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> No Significant Brake Pressure, Brake Experts Chime In
Midtowner
post Jun 26 2006, 10:44 PM
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I'm betting someone here has an answer. The Car: '73 2.0, 90,000 miles. 19mm master cylinder. Brake proportioning valve. New Zimmerman rotors and Ferodo pads front and rear. New inner and outer front bearings. New fluid. All parts installed by reputable shop in Silicon Valley. Master Cylinder not leaking. The Problem: Pedal pressure only results in gliding to a stop. Unable to lock the wheels.

Any ideas what's going on? (IMG:style_emoticons/default/huh.gif)
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DanT
post Jun 26 2006, 10:56 PM
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Air in proportioning valve, Erik.

Bleed, bleed and rebleed.

You may need to do this several times before you get a hard pedal. Proportioning valves are notorious for trapping air.

That is one of the reasons I removed mine and placed a T in the line and went to M calipers up front and front 914-4s are now on the rear. Not what I would suggest for a street car...but for my application it works great.

Jus keep bleeding....have you checked all the lines to make sure everything is tight, no leaks?

Probably just air in the lines.
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DanT
post Jun 26 2006, 11:18 PM
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Erik,
After the shop did the work, didn't they road test the car?

they should have caught that....

with power bleeders that most shops have these days you would think they would have gotten all the air out, but if they didn't road test it how would they know.

(IMG:style_emoticons/default/sad.gif) (IMG:style_emoticons/default/huh.gif)
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bd1308
post Jun 26 2006, 11:19 PM
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mine glides to a stop too...

lol

but my rear R rotor is G-O-N-E.

b
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Bleyseng
post Jun 26 2006, 11:24 PM
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Speed bleeders solve the bleeding issues and make it easy to pump a pint of fluid thru to get rid of the air bubbles in the prop. valve.

When you do this, stomp on the petal a few times then bleed em.
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So.Cal.914
post Jun 27 2006, 12:20 AM
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If everything is new and tight than it is air, unless the M/C is falty and only the rears are working (stranger thing's have happened). But if you just had the brakes redone, take it back and have them fix it. Thats wrong...
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jk76.914
post Jun 27 2006, 12:45 AM
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We're all assuming air in the system, but you didn't say how the pedal feels, nor did you mention the calipers in you list of recent refurbishments.... If the pedal is firm, but the car still just "coasts" to a stop, then you may have sticking pistons in calipers. You can have one or both pistons stick in any given caliper, and it's pretty common with disk brakes that aren't used that often. Especially if they haven't had the fluid changed regularly over their life.

A related question and potentially helpful symptom- how is the parking brake working? Does it hold the car?

No question about one thing- your shop should have found it.
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Dr. Roger
post Jun 27 2006, 12:54 AM
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is your pedal firm or does it go to the floor? i hate to assume anything...

have you properly bedded in the pads?
frodo's, what type? race or street?
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Midtowner
post Jun 27 2006, 10:18 AM
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See? I knew someone would have the answer here! Perhaps I can answer a few questions.

1) Brake issue was discovered during a road test by the shop. Car is still there.
2) Caliper pistons are probably stuck. Never thought of that one but it is very possible given that the car was sitting in a garage for sixteen years.
3) Ferodo pads for street.

Thanks a bunch. I'm calling the shop now.

This place rocks. (IMG:style_emoticons/default/biggrin.gif)
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Pompano Beach 914V8
post Jun 27 2006, 10:27 AM
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If it's air in the system the pedal would be soft.....and if the shop can't diagnose that....OMG!
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Eric_Shea
post Jun 27 2006, 10:36 AM
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Couple of things I see here now, especially after that last post.

1) Car's been sitting for 16 years. You need to rebuild all your calipers. I know exactly what they look like and you don't wanna be driving "anywhere" on calipers that have been sitting for 16 years.

2) Once that's been done, bleed the system and get it out on the road. Do some panic stops in an empty parking lot. Drive it around for a while (2-7 days). Take it back to the shop for a final bleed of the rear circuit.

That final recommendation is what I like to use for a real world p-valve bleeding proceedure. You can have a friend help and mash the crap out of the pedal but, I've found a few days over bumps, up hills and some good panic stops is usually the best for getting all the air out. The final bleed will pick that up and you should be good and firm at the pedal after that.
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jk76.914
post Jun 27 2006, 11:32 AM
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QUOTE(Midtowner @ Jun 27 2006, 08:18 AM) *

See? I knew someone would have the answer here! Perhaps I can answer a few questions.

1) Brake issue was discovered during a road test by the shop. Car is still there.
2) Caliper pistons are probably stuck. Never thought of that one but it is very possible given that the car was sitting in a garage for sixteen years.
3) Ferodo pads for street.

Thanks a bunch. I'm calling the shop now.

This place rocks. (IMG:style_emoticons/default/biggrin.gif)


16 years? Yeah, calipers are probably corroded inside due to moisture in the fluid. Make sure these guys know what they're doing before you let them take apart the rears. There are lots of pointers on this site to shops who know how to rebuild/restore/refurb these things. After waiting 16 years, another couple of weeks of turnaround isn't going to hurt anything.

Good luck!
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lapuwali
post Jun 27 2006, 11:39 AM
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IMHO, don't let these guys take apart the calipers at all. I'd pay them for work done so far, and either take the car to CT Automotive (who do know what they're doing), or take the car home and pull all the calipers off yourself. Send the calipers to Eric. Refit the now shiny and new calipers, bleed, and you're on your way.
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Midtowner
post Jun 27 2006, 11:54 AM
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Thanks for the input. Pedal feel is very firm. The shop is Heyer Performance and Tony definitely knows 914's much better than most. So please don't jump to any early conclusions. Calipers are working fine according to him this morning. Still though, I will most likely contact Eric Shea in the near future. He is re-bleeding too. Tony and I are now trading out the pads to see if I accidentally got shipped race Ferodos pads instead of street compound. (IMG:style_emoticons/default/smile.gif)
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Midtowner
post Jun 27 2006, 11:57 AM
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Oh, and what are your opinions on Speed Bleeder valves?


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rhodyguy
post Jun 27 2006, 12:48 PM
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Chimp Sanctuary NW. Check it out.
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like geoff said. dave hunt and i did dino's in about 30 minutes. well, dave did. he pumped and pumped and pumped and pumped and .... i was the "fluid is clean and there aren't any bubbles", and close the bleeder guy. have them put in the bleeders and redo the system. the bleeders go in the upper port on the calipers. if they used the lower valves to purge the system, the calipers are full of air. did they get the parking brake venting clearance correct? ask them exactly what they did.

k
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Midtowner
post Jun 27 2006, 02:46 PM
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Thanks. I will ask. (IMG:style_emoticons/default/smile.gif)
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DanT
post Jun 27 2006, 04:56 PM
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And? (IMG:style_emoticons/default/popcorn[1].gif)

Tony knows his stuff......period.
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Brad Roberts
post Jun 27 2006, 05:13 PM
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Ha ha.. Tony called me and asked me..LOL

This is what happens when you supply your own parts!!!!

The Ferodo pads are JUNK. BUY real pads.

If you pay under $50 for your pad sets... your car wont stop.

I'm a big supporter of the shops making some money on parts they KNOW work.

I'm also REALLY surprised that Tony took the job on with you supplying the parts.



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Brad Roberts
post Jun 27 2006, 05:18 PM
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Little background on this shop he took his car too:

The owner:

TonyH

Lead tech for Garretson enterprises when ALL the Hot Rod 914IMSA stuff was being raced through their shop (tuna can/Foley Header/stiff kits..blah blah) Was on the team that won Leman in 78+79. First american team to win at Leman and beat all the factory teams running the 935TT's.

He know's his shit (he also knows who to call..LOL)



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