Brake Bleeding Not Holding Pressure, Suggestions?

[Titanws6]

Hey guys, running into some issues trying to get a firm peddle on bleeding the brakes. Simply will not hold pedal.

My car is at my tuners shop right now. I attempted the install myself of some new Centric Rotors, Hawk Pads, as SS Lines. I barely got into the install and realized more knowledge and tools would be needed. I dropped it off and he completed the install right away with no issues. At the same time he was also installing a set of used low mileage stock calipers vs my older ones. Once the install was complete, he bleed the system.
He did the bleeding via Tech II, old school style, and also with a pressure bleeding. Each time though, the pedal will not hold firm. He proceeded to bleed and bleed again, but still not hold firm.

We decided to switch back to my old stock calipers and also install a new brake master cylinder, thinking this might be the culprit. He then proceeded to bleed again using the same techniques as noted above. Again, still the peddle is not holding firm. He did note that his pressure bleeder max's at 20 psi, he is getting another bleeder that will max at 35 psi to see if this will do the trick, but also noted 20 should be enough for this job. I have complete faith in him and his knowledge and skill set, he is a former GM certified tech and even had the lead Tech from the local GM dealer come by to get a 2nd set of eyes on it. This brake job has a gremlin somewhere in it.

Any ideas, suggestions on why/what to possibly check for? I am sure he has covered it all but it will be appreciated as I know there are some techs on the board here too, thanks guys.

[Eidolon]

I pressure bleed at just 10-15 PSI, though I have no clue if that would be enough to flush out any air that had been mistakenly allowed into the system. Still, I would be hesitant to say you need more pressure. Swapping lines shouldn't allow air into the system that couldn't be bled out unless you allowed the master cylinder to run dry. That you drove the car to your tech for the swap says that's probably not the case.

When you say it won't hold pressure, you mean the pedal goes to the floor every time, and doesn't hold pressure enough to actually apply the brakes? The system is one-way displacement, from the reservoir and cylinder out to the calipers. So first thing to do is check for leaks at all the calipers and lines that were changed out. If there is no visible leak and fluid properly runs from the calipers during the bleeding process, then your problem is going to be under the hood either in the ABS/EBD unit, or else in the master cylinder itself.

You changed out the master cylinder, so the part shouldn't be defective. There's a specific master cylinder bleeding process that involves disconnecting the hard lines and flushing the air from the cylinder first. Any idea if that was followed? If not, I can post the process up from the FSM (assuming Paul doesn't beat me to it, of course :) ).

After that, a Tech2 bleed to activate the pump in the ABS unit will be needed to flush air from that. But any air in that unit would result in a spongy pedal, not a pedal with no pressure at all. I guess it's possible a seal in the ABS unit failed, but I don't know enough about those units to tell you whether or not a seal failure in that unit would allow enough fluid to recirculate to allow the pedal to sink to the floor.

You said he did a traditional bleed. So if you crack open the bleeder valve on a caliper and press on the pedal, does fluid flow out to that caliper and out the bleeder nipple?

[GRRRR8]

Make sure the calipers are not mounted upside down. Very common mistake. These cars can be foot bled so that tells me human error might be the cause.

[Titanws6]

Make sure the calipers are not mounted upside down. Very common mistake. These cars can be foot bled so that tells me human error might be the cause.

How would you mount the caliper upside down, seems pretty straight forward?

[STL_G8GT]

How would you mount the caliper upside down, seems pretty straight forward?

Make sure the bleeder is on the top!

[Greg@PacePerformance]

Yes good point Charlie. I has been done in the past by a few

[Oldtimer]

If you put the left caliper on the right side, the bleeder will be on the top, and not the bottom.

Done that before on another car.

[Eidolon]

If you put the left caliper on the right side, the bleeder will be on the top, and not the bottom.

Done that before on another car.
The hose should be on the top or middle and bleeder on bottom if it's backwards. :) You want the bleeder situated such that air can rise up through the caliper and out of the bleeder valve.

Darn good call, Charlie. This is why they pay you the big bucks. :)

[Titanws6]

Gotcha, ok, let me ask him.......yep, bleeders on top.

[Napalm]

Make sure the calipers are not mounted upside down. Very common mistake. These cars can be foot bled so that tells me human error might be the cause.


Make sure the bleeder is on the top!


If you put the left caliper on the right side, the bleeder will be on the top, and not the bottom.

Done that before on another car.

Indeed. and that was my second thought.


Gotcha, ok, let me ask him.......yep, bleeders on top.

OK now for my first thought and a query

WHY were you taking off the old calipers? were they not working for some reason? and did you replace with the right part numbers?

now my thought - its possible to have brake lines on but not tight enough - same with bleeders. they might not leak fluid - but they might leak in air. I've seen it happen once on a GTO where the brake like wasn't very tight. It didn't leak during initial bleeding, but upon first test ride the brakes were soft. turns out when pressing the pedal hard down - it would then slowly fall to the floor. slowly.

Lines had been replaced and it was seeping at the connection to the car - not at the caliper. and because of this - I believe it was pulling air through that loose connection.

Since you replaced your lines - check all your connections and prior to bleeding again or anything else - push the pedal down hard - and check for seepage.

Also with replacement calipers - I always tap the calipers with a rubber mallet when I bleed. Why, empty passages in calipers have bends and ect that might hold some air.

Personally he should not have ever pulled the Master Cylinder - assuming there was no indication of brake issues prior to the install of the calipers and lines.

[dandragonrage]

I always buy a bunch of extra copper crush washers because I rarely get the caliper connection to seal the first time for some reason...

Master cylinders have to be bench bled.

[Titanws6]

I decided to swap the calipers and lines because the car came from New Jersey and everything was rusted and pitted. I planned on installing some nicer rims (sitting in the garage) and could not see having rusty calipers behind them.
One way or another, I was needing new rotors and pads. I wanted to upgrade to Russel SS lines as well. The front rotors had already been turned twice.
Since everything was coming off, the calipers were swapped for some fresher low mileage ones I had sanded and polished.

I will mention tapping of the caliper with a mallet, I did read that on your other posts as well Napalm. I have no clue on the Master.

I have complete faith in my guy, he is all LSX and has been around for 15+ yrs. This job is kicking his ass. He noted 1 in 20 brake jobs he gets always has some gremlin in it screwing it up. Even his buddy lead tech from the local GM dealer came down to take a look and he couldn;t figure it out. I do not doubt his knowledge or skill level and everything mentioned here he has done and tried. I've mentioned the replies and he has tried them all.

[Napalm]

+1 on the crush washers.

I just can't believe he went right to replacing the master cylinder. to that end - he might have induced another issue. Air in the ABS body. You mentioned the tech 2, I hope he has since done the procedures for bleeding the ABS body. (module whatever the manual calls it). After replacing the master - he basically has to start over.

I can see the point on the calipers - you might want to actually check your bleeder screws. if you sanded and polished them - did you take the bleeders out? did they get cleaned on the inside? That might cause a few issues.

I do feel sorry for the guy - chasing down soggy brakes can be difficult. Did he find anything dripping with pedal application?

Somthing to try - but its messy.

with car up in air - and with new washers in hand - remove the brake lines at the calipers one at a time - leave them off until you get a consistent drip out of the end of the line. IE gravity bleed. you can do all at once if you just want to. but I've never done that.

last 2 times I've replaced calipers - I'm put the brake lines in a glass jar while I did the rest of the install - just to get old fluid out of the system.

This cleans the path to the caliper.

[TurboMike]

Are you SURE this guy is using a Tech2 to bleed? Tech2 is veru expensive and very few non-dealer garages would have one. If you have a Tech2, the ABS pumps bleed the brakes for you and you wouldnt need a pressure bleeder. Why is he using a pressure bleeder if he has access to a Tech2?

With that thought: its very easy to drain the system when you change the lines. When he took the lines off to swap in the SS lines if he let the system drain enough to get air in the ABS pump the only way to get it out is with a Tech2.

[Napalm]

The snap on tool and I believe one other company offer a Tech 2 spec device. IE it is an approved substitute for a an actual TECH 2 GM sourced device.

I know a guy with the snap on version - it works exactly as advertised.

And yes if he let it drain completely without keeping tabs on the level in the res - then he got air in the abs module and its a B to get out. As in it takes longer then 5 minutes.

[Titanws6]

Well no update yet, I am going to drop him a line later today. If he can't trace down the issue, I am towing it to the dealer tomorrow who may have better luck with it. I was not there when he swapped out the brakes, so I am not quite sure on how he went about it, procedure wise, but from the posts you guys have made, majority feels there is air in the lines and the ABS module is the issue right now.

Thanks for all the input and feedback guys, I appreciate it. Once I have some good news, I will drop a line on the cause.

[Titanws6]

Well to get a kick out of this, the dealer had it for less than an hour and diagnosed the rear calipers were on upside down......just like you guys said.
They did the swap, pressure bled the system, and now she's back on the road. The pedal is extremely firm, much firmer than before and I did some highway runs to bed in the pads per Hawks......
So now I am stuck with an extra repair bill and new brake master (unnecassarily) because they flippy flopped the rear calipers. I even asked him after you guys mentioned it and he said the calipers were on correct. It sucks but I am happy the ordeal is over. The camaro rims are on and the calipers look very nice behind them. Time to stop spending $$$$ on the "Pumpkin".

[macvicar24]

That sucks. The same thing happened to one of my coworkers in a 2010 Silverado. This old timer gave my coworker a deal on a brake job and screwed everything up. Couldn't bleed the "old school" way and replaced the master because it wouldn't build pressure.

[Napalm]

Well to get a kick out of this, the dealer had it for less than an hour and diagnosed the rear calipers were on upside down......just like you guys said.
They did the swap, pressure bled the system, and now she's back on the road. The pedal is extremely firm, much firmer than before and I did some highway runs to bed in the pads per Hawks......
So now I am stuck with an extra repair bill and new brake master (unnecassarily) because they flippy flopped the rear calipers. I even asked him after you guys mentioned it and he said the calipers were on correct. It sucks but I am happy the ordeal is over. The camaro rims are on and the calipers look very nice behind them. Time to stop spending $$$$ on the "Pumpkin".

who put the rear calipers on upside down? you or the other guy. I think your tech should eat the cost or at least some of the cost of the other bill.

just my 0.03.

[Titanws6]

He did the front, his assistant did the rears which explains it. Yeah, he cut me a break on his labor for the install and everything, which suppluments the dealer bill. He was very sorry about the whole situation and he is an honest guy that will stand behind his word. I will still use him for tuning and installs, sometimes these things happen. Good honest mechanics like him are hard to find.