoir and just keep pumping the pedal but i do not see any air going through, thus my theory to adjust MC push rod.

Abdul.

[Loren]

I think you have a brake booster problem.

Have you checked it?

[wvicary]

You adjust the pushrod for free play so the brakes are not engaged when the brake pedal is at it's upper point not to correct a sinking pedal. Loren makes a good point- check the brake booster for leakage or contamination.

[abbiy]

I think you have a brake booster problem.

Have you checked it?

When i drive the car and do quick stop its perfectly ok ie normal.

Last nite i removed the vacuum line and blew through one way and could not the other. I did some other tests:

1) I pumped the pedal a couple of times ( engine off), with my foot on the pedal with slight pressure, i started the engine, the pedal goes down slight.

2) With my foot on the pedal, i turned the engine off, pedal does not move anywhere ie neither up or down.

If the piston in the MC is not coming back fully, partially or completely blocking one inlet port of the MC from the reservoir, will this cause the pedal to sink (rapid) part of the travel?. Does this sound logical?.

I appreciate the feed back from everyone. :)

[abbiy]

You adjust the pushrod for free play so the brakes are not engaged when the brake pedal is at it's upper point not to correct a sinking pedal. Loren makes a good point- check the brake booster for leakage or contamination.

Hi Wvicary,

Appreciate your reply. What test can i do to check the booster apart form the ones i have done already.

How do i check for contamination ... how can i tell booster has water or crap in it. I hate pulling things apart and finding nothing wrong....especially on a Porsche!.

One thing i noticed though, while i was bleeding the system i left to have lunch and when i came back i noticed some of the nipples were weeping brake fluid at their base, so i removed all of them one by one and cleaned the seats on the nipple and the caliper, some seats were rusty due to Boxster done only 53,000 Klm's since 2002. Could air still be getting through at these points/seats :( ?.

[pk2]

Hi PK,

That link mentioned by Maurice looks like it can be done. what you think?....MC reservoir and just keep pumping the pedal but i do not see any air going through, thus my theory to adjust MC push rod.

Abdul.

Abdul

I'm just think thinking aloud, not necessarily Porsche specific. I'm not quite sold on the booster. brighter bulb than I seem to agree, so maybe it's e a Porsche thing. But In experience with no booster (car dies at speed, no vacuum off the intake, bingo, no boost) is it's just harder than 'ell to push the pedal but, there is no pumping involved, totally predicable. But that is a total los of boost, not just a leak. However, any significant leak should make the car run like s___, loss of vacuum..I'd think. Maybe Porsche ahas an unconventional booster

You could eliminate the booster out of the equation by doing your slow then hard push routine without it running (It's just going take about 50 more Lbs of pressure on the pedal). If the pedal behaves normally (given the circumstances), that is the pedal is always stopping when it should and where it should repeatably. Then if it's your booster alright.

If it still will winds up (with alot of pushing), on the floor, it' s your hydrolics.

If it is the hydrolics, got an idea how you could narrow it down but, gotta run.

Regards, PK

[wvicary]

It could be that you have air in the system still. It sounds like the brake booster is ok. Sorry but I have no specs for the pushrod length. I've always adjusted it so there is approx. 1-2mm free play. You are correct in thinking that if the master cylinder can't return fully it will not uncover the internal transfer ports and you not will able to properly bleed the system.

[abbiy]

It could be that you have air in the system still. It sounds like the brake booster is ok. Sorry but I have no specs for the pushrod length. I've always adjusted it so there is approx. 1-2mm free play. You are correct in thinking that if the master cylinder can't return fully it will not uncover the internal transfer ports and you not will able to properly bleed the system.

Hi Wvicary,

PK was right that MC pushrod cannot be adjusted. the pedal can be adjusted with the procedure in the link that was suggest to me. I tested my booster with a Mighty Vac (genuine made in USA) and i put 20Hg into it, it held no problems. I then put my foot on the pedal and it just fell 4 Hg which according to the Mighty Vac instructions it should not fall more than 6 Hg each push of the pedal. I ended up installing the my original MC back on and problem still exists ....so now i am going back to the basics and replace the front brake pads which looks low and start rebuilding my calipers front ones first which may have rust in them etc. I will let everyone know how i managed to cure this problem.

Thanks everyone.

Abbiy. :)

Edited August 14, 2009 by abbiy