Sometimes it's the craziest problems., Brake bleeding drama Options

[McMark]

I'm working on this 914s brake system, which is already a PITA, as we all know. This system just wouldn't bleed out. We capped all the outlets in the master and pumped the pedal until it was solid. Cool, added in the fronts and bled those until it was solid, added in the rears and it wouldn't bleed.

I pulled the limiting valve (aka proportioning) and swapped in another one, thinking maybe something was bad inside. Same problem.

At this point nothing is making sense. So in a 'hail Mary' move we pull the limiting valve again and use a spare brake hose to connect just the left rear. Bleed that, rock solid. Switch to the right.... same problem. Can't bleed it. (IMG:style_emoticons/default/blink.gif) WTF?

So we pulled the caliper intending to take it apart and check everything inside. as I was pulling it off, I thought maybe there was a dry patch inside the caliper. If it's not coated/wetted with fluid, the surface tension can create a bubble the won't move. I shook the caliper, dropped it in my ultrasonic bath (in a bag) and set it in my vibratory polisher (in the bag). It's back on the car now and it's finally getting close.

I've never had a single caliper be this stubborn, but from now on I'll be adding a little fluid and shaking the calipers before they go on the car. Tim here had a great idea as well, when we're done bench bleeding the master cylinder we'll hook up the calipers and bench bleed those as well, all before it goes on the car.

And people wonder why I hesitate when they ask, "How much is this going to cost?" Who could have known this was gonna happen. And it's a 914--seems like every project has some of this kinda thing. (IMG:style_emoticons/default/wacko.gif)

[Kansas 914]

Tim here had a great idea as well, when we're done bench bleeding the master cylinder we'll hook up the calipers and bench bleed those as well, all before it goes on the car.

I never thought to bench bleed the calipers - makes sense though and can't hurt.

[BK911]

Rubber brake line failed internally???

[stugray]

I always smack the calipers with a hammer while bleeding to try to get the bubbles to move.

Then a quick drive over the local train tracks before the final bleed :-)

[r_towle]

adding the new 914 brake dance to the process, check...

Rich

[Stiffmeister]

adding the new 914 brake dance to the process, check...

Rich

Had my own little Hell. Tried preasure, tried vacum (mitivac?) Pedalmaraton. Nothing worked. Finaly i put preasure in the brakeoil tank and blead between pipe and hose on all corners. Rocksolid pedal.

[76-914]

As soon as I read the title and saw your name attached, I was hooked. I thought WTF, I need to see what stumped The McMan. Since I wrench solo I can't tell you how much your " Long Tube" method has helped me. I recently completed a (commercial plumbing) job that req'd 16 trips to diagnose. I'll never run into that again but if I do I'll look like a genius to the next fellow. I'm impressed with your tenaciousness. It's sadly lacking nowadays. (IMG:style_emoticons/default/thumb3d.gif)

[Jeff Hail]

Mark,

914s have a unique braking system issue affecting all years, early/ late calipers are all included.

Due to being prone to rust the 914 braking components are "hygroscopically magnetized" to air for some reason resulting in air bubble capture.

I guy named Alfred Teves referred to it as the "BTE" problem in the OEM manuals which stood for Bermuda Triangle Effect. In fact Teves was going to stamp "BTE" on all 914 calipers but his neighbor Ferry wouldn't have any of it being it was a German automobile.

Years later they realized if the 914 bodies had zinc applied prior to coatings the BTE problem was non existent. By that time it was already 1976 and the 914 was phased out.

There was a band aid fix that involved 8 gallons of brake fluid and a constant feed delivery pump capable of 90 psi to enemize the hydraulic system. It was expensive and messy.

Hey this is absolutely true! The Ferrari didn't have this problem while bleeding the brakes. They had zinc.

[Perry Kiehl Clone]

I pressurize the reservoir with a special cap that I made that's fitted with a tire valve. I use a little air tank filled to like 15 psi, and I put a clip on tire chuck on the custom cap. Works like a charm ever time without any pumping. It's also an easy way to change fluid (every two years). If you have a helper you can have them watch the reservoir so you don't run it too low, but you can do it solo.

[Chris914n6]

Crazy problems are part of the job. Your lucky you feel comfortable charging more.

BMW e36 blower not working.
- fuse not burnt. swap relay, no air. pull apart cowl covers to get to the blower. Hardwire and it works. Replaced the resister pack. Works and send the car on it's way.
- Week later, blower not working. Wiggle the relay sometimes works. Terminals look ok. Install a relay with longer tabs, works. Send car on it's way.
- Week later, blower not working. Take apart the fusebox. Everything looks ok. Must be a loose wire outside the box. Tell the guy to wiggle the box and it should come back on.
- Later... climate display shuts off. Replaced a capacitor, fixed. Started tracing fusebox wires. Relay ground goes under dash. Pulled off panels - good contact. Traced power - good contacts. Wiggle the fusebox until power shuts off, try to check 12v at the fuse and keeps coming on... rrrr. Closely inspect the fuse - where the tab crimps to the element had loosened, thus intermittent contact.
(IMG:style_emoticons/default/ar15.gif) BMW special fuses.

[r_towle]

Mark,

914s have a unique braking system issue affecting all years, early/ late calipers are all included.

Due to being prone to rust the 914 braking components are "hygroscopically magnetized" to air for some reason resulting in air bubble capture.

I guy named Alfred Teves referred to it as the "BTE" problem in the OEM manuals which stood for Bermuda Triangle Effect. In fact Teves was going to stamp "BTE" on all 914 calipers but his neighbor Ferry wouldn't have any of it being it was a German automobile.

Years later they realized if the 914 bodies had zinc applied prior to coatings the BTE problem was non existent. By that time it was already 1976 and the 914 was phased out.

There was a band aid fix that involved 8 gallons of brake fluid and a constant feed delivery pump capable of 90 psi to enemize the hydraulic system. It was expensive and messy.

Hey this is absolutely true! The Ferrari didn't have this problem while bleeding the brakes. They had zinc.

So, there was magic involved?
All chemistry aside, German use magic on some of these things, I mean how else could you explain a Mercedes fresh air fan replacement?

[Jason74914]

I haven't it done to my 914, but Speedbleeders have been a god-send on other cars I own that I couldn't get bled right with all other methods.

http://www.jegs.com/p/Russell/Russell-Spee...744478/10002/-1

[Jeff Hail]

Mark,

914s have a unique braking system issue affecting all years, early/ late calipers are all included.

Due to being prone to rust the 914 braking components are "hygroscopically magnetized" to air for some reason resulting in air bubble capture.

I guy named Alfred Teves referred to it as the "BTE" problem in the OEM manuals which stood for Bermuda Triangle Effect. In fact Teves was going to stamp "BTE" on all 914 calipers but his neighbor Ferry wouldn't have any of it being it was a German automobile.

Years later they realized if the 914 bodies had zinc applied prior to coatings the BTE problem was non existent. By that time it was already 1976 and the 914 was phased out.

There was a band aid fix that involved 8 gallons of brake fluid and a constant feed delivery pump capable of 90 psi to enemize the hydraulic system. It was expensive and messy.

Hey this is absolutely true! The Ferrari didn't have this problem while bleeding the brakes. They had zinc.

So, there was magic involved?
All chemistry aside, German use magic on some of these things, I mean how else could you explain a Mercedes fresh air fan replacement?

Of course. Both used horse magic. Mercedes on the other hand followed the stars and circles for the quest of fresh air.

[Harpo]

That is why I took my car to a professional (McMark). I pressure & vacuum bled to no avail. This was clearly way beyond my limited skills

Your the man (IMG:style_emoticons/default/piratenanner.gif)

Thanks

David