LS1 Disc Brakes Locked Up

[Formula51]

NEED HELP WITH PROPORTIONING VALVE AND BRAKE LINE ROUTING TO MASTER CYLINDER. SEE PAGE 2.

Yesterday my brakes locked up after about 20-30 minutes of driving. This is the first time I have had this happen, but I just aquired the car and have not driven it much. The previous owner suspected the front brakes may have been dragging due to premature pad wear and put new pads on before I bought the car. When the brakes locked, both front wheels were too hot to hold your hand on and the right rear was actually smoking, but the drivers side rear was cool to the touch.

I pulled the master cylinder and saw where the brake booster rod had been cut-down and two washers added between the plastic rod and the metal nipple that goes into the rod and then into the master cylinder. Installing the master cylinder with both of these washers or just one resulted in the plunger depressing some. Everything I have read is that this will cause the brake lock up I experienced. When installing with no washers, I did not feel any pressure when the master cylinder seated against the brake booster.

So my concern is, why were these washers put here by the previous owner? Ignorance or some other reason....

Does it sound like I am doing the right thing by removing them (shortening the rod) and are there any things I need to be concerned about after shortening the rod?

Thanks for all the help. Threw up some pics of the rod, nipple, and washers on a shutterfly site real quick to help explain what I am talking about.

http://eddies1968camaro.shutterfly.com/

[6'9"Witha69]

If the washers were causing the master to be in a constantly depressed state, that would cause the drag you experienced. If the rod is too short, it may cause the pedal arm to not properly contact the brake switch, meaning the brake lights are always on. If you have a 700R4 or other type of Auto trans w/ converter lock/brake release that will be affected as well. It also means less travel till the pedal bottoms out, so be sure you have full swing. Also make sure that the rod is connected to the proper pin location on the pedal arm. The lower hole is for Power assist brakes, the upper is for Manual Masters. Perhaps he had a Power Master rod, and tried to shorten it to accomodate being a Manual MC length, and did it too short? So he shimmed it too much?

[Formula51]

If the washers were causing the master to be in a constantly depressed state, that would cause the drag you experienced. If the rod is too short, it may cause the pedal arm to not properly contact the brake switch, meaning the brake lights are always on. If you have a 700R4 or other type of Auto trans w/ converter lock/brake release that will be affected as well. It also means less travel till the pedal bottoms out, so be sure you have full swing. Also make sure that the rod is connected to the proper pin location on the pedal arm. The lower hole is for Power assist brakes, the upper is for Manual Masters. Perhaps he had a Power Master rod, and tried to shorten it to accomodate being a Manual MC length, and did it too short? So he shimmed it too much?

Car has a TH350 so no worries there. Pedal arm contacts the brake switch fully. Actually appears to contact the same as before I removed the washers as I recently adjusted this.

Pedal travel appears to be full, approaching the floor board/firewall on full depress.

I am not sure what brakes the car originally had. I took a picture of the brake pedal mounting so you can see if it is in the proper hole. There is a hole below where the rod is mounted that has a return spring on it that is run to a hole in the lower dash. I am not sure if this is the lower hole you are referring to as I cannot see if there is an additional hole above where the arm is currently mounted. Your help is greatly appreciated.

http://eddies1968camaro.shutterfly.com

[6'9"Witha69]

What are you running, power or manula brakes?

[Formula51]

Power brakes. Looks like a booster and master cylinder from an LS1 Camaro.

[6'9"Witha69]

OK. I never looked at the pictures initially and thought this was all manual brakes. I believe the rod needs to be connected to the lower hole, not the upper as pictured. The rod you were talking about is the intermediate piece between the vac booster and MC. I didn't know that before (shoulda looked at the pictures sooner). I have no idea why that was shimmed. Perhaps he was having a knock back or residual pressure issue he was trying to mask or "cure" by adding those shims. Yuo need to measure the thickness of the hat on the rod, and compare that to the depth of the plunger from the flange. They should be the same. If so, then the shims are not needed, but you need to then be careful trying to figure out why this was done.

[Formula51]

Alright. So if I put the rod between the pedal and booster in the lower hole do I need to adjust Its length from where it is currently set? If so, what is the proper way to adjust it?

[Formula51]

Update:

With the rod in the upper hole of the brake pedal and both washers removed from the rod between the master and booster, I have no brakes! The pedal goes all the way to the floor with little resistance.

I went to try the rod in the lower hole and it physically will not go there. The rod bottoms out on the firewall gromet before it gets low enough to connect to the lower hole. Uploaded a picture showing this:

http://eddies1968camaro.shutterfly.com

HELP! Thoughts?

[dhutton]

Normally you can adjust the length by turning the clevis on the threaded rod to shorten it but I can't see how much thread is left in your picture.

[Formula51]

There is enough thread to adjust in either direction but it will never reach the hole because the rod is bottoming out on the rubber gromet where it goes through the firewall.

[dhutton]

The stock booster is angled down. Sounds like the one you have is not.

[Formula51]

The booster looks to be from a 98-02' F-Body and does appear to have some angle to it. Has anyone run into this problem on their LS1 brake swap? What did you do to fix it?

And this may be a stupid question, but why does the rod have to be in the lower hole for power brakes? I see it mentioned all the time that it has to be in the lower hole, but I have never read why other than "because that is for power brakes".

Thanks for all the help so far guys. Hopefully you will keep it coming and I can get this thing on the road again!

[dhutton]

Do a search on pedal ratio to understand why you want the lower hole. I also think you need a first gen booster or at least you may need to use the brackets off one. I'm not an expert on this by any means. DSE sells a booster and master that might work well for you.

[Formula51]

Do a search on pedal ratio to understand why you want the lower hole. I also think you need a first gen booster or at least you may need to use the brackets off one. I'm not an expert on this by any means. DSE sells a booster and master that might work well for you.

Thanks Don. I found this description:

"You should use the bottom hole on the brake arm, that one is for boosted brakes, it allows more fluid that the boosted system needs (bigger MC). The manual MC needs the upper hole for leverage. The boosted system needs the bottom hole for more stroke for brake feel and fluid flow due to the bigger MC. The upper hole is too fast for a proper boosted brake system, it gets too touchy if the system is working as it should."

So my problem currently is getting the rod/clevis to the lower brake pedal hole. I have seen others on this forum that used this booster and similar mounting so that should not be the problem. Hopefully some of those guys will come in.

Perhaps I should trim/notch the rubber gromet in the firewall where the rod is touching so it can reach the lower pedal hole?

[MrQuick]

On top of ratio's, the hole alignment would depend on master/booster rod angle using a stock master/booster.
I believe the LS1 booster has less angle as it would be on a stock replacment booster designed for the car. Which is probably why the previous owner of the booster felt it needed a pair of washers. Question...what happens with one washer?

vince

[Formula51]

On top of ratio's, the hole alignment would depend on master/booster rod angle using a stock master/booster.
I believe the LS1 booster has less angle as it would be on a stock replacment booster designed for the car. Which is probably why the previous owner of the booster felt it needed a pair of washers. Question...what happens with one washer?

vince

Vince, the washers are to lengthen the rod between the booster and master cylinder and do not effect the angle of the booster. Basically, the previous owner cut the rod to short and then added some washers toextend the rod, atleast it makes it adjustable.

However, the booster does appear to sit more flush with the firewall as you mentioned and this is why the rod will not reach the lower hole in the pedal. Even if I got it to reach, it would be at a severe angle, which I have read is a bad thing.

I put the rod back in the upper hole (found one other forum member with a similar setup to me that did this same thing) and adjusted the brake pedal up near the rubber stop and made sure I had some play before engagement of the rod. This put the clevis close to as far out as it can be (few threads sticking through) and I figured gives me the most rod/plunger travel possible into the master with the top hole? I also tightened up the jam nut real good. It was completely lose when this problem occured but I don't think that was a factor.

I have a great firm brake pedal, just like I want it WHEN THE CAR IS OFF! When I fire the car up, the pedal is soft and goes all the way to the floor. That is with no washers (short rod). Is this just a factor of the rod being too short, or something else?

I am gong to try just one washer and see if that firms up the pedal and still keeps the brakes from dragging. Keep in mind we are talking about a roughly 2mm thick washer. Man, is it really that sensitive to length? Perhaps that is a product of using the top hole on power brakes....

[MrQuick]

yep, i got that. the thing about pedal rod position is that you will have a different ratio depending on location. Lower hole will have a longer stroke due to being farther away from the funcrum or pivot point.
Which is why I believe your pedal goes down. The booster is needing more travel to operate properly. Which is another reason why the previous owner may have installed the washers thinking it was a preload issue.

Can I ask how you mounted your booster? I am afraid you will have to change the positioning to get it right.

[Formula51]

Alright, we are making progress!

Looks like the booster was mounted something awful! I pulled it out and the previous owner had literally mounted it with two bolts (one of which the hole was ripped open on the bracket) and cut off the bottom two bolts.

I am going to try and beat those lower two bolts back through the firewall and replace them, then weld up some steel to the booster bracket to extend it to the lower two bolts like I have seen done here:

45584

Then I should be able to shim the lower mounting holes out from the firewall to get the proper angle to connect to the lower pedal rod hole.

I do have one question though. If you look at the pictures of the brake booster I added on my page, there is a a rusty/crudy looking stuff around where the pedal rod goes into the booster. It kind of looks like the remnants of some kind of foam gasket or something. Can I just clean this stuff off and leave it like it is or is there supposed to be a gasket there that is important to function?

https://static1.pt-content.com/images/pt/2011/03/47a1dd04b3127cce985489a3776e00000038100A-1.jpg

Larger picture can be seen here: http://eddies1968camaro.shutterfly.com/

Thanks guys, I will report back when I make some more progress. Hopefully this thread will help someone with LS1 brakes/booster in the future.

[MrQuick]

should be a rubber boot on that end...at least there is on my set up. Its to keep dust and crud out of the booster.

[Vicinity]

That orange-ish, yellow crap was in mine, I just left it in, it's unimportant.

Did you get my diagram?

[Formula51]

That orange-ish, yellow crap was in mine, I just left it in, it's unimportant.

Did you get my diagram?

Got the diagram and got my brackets welded up. Thank you. Everything fits perfectly now just like you said and the rod lines up with the lower hole. I still need to paint everything before I put it all together but I did trial fit everything in the car and have a few observations/questions.

With my clevis turned all the way out on the threaded rod, I still have and inch or inch and a half from where the pedal rests until where it would hit the rubber bumper stop. Does that sound ok, or is that limiting my pedal throw too much?

I fired up the car and the pedal is still real mushy and only firms up near the floor but does not actually contact the floor. I did put the car in gear and roll it forward and back a little in the garage and it stopped the car, but it wasn't very reasuring. Maybe this pedal rod throw is not long enough or there is air in the lines since the brakes have never been setup and therefore bled with the rod in the lower hole???

Finally, I noticed an air gushing sound when pushing the brake pedal only with the car running. It is quite audible and I wondered if this is normal or not?

Funny thing, I always thought the booster rod itself moved in and out, I didn't realize it actually pushed that larger cylinder into the booster. Doh!

[Vicinity]

No, that does not sound right. I think your booster rod may need to be lengthened. I didn't measure mine, I used my fingers as units of measurement while pre-trial fitting.

The mushy part makes no sense to me, are the lines bled properly? It really sounds like you have a leak somewhere.

[a67]

Finally, I noticed an air gushing sound when pushing the brake pedal only with the car running. It is quite audible and I wondered if this is normal or not?

This is normal. As you depress the rod into the booster a valve opens that allows air to enter from the rear of the booster. The yellow stuff that isn't there any more is a silencer for this. It also acts as a filter as eventually that air goes through the engine.

Can use some jute padding if it is too loud. Just pack it in like a large o-ring. Not too tight though. Note that in the past I would remove about 1/2 of the silencer material to improve brake response.

Bob.

[Formula51]

This is normal. As you depress the rod into the booster a valve opens that allows air to enter from the rear of the booster. The yellow stuff that isn't there any more is a silencer for this. It also acts as a filter as eventually that air goes through the engine.

Can use some jute padding if it is too loud. Just pack it in like a large o-ring. Not too tight though. Note that in the past I would remove about 1/2 of the silencer material to improve brake response.

Bob.

Thanks Bob. I am going to call my local GM dealer tomorrow and see if I can get that silencer and a new dust boot if they aren't too expensive.

I finally took that steel braiding off the vacuum line to the booster (not my style) and in doing so I noticed it goes into a small metal nipple on the intake manifold (threaded in fitting with two vacuum connections). The line itself is 3/8" fuel line but the nipple is sized for a smaller line, maybe 1/4". It was clamped on tight with a hose clamp and the engine runs so I don't think there is a vacuum leak, but I was wondering if that could be undersized for the booster? The 3/8" line has to really stretch out to fit over the booster check valve fitting also.

[Formula51]

Update. Got the proper thick wall vacuum hose from Year One and the proper intake manifold fitting with the correct nipple size for the vacuum hose from Rick's. Also got all new brake pedal bushings, clevis pin, retainer clips, and the brake light switch extender for power brakes. I painted the booster, brake pedal, and firewall area and everything should be ready to reinstall his weekend. I will post up pics and results later this weekend.

FYI, I also called the GM dealer and apparently the brake booster and any parts are unavailable according to their system. I guess I will go with the jute padding like Bob mentioned and reuse the old dust boot.

[Formula51]

Replaced the rear rubber line, adjusted rear drums, and bleed all the brakes starting with the passenger side rear, completely flushed the system.

Took the car for a drive and the brake pedal is still not right. The pedal has several inches of soft mush before firming near the floor.

The clevis pin is adusted properly to the brake pedal rod with a little play. Clevis is in the lower hole in the pedal.

I tried adding some washers to the rod from the brake booster to master cylinder, which increased the drag on the front wheels, but did not appear to change the pedal. I currently have two washers in the rod, which only allows the wheels to rotate about 1.5 turns with a good spin. However, since that didn't appear to fix the problem, I think I will remove the washers so the wheels can spin freely (3-4) rotations.

What else can I try?

The car will lock the rears up. Would a bad or improper proportioning valve give me the bad pedal/stop? The nose does dive some during braking.

I am so close, just need to find that final little tweak. Thanks for the help guys.

[a67]

With the rear drums need to have a 10# residual pressure check valve in the line to the rear. This is to maintain pressure on the wheel cylinder seals. To prevent them from leaking when off the brake pedal. Not sure how much they will help in pedal travel.

Wheel cylinders do displace more fluid then disc brakes when actuated. Do a final rear brake adjustment by backing up and pumping the brakes. Do this while the brakes are cold.

Bob.

[Formula51]

Bob,

I am not sure I fully understand what that residual pressure check valve does. Is this going to put more or less pressure to the rears when applying the brakes and keep them lightly applied when off the brake?
I guess I would put the valve in-line after the distribution block and that means getting new threaded fitting(s), cutting a piece of line out and flaring the ends?

I have never heard of this valve before, any idea what size I need or where to get it?

Either way, I am not sure that is going to fix this soft pedal/long travel I am having...

[Formula51]

4652846529

Above is my brake setup. Incase you have not read, car has LS1 discs up front and stock rear drums. It has a brake booster and master cylinder from a 1998+ LS1 Camaro. The brake pedal rod is connected to the proper lower hole.

Symptoms: Car has a soft brake pedal with lots of travel until firming near the floor when driving. Will stop the car and will lock up the rear brakes, but not the fronts. Brake pedal does not inspire confidence. Brake is nice and firm when car off. Brakes have had about 3/4 liter bleed through them.

Proportioning valve and line routing: It is my understanding that the LS1 master cylinder should have the rear line (closest to booster) routed to the front brakes and the front line routed to the rear brakes. This does not appear to be the case with my routing? Can anyone confirm?

Also, I have no idea what kind of proportioning valve that is, how do I tell?

[Apogee]

Eddie, the 10 psi residual pressure valve (RPV) shouldn't have any impact on your pedal feel initially as it's only purpose is to maintain a small amount of pressure (10 psi) on the cup seals inside the rear wheel cylinders so that they don't "burp" air into the system when the brake shoe return springs force the pistons to collapse. Considering how strong the return springs are, there is no way 10 psi on a tiny little piston is going to counter the spring force in any way, nor was it intended to. The RPV's are typically installed under the inverted flare seats in the appropriate master cylinder outlet port (conical brass disc with a little check valve behind it), however you can install an inline unit anywhere between the master cylinder and the rear center hose.

The LS1 F-body master cylinder you have should have the front outlet port plumbed to the rear brakes and visa versa. Based on the pictures of your crusty, unknown combination valve, it appears to be plumbed incorrectly.

Tobin
KORE3

[a67]

What Tobin said about the residual pressure check valve. It can help with the pedal travel if the seals leaked and pulled in air. Which is why I mentioned that it may or may not help with the pedal travel. The check valve will also prevent the seals from weeping fluid out. As it keeps the seals pressed against the bores.

With self adjusting drum brakes need to be fairly aggressive when backing up and pumping the brake pedal. I've found that it does make a difference in pedal travel. The reason to do this cold is that a hot drum will expand, so adjusting them hot can cause them to drag once the drum cools off.

Bob.

[Formula51]

Ok. I will try adjusting the rear brakes again and it sounds like I may need to switch my lines front and rear in the master cylinder. I think I will bleed some more fluid through the rears and try to see which reservoir in the MC goes down to confirm.

This does appear to be a pedal travel issue and not a air/bad MC issue. With the car off and the vacuum gone from the booster (pumped several times), the pedal still travels about 2" before becoming rock hard and not moving. It never bleeds down with constant pressure. For comparison, my daily driver 1995 Olds Cutlass only travels about 1" before becoming rock hard.

I was hoping you guys would be able to tell from the pictures what kind of combination valve that was. It appears to be some type of original as it uses the original wire/connection? Are there any guts to this thing, like a proportioning valve? I was thinking this was a proportioning valve, but it sounds like I do not have a proportioning valve.

Tobin, do you sell the residual valve and fittings I need? How do I contact you?

[Formula51]

Here is my understanding of where the residual valve needs to go and how I may need to switch my lines a the MC:

46540

Does this look correct?

[Formula51]

Alright, ordered a new Wilwood combination valve (#260-11179) and a residual pressure valve from Tobin. Went ahead and bought a new MC as well. Going to be making new lines from the MC to the combination valve and routing them to the proper reservoirs! Should be good to go after that. I will report back with the results as I have searched everywhere on this forum and others for info on LS1 brakes with stock rear drums and there is very little so hopefully this will help others.

[a67]

Somethings not right about the way the current distribution block is plumbed. It's function is to provide for splitting the front lines left & right, and to provide a differential brake light alarm switch. That is it turns on the dash light if there is a difference in pressure between the front & rear brakes.

Now unless the switch part has been gutted, the plumbing is incorrect.

Where the electrical connector is splits that block in half, front and rear brakes. There is a line from the M/C into the front portion. Then it has one front brake on one half, then the other front brake on the other half (rear brake half).

However, with the Wilwood combo valve you listed this all goes away. Although, I would go through that braking system with a fine tooth comb. With what you have been finding there may be other surprises in it.

Items such as having red locktite on the abutment to spindle bracket bolts. And blue locktite on the abutment to bracket bolts. Along with the proper grade 8 bolts tightened to the proper torque. Proper routing of the flex lines (no rubbing), and so on.

Bob.

[Formula51]

Got everything hooked up (still need to make a bracket for the Wilwood block) and bench bleed the MC, but I am having problems with the residual pressure valve sealing.

The fittings that came with the valve that go from 1/8 NPT male to 3/8" female appear to "seal" by nothing more than the threads and teflon tape/thread sealer? There is no seat or anything like that inside the valve for them to seal against. That just doesn't seem right.

I bought a union adapter to go from 3/8" to 1/8 NPT to connect the residual pressure valve directly to the Wilwood distribution block instead of cuting and flaring a short little piece of tube between the block and valve. However, I am having trouble getting it to seal and thus I have not been able to bleed the brakes. It appears to be sealed now, but I will not know until later this week when I have time to mess with the car again. Worst case I will remove that union and cut/flare a short piece of line between the distribution block and valve although I am still not confident in the residual pressure valve fittings sealing.

Here is what it looks like:

46605

Turned the valve around and the lines underneath so I could have the lines from the MC go to the front and rear ports without crossing each other since the rear port of the MC is for the front brakes and the front port is for the rear brakes. It came out pretty nice.

Should the proportioning valve be screwed all the way out or all the way in when bleeding the rear brakes?

Note: It appears the MC that was on the car was not from an F-body as it did not have the same fittings or reservoir shape as the new MC I bought for a 1998 Camaro Z28. The MC I removed has M11x1.5 fittings front and rear and the new MC has one M11x1.5 and one M12x1.0 fitting. I will have to get the part number off it to see what it goes to.

[dhutton]

NPT is a pipe thread which is a tapered thread and it gets tighter and seals as it is threaded together. Hopefully this makes sense, the more you tighten it the tighter it gets and it seals.

[Formula51]

Duh, yes, that makes perfect sense! You would think I should know this (Masters in M.E.) doh!

I am thinking my sealing problem was/is the union seating on the distribution block, but I did not have the NPT adapters in the pressure valve very tight either (always afraid to overtighten) so I tightened those some more and pumped the brake a bunch of times and no leak. We will see if one develops overtime or when I bleed the brakes.

[Vicinity]

Glad to see you got it solved!

OT question, what is your prop valve mounted to?

[Formula51]

Right now it is not mounted, just suspended/supported by the brake lines, but I have already made a cardboard template for a bracket. I am going to make a metal bracket that will bolt to the lower inner fender and then have two holes to run bolts through the proportioning valve mounting holes (5/16"). I will capture the valve with washers/nuts on the other side of those bolts, so the bracket is essentially just a steel plate on one side of the valve. I will take some pics when I get that fabbed up and mounted.

[Formula51]

Finally on the road and all fixed for good this time!

Got the residual pressure valve sealed by adding a short piece of line between the proportioning valve and residual valve.

Had a leak at the passenger front line to the proportioning valve. Pulled it lose and bent into the fender well so I could see it and the flare (reused the old existing one) was split! Doh, managed to cut it off in the wheel well with the pipe cutter and reflare it and then bend it back in place. All sealed so far!

And now the big one! This was the "excess pedal travel" I was having. I had no drivers side rear brake!!!! I decided to have the rear drums turned because I remembered the drivers side had a bad groove in it. After closer inspection, the wheel cylinder on that side had been replaced once before and I noticed THIS:

https://static1.pt-content.com/images/pt/2011/06/22813184024_large-1.jpg

The wheel cylinder plunger was completely out of the brake shoe! This explains why that side would never lock up or feel even the slightest bit hot after a drive. That wheel cylinder was also leaking. Passenger side had the original wheel cylinder, which was not leaking. I kept that incase someone wants it. Just shoot me a PM or email.

Decided to dive in and replaced both wheel cylinders, new stainless rear lines to the already new flex line and rear shoes.

Gave the brakes a good bleed and took it for a drive and THE FRONTS LOCKED UP FIRST!!!! I was exstatic! I have a much nicer pedal now, firmer and shorter, but still not exactly the same as a newer car, but confidence inspiring atleast. Finally got to drive the car to work and show it off!

Thanks so much to all who helped and I really hope this thread helps some others in the future with things to look for if nothing else!

Regards,
Eddie