Menu
What's new
By:
Advanced search...

Bizarre Pad change problem

E

elec12

Members
Messages
18
Reaction score
1
Location
Ireland
Car
Accord 2.2 i-CTDI Ex
Hey Guys, Just joined the site there and said my hellos in the newbie section. Have been doing my own servicing for a while now and recently went about changing the front pads and came across a very strange problem when job was done. Wondering if anyone has seen this before.

Have changed pads before on other cars. All went according to plan, when I finished started up the car and the brake pedal was very soft to the point where it went all the way to the floor. After a few press/depress the pedal went easily all the way to the floor with zero braking at all. Couldn't understand why. Checked the brake hoses for leaks - nothing. Reservoir level hadn't changed. Followed the brake lines from Master Cylinder down to the VSA unit and beyond to each corner and no sign of any leaks.

At that point the only thing I could think of was perhaps when pushing the piston back in the caliper it may have damaged the seals in the master cylinder. If this was the case I still thought it would be strange for there to be zero braking.

Decided to replace the piston in existing MC (new seals etc), refilled with brake fluid and bled system. Same problem, no change. Lost the will to live at this stage...

Now, some may be thinking why didn't you put the old pads back on before going to the trouble of replacing the MC piston. This never crossed my mind until after replacing the MC piston.

So when I put the old pads back in, brake was perfect. Can’t understand it! There is some pad left on old ones which will keep me going for few weeks but if the same thing happens again when I try the change a second time the only option will be to bring it to local garage.

Anyone got any opinions on what might be the cause?

Cheers,
Ken.
 
You have air in the lines, I'd imagine?

When you pushed the pistons back to accommodate the new pads, it was probably pushed upwards into the lines. Thus when you used the new pads the air was sitting at a critical pressure point (up the line) rather than nearer the caliper (if not in it). I'd put the new pads in a bleed the brake lines. Go in the following sequence:

1. n/s/f
2/ o/s/f
3. o/s/r
4/ n/s/r

How do I know? Had the same problem with an Accord over the summer, the line bleed produced the following:

photo_zpse25a3fd3.jpg
 
Nice advice mate, I think that could be the problem. Are you loosing any fluid at all?
 
Thanks for the replies guys,

@Jayok, air in the lines is certainly something I suspected. I should have included in my original post that after first experiencing the problem after the new pads went on I bled the system to no effect.

With no sign of any fluid leaks I then decided to change the MC piston in case the seals may had been damaged, which involved bench bleeding the MC and a complete bleed of the system when it was back in so I'm pretty sure there was no air left in the lines after this.

Interesting point you make about the air sitting at different points, wasn't aware this would make a difference.
 
Did you pressure bleed the system? Reason I ask, is that it can be a complete pain in the proverbial to get air out of the ABS/VSA unit if its in it with out pressure bleeding. Alternatively you could try reverse bleeding, seems to work better and than reservoir down.
 
TRY BLEEDING WITH THE ENGINE RUNNING??

Sorry did not mean to shout.

Brake System Inspection and Tests

Component Inspections: Component Procedure Also check for:
Master Cylinder Look for damage or signs of fluid leakage at:
•Reservoir or reservoir grommets
•Line joints
•Between master cylinder and booster
Bulging seal at reservoir cap. This is a sign of fluid contamination.
Brake Hoses Look for damage or signs of fluid leakage at:
•Line joints and banjo bolt connections
•Hoses and lines, also inspect for twisting or damage
Bulging, twisted, or bent lines.
Caliper Look for damage or signs of fluid leakage at:
•Piston seal
•Banjo bolt connections
•Bleeder screw
Seized or sticking caliper pins.
ABS Modulator Look for damage or signs of fluid leakage at:
•Line joints
•Modulator






Brake System Test

Brake pedal sinks/fades when braking



1. Start the engine, and let it warm up to operating temperature.





2. Attach a 2-inch piece of masking tape along the bottom of the steering wheel, and draw a horizontal reference mark across it.





3. With the transmission in Neutral, press and hold the brake pedal lightly (about the same pressure needed to keep an A/T-equipped car from creeping), then release the parking brake.





4. While still holding the brake pedal, hook the end of the tape measure behind it. Then pull the tape up to the steering wheel, noting where the tape measure lines up with the reference mark you made on the masking tape.





5. Apply steady pressure to the brake pedal for 3 minutes.





6. Watch the tape measure.


•if it moves less than 10 mm, the master cylinder is OK.

•if it moves more than 10 mm replace the master cylinder.






Rapid brake pad wear, Vehicle vibration (after a long drive), or High, hard brake pedal



1. Drive the vehicle until the brakes drag or until the pedal is high and hard. This can take 20 or more brake pedal applications during an extended test drive.





2. With the engine running, raise the vehicle on a lift, and spin all four wheels by hand.


Is there brake drag at any of the wheels?



YES - Go to 3.




NO - Look for other causes of the pad wear, high pedal, or vehicle vibration.n





3. Turn the engine off, pump the brake pedal to deplete the vacuum in the brake booster, and then spin the wheels again to check for brake drag.


Is there brake drag at any of the wheels?



YES - Go to 4.




NO - Replace the brake booster.n





4. Without removing the brake lines, unbolt and separate the master cylinder from the booster, then spin the wheels to check for brake drag.


Is there brake drag at any of the wheels?



YES - Go to 5.




NO - Check the brake pedal position switch adjustment and pedal free play.n





5. Loosen the hydraulic lines at the master cylinder, then spin the wheels to check for brake drag.


Is there brake drag at any of the wheels?



YES - Go to 6.




NO - Replace the master cylinder.n





6. Loosen the bleeder screws at each caliper, then spin the wheels to check for brake drag.


Is there brake drag at any of the wheels?



YES - Disassemble and repair the caliper on the wheel(s) with brake drag.n



NO - Look for a bulging master cylinder cap seal, discolored or contaminated brake fluid in the master cylinder, or damaged brake lines. If any of these items are damaged, replace them. If all of these items are OK, replace the ABS modulator.n
 
Thanks Jayok, didn't pressure bleed, old 2 man method. Will look into the pressure bleeding kits and try to magic up a solution for the reservoir cap. Hopefully that'll make sure there's no air left.

@edgeoftime, many thanks for the brake testing procedures.
 
Yeah, I've the sealey pressure bleeder (pump action) and getting a seal on the master cylinder is a fupper. No problem with the German marques, but Honda being Honda, they went off and done their own thing :rolleyes:
 
You must log in or register to reply here.
Top