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:



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?



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?