Luis de Prat

I had this happen years ago to my 83 and it was repaired with a fabbed 1/4" thick steel plate affixed to the firewall with rivets plus a bracket for additional support.

Doing a search for this topic, I noticed several people have had their cracked firewall welded and would prefer to go this route for my 951.

I would appreciate any info on both options. Thanks!

Legoland951

Welded firewalls only will crack other places along the same vicinity IMO welds are uglier also depending on how many cracks you have let alone the bulged surface where the clutch master sits.

Luis de Prat

Thanks for the input!

Rich Sandor

I'm in the process of removing everything to weld mine, however I'm not just welding up the crack but actually welding in a plate to reinforce the area. I will take pics.

I did a search and actually found some pics both on rennlist and 968forums.com.

V2Rocket

what are symptoms of a cracked firewall? how common is this?

FRporscheman

It's most common on the 968, and 951. It's caused by having a heavy pressure plate, which means you have to push the clutch pedal hard, which means the clutch master mounting place (on the firewall) gets flexed more and more until it cracks. 968s had heavy PPs and 951 guys like to use heavier PPs.

The syptom is your clutch pedal becomes super ultra heavy. Or if your cracks are really bad, it can actually become hard or impossible to shift because all your pedal force goes to firewall flex instead of into the hydraulics.

I have this problem on my '95. It hasn't changed in all 3 years I've had it, but I just can't stand it anymore. I don't see any cracks though, so maybe the crack is tiny, or the metal has just weakened. I really can't afford to have that car down again right now so I'm interested in learning about different bracket options. The only bracket option I've seen which doesn't involve drilling into the body, looked a bit janky. But it is reversible... I want to know which arrangement is best and just go with that one off the bat.

Luis, I would recommend if you decide to weld, you weld in a reinforement plate like Rich. It's really involved work though - I figure you have to remove the intake, the brake master, booster, and clutch master, along with any pedal related work which will hurt your back. If you do this, please install 2 new master cylinders while you have a chance. The bracket isn't exactly pretty but if it worked well on your 83 why change from something that works? Just my 2 cents.

PorscheDoc

A local spec car that had the same problem. The solution.....It's not pretty, but it works.

Rich Sandor

Another thing to consider is that it's called a "firewall" for a reason.

You want to seal the engine bay away from the cabin, in case you have a fire you don't want flames or smoke/fumes seeping through the firewall into your face.

Using rivets and a plate or just a bracket doesn't do that.

Mike951

did this repair on a '95. basically just had a friend who welds weld up the seam then weld a plate in the area that was shaped to fit nice.

had the typical super heavy clutch before it was fixed.

V2Rocket

ok so its not a common thing on NAs..

what would cause my clutch pedal to squeak when i press it?

Rich Sandor

Try spraying some silicon spray or wd40 on the moving parts of the clutch pedal/spring/lever assembly and see if that works.

Mike C.

I preferred to anchor the tip of the ms via a u-bolt into the fender well (I posted in one of the threads but picture was poor). This method takes most of the bending load out of the firewall and uses the heavy body of ms as leverage against bending. I also used a 1/8 thick steel reinforcement behind ms and sealed to firewall. I think welding a thick bracket is overkill.

V2Rocket

my dad said it was the clutch fork lol

Legoland951

It would be amazing if you can hear the clutch fork considering its shielded inside the bell housing... I doubt that is where the noise is coming from since the only movement on the fork is rotational around the pin needles.

MPD47

Both of my past 951's had the crack. One of them got fairly bad and we patched it as a temporary fix (lined the metal up and just filled it). Certainly the proper way is reinforcement plates on BOTH sides of the firewall.