melon

Hi Steve and Andrew,
Just been checking through the manual this morning and there is a section on the 'brake booster' and a checking operation. I'll try this at lunchtime to see if it's operating as it should be.
In saying that I can't find anything that states there would be difference in pedal travel upon first application though!!
I've been paying a lot of attention to it this morning and there is definately a difference from first application and then a second one very soon after that.
Maybe need to be making that call after all...bugger
thanks for your replies..melon

[Edited by melon - 7/4/2002 8:16:18 AM]

melon

Hi,
Just had OEM Subaru 4 pot kit and braided hoses fitted at the same time on my MY98, I'm happy with the braking performance but on the first application of the pedal I get quite a bit of travel before it 'firms' up and brakes kick in but after this initial push if I brake again it's very firm and kicks in straight away I'm now finding myself depressing the pedal quickly once then braking again the second time to get the fast bite at the top of the pedal travel(mostly motorway driving)...hope you understand me. Is this normal??
I'm am gonna speak with the dealer who fitted but I thought I'd see what response I got here first...the real experts
here's hoping for some advice...melon

dbasteve

This sounds like pad knock back from rotor runout ( Disc not fitted correctly ). If the pedal was spongy all the time I would say you had air in the lines.
Anyway its not normal for the street and your dealer should fix it.

Regards
Steve

AndrewC

To a certain extent what you are experiencing is normal, something to do with the 2 stage vacuum assist in the servo, there is a section in the owners manual about brake pedal operation which is worth reading.

Andrew...

melon

Thanks Steve,
I'd been thinking that maybe there was air in there and they needed bleeding again..but they're not 'spongy' and they do kick in straight away after the first push.
You do have me worried about the rotor runout statement though!!
I'm not getting any vibrations or other feedback though just the initial travel when they've not been used a little while so I'm hoping it's not anything like that
cheers...melon

melon

Andrew C,
I must have been typing while you answered....but I'm glad you did as I'm hoping this is more like what is happening. I'll have a look in my manual tonight before getting back to dealers and being redfaced
Thanks Andrew

dbasteve

I'd be interested in this info in your manuals because a vacuum booster should only reduce pedal effort not pedal travel. Pedal travel is directly related to fluid transfer through the M/Cyl and brake lines.
If it was run out on the discs, they may not need machining. They probably only need to be removed and the mounting faces cleaned and refitted. Minor disc runout doesn't necessarily produce brake shudder intil the high spots are worn off which can take weeks.

Regards
Steve

melon

Hi Steve,
Thought I'd just let you know I took my car into the dealers on friday and the first thing they did was bleed the system which didn't solve the problem, I left the car with them and they checked for leaking calipers etc..no problems..the next suggestion was the master brake cylinder, covered on warranty phew!, this was ordered and replaced tuesday morning...still not cured. The dealer confesses to being slightly baffled and continues looking for problems, he tells me that the only time he has ever heard of such a problem is on rally cars..a problem known as 'pad knock' caused by vibration or disc runout pushing the pads back as previously mentioned by you..thanks, trouble is he has checked the wheel bearings and discs and all seem fine but still the problem is there. The dealer admits to being non the wiser but is being very persistant and will not stop until he gets the bottom of it.
Just wondered if you had any other suggestions or checks as I now realise that you were obviously speaking as an expert and I admit to being impressed with your early diagnosis based on my sketchy explanation.
thanks..melon

dbasteve

I still think there is air in the system. If the bleeding procedure is not done correctly you will get this result.
Here are two similar cases

http://forums.i-club.com/forums/showthread.php?s=&threadid=190755
http://forums.i-club.com/forums/showthread.php?s=&threadid=183883

Steve

dmel

I am experiencing a different problem but still brake pedal related.
Is it normal to be able to reach the end of the brake pedal travel when the car is idlying? (Highish pedal pressure required but nothing like squating). Pedal feel is similar nomatter how many times I press the pedal.
I changed brake fluids (1 litre DOT 5.1) and made no difference. The previous ones were clean. I have braided hoses, Tarox grooved discs, Tarox pads.

I am not satisfied by the performance of the brakes at the moment. Maximum decceleration should have been higher than what I am experiencing right now. Could it be the master cylinder that needs changing?

Thanks
MY99, 50K miles

melon

Hi Dmel,
Sorry to hear that you're having problems with your brakes
I can tell you that there's no way I could get to the bottom of my travel (now!!)so there must be something wrong...maybe air in the system somewhere?
I'm afraid I'm no expert, but when I was checking the manual there was a test (I mentioned earlier in my post) that you could do to check the servo assist, I can't remember the details now but check your manual if you have one, as it was all related to how far it should travel and feel etc....It involved pressing the pedal while running engine then switching off and back on
Let me know if you don't have the manual available and I'll check in mine later and post it for you
It might be worth posting a seperate topic to get more attention
Have you always had problems or is it something you have had done as it may help others to diagnose, i.e have you fully replaced and bled the front and rears, do you have braided hoses on the rears?
hope you get it sorted soon...melon

dmel

Hi Melon,

I have fully bled the system as the brake fluids were totally replaced. There is no air in the system. After bleeding the system there was no change in brake performance and feel. By the way, there seems to be no leak of brake fluid.

Braided hoses are present in all 4 corners.

Previously I could not reach the end of the pedal travel (If if remember correctly). I first noticed this a warm day when my brakes were underperforming.

Do I need to change the servo assist assembly? Has anyone else had such a failure and if yes what is the cost?

Cheers.

dbasteve

Have a look at the links I posted, if you haven't already. You should not be able to push the pedal to the floor at any time when the fluid system is charged completely. Quite often air is trapped somewhere you may not expect, like the ABS solenoid valve or in the master cylinder. Sometimes bleeding a full system can be quite tricky and requires at least two people to do.

Steve

melon

Just got my car back from the dealers..Beechdale at Notts.
Just feel that I must give them a bucket load of praise...
As original post, I had 4 pot caliper setup fitted, supplied by me..cheers Mikee@derby, but had problems with pedal travel. I took the car back in last fri, they refilled fluid, replaced master brake cylinder, checked calipers,discs etc and eventually replaced wheel bearing at front with the diagnosis being 'pad knock' my wife picked the car up yesterday dinner and returned their courtesy car, which we have had all the time, He explained what had been done and that the car was now OK. How much is that she reluctantly asks....It's been done under your extended warranty, no problem I called to say thanks and pass on my gratitude to be told 'I'm sorry it took so long'!!!
Needless to say I'm over the moon and after driving it for the first time this morning all I can say is it's fantastic the brakes are so reponsive now I'm actually enjoying the braking
A massive thanks to Tim at beechdale, I'll never complain about my servicing costs again....honest
Edited to add thanks to dbasteve, I've been mailing offline and he's given me lots of useful help and advice.
a very happy melon

[Edited by melon - 7/12/2002 8:14:51 AM]