s'ko Posted July 31, 2008 Share Posted July 31, 2008 So I have a pretty scary problem. The front brakes on the RX lock up if I do panic braking. I replaced the brake fluid and it helped a little but it still locks up. Seems to happen to one wheel and not both at the same time. Also there is no pattern to it affecting the driver or passenger wheel. The pedal is firm but then after I stand on it for a long time, the pressure goes away. The front pads are new, rear pads I have to take a look at, but IIRC they still had meat on them. This car has a hillholder, but it's not presently connect. Could that have something to do with the front locking up? Is this air still in the lines or are we looking at a busted master cylinder? BW Quote Link to comment Share on other sites More sharing options...
Caboobaroo Posted July 31, 2008 Share Posted July 31, 2008 if it has a pedal fade, basically like you mentioned where it'll have pressure then gradually fade to the floor, it means you either have A) a bad brake flex line somewhere a bad fitting on a caliper like where the banjo bolt holds the line onto the caliper C) a bad master cylinder or a bad HH. You can help determine at which part of the system is causing the fade just by crmping off the solf lines that feed into the calipers by the connection between the hardline and the soft line which will let you know if its a line or the MC/HH. If you do this and the fade isn't present, then its a line, if not its a MC typically. You do this with the car off, not running. As for the locking up, also check the brake pads for contamination from grease or oil since it'll make the pads brittle and actually cause them to grab the rotor. Check for heat cracks as well in the rotors. Quote Link to comment Share on other sites More sharing options...
Frank B Posted July 31, 2008 Share Posted July 31, 2008 You don't have anti-lock brakes so this is normal during hard panic braking. This is why anti-lock brakes are used now. If you mean that you loose pedal pressure after long braking periods, downhills and such, that is normal. Friction, the reason brakes work like they do, creates heat as you know, but after the brakes reach a certain temp, the brake pads and the rotors will be the same temp and no longer create friction becuase they can't get any hotter, then they do not work! This is the problem with tractor trailers, that's why they have an engine brake and go slow down hills. If you mean that if you hold the pedal down while parked and the pressure fades, it could be the MC if this is when the engine is off, if it does it while the engine is running, it may be the power booster, it uses engine vacuum to boost the line pressure. Test it like this. Engine off pump the brake pedal untill it gets hard to push, but don't use both legs to try and push it theough the floor! Just even steady pressure. When it's hard and pumped up hold it down and see if the pressure fads. If not, good MC. Now start the engine with the pedal pumped up the pedal shoul go soft and lower to the floor, that means good booster. I suggest a good set of brake pads, metallic. Clean and re-grease the caliper slides too. And not standing on the brake so hard. Do it a bit more to find that point that they lock up and train yourself to not apply that much brake, or to let off a bit and pump the pedal at that point to keep them form locking up. Quote Link to comment Share on other sites More sharing options...
s'ko Posted July 31, 2008 Author Share Posted July 31, 2008 I realize that it's part of the reason that most cars not have anti-lock brakes. Part of my concern is that I have a BRAT disc brakes all around and it on 225/60/16s and the tires do not lock up under more extreme braking situations. Would wheel size have something to do with this? I have 205/60/13's. I will check when the brake fade occurs. If it's a bad MC, I have been reading that Legacy MC swap with interest. Caboo...when you say crimp the soft line, you mean bend it in half to stop the flow right? I kinda hope it's the soft lines b/c then it will give me an excuse to get stainless steel lines. Plan to take the wheels off today after work and see what the pads look like. I know the front pads were new and I am pretty sure they were clean. Rear pad age is unknown. It my just be adjusting to driving a car w/o ABS and w/o bigger tires. BW Quote Link to comment Share on other sites More sharing options...
NorthWet Posted July 31, 2008 Share Posted July 31, 2008 Not meaning to speak for Caboobaroo, but I believe he means for you to clamp off the soft (rubber) line with a pair of locking pliers ("ViseGrips"/et al). Did this locking issue just start, or has it been an ongoing issue? If it just started, examine what has been done previous to it starting. did it just appear one day, or did it gradually develop? (Given we are talking hard braking lockup, some of this may be ambiguous unless you regularly do screeching halts.) You mention new(ish) front pads. Two things pop out in my mind: 1) The calipers pistons were not oriented properly to take the pins on the back of the pads (unlikely cause of this problem) 2) The caliper pistons have not self-adjusted, leaving excessive clearance between pad and rotor. The clearance might not be taken up smoothly/evenly during hard braking, causing one side to grab. (This might also be caused by a warped rotor causing pad "knock-back".) Quote Link to comment Share on other sites More sharing options...
ahole Posted July 31, 2008 Share Posted July 31, 2008 the bigger wheels and tires (tires mainly) setup has a substantialy larger contact patch than the smaller ones. This will contribute to quicker lockup. Also if the 16's are a high performance tire compared to the 13's, they won't lock up as easily. As for the brake fade, maybe your pads aren't of a high quality. Quote Link to comment Share on other sites More sharing options...
s'ko Posted July 31, 2008 Author Share Posted July 31, 2008 Not meaning to speak for Caboobaroo, but I believe he means for you to clamp off the soft (rubber) line with a pair of locking pliers ("ViseGrips"/et al). Did this locking issue just start, or has it been an ongoing issue? If it just started, examine what has been done previous to it starting. did it just appear one day, or did it gradually develop? (Given we are talking hard braking lockup, some of this may be ambiguous unless you regularly do screeching halts.) You mention new(ish) front pads. Two things pop out in my mind: 1) The calipers pistons were not oriented properly to take the pins on the back of the pads (unlikely cause of this problem) 2) The caliper pistons have not self-adjusted, leaving excessive clearance between pad and rotor. The clearance might not be taken up smoothly/evenly during hard braking, causing one side to grab. (This might also be caused by a warped rotor causing pad "knock-back".) I just got the RX resurrected w/a Ej22t swap. got the car w/o a motor so I don't know if this was a problem. I am pretty sure that the calipers are moving correctly. The car has good stopping power other than it locking up w/panic stopping. If I drive defensively and don't try to put the pedal through the floor, there are no problems. The two times it happened while driving was 1) on the freeway, car infront of my stopped suddenly and I was a bit close and i had to jam on the brakes. 2) on a 3 lane main road in the rightmost lane. cars in the two lanes to the left stopped to let a pedestrian pass. Stood on the brake and it locked up. Luckily there was no car in front of me and the pedestrian stopped crossing when he heard the screaching. One thing about the BRAT is that the bigger tire maybe giving more leverage against the brake and keeping the wheels from locking. The 205-60-13s are a 22.69 inch tire while the 225-60-16s are 26.63 inch tire. will check on the things you guys are talking about, but it's looking more and more like I will have to adjust my driving style or try to retrofit ABS into the RX. When I say brake fade I mean that the pedal pressure gives out. Brakes stop fine. BW Quote Link to comment Share on other sites More sharing options...
Numbchux Posted July 31, 2008 Share Posted July 31, 2008 I think this is relatively normal for a light car without ABS. my car RS brakes and pretty good tires still locks up the fronts when really hard on it. heck, at an autocross a few weeks ago, I locked up all 4 at about 55mph coming into a tight corner (see avatar...) but the pedal pressure giving out is not normal..... Quote Link to comment Share on other sites More sharing options...
NorthWet Posted July 31, 2008 Share Posted July 31, 2008 ...but the pedal pressure giving out is not normal..... A big +1. Front brakes locking up, especially with lots more weight on them to try to stop and probably no more traction from the tires, is fairly normal; but the brakes locking, and inconsistently so, side to side is not all that normal. Again, this could be because of the extra weight, this time just overloading the suspension components. I.e. - "radius rods" aka "tension-compression rods" aka "leading rods" might have marginal bushings for the loads being put on them, and oscillating a little. Quote Link to comment Share on other sites More sharing options...
zyewdall Posted August 1, 2008 Share Posted August 1, 2008 By locking up, do you mean that they lock the wheels and skid because you are applying too much braking force for the ground contact that the wheels have? Brake fluid on drum brakes can cause this, but I'm not sure on disc brakes. OR That they lock the wheels, and then don't release after you let off on the brake pedal? I had the second issue once, and it turns out it was the hill holder being out of adjustment. I'd pull up to a stop, and if I had hit the brakes too hard, it would not release, and I could not drive off afterwards -- actually stalled the car in low range 1st gear once it was so tightly locked. I had recently adjusted the clutch cable quite a bit tighter, but hadn't changed the hill holder cable setting, so it thought that I was never letting the clutch out... Quote Link to comment Share on other sites More sharing options...
Turbone Posted August 1, 2008 Share Posted August 1, 2008 Some of you are trying to over-analyze this. And everyone needs to read the OP's posts carefully. Its a RX with 4 wheel disc brakes and 13" tires. It has new pads on the front, unknown on the rear (TAKE NOTE). Brake fluid has been replaced and of course, brakes bled. The HH has been disconnected. He has brake fade. The brake lock up is common for cars without ABS. Since he just put new pads on the front and doesnt know the condition of the rears, this could be the biggest reason of lock up in the front. The brake fade is most likely due to a weak MC. Install new rear brake pads and change out the MC for the Lego. Quote Link to comment Share on other sites More sharing options...
torxxx Posted August 1, 2008 Share Posted August 1, 2008 I have a similar problem with front lock up like that drivers side likes to lock up before the passenger side. Only thing that I can figure is the length of brake lines (farther distance to the passenger side) fluid takes the shortest path first and thats why they lock up like that? (my car was converted to 4 wheel discs and I kept the drum brake Proportioning valve because I like the way the rear locks up first on ice As far as the brake fade, how long are u pushing on the pedal? Keep in mind the brake setups on the GL series are VERY very underated Hill holder is not causing the problem, all that does is "dog" the fluid into the MC so it locks the front brakes when u use it My suggestion, drive faster and brake less Quote Link to comment Share on other sites More sharing options...
TheSubaruJunkie Posted August 1, 2008 Share Posted August 1, 2008 I think you may want to consider larger brakes. Your EJ22T is much more powerful than the EA82T and it maybe heavier (not certain, but very possible). The car is probably trying to stop more weight, at higher speeds, than it was originally intended. 5lug swap with legacy brakes maybe a good solution. -Brian Quote Link to comment Share on other sites More sharing options...
PoorManzImpreza Posted August 1, 2008 Share Posted August 1, 2008 I have a similar problem with front lock up like that drivers side likes to lock up before the passenger side. IMHO, this is caused by either grease on the rotor/pad, odd tires, faulty MC, bad soft line or incorrectly bleed brakes... I've found that ea subarus require aggressive bleeding ie with the engine running so you get vacuum assist and move ALLOT of fluid through the system so have about 2 quarts handy...Since I've been bleeding like this my pedal has been rock hard (that sounds wrong..) HTH Kaz Quote Link to comment Share on other sites More sharing options...
torxxx Posted August 1, 2008 Share Posted August 1, 2008 IMHO, this is caused by either grease on the rotor/pad, odd tires, faulty MC, bad soft line or incorrectly bleed brakes... I've found that ea subarus require aggressive bleeding ie with the engine running so you get vacuum assist and move ALLOT of fluid through the system so have about 2 quarts handy...Since I've been bleeding like this my pedal has been rock hard (that sounds wrong..) HTH Kaz we bled the hell out of the brakes (I power bleed all brakes I do) tires are the same size, new pads and rotors etc. no leaks. its an offroad/daily driver I've had the car for 10 years now so I got driving it like that down. For me, as long as it stops thats fine with me. car dont go over 80 mph (carb'd ea82 with a lift and bigger tires) and if there is need for emergency stopping, thats what the lift is for. whip it off the road into the trees if neccisary Quote Link to comment Share on other sites More sharing options...
s'ko Posted August 2, 2008 Author Share Posted August 2, 2008 ok. So I did some review. Back brakes are about in good condition. Brake pedal is firm when pumped and the engine is off. When the engine is on, the pedal will slowly sink to the floor. looks like I am being a dofus and I need to learn to re-drive a car. I have a line up on a 1 inch MC from a lego. Thanks for all your input. BW Quote Link to comment Share on other sites More sharing options...
Frank B Posted August 2, 2008 Share Posted August 2, 2008 When the engine is on' date=' the pedal will slowly sink to the floor. [/quote'] Do you mean when you start the engine with the pedal depressed, that it goes down farther, or gets softer? Or if you hold the pedal down with the engine running the pedal will touch the floor? It really should not go all the way down either time. If it goes all the way down, you may have a problem. Quote Link to comment Share on other sites More sharing options...
ahole Posted August 4, 2008 Share Posted August 4, 2008 He said he's getting a new MC. I think it will solve his problem. Any time the brakes sink to the floor, I get a new MC-problem soved. Quote Link to comment Share on other sites More sharing options...
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