Merlin49

Special thanks for ATGORDON for giving me just courage to attempt the booster replacement.
I found that on my 1990 apparently the mechanical spacing's are slightly different. I DID have to remove the cross brace to get my booster out. I also had to remove the seat and unbolt and lower my steering column to be able to reach all the under dash nuts and clips from kneeling on the floor next to the car.
And yes, I had the same problem with the pedal mounting bracket dropping down in the way, just to make reinsertion of the mounting studs very difficult. The slipped bracket turned out to be my biggest problem, and it took me almost 2-hours and a LOT of prying, plus the help of a friend to get it back up enough to get booster studs inserted.
AND thanks for the tip about using the tape in the socket to hold the nuts. That worked very well as I wrenched it all back together. Job is now done and it took me a total of about 4-hours and the help of another person. Thanks for the incite and the video.

Klondike

Helping people "do it right" never gets old!

Gmatech

Thanks for this, saved my day. Been wrenching at Chevy since 2000. Never done one and still beat the book time. I hate getting in them cars right side up... fat guy stuffed in head first must have looked pretty funny. If the lines aren't rusty don't be afraid to gently customize them. There's no reason you HAVE to take the master cylinder out. No time for that or the seat in the flat rate.

SnorT91Man

Here it is ten years after you wrote your article and people like me are still learning from it. Great job, man, and keep up the good work! Until I saw your pic of the retaining clip I couldn't figure out exactly how it was supposed to come off.

Out of curiousity, are you still working on cars? A C4 isn't exactly the easiest vehicle to develop your skills on!

SnorT91Man

jwardg

Great write and pics, very helpful.
Hey John, any tips you can give me on how to get the new booster bolts inserted past the metal plate thats blocking the hole openings from the inside?.
Ive been trying for a couple of days to get the new booster inserted through the firewall, but that plate is ruining my day(s)..

Would appreciate your sharing any tips or wisdom!

Thanks,

jw

lt4red

Wanted to see if anyone has a source for a new or reman-ed booster? Not finding anything from the part stores. One on amazon for 300$, but I'll buy junkyard before I pay for that.

belairbrian

Guessing your looking for a 96. If so rock auto has the ACDelco 14PB4300 For around $170. It 's what I used on my 92 two years ago and have had no issues since. There is a core charge. When I bought mine AC Delco had a $40 rebate so I ended up spending about $120 after returning the core and getting the rebate.

But I would never replace a failed brake part with a possibly 25 year old part from a junk yard. Just not worth the risk to me. Add how fun these are to change and used makes even less sense..

lt4red

Yes, for a 96. That part number is out of stock on rock auto and everywhere else i checked. Rockauto had the option for some rebuild service where you ship yours out to them.

vette196

don't ask Johno504

lt4red

I have tried Rockauto, Oreiley, Autozone, Advance, Napa and Scoggin Dickey, show it available, but try to order it and "nope" order cancelled.

95wht6spd

Thanks for the wright up, looks like a huge PIA, but I will probably be tackling soon....sigh

So do you have to lower the steering column, or just remove the under panel? Someone mentioned lowering column. I did this once to change my gauges, and it was also a huge PIA.

Charsel

Just did my booster; no need to lower the steering column, just remove the bottom cover. Definitely remove the driver seat, less pretzeling needed. Thanks Corvette Steve for the metal booster.

belairbrian

I'm the one that said lower the column. Lowering the column takes about 10 minutes. Then you don't need to remove the seat and contort yourself to get at the nuts. You can sit in the seat and use a couple of long extensions to remove and replace the nuts.

Furias15x

Done! 1 hour out and 1 hour back in. I was able to leave seat in as well. Luckily I saw in this thread about how aluminum support bracket can move down some. At first try it didn't look like it had moved but the booster wouldn't easily go back in. I got my 12 year old to push the booster in while I held the bracket place with a screw driver. Went in easy for my 12 year old.

Thanks for the information.

95wht6spd

Yeah, I got it done, and left seat in, and steering column in place.

jeanpreston

I have a 1994 C4 Convertible Corvette.

Can you detail the bolts and process to “lower the steering column”.

I’ve got that one last brake booster bolt left on the transmission side and I just can’t seem to get it to move from down below. Thank you.

belairbrian

Remove the under dash (hush) panel.
I remove the instrument cluster surround (4 screws). You can drop it with it in place but it's really close.
Remove the tilt lever. It's threaded and screws out
The column is supported by two bolts, one on each side under the dash. They go through a a plate welded to the steering column. As those bolts are loosened the column starts falling

jeanpreston

Many thanks to littlesk8cracker for starting this thread way back in 2009. I would have never attempted this project until finding and reading his well documented process nearly 11 years after he first posted it. And thanks to all the others that have supplemented the thread with their experiences and helpful tips that made doing it a much simpler project also. I owe a special thanks to belairbrian for his late night reply to my question about dropping the steering column. I ended up not needing to drop the steering column but at one lonely point after trying multiple times to get the bolts back on the brake booster inside the firewall I thought it was going to be necessary.

I would highly recommend that anyone wanting to perform the C4 Brake Booster replacement themselves that they read this thread top to bottom before starting. The additional tips and gotcha’s to look out for are very helpful and will save you a lot of time and avoid unneeded frustration. The tips about using a little plumber’s caulk in the socket to keep the nut from falling out, putting tape on the socket extension knuckles to keep them from flopping all over the place and watching out for the drop in the inside firewall brake booster mounting bracket (mine did drop ever so slightly but thanks to the posts recognizing it and addressing it was easy) , and unbolting the mounting of the ASR unit to clear space to remove the brake booster without disconnecting the brake lines from the master cylinder are all examples of the awesome time saving tips.

My C4 brake booster replacement project here was done on my 1994 C4 Corvette convertible. My old brake booster was the plastic Delco model. It was professionally installed at a great expense less than 7 years ago. After reading the thread I realized how flawed the plastic ones were and found an all metal one from the Corvette Hangout folks on Ebay for $265 plus tax. It actually shipped from the Lone Star Caliper Company out of Texas. Its an MBM brake booster part number PB9013-1M120. Again it’s all metal and its 3 inches smaller in diameter than the Delco plastic booster. The new metal brake booster did not have a fiber mounting gasket on it like the plastic one did. So I just removed the fiber mounting gasket from the old plastic booster (it just came right off) and placed it on the new metal booster.

After reading some of the thread I realized that heat from the exhaust (especially if you have headers) was a killer to the plastic booster. While I don’t have headers I do have plenty of heat under the hood. So I’m hopeful that the extra space between the smaller metal booster and the exhaust as well as its all metal construction will result in a longer lasting brake booster. Time will tell. My plastic brake booster had a visible crack right around the check valve area.

Throughout the thread you will see different methods of removal and installation. I used a combination of all of them to get the job done.

I did remove my driver’s seat and the hush panel below the steering column in preparation for the project. I also discounted the wiring from the ASR unit and removed its 3 mounting bolts so that it had free movement to create enough space to pull the master cylinder out of the way without having to remove the brake lines from the master cylinder. This creates enough room to pull out and remove the brake booster. And, because you don’t have to disconnect the brake lines there is no brake line bleeding to be done at the end of the project. I would also suggest you take a few pictures as you remove things to help you remember where they go and what holes things go into. Like which hole the cruise control cable was attached to on the CC vacuum actuator. When it came time to hook mine back up I sure was glad I had taken that picture. There are 6 holes and I couldn't remember which one it was originally attached to. The picture nailed it and will save you a lot of time from having to adjust, test and retest.

Then I pretty much followed littlek8crakers and the others process and tips. I did find that laying on my back in the drivers compartment and trying to get the space and leverage to remove and install the firewall brake booster bolts to be problematic. You will see how others did not remove the seat and used long extensions and multiple flex knuckles to go directly to the inside firewall brake booster nuts without getting on their backs and under the dash. In the end that’s exactly how I was best able to remove and install my under dash firewall nuts. I knelt beside the driver’s door, used long ratchet extensions and several lightly taped knuckles, located the bolts and then was able to unscrew and screw them back in much easier. On the re-install the trick is to use the plumber’s caulk to make sure the nut doesn’t fall from the socket, line it up, get it started properly by hand twisting and then use the long extension and knuckles on the ratchet right out in front of you while kneeling there at the driver’s door.

I did create one interesting problem or gotcha with the brake light and cruise control switches on the brake pedal that I haven’t seen mentioned before. As I tried to pull myself out from under the dash at one point I grabbed onto the brake pedal and pushed it hard up and towards the rear of the car and heard a clicking sound that I knew sounded really bad. After investigating what I may have done, I discovered that since the brake pedal was no longer attached to the brake booster it was totally free to move in both directions. The clicking sound was the result of the plastic threads of the brake light and cruise control switches being pushed through the treads of the metal bracket they are mounted into. I had almost pushed the switches all the way out! Once I put everything back together I was able to just apply the opposite push force and push each switch fully to the brake pedal bracket as they should be. They just clicked ring by ring back into position as I applied push force. Thank goodness I didn’t have to remove the wiring and vacuum lines to screw them back into position.

The FSM says the firewall Brake booster bolts should be torqued to 15 FT LBS (21 Nm) and the Master Cylinder bolts and ECM Housing bolts should be torqued of 13 FT LBS (18 Nm). I didn’t use a torque wrench but here are the values in case you do.


Driver seat and hush panel removed for optimum access and
visability up under the dash and to the firewall. It was nice to have
been able to clean below that seat too!



As you take things apart take a few pictures before you do. Especially where cables and wires are attached and
there are multiple holes or settings. You'll be glad you did. This is the cruise control cable attached to the vacuum actuator.



This is my original plastic brake booster. Notice the crack right there at the check valve. This plastic booster was installed just 7 years ago.
No more plastic brake boosters for me.



Another picture of the failed plastic brake booster for comparison to the all metal construction replacement.
Make a note of the space and footprint it occupies.



The original Delco plastic brake booster next to the all metal construction replacement unit.
Notice the replacement unit does not have that fiber mounting gasket the plastic one does.


I just moved the fiber mounting gasket from the plastic unit over to the metal one and moved on.

The Delco plastic booster is 30 1/2 inches in diameter and the all metal construction replacement brake booster is only 27 1/2 inches in diameter.

Pictures of the completed job with the new all metal constructions brake booster installed. Much smaller footprint than the plastic one.

The left side picture shows the problem I created by pushing out and rearward on the brake pedal and forcing the cruise control / traction control
switch (left) and brake light switch (right) away from the snug position settings they should have been at on the brake pedal bracket.
Luckily equal push force brought them back to the correct flush position you see in the right side picture. I was really afraid that I was
going to have to remove the wires and vacuum lines to get them back in. Thank goodness that wasn't the case.
If you hear a clicking sound when you put rearward pressure on the brake peddle when then booster is not attached be aware that
you have inadvertently moved your switches. You will need to put your switches back flush to the peddle bracket when you
have everything back together.


Replacement booster boxes and info if you should you wish to do some research on the companies or their products. I think you can expand
the picture to see the Corvette Hangout's info too. I bought it through them on Ebay. Lone Star Caliper actually distributes the product.

Casethecorvetteman

Hi all

Some of you may know who i am, a lot of you may be too new to this forum to remember me.

I used to rebuild these PBR / Repco plastic brake boosters. I did quite a lot of them.

The Cardone is a cheap knockoff.

The OEM booster is made in Australia, by Repco in the earlier models, and by PBR in the later cars. AC Delco never made them, so any that come with their branding are either a rebuilt core or a rebranded original.

I used to buy the kits for a Ford Falcon AU series 1 (Australian car, the 6 cyl models used the same booster) and use them in the Corvette booster, they were 100% identical internally.

to do this job correctly, you really should be following the correct procedure in the appropriate factory service manual applicable to your year model.

Someone else mentioned this, but there is a specific thickness the booster should be with the nuts done up. This is very important if you want it to last.

I used to grease up all internals with Castrol red rubber grease. It is important that you use the correct type, as it is non-injurious to rubber, and will also improve lifespan. The OEMs used something similar to french chalk.

There are a number of parts and seals that came in the kit.

Under no circumstances should anyone attempt a repair on a split diaphram. It will almost certainly split again somewhere else.

Any members from Australia that needs a booster, i can usually help. I have one spare still sitting here, but the one in my Callaway split it's diaphram a couple days ago. It has survived 28 years, so they're not always terrible. In a couple months i should have a spare rebuilt unit sitting there ready, can even give the option of left or right hand drive.

Casethecorvetteman

This is the correct OEM Repco booster for earlier models.