What is going on with my brakes? They really suck.
10-02-2010, 10:27 AM
#41
I have a LS1 car. I went to LT1 rear brakes. To get them to work properly, I had to install the LT1 master cylinder. It made a difference.
Prior to the master cylinder change, using the LT1 rear brakes with the LS1 master cylinder wasn’t great. Upon stepping on the pedal, it would first pass what I would call a "free zone" as the pressure went to the rear brakes to move the pads pulled back by the springs. After this initial free movement of the brake pedal, it would "catch" and the brakes worked normally.
It’s the front line that has a different thread fitting. The line size is the same but the fitting on the LS1 master cylinder has a corse thread. The lines, fittings and threads going into the ABS module are the same through the years.
Prior to the master cylinder change, using the LT1 rear brakes with the LS1 master cylinder wasn’t great. Upon stepping on the pedal, it would first pass what I would call a "free zone" as the pressure went to the rear brakes to move the pads pulled back by the springs. After this initial free movement of the brake pedal, it would "catch" and the brakes worked normally.
It’s the front line that has a different thread fitting. The line size is the same but the fitting on the LS1 master cylinder has a corse thread. The lines, fittings and threads going into the ABS module are the same through the years.
10-02-2010, 02:39 PM
#42
I did not disassemble either master cylinder to compare anything. I was advised that due to the needs of the LT1 rear brakes, I needed to install an LT1 master cylinder. It was explained to me that the rear brakes work like drum brakes and needed some residual pressure to prevent the pads from retracting, which is what I believed was causing the brake pedal to drop before grabbing.
It all seemed to make sense and it did fix the problem.
The lines appear to be the same size, the difference is in the one fitting’s thread pitch on the master cylinder. The fluid reservoir on my LS1 car has a sensor plug and I had to swap it to the LT1 master cylinder.
It all seemed to make sense and it did fix the problem.
The lines appear to be the same size, the difference is in the one fitting’s thread pitch on the master cylinder. The fluid reservoir on my LS1 car has a sensor plug and I had to swap it to the LT1 master cylinder.
10-02-2010, 04:10 PM
#43
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Just an idea but I removed my intake tonight to verify there are no leaks or anything unusual. When I took it off I found the little rubber coupler that connects the HVAC hose to the intake had cracked on both ends and was leaking. I had noticed the vents taking a long time to go from floor to face and this must have been why. Just an idea, I will know more tomorrow when I hook it back up as this is also right where the booster gets its air from so that leak would have reduced that as well.
Just an few things that you might want to check on yours.
10-03-2010, 10:56 AM
#44
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10-03-2010, 12:33 PM
#45
Just as an fyi vac assist brakes need at LEAST 12" of vac. to operate. So if you're running under or at that level, you would benefit greatly from either a vac can, vac pump, or converting to a hydraboost setup. Or you can just go to manual brakes which are clearly harder to stop. just a little insight. And to bleed the ABS block there is a tool required to be plugged in to open all the ports to allow for bleeding. IIRC the Tech 2 has the ability, but for the most part it's a shop tool...
10-03-2010, 02:28 PM
#47
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The two most complex components in the braking system are the master cylinder and the ABS block. I would say the ABS block still has trapped air causing your problems. I just broke a line in my system which drained the block. I've bled that bitch with several cans of fluid. Brakes feel firm before engine is started, once engine is started they get spongy as **** again and take several pumps to stop. I've ordered the ABS delete since it hasn't been operational for the last 12 years. I'd suggest you do the same. I think your problems will be solved. Either that or take it to a dealer.
10-03-2010, 08:08 PM
#50
Regarding the ABS module (ABS XI) for the 1995 model year. You dont need the scan tool to home the 3 pistons. When the three pistons are homed they open a check valve to allow flow. If the pistons are not homed then no fluid flows and its obvious when trying to bleed cause fluids wont flow. Also I dont want to delete it because its a fun car, not a race car. ABS VII on 96+ requires the scan tool to home it. No way around it from what I know.
I actually removed the ABS module, removed a cover and manually homed the pistons by hand to make damn sure they were homed and then I moved on to bleeding the brakes. I also found a nut loose and one of the gear sprokets loose but the thing had not yet fallen off because it was captured by another sprocket. I bolted it back up and loctited the nuts. I am confident there are no other issues with the ABS but it is still possible there might be an air bubble somewhere.
Its also my understanding that the ABS homes the pistons when the ignition is turned on and if you dont get a ABS light, then the pistons are properly homed. I agree with this because I verified this again by inspecting the module. I feel like I am intimately familiar with the damn thing now.
I appreciate all the input provided in this thread. I might still take it to a shop that can pressure bleed the system to rule that out.
I actually removed the ABS module, removed a cover and manually homed the pistons by hand to make damn sure they were homed and then I moved on to bleeding the brakes. I also found a nut loose and one of the gear sprokets loose but the thing had not yet fallen off because it was captured by another sprocket. I bolted it back up and loctited the nuts. I am confident there are no other issues with the ABS but it is still possible there might be an air bubble somewhere.
Its also my understanding that the ABS homes the pistons when the ignition is turned on and if you dont get a ABS light, then the pistons are properly homed. I agree with this because I verified this again by inspecting the module. I feel like I am intimately familiar with the damn thing now.
I appreciate all the input provided in this thread. I might still take it to a shop that can pressure bleed the system to rule that out.
10-03-2010, 08:19 PM
#51
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http://www.amazon.com/Motive-Product...6155277&sr=8-1
10-03-2010, 08:22 PM
#52
wrd1972, thanks for the info and sharing your experiences with the ABS module.
While my brakes are really good, I would consider re-pressure bleeding them with the ignition key in the "on" position to home the ABS pistons as you described.
Good info to have, there’s so much to share and learn on this forum.
While my brakes are really good, I would consider re-pressure bleeding them with the ignition key in the "on" position to home the ABS pistons as you described.
Good info to have, there’s so much to share and learn on this forum.
10-16-2010, 06:29 PM
#53
Update:
I bought a used Classic Performance vacuum pump off Ebay for $175 that is in like new condition. I mounted it behind the driver side headlight and plumbed it directly into the front of the brake booster. I drilled a hole in the booster, installed a grommet and a barbed fitting and this eliminated the need to tap into existing vacuum line.
Just to recap, when I panic stop while pushing the clutch (low vacuum condition), the brakes do not work very well and really cant engage the ABS. The amount of vacuum available in this condition is about 10" or so and with the AC on, about 8".
When I panic stop and without pushing the clutch (high vacuum condition), the brakes grab hard and easily engage the ABS. The amount of vacuum available here is around 20" or so.
Its my understanding that a stock cammed LT1 will easily make 20" or so of vacuum at worst. Clearly my cam and its 107 LSA is robbing the vacuum available to the brakes. Also to recap, I have eliminated everything in the brake system as being the problem.
WOW the brakes work big time better now. I can panic stop while pushing the clutch and the car stops hard and the ABS easily kicks in. This did not happen before the vacuum pump. Very happy with this mod so far.
The pump is a little loud when the key is turned on but once the engine is running, you cant here it at all. I am going to try to find a way of delaying it about 15 seconds or so once the key is tuned to on and if anyone has a suggestion on how to do this, I am all ears. It is my understanding that the pump kicks in when vacuum drops to 16" and kicks off at 23" or so.
I have powerful breaks again regardless of the vacuum being provided by the motor. Wooohoooo.
I will post picks once I button it up.
I bought a used Classic Performance vacuum pump off Ebay for $175 that is in like new condition. I mounted it behind the driver side headlight and plumbed it directly into the front of the brake booster. I drilled a hole in the booster, installed a grommet and a barbed fitting and this eliminated the need to tap into existing vacuum line.
Just to recap, when I panic stop while pushing the clutch (low vacuum condition), the brakes do not work very well and really cant engage the ABS. The amount of vacuum available in this condition is about 10" or so and with the AC on, about 8".
When I panic stop and without pushing the clutch (high vacuum condition), the brakes grab hard and easily engage the ABS. The amount of vacuum available here is around 20" or so.
Its my understanding that a stock cammed LT1 will easily make 20" or so of vacuum at worst. Clearly my cam and its 107 LSA is robbing the vacuum available to the brakes. Also to recap, I have eliminated everything in the brake system as being the problem.
WOW the brakes work big time better now. I can panic stop while pushing the clutch and the car stops hard and the ABS easily kicks in. This did not happen before the vacuum pump. Very happy with this mod so far.
The pump is a little loud when the key is turned on but once the engine is running, you cant here it at all. I am going to try to find a way of delaying it about 15 seconds or so once the key is tuned to on and if anyone has a suggestion on how to do this, I am all ears. It is my understanding that the pump kicks in when vacuum drops to 16" and kicks off at 23" or so.
I have powerful breaks again regardless of the vacuum being provided by the motor. Wooohoooo.
I will post picks once I button it up.
Last edited by wrd1972; 10-16-2010 at 06:37 PM.
10-20-2010, 09:17 AM
#54
I did not disassemble either master cylinder to compare anything. I was advised that due to the needs of the LT1 rear brakes, I needed to install an LT1 master cylinder. It was explained to me that the rear brakes work like drum brakes and needed some residual pressure to prevent the pads from retracting, which is what I believed was causing the brake pedal to drop before grabbing.
It all seemed to make sense and it did fix the problem.
The lines appear to be the same size, the difference is in the one fitting’s thread pitch on the master cylinder. The fluid reservoir on my LS1 car has a sensor plug and I had to swap it to the LT1 master cylinder.
It all seemed to make sense and it did fix the problem.
The lines appear to be the same size, the difference is in the one fitting’s thread pitch on the master cylinder. The fluid reservoir on my LS1 car has a sensor plug and I had to swap it to the LT1 master cylinder.
You are 100% correct that the LT1 MC and LS1 MC are different. The flow holes on the rear line port of the LS1 master are different and smaller. The front line flow holes look the same.
Rear lines looking down where the resovoir drops brake fluid.
LT1 MC on top, LS1 MC on bottom.
The parts house I bought the LT1 MC from actually allowed me to swap it out for a LS1 MC since the LT1 had a defect with the retainer clip. I will put it on this weekend.
Last edited by wrd1972; 10-20-2010 at 01:04 PM.
11-22-2010, 08:05 PM
#56
The lions share of the problem was the bad booster. Next the lack of vacuum in certain conditions. The vacuum pump is working very well and does not run long or much and nicely supplements when vacuum is low. I can get away without using it but what the Hell, it will guarentee a minimum of 16" of vacuum at all times and it was half the price of new. The correct master made the pedal feel much better but I cant tell a big improvement in the braking. I also installed some Hawk HPS pads and so no real improvement their either.
Overall the braking is very good but if I compare it to my 2007 Silverado or even my wifes 2008 Toyota Sienna mini van, they still dont stop quite as strong. Maybe its fair to say that a vehicle with 13 years newer technology should just stop harder.
Bottom line is the scary situation where the brakes just were not up to par, is gone.
Overall the braking is very good but if I compare it to my 2007 Silverado or even my wifes 2008 Toyota Sienna mini van, they still dont stop quite as strong. Maybe its fair to say that a vehicle with 13 years newer technology should just stop harder.
Bottom line is the scary situation where the brakes just were not up to par, is gone.
11-22-2010, 11:26 PM
#57
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The lions share of the problem was the bad booster. Next the lack of vacuum in certain conditions. The vacuum pump is working very well and does not run long or much and nicely supplements when vacuum is low. I can get away without using it but what the Hell, it will guarentee a minimum of 16" of vacuum at all times and it was half the price of new. The correct master made the pedal feel much better but I cant tell a big improvement in the braking. I also installed some Hawk HPS pads and so no real improvement their either.
Overall the braking is very good but if I compare it to my 2007 Silverado or even my wifes 2008 Toyota Sienna mini van, they still dont stop quite as strong. Maybe its fair to say that a vehicle with 13 years newer technology should just stop harder.
Bottom line is the scary situation where the brakes just were not up to par, is gone.
Overall the braking is very good but if I compare it to my 2007 Silverado or even my wifes 2008 Toyota Sienna mini van, they still dont stop quite as strong. Maybe its fair to say that a vehicle with 13 years newer technology should just stop harder.
Bottom line is the scary situation where the brakes just were not up to par, is gone.
11-23-2010, 08:00 AM
#58
Glad to hear it! Good brakes feel great in any car but especially a fast car. Remedy confirms the high vacuum required for our boosters. Note to self- look into a 9" dual diaphram booster for the T/A as stock booster must have really tuff old diaphram. I remember a hard brake pedal before the car was even cammed.
