Hydratech: Hydroboost Pedal Rod Swap Tips?

[CTX-SLPR]

Hydratech,

Would you mind posting tips or a how to on how to properly pull and reinstall the pedal rods from a factory hydroboost unit?

Thanks

[Hydratech®]

This is a trade secret, but I'll get you as close to the process as possible where you can fill in a few blanks using some ingenuity on your end. First, never ever try to just yank the rod out. There is an outfit in California that I will not name that shockingly uses a slide hammer to brutally yank the rods out. That was fine back when the rods were only retained by a rubber grommet back in the '70's, but all modern hydroboost units are the superior "staked" models (because the rubber grommets would dry rot allowing the brake pedals to shockingly pop out). The input pistons are hardened, and will crack using this method - I hate to think how many they wreck versus how many somehow survive this. Take a good close look at what is holding the ball jointed end of the rod in. It should be rather apparent that there are three STRONG peened points doing the job. The trick here is to figure out a mechanism that will hold the main body of the piston in perfect form / diameter, only allowing the 3 peened points to push back out without allowing this stress to swell the input piston outward, otherwise it WILL crack 99% of the time (because the factory rods are drop forged tough too).

ONCE THEY HAVE HAIRLINE CRACKED, THEY ARE JUNK, as the hairline crack will continue further into the piston with any attempted further use. This of course brings a very harsh reality of the brake pedal separating from the brake unit when you least expect it, leaving you without any brakes what so ever, save for possibly still having your emergency brakes still functional. One DIY guy that had this happen to him purchased one of our units after this close call happened to him. He managed to downshift the car severely, steering the car wildly from side to side to scrub off enough speed to just barely avoid a nasty collision. Even the slightest sign of the tiniest hairline crack is downright dangerous. It is like a crack in a windshield - you know it is going to spread, you just never know when, which is what makes a hairline crack in the input piston so dangerous. If it has cracked, there are no service parts available save for Precision Rebuilders in St. Louis possibly having a complete "gut set" they could spare (prepare to pay).

Next, never ever pry or pull against the rear of the brake unit casting. This can deform the "gut set" inside of the brake unit, once again potentially rendering it internally damaged. ALWAYS pry or pull directly off of the rear of the input piston itself, which again will take some imagination and creativity to properly set up.

Re-installation? Be advised that whatever method you came up with to contain the input piston from swelling outward during extraction is also going to be key to not breaking the input piston while attempting to get the replacement rod in past the three peen points. The input pistons are hardened for longevity, but that makes them brittle - VERY easy to accidentally crack. Even with all of our specialized equipment and techniques, we still "lose one" occasionally. It drives me nuts to see that much money go up in smoke with one evil distinct sound - "TINK" and you have just lost a unit. Again, you cannot just hammer the replacement rod in thinking that the gut set will make for a stopping mechanism. That again can distort the internals causing damage.

Here is where it really gets tricky. You have to figure out a way to compress all three peen points inward to properly capture the replacement rod. Installed properly, it will be stiff to move around, meaning it has to be tightly installed - no slop. All brand new Bosch units have a label on the brake pedal rod warning that brake pedal removal will damage the brake unit.

We make all new hires sign a very stiff non disclosure agreement regarding our technologies, applying well beyond any possible termination. There is a LOT more science and engineering in our systems than meets the eye upon inspection, which isn't evident even if you are holding one of our units directly in your hands.

Maybe this will help, but that is where I have to draw the line. Please please please do not attempt to continue to work with a brake unit that has a hairline crack in it. Even if you were to micro TIG that crack, another one typically about 3/8" to 7/16" away will show up seemingly out of nowhere. Most all people usually amputate the eyelet of their brake pedal rod off, leaving lots of blank area that can be carefully threaded 3/8-24. Just work the die as straight as you can so that it doesn't run away sideways. Even if it did run away off center a bit, it is still vastly better to go this route as opposed to risking ruining your brake unit. If you truly booger the hell out of the threading process, you can still put a metal sleeve over the rod and pin it in place or other creative means. Welding the rod is possible, but not advised unless you are highly versed in welding - take it to a certified welder. Not enough penetration, too much penetration, wrong metallurgy, improper cool down can all also lead to disaster if not done properly (could snap at the outskirts of the weld points).

Hmmm - it only took about twenty years for somebody on this forum to ask me this (seriously!), but that's all I'm going to say...

[CTX-SLPR]

Paul,

I neglected to say thanks for that post and totally understand the desire to protect your intellectual property.

Thanks

[Hydratech®]

As mentioned, we have custom tooling and specialized techniques to carefully work with removing and replacing the brake pedal rods. Again, the object of the game is to control the brake unit's piston from expanding while extracting the rod - easier said then done of course...