After pad change - brake pedal goes to floor

[Jonski]

I just changed all the brake pads on my 2000 W210 E320CDI. When changing the pads, I opened the bleed screws on the front calipers to let out the fluid when pushing back in the pistons. I did not do this for the rear calipers.

Following the pad change, the brake pedal now goes slowly but steadily to the floor when the engine is running. Pumping it brings it back up, but it again steadily sinks down to the floor.

I have tried bleeding all four calipers (I pumped through about a pint of brake fluid all together) and though the pedal is firmer now, it still goes slowly down to the floor when the engine is running.

I've heard rumours about dirty fluid going back up the line, (when pistons are pushed back in for a pad change) and this maybe causing such problems.

Has anyone else had this problem, any ideas for a solution please?

 

[huey]

Hello, did you put a block of wood under the pedal when you bled them to stop the pedal going to the floor? you can sometimes damage the seals if not, or there is possibly still some air in the system, i had this trouble with mine once and bought a gunsons eazibleed kit which plugs onto a spare tyre, and make's bleeding the brakes much easier and trouble free. hope this helps

 

[mersum1es]

sounds like still air in the system. DIY pressure bleeder: http://faculty.ccp.edu/faculty/dreed/campingart/jettatech/bleeder/index.htm

 

[Colin_P]

My vote is on air in the system too.

 

[WG M-B]

It could well have air in the system, although it could just be that the pad lining needs to bed in a bit.
It depends how badly the pedal is creeping.

 

[mercmeck]

I just changed all the brake pads on my 2000 W210 E320CDI. When changing the pads, I opened the bleed screws on the front calipers to let out the fluid when pushing back in the pistons. I did not do this for the rear calipers.

Following the pad change, the brake pedal now goes slowly but steadily to the floor when the engine is running. Pumping it brings it back up, but it again steadily sinks down to the floor.

I have tried bleeding all four calipers (I pumped through about a pint of brake fluid all together) and though the pedal is firmer now, it still goes slowly down to the floor when the engine is running.

I've heard rumours about dirty fluid going back up the line, (when pistons are pushed back in for a pad change) and this maybe causing such problems.

Has anyone else had this problem, any ideas for a solution please?

test the system with the engine stopped ..pump the pedal till it goes hard release the pedal . then 20 seconds later apply the brake if the pedal is still hard thats ok if soft you have a problem with poss air in the system

if the pedal is still hard ,start the engine with pedal depressed it should sink ,,the pedal will keep sinking on the 210 as it has the twin can servo
you will never get the pedal completly down on the road as the abs will have kicked in long before you reach max pedal deflection
also give at least 30 miles to allow the pads to bed in.. hope they are o/e quality ////

now bleeding the system if req , only use dot 4 spec saej 1703 fluid from a new unopened tin . never use b/ fluid thats in you garage that been lying about for ages.
you dont need a pressure bleeder to do the bis , get your mate to help . always start at the n/s rear caliper ,engine off bleed bottle attached with see through hose that a tight fit over the nipple . open the nip/ get him to pump the pedal 10 complete full depressions and on the last one on the downward stroke close the nipple watch the fluid level , ask how the pedal feels ,,,is there an improvment in the feel of the resistance . now move on to other side ,repeat then n/s front then o/s front . always close nipple on the last downward stroke this stops air ingress into the system . top up master cylinder

job done
hope this helps
geo p

 

[turbopete]

master cylinder fault?

 

[Jonski]

Seems to be OK now....

Thanks to all for your replies, and particularly to Mercmeck whose advice I followed :

- I checked and, with the engine not running, the pedal does not sink (once its firmed up). So I concluded probably no air remaining in the system. So, I took the car out for a road test. I repeatedly applied the brakes to try to bed in the pads (Bosch). Braking performance rapidly improved, and I think its all OK now. Sinking of the pedal seems less pronounced. But I will report back to this thread if there still seems to be a problem when I driven the car more.

- Unfortunately, I had already used an old, already opened, bottle of Brake fluid for bleeding. So, I hope there are no serious consequences of that?

- Just for information of anyone who may read this thread later on, I did not use anti-squeal paste on the new pads. I now note a slight squeal on heavy breaking, towards the end of braking, when the speed is much reduced, but nothing serious for the moment.

 

[mersum1es]

Brake fluid gets water from the air moisture, and basically result is same than in the car where fluid reservoir breaths. Water in the system lowers boiling point and increases corrosion. If your fluid bottle has been tightly closed, thing is not so bad. Some degeneration of the fluid may also happen, I'm not sure...

Pedal feeling of my W210 has always been mixed, when pressing heavily the pedal goes further but finally stops well before the bottom. System has been similar if I've done the bleeding of the garage has done it.

 

[scotty2hotty81]

You have let air in the system by opening the bleed nipples (which you don't need to do)

 

[bembo449]

you should never crack a bleed nipple to force the piston back , do it without and all will be well , buy a decent sized set of grips to help squeeze them back

 

[drbc43amg]

Empty some fluid in the reservoir (I use a large size syringe) to get some space to compensate for the fluid backing up when you push back the pistons...

 

[television]

Interesting advice here.

when a car is 10 years old, it is better to undo the bleed nipple to stop pushing possible contaminated fluid back into the expensive ABC pump.

To check for air, simply press the brake pedal down till hard or pump up, slightly release the pressure (not foot right off) pause ½ minute then press again, if the pedal goes down further you have air in the system.

 

[wireman]

Bleed the rear first.
Are your disk surfaces in good order? i.e. flat and score free, it sounds to me that this is your real problem, with nice disks there is very little bedding in to be done or as suggested already you may have a tired master cylinder.


The rules as I understand them:-
Always use a new sealed can of fluid to top up.
Change the fluid completely at no longer than two year intervals.
Change all rubber seals and hoses at no longer than ten years.
Always fit a bleed hose immersed in fluid before you open a nipple.
Always empty the fluid from callipers out of the system, don't push it back thru the abs to the master cylinder.

 

[Pathfinder]

Air trapped in the ABS. Bleed again with the engine running and bleed at least half a litre out of each caliper.

 

[Jonski]

Just an update on this after using the new brake pads for a year :
- Brakes have been fine ever since.
- No squealing apparent.