carguy123 UltimaDork
Nov. 10, 2016 12:19 p.m.

I replaced the front brake pads on my 2010 F150 a couple of days ago.

Silly me I thought they still wanted your old pads for cores so I took off both sides which I usually do not do (see where this is going) and headed into town. I got the pads and when I got back I immediately compressed the pistons on the driver's side and installed the pads on that side.

When I arrived at the passenger side I did a face palm when I realized what I'd done, but upon inspection it appeared that no harm no foul. Yes the pistons were a little more extended than I would have liked but there did not appear to be any damage so I compressed that side and installed the pads. One pump and instant rock hard brakes. So far so good.

But when I drove the truck it stopped straight with no pulling & I got a hard pedal and then a leak down softer pedal. The truck stopped straight but anticipating brake fluid everywhere I didn't do this often.

When I got back I could not see any immediate signs of any brake fluid leaking nor was the reservoir down much. It was down from the level of when I pushed the pistons back in, but not low. It appeared to be down just from the fluid being used to push the pistons back out.

I parked the truck and haven't been able to look at it for 2 days due to rain. When I removed the passenger caliper I expected to see signs of brake fluid leakage but it looks OK.

Other than hyper extending the calipers slightly what else could it be? Nothing was touched except what was necessary to replace the pads.

I haven't torn down the caliper to see if the O ring might have gotten twisted or kinked but if that happened wouldn't I see signs of leakage?

I don't want to get that messy if I don't have to.

I hadn't wanted to remove the drivers side too, but I'm going to go do that while everyone here tells me exactly what's wrong and how to fix it quickly. Thanks

NEALSMO UltraDork
Nov. 10, 2016 12:25 p.m.

The back pressure pushed through the master cylinder when you compressed the pistons may have damaged the seals in the master cylinder.

I've NEVER had it happen to me, but the "proper" way to compress the caliper pistons is to crack the bleeder when you do it.

akylekoz Reader
Nov. 10, 2016 12:25 p.m.

It is possible that your master cylinder traveled a distance that is has never traveled before and took out the seals. If I'm not using a vacuum or power bleeder when bleeding brakes I try to use a short stroke. This also applies to seating calipers.

GameboyRMH MegaDork
Nov. 10, 2016 12:26 p.m.

It could be that some air got into the system when the brake piston nearly popped out. I'd bleed the corner where that happened first.

NEALSMO wrote: I've NEVER had it happen to me, but the "proper" way to compress the caliper pistons is to crack the bleeder when you do it.

Also, this.

carguy123 UltimaDork
Nov. 10, 2016 12:34 p.m.

OK I'll try bleeding that corner.

I didn't have to bleed them the first time around so I didn't expect an issue there.

The reservoir over filled when I compressed the pistons but then dropped back to normal once I pumped the brakes.

One thing I did notice is that when I removed the Drivers side caliper it was clamped more firmly on the pads than on the passenger side so possibly it is just bleeding. I hadn't thought of air entering the system through the piston. I'll try that.

Please be that! I don't really have time to fool with this much today but I'm loaning my truck out tomorrow so I've got to take whatever time it takes to fix it.

keethrax Dork
Nov. 10, 2016 1:09 p.m.
NEALSMO wrote: The back pressure pushed through the master cylinder when you compressed the pistons may have damaged the seals in the master cylinder. I've NEVER had it happen to me, but the "proper" way to compress the caliper pistons is to crack the bleeder when you do it.

New to me, but it makes a kind of sense. Will keep it in mind in the future.

carguy123 UltimaDork
Nov. 10, 2016 1:26 p.m.

OK a Mityvac is useless for bleeding the brakes. I remembered that but had hoped I was remembering wrong. You get a stream of bubbles the whole time there's a vacuum. I've replaced the hose, but it still does it. Because the nipple is so short the hose doesn't seal well enough to hold a vacuum. I've always wanted one of those pressure bleeders but I don't do brakes often enough to make it a worthwhile investment.

Now I've got to wait and twiddle my thumbs till the wife gets back from the store so we can bleed them. Yes, I've tried the one man bleed of a hose in a bottle of brake fluid, but I don't trust the results so if I drive the truck and it still doesn't work properly I won't know if it's the brakes or the bleed so rather than put it all together and then have to take it all apart I'd rather wait.

This is one thing the kids are good for and one of the little things you miss once they leave home. There's a whole lot of little things you need help with you'll miss when the kids are gone.

GameboyRMH MegaDork
Nov. 10, 2016 1:37 p.m.

Would it be faster to go and buy a set of speed bleeders than to wait for the wife?

Streetwiseguy PowerDork
Nov. 10, 2016 2:40 p.m.

Just open the bleeder and gravity bleed. If you didn't lose fluid, you didn't admit air.

You either damaged the master by pumping the pedal too low, your rotors are worn and the pads are only touching on the outside edge, you have a seized slider, or the pad is hanging up.

wvumtnbkr SuperDork
Nov. 10, 2016 3:50 p.m.

Did you properly break in the pads?

I have had what I thought was a great pedal because the vehicle stopped quickly.

Once some heat was in the pads, the friction of non broken in pads was minimal. I had to push the pedal quite hard and far to stop.

Once I broke in the pads correctly, the problem dosappeared.

outasite
outasite Reader
Nov. 10, 2016 4:33 p.m.
akylekoz wrote: It is possible that your master cylinder traveled a distance that is has never traveled before and took out the seals. If I'm not using a vacuum or power bleeder when bleeding brakes I try to use a short stroke. This also applies to seating calipers.

+1 on this suggestion: Depending on mileage/flushing brake fluid schedule you may have caused damage to either 1 or both master cylinder piston seals. First pump/hard pedal you are putting enough pressure on the cup seal to cause to expand and seal. As you are holding the pedal, your foot is not pressing as hard and allowing the cup seal to loose it's sealing ability, thus allowing fluid to leak by and the pedal will slowly move down ward. Try pushing harder when it starts to move down. Slow, short strokes next time you replace the pads.

carguy123 UltimaDork
Nov. 10, 2016 9:44 p.m.

I bled both wheels with no apparent air and now I just have a softer pedal and more travel than I remember. I can activate ABS, but it seems like it takes more to activate it.

It is still stopping straight and true but on the way back from town I got a little vibration which I normally don't have, but I rotated the tires so maybe it's from that.

I did a couple of quick stops just before I turned into the driveway and then hit the rotors and calipers with a temp gauge and the rotors were pretty even at about 500 degrees and the outside of the calipers was about 284 on one and 270 on the other. Not a big enough disparity to cause me to get worried.

I have in laws flying in from Colorado tomorrow and they were going to borrow the truck and drive down to San Antonio. I may give them a car instead just because I'm not 100% on these.

I've never had this happen before but I always do 1 wheel at a time since I had a piston pop out back in the 80's by forgetting to block off the 2nd caliper before pressing the piston back in on the other. That's something that sticks with you.

I always do the brakes this way and this way I don't have to bleed the brakes unless I want to. I will use the bleed screw the next time just because it seems it would make it easier to retract the piston.

This has me scratching my head because nothing like this has ever happened to me before and because there's no clear cause.

Still no loss of fluid and once it's light I'll see if I can find evidence of a fluid leak somewhere. My thought is if it's a piston O ring that I will see it on the inside of the caliper on the back side of the brake pad, correct?

Oh, this all happened before I could bed in the pads. It was an instant issue so I didn't do any more braking than I had to because I thought I'd get back and see the problem and fix it.

On my run into town, probably 5 miles there & back, I didn't try to heat them up more than necessary as I was till testing the firmness and stopping capacity. If I can't find evidence of a problem in the morning I'll abuse the system & bed the pads to see if I can break it.

And the pedal doesn't sink when I'm sitting at a light which I would expect if the O ring had kinked or blown. I feel like I'm dating again and it's giving me mixed signals.

Stefan MegaDork
Nov. 11, 2016 8:59 a.m.

BTW, next time you need to bleed brakes, build yourself a pressure bleeder first:

$20 Pressure Brake Bleeder

Then bleed all four calipers/cylinders and make sure the rear drums (if equipped) are adjusted as the auto adjusters don't always work as well as they should.

Finally, make sure the calipers, pads and/or shoes are clean and lubricated so they can move properly and evenly.

If the braking is still inconsistent, then perhaps some of your brake components need to be replaced or rebuilt.

Streetwiseguy PowerDork
Nov. 11, 2016 11:01 a.m.

Are the pads making contact across the entire face, or are they only rubbing the edges because the rotors are not flat? This is an extreme example, but not unusual:

carguy123 UltimaDork
Nov. 11, 2016 11:12 a.m.

I replaced all the components on the front and lubed all the proper places to be sure everything moved when it was supposed to.

The brakes worked just fine, except for they were noisy. They weren't worn out, but had cracks across them so since I already had them off I replaced the pads and all the SS hardware. The rotors are fine, the pads sit properly and everything moves as it should.

And then the problems began. I haven't touched the rears. I can find no obvious signs of leakage or loose anything. The brake fluid level hasn't dropped.

I am going to drive it into town again and while I'm out I'm going to bed in the pads. I've never had any type of brake issue before from just replacing one axle of pads. I have had issues when I went much deeper and forgot to tighten something or had a stuck caliper. I've tried to learn from those experiences and consequently brakes have become so routine for me that I haven't had an issue in years if not a decade or longer. That's what's got me so puzzled about this. Literally the only thing I can think that is possible to have gone wrong is a hyper extended piston, even tho it didn't appear to be hyper extended and there are no leaks.

If it keeps it up I'm going to get a rebuild kit to rebuild the calipers. It's messy, but not a hard job. Unfortunately it takes time I don't have right now. Since the election business has been booming.

People feel so confident things are going to get better which will cause rates to rise that they are rushing to buy a house before prices & rates rise even more. I love it!!!

And then there's the brand new grandbaby, the first girl, relatives in town, organizing the fight to take over our HOA, the list goes on & on.

Streetwiseguy PowerDork
Nov. 11, 2016 11:31 a.m.

Did you install Wagner thermoquiet pads? They have a thin layer of what appears to be friction material on the back side of the pads, and certain applications create a lousy pedal. This photo shows the stuff on the back side.

carguy123 UltimaDork
Nov. 11, 2016 11:46 a.m.

I used Wagner OEX

GameboyRMH MegaDork
Nov. 11, 2016 12:10 p.m.

I'm going to say +1 on MC seal damage now...I'd recommend rebuilding the MC before the calipers. At this point you should've seen leakage if there was a problem with the caliper seals, while the MC can leak internally causing the problem you describe without the fluid level changing.

carguy123 wrote: People feel so confident things are going to get better which will cause rates to rise that they are rushing to buy a house before prices & rates rise even more. I love it!!!

LOL oh that's kind of sad...

carguy123 UltimaDork
Nov. 11, 2016 12:28 p.m.

Not sad to me.

outasite
outasite Reader
Nov. 11, 2016 1:24 p.m.

I am putting this out there because of experience with students. I know you have been a DIYer for quite a while and have previous brake experience. After brake work which required bleeding, they would tell me the pedal was still soft/spongy. I had to explain that when we drive the car/truck, we do not have to apply a lot of pressure to slow/stop the vehicle because of the brake booster. With the engine running, the pedal will be soft/spongy with heavy brake pedal pressure. I would have them shut engine off, deplete booster reserve pressure and push on the brake pedal. To add to that, I would always road test the vehicle with them and demonstrate the proper procedure to break in the new pads. After this procedure, I would have them drive the vehicle to notice the pedal pressure required to slow/stop. Again, I am sure you are aware of this. Just putting it out there.

carguy123 UltimaDork
Nov. 11, 2016 2:23 p.m.

EUREKA!! It fixed itself!

As I was leaving the neighborhood as I was coming to a stop at the intersection I unconsciously pumped the brake pedal because it was so much softer than normal. Immediately the pedal firmed up and engagement moved much closer to the top.

Obviously it was a seal or O ring somewhere just slightly out of place and it popped back to where it belonged.

I have a slight amount of shuddering under firm braking but I'll attribute that to the design of these brake pads &/or they are just new and not totally seated to the rotors yet.

Thanx for the hand holding guys.

GameboyRMH MegaDork
Nov. 11, 2016 4:21 p.m.

Well you know what it is now but you should still do a brake MC rebuild. That seal could pop back out of place again.

BrokenYugo UltimaDork
Nov. 11, 2016 4:45 p.m.

A low/soft pedal that will pump back up generally indicates a dying master cylinder. They usually last longer than 6 years though.

outasite
outasite Reader
Nov. 11, 2016 5:35 p.m.

Many years ago I had a VW Rabbit in for brake work. We replaced front pads and rotors, rear shoes and hardware and resurfaced the drums. After the work was completed, the brake pedal was low and spongy. After checking rear brake adjustment, bleeding brakes, checking caliper bolt torque with same pedal, I replaced the master cylinder. After installation/bleeding the same pedal. This brake job had been performed by students. I asked them to disassemble the front brakes for a closer inspection. We found one of the brake pads on the piston side of the caliper was not installed properly and the steel backing on the pad was bending when the brakes were applied. It was acting like a very stiff spring thus the spongy/excessive travel. Perhaps you had a pad that was hanging up/stuck.

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