another broken firewall plate
12-27-2015, 11:47 PM
#27
ok so here is the fix.
thats the piece i had machined up.
this is the dashbar with the clutch pedal bolted to it.
and here is the piece on the clutch pedal bracket
again, here is the firewall again. it needs to be modded, the whole needs to be opened up so the master cylinder will slide right through it. i didnt get a pic of the firewall after triming it, however just image roughly a 2" hole, its pretty close to the studs.
and the firewall with the piece in place for test fitting the master cylinder
the piece is sealed against the firewall with some strip caulking called dum-dum.
now i started reassembling at this point and forgot to take more pics. it was a long night, 6 hours to get it reassembled. as i feared, i ended up with one left over bolt, and i have a dash rattle. gonna have to pull the top of the dash back off and track it down.
i have to say, my clutch hasnt felt this great in a long time. for at least a year i havent been able to shift fast, and the clutch never felt that precise. i now have a very consistant release height and can slam through the gears as fast as i want without issue. the only downside here is due to the design of the entire repair is the clutch pedal height it a tad higher. this is because the actual mounting surface of the clutch master cylinder is inside the car, aproximately 0.100" closer to the pedal (thickness of the firewall plate and a little in the machining). this in turn has moved the whole pedal assembly closer to the seat. its nothing terrible, its one of those things i did notice. i am however not sure how much of what i noticed is caused by the design of the piece, and how much of it is because the firewall is no longer flexing.
so here is the best part of this fix, once i refine the piece a little it will be possible to install by only removing the steering column and the clutch pedal assembly (as well as the fuse block so you can access the master cylinder from the outside). to change the firewall plate requires complete removal of the dash and heater box, and you need to devac your a/c to do that. i was roughly 4 hours of disassembly before finding out i couldnt get a firewall plate new, and it took 5 hours to put it back together. from that point my best guestimate to fully disassemble the car, remove the firewall plate and install a new one, and reassemble the car would be 12-14 hours. to remove the master cylinder from the outside, drop the column, remove the clutch pedal, mod the hole in the firewall and reassemble it all im estimating 2-3 hours for the average person. my shop just picked up an insurance total loss cobalt we are rebuilding, its a 2.4l ss 5 speed, im going to be using it to make the changes, and ill be timing the install start to finish, and writing up instructions.
thats the piece i had machined up.
this is the dashbar with the clutch pedal bolted to it.
and here is the piece on the clutch pedal bracket
again, here is the firewall again. it needs to be modded, the whole needs to be opened up so the master cylinder will slide right through it. i didnt get a pic of the firewall after triming it, however just image roughly a 2" hole, its pretty close to the studs.
and the firewall with the piece in place for test fitting the master cylinder
the piece is sealed against the firewall with some strip caulking called dum-dum.
now i started reassembling at this point and forgot to take more pics. it was a long night, 6 hours to get it reassembled. as i feared, i ended up with one left over bolt, and i have a dash rattle. gonna have to pull the top of the dash back off and track it down.
i have to say, my clutch hasnt felt this great in a long time. for at least a year i havent been able to shift fast, and the clutch never felt that precise. i now have a very consistant release height and can slam through the gears as fast as i want without issue. the only downside here is due to the design of the entire repair is the clutch pedal height it a tad higher. this is because the actual mounting surface of the clutch master cylinder is inside the car, aproximately 0.100" closer to the pedal (thickness of the firewall plate and a little in the machining). this in turn has moved the whole pedal assembly closer to the seat. its nothing terrible, its one of those things i did notice. i am however not sure how much of what i noticed is caused by the design of the piece, and how much of it is because the firewall is no longer flexing.
so here is the best part of this fix, once i refine the piece a little it will be possible to install by only removing the steering column and the clutch pedal assembly (as well as the fuse block so you can access the master cylinder from the outside). to change the firewall plate requires complete removal of the dash and heater box, and you need to devac your a/c to do that. i was roughly 4 hours of disassembly before finding out i couldnt get a firewall plate new, and it took 5 hours to put it back together. from that point my best guestimate to fully disassemble the car, remove the firewall plate and install a new one, and reassemble the car would be 12-14 hours. to remove the master cylinder from the outside, drop the column, remove the clutch pedal, mod the hole in the firewall and reassemble it all im estimating 2-3 hours for the average person. my shop just picked up an insurance total loss cobalt we are rebuilding, its a 2.4l ss 5 speed, im going to be using it to make the changes, and ill be timing the install start to finish, and writing up instructions.
The following 7 users liked this post by Sharkey:
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12-28-2015, 01:32 AM
#30
That's a good looking fix there. You could pickup an adjustable clutch rod to fix the pedal height issue if it bothers you, might be a good idea since now that the pedal is further away you're getting more travel when it hits the floor. That might translate to more wear on the slave cyl, not sure how far from its "bump stop" it is when depressed normally.
12-28-2015, 01:55 AM
#31
an adjustable pushrod wont fix the height change without causing issues. something i discovered while reassembling is the clutch pedal stop is actually the collar on the pushrod hitting the end of the master cylinder. so as it is you have the exact same clutch pedal travel, the height has changed with both the pedal out and in. using an adjustable pushrod would bring the clutch out position down, however id have less pedal travel and likely end up with notchy shifting again.
Moderator
12-28-2015, 12:12 PM
#33
an adjustable pushrod wont fix the height change without causing issues. something i discovered while reassembling is the clutch pedal stop is actually the collar on the pushrod hitting the end of the master cylinder. so as it is you have the exact same clutch pedal travel, the height has changed with both the pedal out and in. using an adjustable pushrod would bring the clutch out position down, however id have less pedal travel and likely end up with notchy shifting again.
This is all armchair speculation, I haven't rolled under there to look at that particular assembly before.
12-28-2015, 08:42 PM
#34
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this happened to my car 2 years ago. I bent it back as much as a could without ripping whole dash out. And jb welded it. The whole firewall area was flexing in and out Bc of how strong my clutch was. It was too much pressure on that thin firewall metal. Let's just say that was the reason I sold my car.
12-29-2015, 02:10 AM
#37
its not even a problem with a very stiff clutch, its just a problem. i have a gmpp clutch, its not really stiffer than the stock clutch. ive had that clutch in there for 4 or years now, the car has just over 210k km on it. so to me it seems like a design problem, not something caused by aftermarket parts.
i do plan on marketing and selling it. like i said above, i need to refine it and get some instructions. i need to wait till the new year before ill have any info on pricing, i need to talk with the machine shop about it.
i do plan on marketing and selling it. like i said above, i need to refine it and get some instructions. i need to wait till the new year before ill have any info on pricing, i need to talk with the machine shop about it.
01-28-2016, 02:47 PM
#44
Do you have a picture of what your plate looked like?
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