mark kibort

Ok guys., i have a sutation that happed after the race, The clutch pedal has been a little dicy. sometimes after the race, the pedal is parially depressed and then after pumping it up, it works wellll, no issues during the race. after it stits for a while, its like there is a leak or air in the lines and it gets soft again. at home , for street driving it doesn ever happen. however, recently, the pedal feels fine, but as soon as i shift near redline (not at 3-4 krpm, ) after the shift, the pedal doesnt come back to the top. after decelling, the pedal comes badk and it shifts normal. im wondering if during full throttle the lack of vacuum is creating some differential pressure that doesnt alllow the pedal to come back. I dont know how this is possible as the power steering vacuum is not connected to the brake master cylinder. so how does flooring the car, and high rpm (need both) effect how the pedal and the clutch react?????? im perplexed!

any ideas??

IcemanG17

are you losing fluid? Have you changed the infamous blue hose that is know to fail? When was the last time you bled it? I found it helps to get the front of the car really high when bleeding the clutch....

UKKid35

There are only three things worth replacing, and none of them are expensive: Slave $80, Master Seals $20, Blue Hose $10?

I would suggest the master seals are the most likely culprit, but no harm in replacing the slave as well. If the blue hose is leaking it should be pretty obvious (because eventually you'll have no brakes!)

mark kibort

No, the blue hose is the original from the anderson donor chassis. isnt the blue hose what ends up down at the slave. so, if it leaks, you obviously get some pedal issues. sounds like that could be it. it does to be leaking some , not much, but usuallly you dont lose any fluid excpet for pad wear, where fluid goes to calipers. you might be on to something. But, why the soft pedal ONLY on redline shifts??

.

I think i replaced the master on the '79 racer , as the fluid was leaking into the vacuum booster. I dont think it was that expensive.....
but why the pedal hight issue, atfter a near redline shift? high vaccum off throttle , pulls fuid from the master , but then you would think that the brakes might be softer for a cycle., and they are not. come to think of it , on the decel, the clutch pedal comes back, so maybe there is some requirement for vacuum to keep the clutch pedal up.

jon928se

There is an internal dam in the fluid reservoir which prevents a total fluid loss in the brakes or in the lcutch system affecting the other one. Thus forget vacuum related issues.

Leaking m/c or slave seals. It happens at the end of the straight (i think you siad that ) because that is the probably the longest period of time during a lap that you haven't used the clutch - after the change into 5th gear (or maybe still accelerating in 4th)

Mike Simard

You probably need a MC but sometimes a problem may be your fluid being old and affected by exhaust heat. The older it gets, and once it has boiled, the worse it will be next time.

Is the line near your exhaust?

Have you flushed the fluid lately?

UKKid35

Good to know - thanks.

the flyin' scotsman

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Lizard928

Mark,

Your post was completely full of jibberish this morning. Most of all the statement above.

The power steering doesn't have vacuum and isn't connected to the brakes or clutch at all.

Vacuum to the brakes will not cause a soft or not fully returning clutch pedal.

If I were you I would replace the guts of the MC and the blue hose and fully bleed the system replacing all the fluid to ensure fresh fluid.
Then see if the problem disappears.

Oh and don't take any more spelling, grammar, or sentance structure lessons from rpetty2 as it was hard enough to understand some of your posts before.

mark kibort

i bleed the brakes after every few events. I dont boil the fluild, so its not that. plus, ive been racing the car for many years and if it was a problem, it would have shown itself at some other point in time, and it hasnt.

with this car, (the new chassis) it has its original or the one it came with, master cylinder. sure that could be it.

yes, it happens after any kind of quick acceleration. i can drive around all day long. (*remember, this car is kind of a daily driver) the clutch is perfect. then, if i want to go to redline, the cliutch pedal fails after the shift. so the shift occures flawlessly, and then letting the clutch out after the shift, the pedal is half way returned. if i slowly ramp up to redline and then shift, no problem . its a WOT , no vacuum in the intake that seems to follow the problem. so, its puzzling.

Hey, give me a break - I was exhausted late last night when writing it. anyway, i meant the brake booster, not the powersteering system. sorry.

anyway, if it wasnt vacuum related then why is it narrowed down to full throttle WOT, only. it seems when the system vacuum is removed, the clutch doesnt return. kind of strange. but, the only way that the MC can see any vacuum removed from the brake booster , is if the brake booster actually loses all its vacuum. remmber, i had a situation with a bad master where the vacuuum in the booster would drain the brake reservoir. but again , as was just mentioned , those systems are separarte in the MC.

I can replicate this, at any time. anytime i shift WOT to redline,or near redline, the clutch action is such that the pedal doesnt return. ANY other shifting situation, its fine. Its very strange.

maybe ill start by pushing the plunger back in the slave to get some of the air out. and thats another thing. in this car, when i do this, the piston is very easy to push back in, and the distance that it is pushed in is very short , compared to the slave on the Holbert car when i would do this. I think the slave is the same as the holbet car, but the MC is the one that came on the chassis.

the flyin' scotsman

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davek9

AO had this issue at SITM a few years back, header too close to cluch hose, try some heat shielding wrap, wouldn't hurt.

the flyin' scotsman

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Mrmerlin

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aj986s

FWIW, 944's are know to have a flexing firewall issue as the cars get older. Sometimes a crack, but usually seam separation on the firewall. Can cause pressure on the brake and clutch pedals to flex the firewall a bit, causing alignment of the shaft/pedal to deviate and the pedal temporarily sticks. Not sure if 928's also prone. Fix for many has been a brace bolted between the firewall (at one of the brake or clutch master bolts) to the shock tower.