whattingh

Good day.
Just replaced my front brake pads. Now I have a weird case. When the car is off and I pump the brake peddle it hardens. When the car is on I can pump as much as I like it stay very spongy and and almost go to the bottom. I did not open any brake lines. Normal spongy brake is because of air, but how. Did not open any lines. The brakes was not spongy before I replaced the brake pads.
Could there have slip air in some how when I compress the piston?

Any advice or ideas please help?

mikekantor

iTrader: (5)

You may want to check for leaks at the pistons.

Rider

Same thing happened to me. I didn't open the lines but somehow air got in the lines. I had to flush the brake fluid anyway. Pedal is back to normal now.

whattingh

I had a look and can't see any leaks. Will bleed the whole system tomorrow with new fluid as the fluid in there is a bit old anyway so it is good idea anyway.

Thanks for your ideas

Matt93SE

iTrader: (44)

yeah, just bleed the brakes. it's good practice to bleed thenm any time you change pads on a street car anyway. for how long pads last, the fluid is old and crap by the time you need new pads again.

Wiking

Pondering the variables:

Dirtier ol (o how blk is blk?) fluid has now been pushed via ABS to main reservoir. What could result? ABS valves and pump might have caught asthma from the dirt...

When engine is OFF, pwr is on, ABS pump is working ctrlled by ABS computer. Is ? it, and how, check:
http://www.cardomain.com/ride/748507/18

When engine is ON, theres the vacuum... hope its ok. This shouldnt have any connection with pad swap.

Less fluid [with new pads] in wheel cylinders, calipers 'new' position should result in better response.

Positive side: If fluids have never been changed, its a miracle that the system works at all

whattingh

I don't have ABS. I bled the brakes yesterday and was a little better but not much. As I drive and the pads settle it is also getting better. Will drive for a while and see what happens. Thanks for the response.

Matt93SE

iTrader: (44)

Brand new pads and rotors that have a grooved (cheaply machined) surface will cause this as well, but the pedal shouldn't go to the floor..

drive on 'em a little while and see what happens.

LvR

Fitting new pads on used or non-skimmed disks always results in an initial degradation of the brakes because the whole pad surface is not immediately in contact with the disk surface ................... driving a few 10s of miles and seriously using the brakes, soon wears the pads to perfectly fit the surface of the disks again and the brake feel will improve with time. In general - skim the used disk or fit new disks if you want best results immediately.

Wiking

The pistons are now workin in 'new region'. If this region has been living with moisty fluid, it is rusted. The seals workin on rusty hills will never seal properly, seals will leak until the rust has been honed off - at least will leak air in. Or will start leaking as seals rip...

From this standpoint, its also wise to replace pads before they are all worn out.

The brake fluid always will be saturated with/from ambient air moisture. The longer it stays in the brake system, to greater is its water content. This poses a boiling/steam threat: brakes will vanish in a critical hot moment... also water will rust the whole system inside out. Thus it has to be changed semi annually.

When was - was there - last fluid change...

whattingh

I only have the car for a +- 9 months now. The old brake fluid was almost the yellow brown like new engine oil so it was due for a change. I bled the system at all 4 wheels till clear brake fluid came out at each wheel. (order RR LR LF RF)

Like LvR said the new pads and old disc must wear in to get a good match.

Will go for a while and see what happens.
Thanks for advice

Wiking

True. The mismatchin grooves still wont play spongy (I guess that was your problem). The fluid wont compress, system wont expand - compression has to be gas = air. (except ol rubber hoses)

Rust can/may become honed off, and situation correct itself. Lets hope so. I'd bleed each wheel again after few weeks.

internetautomar

iTrader: (30)

if you installed ceramic pads, that explains the feeling. some ceramics have a crappy pedal feel for a while, until they transfer a sufficient layer of material to the rotor.
did you cut the rotors when you put on the pads?

whattingh

I put in Ferodo pads. On the box stands "Ferodo Ceramics". When I got the old ones out it was the same ferodo's that was in there.
I did nothing to the rims. I do not know much about brake.

I thought some what about my problem. Here is a few thoughts.
If had a leak some were, the pedal would slowly go done to the bottom if I kept my foot hard on the pedal few a while, and it does not.
Second, if I had air somewhere in my system the wouldn't the pedal feel spongy with and without the car running? Currently it is rock hard when the car is off and is spongy when the car is on.

salsaguru

must be a air bubble in break lines somewhere.

internetautomar

iTrader: (30)

the question from me was did you have the brake rotors cut (no relationship to rim).
whether the pads are the same brand as previously used or not, the rotor needs to be cut or replaced EVERY time you change pads in order to achieve optimum brakes.

whattingh

Sorry. I mean did nothing to rotor.(typing and think different things ). I'm not looking for high performance from the brakes, I'm just not the spongy feel I have now.

internetautomar

iTrader: (30)

cut the rotor and you will feel an improvement in the pedal feel after about 5 hard stops.

Wiking

Yes, be it air or pads, feeling wont change with engine ON/OFF

This leaves only one variable: vacuum booster.

mikekantor

iTrader: (5)

The bleed was in the wrong order, the way it should be is: LR, RF, RR, LF.

Bleed it again and make sure you dont let the reservoir fluid get too low. When I had air stuck in my calipers, the pedal was hard when the car was off, and soft when on.

What bleed method/procedure are you using?

internetautomar

iTrader: (30)

no, you bleed with the wheel furthest away from the master cylinder first and work your way closer. I.E. RR LR RF LF

mikekantor

iTrader: (5)

Wiking

I guess its distance to ABS dictating the sequence, both circuits. If no ABS, then distance to main cylinder is the deciding factor. No magic, just shoot the bubbles = Longest line first...

The possible fight with pressure regulator is seldom mentioned - smtimes needs extra exercise.

mikekantor

iTrader: (5)

Its done distant then closest, but one proportioning valve at a time. No load sensing valve (pressure regulator) in third gens without ABS.

Wiking

Yes. As ABS is opposite side than main cylinder, the line L/R lenght depends on it...

That would be weird [= no regulator] as even sentra/bluebirds have regulator. Cant believe that, but that should not alarm anybody as I really dont know...

LSV is another issue, that may be extra feature added only with ABS?

Both systems may keep & hide air bubbles which wont come out with normal bleed.

Maxteca

iTrader: (1)

Did you have to compress the pistons on the caliper and if so did you take the cap off of the brake fluid reservoir. Because I know if you don't take the cap off
air will get in. So you might try to bleed the breaks.

internetautomar

iTrader: (30)

experience > FSM.

walt does bring up an interesting point about the ABS unit being on the opposite side which changes distances a bit. it may also have to do with the way the circuits are laid out.

LvR

WHAT!?

Wiking

I guess we all agree about line length being one key factor.

The line lengths between Main cyl --- ABS are equal. Then ABS is kinda 'last' hub in the delivery chain: the competing bubble formations on the separate circuits wont know whats 'beyond ABS' as the flow time is equal on that piece of 'trip'.

Oh boy if the problem would be as easy as forum -reasoning: dirty hands experience tells that one in 10k bubbles have encapsulated blondie logic

CMax03

iTrader: (3)

That's kinda normal for you to get a harder pedal with the car not running, and then once you do start the engine the pedal goes down a little lower! If I were you, I would bleed the brakes thoroughly. If you think the brake pedal is going low enough to be in the second stage of braking it's your M/c!

CapedCadaver

iTrader: (8)

i'm a noob to that terminology. is it can be storie tiem now pleez?

whattingh

When I replace the pads I did open the reservoir and compress the pistons. Read somewhere that if you open the reservoir the pistons compress a little bit easier. For those that did not notice I'm from South Africa. There is minor difference to my maxima but nothing major.
I do not have ABS (only our auto models had ABS)
I have Load sensing valves.
I have 2 lines out of the mater cylinder going to 2 splitters(each splitter front rear split)

I'm not going to have time in this week so it will happen the weekend. Not going to drive much the week anyway.
I also heard another theory. It could be that one of the pads is not moving correctly, not flush with disc.
This coming weekend I'm going to take the wheels off, check that all the sliding pins in moving freely pads in pressing flush on disc's. Then bleed the system again and make sure the LSV open enough.

My method of bleeding the brakes are someone is pumping(pumping a few times and hold the pressure) in the car and I open and close the bleed valve.

The car have that stock rubber brake lines that is as old as the car if I must guess, so I also might go and maybe replace them with SS lines.

Thank you for your comments

LvR

Imagine that - another South African here - only 1400km away.

Since by your own admission you have not skimmed or replaced the disks, I think way too much has been made out of this whole issue already - if you are sure you don't have leaks, just get in the car and drive it cautiously for some 100km while jumping on the brakes every now and again - I am willing to bet that you will get normal pedal feel back soon as the pads have set on the disks.

Oh and btw - the biggest difference is that our cars do not have O2 sensors on the ECU.

whattingh

no o2 sensors
no cat
no EGR
Have H4 headlight bulbs instead of 9004
And parts not so easy to find unless you go to the agents.

LvR

Yep,indeed - how is our local rust treatment holding up in Cape Town when you compare to the other guys here often posting a lot about rust issues?

whattingh

The only place I had rust so far that I know of was the battery stand. I took it out out the other day and gave it some rust converter and some paint. I wash the car regularly and polish it for time to time to help prevent rust.

Tina Graefe

ITS EASY..... REPLACE CALIPERS..TRUST ME I DELT WITH THIS PROBLEM OFTEN,,CALIPERS WILL GO IN EASY BUT BEAUSE OF DIRT BUILD UP ON PISTON IT WILL NOT COME BACK OUT PROPERLY AND WILL GIVE A SPONGEY PEDAL AT THE TOP..HAVE A GREAT DAY..

Laevateinn

iTrader: (3)

Opening the reservoir cap may help but opening the bleeder valve is the best way. Why? With the bleeder valve closed, dirt behind the piston will be pushed back in the system and will be worse if you have ABS.