Soft brakes (1 Viewer)

[linuxgod]

Sorry for cross-posting, but I posted to the SQOD but didn't get any responses, and I'm trying to figure out an answer today.

Tough Dog 2" lift completed yesterday. I have yet to get an alignment done. (it's scheduled for Tuesday) My mechanic's helper tore the CV boot when helping to pry out the old front struts, so we had to pop off the calipers, rotors, and CV axles to replace the boots. Truck rides great (a little squirrely since the suspension hasn't settled yet and I have can see some negative camber). However the brakes seem much softer/have more travel than before. I thought this might happen when driving due to different spring rates/front end angle, etc, but it feels this way even when I'm in Park when I first start the vehicle.

Question 1: Has anyone else experienced this? Is this due to excess negative camber or something weird where a sensor reading is off? My mechanic is convinced it's due to brake proportioning and the Toyota system detecting less rake. I'm really not convinced, since if that were the case anytime you parked slightly uphill the braking feel would change. I checked the brake lines and I don't see any leaks, twists, kinks, etc. But since a bunch of you guys have lifts I'd really like to hear from you if you noticed a change.

I was thinking perhaps there was a very small amount of air previously trapped in a bend in the system, and when removing the calipers from the rotors the air bubble migrated somewhere else in the system. I'm going to pick up a one man brake bleeder and try to purge the system. The Toyota instructions to bleed the lines at GSIC - Global Service Information Center seem easy enough, but there's a second set for "bleeding the system".

Question 2: Is bleeding the brake system necessary (or in my case a likely/possible cause), or is that only when the master cylinder and/or abs has been repaired/replaced? The instructions mention to always use the GTS when bleeding air from the system, but I have no idea what that is (I assume a specialized tool?)

Question 3: How much fluid does it normally take to flush the brake system?

I'd like to clear this up before I drive 2000 miles this week.

Thanks for your help guys

 

[NLScooby]

I just lifted my 200 last week and did not experience any change in brake feeling. In fact, the firmer shocks make the nose dive less - and thus braking actually feels better!

A few weeks ago I replaced all my flexible brake lines with extended length stainless steel braided lines in anticipation of the lift....and I flushed the brake system while I was at it. I went through two 12 oz containers of fluid. I did notice a slight improvement in brake feel after this service.

New fluid flushing should be done every other year or so. And whenever you change brake pads/rotors. For the lift - there should be no reason why your brake pedal feel changed.....unless the installer got some grease on the rotors and didn't clean them off well prior to reinstallation.

 

[linuxgod]

I considered grease on the rotor, pads no longer seated perfectly, etc. But what's weird is that the pedal feels softer and has more travel even when sitting idle in Park.

 

[TonyP]

I had no issues with the brakes. I'd start with a simple bleed and maybe some brake clean. It's very easy to get some grease on your rotors. That doesn't explain all the symptoms though.

Rake has nothing to do with it. If you're on a hill would the brakes feel that much different? Nope

 

[NLScooby]

I wonder if your line was somehow flexed to a point where air got in. That is really the only explanation I could think of for such a soft pedal....
I'd definitely do a bleed and go from there....

BTW, the easiest way to bleed was to have the ignition on (not engine), and have someone just press and hold the brake pedal - you don't need to mash it down to the floor - while you handle the bleeder valve end of it. I messed around with a silly micro vacuum pump for too long before my son finally came home and was able to help by pressing the pedal. The active brake system engages a pump (or something like that) so that simply engaging the pedal will keep a constant pressure/volume of fluid moving. No pumping of the foot is required. This method took mere minutes to complete - but you can run through fluid quickly so make sure you have the master topped off....

The order of bleeding was also different than what I've traditionally followed. The FSM, states to start with Pass Front, then Drivers Front, then Pass Rear and then Drivers Rear....- which is different from how I was taught on older vehicles - where you started at the furthest point away from the master cylinder.

 

[linuxgod]

I had no issues with the brakes. I'd start with a simple bleed and maybe some brake clean. It's very easy to get some grease on your rotors. That doesn't explain all the symptoms though.

Rake has nothing to do with it. If you're on a hill would the brakes feel that much different? Nope

Thanks Tony. I don't think there's grease on the rotors, but I'll spray some cleaner on them to be sure. Truck still stops ok, just seems like the pedal has more travel before the brakes start to grab. If I'd never driven the truck before I probably wouldn't think twice, but I'm so used to it grabbing with the pedal up high (where I have to almost baby the brakes) that it's definitely different.

 

[linuxgod]

I wonder if your line was somehow flexed to a point where air got in. That is really the only explanation I could think of for such a soft pedal....
I'd definitely do a bleed and go from there....

BTW, the easiest way to bleed was to have the ignition on (not engine), and have someone just press and hold the brake pedal - you don't need to mash it down to the floor - while you handle the bleeder valve end of it. I messed around with a silly micro vacuum pump for too long before my son finally came home and was able to help by pressing the pedal. The active brake system engages a pump (or something like that) so that simply engaging the pedal will keep a constant pressure/volume of fluid moving. No pumping of the foot is required. This method took mere minutes to complete - but you can run through fluid quickly so make sure you have the master topped off....

Thanks. I had planned to get my 9 year old son to give me a hand, since I know he gets a kick out of wrenching with me. Last time I did a bleed it was on my '66 Mustang, so it's been close to 20 years.

Man I suddenly feel old.

 

[linuxgod]

One update - my wife said she felt like the sponginess in the brakes was intermittent this morning. It would be spongy, then the next few braking attempts were fine.

 

[Yossarian]

Another thought is that the flexible brake lines might have been damaged? Were the calipers properly supported, or were they hanging on the lines? If they were stretched enough it's possible to have internal damage that might cause what your describing. Does the vehicle brake normally other than the soft brakes, no pulling?

 

[linuxgod]

The calipers were rested on the LCA and were secured with a rubber bungee. It's always possible they got twisted, stretched, etc in the process but the mechanic I was working with seemed to know what he was doing and I definitely didn't see him dangling the caliper by the line or anything like that.

Vehicle seems to brake normally. Granted it needs an alignment and camber is visably negative.

 

[Yossarian]

I was thinking if you did have damage, it would be unlikely (maybe) that both lines suffered, hence pulling during braking. What you describe here doesn't add up, a lift should not result in "soft" brakes.

When you bleed the system, inspect everything. Maybe one of the electrical ABS lines got pinched and the system is getting intermittent signals? But wouldn't that throw a code also?

 

[linuxgod]

If it was anything ABS-related I would think that would throw a code. Plus the softness/longer pedal travel happens when in Park.

 

[linuxgod]

[Duplicate]

 

[chilibit]

My first guess would be air in the system. Maybe the master got too low. Are you sure all the brake pads were installed? Not sure how it would behave with one missing. Sounds silly I know. In a rush I installed some pads backwards at the track but you notice that pretty quick. Did these rotors come slotted? Uh, no.

 

[linuxgod]

Nope. Stock Toyota rotors and pad. Pads have 50% on them and didn't get removed.

I'm hoping it's just air. We'll see this weekend. Really hoping it's not the master cylinder. I would just think air but the occasional long brake travel concerns me. But at 66k miles it seems odd for the master to suddenly go bad.

 

[linuxgod]

Bled the brakes this weekend after driving about 250 miles, both the lines and the full system, per the GSIC instructions (the latter required my OBD2 dongle and Techstream). Still feels wrong. I'm going to drop it at Toyota first thing in the morning. The low pedal, especially at engine start while Parked, really feels like a bad master cylinder. I know it seems highly unlikely, but I can't come up with anything related to the suspension that would make the brakes feel low until pumped when I first turn the vehicle on.

 

[TeCKis300]

Another guess would be that they didn't install your axles correctly and/or the axle nuts were not torqued to spec. This could cause the stub axle to deflect when cornering or braking, such that it pushes the brake pad/piston in (pad knockback). In turn, making for inconsistent brake feel as the pad would need to make up some travel before really engaging the rotor.

I would definitely not tow anything until this is resolved as this is a more serious issue.

 

[linuxgod]

Another guess would be that they didn't install your axles correctly and/or the axle nuts were not torqued to spec. This could cause the stub axle to deflect when cornering or braking, such that it pushes the brake pad/piston in (pad knockback). In turn, making for inconsistent brake feel as the pad would need to make up some travel before really engaging the rotor.

I would definitely not tow anything until this is resolved as this is a more serious issue.

Thanks. I may have my mechanic go back and retorque these as per the GSIC before I drive across town to Toyota. I agree I'm not going to make the long trip out west until this is resolved. Worst case I'm going to drop it off at Toyota tomorrow and get the pros to look at it.

 

[TonyP]

Whatever it is, bring the bill to the dudes who put on the suspension and have them deal with it. Assuming it was related to the install.

 

[linuxgod]

Whatever it is, bring the bill to the dudes who put on the suspension and have them deal with it. Assuming it was related to the install.

Sucks because the guy who owns the shop is a friend of mine, and his shop was very busy so he was doing me a favor by squeezing me in and tying up his bay. He's already offered to reimburse me for any costs to fix it.

Thinking back, twice yesterday I backed out of my driveway a full lock right, the full lock left to get onto the road, then the first time I braked at the stop sign a few hundred feet down the road I experienced the long pedal travel issue. Next braking attempt was normal. Not sure if it's right but I like @TeCKis300 explanation. If there's a slightly wobble in the disc causing the pad to back out and leave an small gap that would explain why sometimes the pedal travel is too long, but pumping the brakes once fixes it. (So would a failing master cylinder, but it failing at precisely the same time as this work was done just seems soooo unlikely). Then again isn't the hub attached to the UCA, LCA, and steering linkage? So if there was CV movement in and out wouldn't the caliper be moving with the disc (i.e. the entire disc/caliper/etc assembly would move)?