Need help--Brake pedal goes all the way to floor after several new parts replaced Options

[914xr75]

I posted a few weeks ago about leaking reservoir tubes under the gas tank. I replaced those and the leaking stopped. I bled the calipers, but did not bleed the master cylinder. This was the first time I had about 5% stopping power and the pedal went to the floor, not sure if you'd call it spongy, but there was no resistance. That was a couple weeks ago.

Today I replaced the master with a 17mm ATE, rebuilt one of the front calipers, replaced the front soft lines. The rear steel lines still looked good, so I left them. I bled the new master. It took about an hour of pushing out air bubbles, and two quarts of brake fluid into the system to complete the MC bleeding. Once done, the pedal was still pillow soft.

Now on to the caliper bleeding--I purchased the Motive pressure bleeding system. Pumped it up to 5 psi as recommended by Ian Karr. About 30 seconds later the Motive bottle was at 0 psi. There aren't any fluid leaks in the brake system. I replaced the reservoir seal and added Teflon tape to the fitting in the Motive hose. Still loses pressure.

I tried the HF bleeder you hook up to your compressor. For 3 minutes about 5% fluid and 95% air entered the bottle. About 8 ounces of fluid came out. That is where I left off after a full day of brake work. Then I thought, did I cross the reservoir lines? I don't believe I did that, and I don't think that would cause my situation.

Any help you can offer would be greatly appreciated. Sean

[Artfrombama]

Are you bleeding from the TOP of the calipers?

[porschetub]

I posted a few weeks ago about leaking reservoir tubes under the gas tank. I replaced those and the leaking stopped. I bled the calipers, but did not bleed the master cylinder. This was the first time I had about 5% stopping power and the pedal went to the floor, not sure if you'd call it spongy, but there was no resistance. That was a couple weeks ago.

Today I replaced the master with a 17mm ATE, rebuilt one of the front calipers, replaced the front soft lines. The rear steel lines still looked good, so I left them. I bled the new master. It took about an hour of pushing out air bubbles, and two quarts of brake fluid into the system to complete the MC bleeding. Once done, the pedal was still pillow soft.

Now on to the caliper bleeding--I purchased the Motive pressure bleeding system. Pumped it up to 5 psi as recommended by Ian Karr. About 30 seconds later the Motive bottle was at 0 psi. There aren't any fluid leaks in the brake system. I replaced the reservoir seal and added Teflon tape to the fitting in the Motive hose. Still loses pressure.

I tried the HF bleeder you hook up to your compressor. For 3 minutes about 5% fluid and 95% air entered the bottle. About 8 ounces of fluid came out. That is where I left off after a full day of brake work. Then I thought, did I cross the reservoir lines? I don't believe I did that, and I don't think that would cause my situation.

Any help you can offer would be greatly appreciated. Sean

I have all the clever toys but always fall back on my budget on man bleeder ,bleeder on to the nearest caliper to mc ,just keep the reservoir topped up , can't see you could mix up the lines but worth checking ,cheers.

[infraredcalvin]

Fluid is going somewhere, did you plug the overflow at the reservoir? I use a small piece of tubing with a golf tee shoved in the end…

The overflow is sometimes directed into the steering rack cover plate, check for pooling there or under the fuel tank…

I recall the motive needing more than 5 psi, but you do have to keep pumping if your bleeders are cracked open for any period of time…

I gotta ask, have you bleed brakes before? Used a motive bleeder before?

[rjames]

Where did you find a 17 mm ATE MC?! Good find!

Bleeding the breaks on these cars is such a joy. I couldn’t get a stiff pedal until I swapped the stock bleeders out for speed bleeders. I also used the ‘long hose’ method where once you get all of the old fluid out you run a long tube from the bleeder back to the reservoir. You can sit in the cabin and pump the brakes while you watch the bubbles go by and you don’t have to waste fluid or recruit a helper.

Good luck!

[914xr75]

rjames--long tube method is brilliant! Pelican had the master. First time buyers get a 10% discount.
Artfrombama--yes. using top bleed screw.
infraredcalvin--I didn't see an overflow on the reservior, but I will investigate today. First time with Motive system. I have bled brakes many times through the years. First time bleeding a new master.

I will bleed again using the long tube method since all the fluid is new. I could be wrong, but I feel like I should have had some pedal pressure after bleeding the new master. A member mentioned tapping the pressure regulator with a rubber mallet to dislodge air. I still haven't located it, but maybe that could be an air problem.

I'm really looking for a win soon on this, need to get Lilly's teener back on the road for the WCR. Thanks again all!
s

[davep]

Your profile does not list a 914, so that does not help.
Normally, when bleeding brake system, you start bleeding at the furthest point which is the right rear, then the left rear, right front and finally the left front.
While I do use a vacuum bleeder tool to do initial bleeding, I always use the foot on the pedal method (two people) to do a final bleed. The foot on pedal method can build the pressure to a much higher level that squashes the bubbles much smaller to get through the pressure regulator and the calipers. Also provides great feedback as to how the system is clearing up.
If fluid is disappearing, then check under the master cylinder, and in the pedal cluster.

BTW, I almost always drain the calipers of all fluid first; just to get rid of all the old fluid. I have rebuilt a lot of calipers since 1975, and the outer pistons are often full of sludge because ordinary bleeding does not force a fluid exchange in the outer caliper halves. Particularly in the rear calipers with the adjusting mechanism in the pistons, no fresh fluid can displace the old fluid with a normal bleeding process.

[fiacra]

Your profile does not list a 914, so that does not help.
Normally, when bleeding brake system, you start bleeding at the furthest point which is the right rear, then the left rear, right front and finally the left front.
While I do use a vacuum bleeder tool to do initial bleeding, I always use the foot on the pedal method (two people) to do a final bleed. The foot on pedal method can build the pressure to a much higher level that squashes the bubbles much smaller to get through the pressure regulator and the calipers. Also provides great feedback as to how the system is clearing up. If fluid is disappearing, then check under the master cylinder, and in the pedal cluster.

BTW, I almost always drain the calipers of all fluid first; just to get rid of all the old fluid. I have rebuilt a lot of calipers since 1975, and the outer pistons are often full of sludge because ordinary bleeding does not force a fluid exchange in the outer caliper halves. Particularly in the rear calipers with the adjusting mechanism in the pistons, no fresh fluid can displace the old fluid with a normal bleeding process.

I think this is spot on advice. Not much to add to it other than to say I am a big fan of the Motiv pressure bleeder, but I've never used a vacuum bleeder so maybe it's better (IMG:style_emoticons/default/confused24.gif)

Here's my take on what's going on: First off, if you've never bled a 914 before it is a very different experience than bleeding the brakes on just about any other car. It takes forever (at least for me) to get all the air out of the system. While on my other cars I might use somewhere around 1 to 1-1/2 pints of fluid to bleed the system, in a 914 I often use up to three quarts after replacing calipers, lines, and MC. I have been told by another member that that is ridiculous, but brakes are the things that stop your car, save your life, and save you from hurting others. If I get a bit carried away making sure the system is free from air I have no shame about that. I'm going to assume that you have confirmed that there is no brake fluid on the floor by the pedal cluster (a common spot to find fluid when the MC fails, and yes a new MC can be defective) and that there are no other areas where you are seeing brake fluid leak. Failing that, and being sure that all your connections are solid (especially at the lines into the MC from the reservoir) you just still have air in the system. Be persistent, keep bleeding, and recognize that it may take several cycles to get all the air out. You can't just work your way around all the calipers and assume you've gotten it all. Keep doing the circuit. And yes, tap the pressure regulator to make sure you are dislodging air from it. Shake the soft lines to dislodge air, etc. If you don't know where the pressure regulator is, then just follow the brake lines and they will take you there. It sits low on the firewall between the engine and the passenger compartment. I keep the Motiv at just between 5-10psi and no higher. It should hold there pretty well, so if you are having rapid loss of pressure after filling the system then there is a leak somewhere. Like Dave I finish with a cycle of pedal bleeding. I'm lucky that my wife is willing to help out in the final step. If she had to be there for the whole process we would end up in counseling. That to me is the real value of the Motiv (IMG:style_emoticons/default/biggrin.gif) .

Bottom line, assuming the system is closed then you just have to be even more persistent to get the air out.

Finally, I don't think it makes any difference which feed line goes into either the front or rear position on the MC. All the MC cares about is that it has a fluid source to each circuit. What does make a difference is how well those lines are seated in the grommet, and that the grommet is properly seated in the MC. Also, be sure you put the washer in place under the grommet.

To help you find it, here's a link to a picture of a pressure regulator on the PMB website. Good luck!!!

https://pmbperformance.com/products/porsche...01840&_ss=r

[76-914]

Where did you find a 17 mm ATE MC?! Good find!

Bleeding the breaks on these cars is such a joy. I couldn’t get a stiff pedal until I swapped the stock bleeders out for speed bleeders. I also used the ‘long hose’ method where once you get all of the old fluid out you run a long tube from the bleeder back to the reservoir. You can sit in the cabin and pump the brakes while you watch the bubbles go by and you don’t have to waste fluid or recruit a helper.

Good luck!

I 2nd the long tube method and speed bleeders. (IMG:style_emoticons/default/beerchug.gif)

[PanelBilly]

Did you plug the air vent on the top of the reservoir? I used a few inches of hole with a drill bit to plug the opening. If you don’t do this the system isn’t sealed. Also after you push some fluid with the pump. Pump the brake pedal a few times.

[914xr75]

Tonight's update. Pulled the tank again to look underneath for leakage. No leaks, but I jiggled the reservoir tubes and bubbles came up from the master. Finally located the pressure regulator, thanks
fiacra. Gave it some rubber mallet love.

Pedal cluster floor was dry. Took my time using the long tube method. Began the bleeding process once again. At the end I finally had a hard pedal. Hooked up the Motive to see if the system holds the pressure steady.

Pumped it up to 15 psi and lost about 2 psi every 30 seconds. This is light years better than yesterday. I could not locate an air vent or a overflow on the reservoir. Tomorrow I will inspect it with a microscope to find the vent and overflow. That is probably the last issue. I did put my ear up to the reservoir while the system had the 15 psi in it. I did not hear air escaping.

Had I not hooked it up to the Motive bottle, I would have thought the job was done.

[emerygt350]

How did you bleed the mc? If that's not done right it will take you forever.

[davep]

The reservoir cap or the reservoir itself has to have a vent otherwise there would be problems.
When bleeding, you can only draw out about 4 oz of fluid without checking and refilling the reservoir. The fluid should never go below the interior barrier. If you pull out too much fluid, and air gets down into the MC fill tubing then you will always have to start over. If you are using over a quart during the process, then you are using the wrong procedure. Since 1975 I have replaced perhaps 10 MC and 50 calipers without issue. If driving at Watkins Glen, or Mosport, then one needs to have perfect brake systems.

[914sgofast2]

Was the 17mm master cylinder NOS or a recently manufactured one? If it was NOS, then it’s likely the seals in the master cylinder have gone bad from sitting on the shelf for too long.

[fiacra]

Tonight's update. Pulled the tank again to look underneath for leakage. No leaks, but I jiggled the reservoir tubes and bubbles came up from the master. Finally located the pressure regulator, thanks
fiacra. Gave it some rubber mallet love.

Pedal cluster floor was dry. Took my time using the long tube method. Began the bleeding process once again. At the end I finally had a hard pedal. Hooked up the Motive to see if the system holds the pressure steady.

Pumped it up to 15 psi and lost about 2 psi every 30 seconds. This is light years better than yesterday. I could not locate an air vent or a overflow on the reservoir. Tomorrow I will inspect it with a microscope to find the vent and overflow. That is probably the last issue. I did put my ear up to the reservoir while the system had the 15 psi in it. I did not hear air escaping.

Had I not hooked it up to the Motive bottle, I would have thought the job was done.

I think you have basically won the battle!! It is a PITA to get the air out of this system. Someone can correct me if I am wrong, but the vent is on the cap and therefore when you are using the Motiv the cap is off and the vent cannot be a source of pressure loss. Given what you wrote about that amount of pressure loss when the Motiv is hooked up and pressurized I'm more suspicious that there is a loose or leaking connection on the Motiv. Check those carefully, use a bit of soapy water to look for bubbles at the cap, on the hose and hose connections, and make sure the Motiv cap has the gasket in place and is on correctly. If you truly were losing that much pressure because of a leak in the system you would see fluid leaking somewhere. Once the Motiv is pressurized it should not lose pressure until you open the system. Even if there is air in the system the Motiv should still hold steady pressure. Be careful about how high you pressurize the Motiv. Some people have expressed concerns about possibly blowing connections at higher pressure. Not sure how valid a concern that is, but I keep it below 10psi to be on the safe side. I know some people bleed the system and then, as long as they have reliable pedal pressure, take the car for a ride on a bumpy road with the theory being this will dislodge the last of the air bubbles. A final re-bleed at that point should get rid of the last of the air. I know you have experience bleeding brakes so this point is probably well known to you, but if you have a solid pedal and pumping it does not bring the pedal up higher I think it is fairly safe to assume that you have the air out of the system. If you have a firm pedal but holding pressure on it causes the pedal to slowly sink to the floor, then you likely have a defective MC.

I've not used the long tube method before but I may also try it next time I have to do this. PMB refurbished calipers are on the shelf right now so that will be soon. Maybe I'll get the job done without wasting so much brake fluid. Dave is probably right that using more than a quart of fluid means that I'm not being efficient in my method. I need to have absolute confidence in my brakes so it may be that I'm overdoing it when I'm bleeding them (IMG:style_emoticons/default/confused24.gif) . In any case, brake fluid is cheaper than body work and way cheaper than surgery, a law suit, or a funeral.

[914xr75]

Update------defective brand new Motive Power Bleeder!!! Last night I couldn't understand how the Motive system was telling me I had a leak. I had rock solid pedal pressure after my second bleed.

I checked everywhere--near pedal cluster, under gas tank, master, all calipers, everywhere. Even though I could not hear any leak in the Motive bottle, lines, and adapter cap, I decided my Unsolved Mystery might be the new Motive.

Called all my neighborhood Euro car cronies to see if they were home for a quick couple minutes. Went to Norm's place and hooked it up to his modern BMW 8 series.

10 psi in and watched the needle slowly go down. Mystery solved. Thanks for everyone's help. A new Motive will arrive in a week from their customer service dept. Hopefully that one is not defective.

[fiacra]

Update------defective brand new Motive Power Bleeder!!! Last night I couldn't understand how the Motive system was telling me I had a leak. I had rock solid pedal pressure after my second bleed.

I checked everywhere--near pedal cluster, under gas tank, master, all calipers, everywhere. Even though I could not hear any leak in the Motive bottle, lines, and adapter cap, I decided my Unsolved Mystery might be the new Motive.

Called all my neighborhood Euro car cronies to see if they were home for a quick couple minutes. Went to Norm's place and hooked it up to his modern BMW 8 series.

10 psi in and watched the needle slowly go down. Mystery solved. Thanks for everyone's help. A new Motive will arrive in a week from their customer service dept. Hopefully that one is not defective.

Way to figure it out! From what you wrote I was pretty sure that was going to be the issue but you got there on your own.

[914rrr]

I'll likely not have a pedal pusher assistant, so I'd like to know specifics about the "long hose bleeding method", such as hose ID size, material, length, positioning of the hose, etc.

I'm trying to get the brakes bled so I can drive my teener to the Sotheby's C&C in Nashville this Saturday.

After 2-3 tries I FINALLY have my rear calipers back together without leaking. My local friend who helped me rebuild them the first time rushed / missed several steps and they had to be be disassembled to fix E-brake levers not working, leaks, etc.

I tried using a HF vacuum / pressure pump to bleed the brakes initially, but there seemed to be a steady stream of bubbles coming out of the bleeder hoses and I wasn't seeing much progress with it.

I then tried gravity drip bleeding all 4 calipers at the same time which got me in the ballpark, until one of the outer adjuster o-rings started weeping. So I have to start bleeding all over again after disassembly.

[Jack Standz]

Tried using a Harbor Freight vacuum bleeder quite a while ago. Didn't work, but YMMV.

Here is Ian Karr's video where he uses a Motive pressure bleeder, which is our "go to" bleeder:

https://www.youtube.com/watch?v=ymHHD6uKhfc

Best wishes with getting it bled. If you have defective or improperly restored parts, you'll need to fix them otherwise it's just not gonna work and it's jut not safe. When it comes to brakes systems, it's all about safety.