I did the LS1 brake conversion on my 96 LT1 car. I bled all the air out with the Mitivac hand pump and then bled them the traditional way with two people. The peddle felt solid until I stared up the car, now the peddle goes to the floor. What is the problem? I don't have any obvious leaks.

 

bleed....bleed.....and bleed some more

 

I've gone through 4 bottles of brake fluid bleeding. I've done a lot of brake jobs but this one is turning out to be difficult. I'll try bleeding more. Why is it that when I start the car up that the peddle goes to the floor but when the car is not on, the brakes pump up well?

 

The brake booster is provided vacuum with the engine started

 

Make sure when you installed the calipers the bleeders are on TOP, when I bought my rear the rear calipers were on the wrong side and I bled and bled and bled till I figured it out, swapped calipers to the other sides, and BAM perfect petal.

 

Bleeders are on top. Any other suggestions?

 

Sounds like you have air in your abs unit, do a search for that, but I think you jack up the car and spin one front tire over 6mph then hit the brakes and it opens it up, then bleed.

 

Ya, I tried that too. I'll keep trying different things and then bleed. If all else fails, I guess I'll borrow a Tech II or get it towed to the shop but that's a last resort.

 

i just did mine and i had 0 issues... interesting

 

My ABS hasn't worked in years, maybe that has something to do with not getting all the air out of it. Or maybe a bad caliper? both calipers have been rebuilt.

 

The calipers are moving properly right? see if there are any leaks. It could be the ABS...

 

I'm sitting in the garage doing my ls1 fronts right now, hopefully I don't hit your issues.

 

So when you bleed and pump them up with the car off, you get a good petal but as soon as you start it it goes away? If you pump them up and then wait 2 minutes with it still off and press them again is it still hard? Put a piece of cardboard or white paper or newspaper under each wheel and then pump and play with the petal alot. I had this issue and found a very slow leak from 1 caliper connection, got new brass rings and tightened it up and it was ok. It's hard to see brake fluid on a dark garage floor.

 

It may be a leak on one of the calipers but not an obvious one. But yes, the peddle is firm when the car is off and continues to be firm until I start the car up. The front brake lines are new stainless steel with a new bolt and two new brass washers. One of the calipers is a rebuilt unit from the auto parts store and the other is from ebay that I rebuilt with a rebuild kit. Went together fine. I have checked the lines for leaks and there is no fluid leaking. I am now thinking about the SJM manual set up since my ABS dosn't work anyway.

 

One way to be sure that you have moved fresh fluid through your system is to buy a can of Super Blue racing DOT 4 fluid. Then use the MitiVac and pull fluid until you see blue to all four wheels.

I change my fluid each year. One year blue DOT 4, next year amber DOT 4, etc.

 

Turns out, the brakes were bled all the way. The new pads just needed to mate with the new rotors. Stops really good now! Still going through some heat cycles. They will probably get a little better yet. Thanks for all the suggestions.

 

So the front calipers are mounted with the bleeders on top as well?

 

Yes, like bufmatmuslepants said to do. My pedal was goin' to the floor till I read his tip to ensure the bleeders were on top. Now the pedal is firm & short travel.

 

next time, pick up a Motive speed bleeder for quick bleedin, best thing i ever did for my brakes

 

I just got the cheapo one from advance with the little reservoir that you put on top of your tire and pump till it fills. $9 way cheaper than mityvac