Last Lemming

I'm changing my brake booster and master cylinder in my '86 951 in an effort to firm up my brake pedal feel after I've gone through effort of installing better pads and bleeding enough times to make the stock I should have bought in brake fluid go up several dollars a share.

I've read several threads in what is required to get the booster out - and if I ever meet any of the engineers who worked on the packaging of this car I'm gonna slap them right in their German mouths.

If if I understand what is required to remove the booster I must remove:


the front seat (I'm not a midget)
the steering wheel (again - No midget here)
the Intake manifold
the dip stick tube
the heat shield
the starter (I'll have to bleed the clutch slave cylinder)
all the intake pluming and air filter box

Seriously all this to change a brake booster? Yeah - right in the mouth - that's where I'm gonna slap'um.

The question I have is there any tips any of you guys found along the way that will make my life easier and keep my hands less cut up doing this masochistic project.

In the mouth . . .

odonnell

I also had to loosen my clutch master line fitting and rotate it a few degrees. Sorry to add insult to injury. NA is way easier to work on.

All I had do besides that was remove the master cylinder and that fuel line clip thing. Took 20 minutes to have the new one in, I didn't even remove the seat or steering wheel and I'm 6'2"... I should stop.

mj951

If it's original and while you're in there you might as well change the blue/hard clutch line.
Good luck.

jeffro951

I have to do the same job on a 91 cabby and I am not looking forward to it...

Last Lemming

Ok, I'm 9 hours into this and I've gotten off the heat shield and master cylinder. The heat shield was a MAJOR pain. Those bolts were never placed with removal while the engine is in the car kept in mind.

Jay Wellwood

If you're going to this much effort, have you considered adding a firewall reinforcement bracket WYAIT?

Last Lemming

I finally got the booster out - that's good, had to tear out the padding against the firewall, it was too fragile to just pull back - that's bad.

Question: I noticed when the booster is out I can see there is some slack in the steering knuckle of the steering shaft. I can get to the bolts that hold it to the steering pump and at the top, my question is if I undo the bolts can the shaft be pulled out through the top of the car where the booster was, or am I going to have to do the typical 951 path and pull the engine or something?

MAGK944

The shaft can be pulled out through the top but you will need to drop the steering rack some to give you clearance. Make sure you source a new one first as the last I heard they were nla from the dealer. You may find nos in the aftermarket or iirc someone posted a repair service on this forum.

Last Lemming

I figured out the "need to drop the steering rack" bit after figuring out there wasn't enough free range in the splines to get it off alone. I found a steering shaft online so I'm good there.

How much latteral play in the unoints are allowed btw?

You know these 951's have got to be the most complicated machines to work on everything is difficult - pure evil in my opinion. Lucky for them they are fun to drive or no sane human would keep them.

MAGK944

I don't think the engineers at Porsche even thought about anyone removing the brake booster, after all they are very simple, proven devices that last years without any maintenance. If you want to make it easier for the next time, use some rivet-nuts on the bulkhead and drill the booster plate to accept bolts from the engine bay. The actual pedal linkage you can remove/install by feel so that's not an issue.

As for the steering intermediate shafts, new ones have zero play so I wouldn't accept any play in used ones. It's definitely a job to do wyit and aos seals are another.

Last Lemming

While I agree with the "wyit" credo, I've looked at what it takes to do an AOS job and frankly that's waaaay more work to do on something that isn't even broken. I'm going to throw the dice and skip that chore, after all I'm doing all this work because I want better brake pedal firmness, and the booster and master cylinder are the last unknown variables for me. I'm doing the steering shaft because I have what seems to be excessive play in the steering wheel at higher speeds and all my bushings are fine and my suspension is new. I found an OEM new steering shaft so using that will eliminate that variable from the equation.

As for engineers having forethought on future maintenance just look at old Datsun 240's, my brother has restored one and you can tell they clearly thought of maintenance. The 944 turbo strikes me as a car that was never originally conceived of as a turbo platform and then they thought "let's shoehorn one in there" - the overall packaging is pretty horrendous. I'm sure there are other worse cars out there, but of the 15 or so I've owned and worked on this is by far the worst.

mel_t_vin

Well done.

After installing the new part, you should consider documenting your endeavor with a DIY and some photos.

Last Lemming

So after I got the booster out I noticed some black oil like material came out of the back. It was very black almost, like a low viscosity oil, I'm not sure what it is and I'm not sure how it got in there, any thoughts? Also what are the torque specs for the master cylinder to booster. I can't seem to find this spec, there is an oring seal and I don't want to over tighten it.

odonnell

Mine has grease inside it in. Not a ton but just enough to seal around rubber parts better. It could also be brake fluid that worked its way around due to the pressure changes.

Just evenly tighten the nuts, I used nylocs and went wrist tight. A little ATF on the seal doesn't hurt either.

Last Lemming

WTF!!!!! I CANNOT for the life of me get the passengers side brake line to screw into the master cylinder. I've been at it for 3 hours it just won't start screwing in. It looks like it's linning up but I just can't do it. I've tried pushing the brake line in all the way first then a screwing the fitting in, I've tried pushing the line and the fitting in at the same time, I've tried installing with master cylinder attached and unattached. Nothing seems to work. I verified the threading is the same.

I'm out of ideas. I need some advice. Is there a good tool to use . . .help!