[corvette jim]

help! i will start by saying what i didn't replace. the rear calipers and the power steering actuator which is addjusted and has about one eighth of an inch of slop. but everything, i mean everything else has been rplaced or properly rebuilt!!!!! when the car is still cold out of the driveway upon braking it pulls to the left , and as i drive and brake some more it goes straight, then as you drive some more it pulls right. aaaaaaaaaaaaagh! its been doing this since the restoration. i figured new parts adjust and align, it should be ok. however its not. there is 563 miles on it since i put it back on the ground. i looked at all the dumb stuff tires, air psi, lose stuff i might have missed, but it all checks good. the frame is straight, i have had the car for 20 years and i know it has never been in an accident. one thing, i am using organic pads instead of metalics. i would also like to thank everyone who has helped me out in the past. this is a great web sight and appreciate all the information. thanks again, jim.

 

[poncho62]

Wonder if your organic pads might be overheating and fading?

Just a thought.

 

[corvette jim]

thanks, i was thinking the same, if i dont get any more input, i might re bleed, and probably goto semi metal.

 

[HotRodMan]

When you replaced the front end parts, did you have the front end re-aligned? Did you replace the brake flex hoses up front? When you bled the brakes what procedure did you use? When you replaced the front calipers, did you rebuild them yourself or buy the pre-built units. Did you check the front rotors for run out? Give me a little more information and I'll bet we can figure it out.

 

[corvette jim]

yes to all, the calipers are napa rebuilds, and my wife helped me bleed the brakes by pumping the pedal. and then i messed around with my vacuum pump to draw out any air and got solid fluid. when i drive it and pump the brakes and then apply them, it stops straight. but then after some application it starts to pull right. i wonder if the right still has air, and the left applies to the point of fading to where it equals out to the right. and with further application the right pumps up and becomes more eficient. i am also not to jazzed about the caliper design using cup seals on the pistons. i wonder if switching to o ring piston will help. one other thing i did not apply anti squeal to the pads, i learned that lesson the hard way. thanks

 

[HotRodMan]

After examining all the info I think you either have air in the system or the calipers were not rebuilt properly. Try this.

1. Tap all four calipers all around with a hammer to dislodge any air that might be trapped. Instead of pumping the brake pedal, gravity bleed each wheel starting with the longest line and going to the shortest. You simply put a hose on your bleeder valve crack it open, let the fluid drain into a container, while maintaining fluid in the master cylinder. Watch for any air escaping. If you have two bleeder screws on the back bleed the inside first, then the outside. Your bleader screws should be on top of the caliper, if not the caliper is mounted incorrectly. Road test the car if you have a firm pedal.

2. If that should fail I can tell you it is tricky to get the seals on the pistons and into the bore without buggering up the seal. I have even seen brand new seals right out of the box that were bad, and if you weren't paying close attention you would never see it. I've seen seals installed backwards. If you have tried everything else, I would then disassemble the front calipers paying close attention to the rubber seals when you take the pistons out. The edge of the seal should have no crimps, and should be pointed to the inside of the caliper. The piston bores should be smooth with no pitting. If you discover problems, take those back to napa and order calipers from one of the specialty corvette suppliers. I have never had a bad one from them.

Let us know what you find out.

 

[corvette jim]

thanks. i tend to agree with the air problem. i am going to bleed the brakes by gravity. i was trying to be... i guess cheap but, not to cheap, in replacing the calipers. you would think after 40 years i would have learned my lesson. i work on multi million dollar jets for an airline, and you would be suprised evan in this area the "new" multi thousand dollar parts that are bad from the vendors. good advise i appreciate your time, and i will let you know. thanks again jim. oh yea, don't worry, we don't leave the bad parts on the planes, we enjoy our freedom to much.

 

[Pony]

We should start a club called " Corvettes Without Brakes" I also have an active post on Vette brakes. "The brakes worked before I fixed them!" I'd bleed them some more. They seem to really be a chore and a half to get right.

ps; I worked at Boeing in Everett WA. as a flight line mechanic & electrician for 16 years. It's amazing how new parts work sometimes. New gear-three flights=seals leak big time.. New engines-ground run ups=metal in the filters, compressor stalls-backfires=blown compressors. Ect, Ect. But as you stated we would beat the into shape and they all leave happy and ready to fly.

 

[HotRodMan]

Jim

Where do you go to school to learn to work on jets? What does it cost? I saw an interesting show on TV one time about why airplanes crash. It turned out that routine maintenance was be signed off as being done when it wasn't. The rear tail rudder was controlled by a threaded rod going thru a threaded nut. It was supposed to be lubricated every so often, then replaced every so often. It was cheaper for them not to do it, forge the paper work like it was being done, and send the plain on its way. The plane went down killing all 262 passengers and crew. Is any of this stuff going on any longer?

 

[corvette jim]

just to start off, i got the brake issue solved, it was just air, but i still took a look at the calipers to make sure they were good, and they were. thanks for your help. for your jet maint safety question. i was in the air force and received my FAA airframe and powerplant license that way. there are several schools through out the country, and tuition and length o f degrees vary from associate to bachelors. the tuitions can be as low as $15,000.00 to @ $30,000.00. now, i have been in this buisness for 20 years, i really enjoy going to work each day and enjoy the challenges that come with the job. your question brings up a good point. the particular aircraft you are referring to i believe was a md-80, i won't mention the airline but i know who they are. the maint performed on that jet was done by a third party maint contractor. allot of the airlines use these companies instead of doing there own maint. in house, to cut cost so the flying public will quit *****ing about the high cost of airfare. however the cost of a ticket is today what is was 20 years ago! however, the cost of everything else has gone up. generally the contractors are under a very strict program to meet financial and chronological deadlines to avoid paying penalties to the airlines. on the other hand, when maint. is performed in house we to are under deadlines, but we have greater flexibility to keep the aircraft out of service longer if we find other issues. now i am not going to say it out loud, but i think you can read between the lines. there are allot of reputable contractors and mechanics out there, these kind of incidents involving maint are few and far between. the majority of accidents are still caused by pilot and controller error. my point is, you are taking a 35,000 to 800,000lb hunk of tin, fill it with fuel, people and bags and throw it 40,000ft into the air! you really have no margin for error. so we all must ask our selves, what are you getting when you buy an airline ticket? and what price are you willing to put on your life? you obviously opened up a can of worms with me hot rod man, and i have only one issue left regarding airlines. my wife is a gate agent, its not there fault the weather turned to crap or there is a maint delay so i wish every one would quit yelling at them. she take it out on me when i get home! well i'll get of my soap box now. hope that helped answer your question. thanks again for your help and take care. oh yea, if any pilots or controller's read this, i don't want to hear it, records speak for themselves.

 

[Pony]

David. You'r right it was an MD-80. Got a question, we had a long running debate about that crash at work. The jack screw stripped, the stab locked and put the plane in a dive. The earlier jets didn't have a lock out on reverse thrust, SO the arguement is: If the pilots went to low thrust to keep the engines running and at about 10,000 feet went to reverse thrust gradually increasing it to full as needed could they have stopped it from crashing and just flopped onto the surface of the water?? I said Yes if they didn't pull the back half off the plane. What do you think??

 

[corvette jim]

hey pony, the names jim, i have worked on md-80's, and i have yet to see one, or any aircraft that could deploy there thrust reverser's in flight. and the operation of them is deployed or stowed, and when deployed the engines go to full throttle or highest trimmed rotation. so there is no way to just gradually deploy them, at least the aircraft i have worked on. i have not seen everything or know everything, however if such an operation exist, it is news to me. what i do know is about 10 years ago a certain engine manufacture selected a style of thrust reverser that had bad habit of deploying in flight. if you can recall there was an airliner in Brazil that such an incident happened at 35,000ft, ripping the aircraft in two, killing 200+ people. in fact there was a pbs special about it, and an air and space mag. article on it. around that time a fellow co worker and i chased two particular aircraft types around the country that our company flew to lock out the thrust reverser's from operating. what few people know is that the trust reverser's only assist in stopping the aircraft, the brakes actually do the majority of the work. basically thrust reverser's are not needed. but to deploy them in flight at any amount of speed or angle of attack would, in my knowledge, be nothing short of catastrophic. i Even asked some old timers at work if the had ever heard of such a thing, and the general answers were no.
if you have any reference material to support this, i would be very interested. i understand your concept of thinking, but with a non augmented symmetrical wing, one without flaps or slats deployed, the only thing keeping it aloft is straight and level acceleration, and lots of it! we may not be talking about land based hot rods, but at least we are discussing brakes. let me know more of your thoughts, take care, jim

 

[Pony]

Haven't a clue where the David came from.. Sorry! We had a Lauda Air 767 200 (earlier Model) go into TR over the North Adlantic quite a few years ago, the result as you said was catastrophic. All of our newer aircraft have a proximity switch on the nose gear and have to be be on the ground with pressure on the nose gear for T/R to activate. Most of the old timers I asked didn't think the older models had a lock out. We had no idea how the MDs are set up but it was a lunch time topic.