Will

I recall reading somewhere that a Bosch Hammer was necessary to do a complete job of bleeding the brakes. Apparently, it is some sort of electronic device that has as one its functions something to do with the ABS. What's the scoop on this thing? Does a normal flush and bleed miss something without the B.H.?

Will

Robin 993DX

Hi Will,

Using the "Hammer" during the brake bleeding process is a process that's call for "by the book", the "Hammer" can activate the ABS unit while the brake fluids are being bled through the system, which in turn flushes out any trapped air bubbles inside of the ABS system.

It is a procedure that is not neccessary, unless you have air trapped inside of your ABS system.

Curtis - '97 Targa

From what I remember in the manual, using the hammer is only required when bleeding ABD-equipped systems.

E. J. - 993 Alumni

I have ABD/LSD on my 95 and I have never used the hammer to bleed the brakes. No problems yet...

Good to meet you last night Curtis - I Like the Targa. Thanx for the tour.

E. J.

DougB

Hammer is only required to bleed diff locks on 964 Carrera 4--not needed for 993.

Curtis - '97 Targa

Let me clarify. In the 993 book, there is a section that uses the Hammer to bleed the brakes on ABD-equipped cars only. The section doesn't apply to regular ABS.

I don't know when or why you would need to do this, only that it is in the book and available on the Hammer.

E.J. ditto - nice meeting you, too.

Ray Calvo

Shop manual (buy it!!!!!) has different procedure for bleedng brakes on 2WD vs. 4WD cars, due to vacuuum vs. hydraulic brake boost circuits, resp. The hydraulic boost circuit supposedly requires actuation of the system to best bleed the system,and they use a Porsche tool called 9288 which appears to function similar to the Bosch Hammer. However, I think there are board members with hydraulically assisted C4/C4S/TT cars who have bled their brakes successfully without using this tool.

On 2WD vacuuum boosted brakes, I would imagine it's only needed if you get air in the ABS/ABD cirucit, which shouldn't happen unless you open a line going to the ABS system. I have bled my '95 993 brakes prob. 20 times and haven't had a problem using the pressure bleed system. This includes one time blowing all the fluid out one brake line because I forgot to check the fluid level in the reservoir as I was bleeding the brakes!

Adrian

Guys, the Bosch Hammer is the nickname for the Bosch 9288 Tester. This equipment is mandatory for any 911 fitted with electronic forms of traction control or hydraulically boosted brakes system with ABS. The reason is simple. As the 911 ages so do the components. Just bleeding the brakes system requires a power bleeder but not a Bosch Hammer. However how can you know or be 100% certain that doing this bleed with power off that the solenoid valves are not leaking into the other circuits. Yes just for bleeding brakes on a C4 you can get away with not using a Bosch Hammer if you are prepared to take the risk. The risk is less on the 993 series vacuum boosted systems but is still present on the hydraulic boosted systems. Same applies to the 964. My files are full of people who have go into some serious problems when not following the approved procedures. These owners include models such as 928s with ABD, 964 C2s C4s, 993s and 996s. Worst case scenario is the uncommanded application of a brake at very high speed. Also remember in the hydraulic boosted system. Very hard pedal means no pressure. Soft pedal to the floor means, big hole in system and no fluid.
Ciao
Adrian
911C4