R154 question

[Stomps]

Hey got a gearbox question... brainstorm/sounding board..

A few weeks ago i was at a khana/track day.. only 6 of us so the car basically copped 2.5 hrs straight of limiter bashing...

towards the end of the day i let a mate drive it... he's never driven a car with a clutch like mine so he rode it a shitload at the start..


when he finished the run he asked my "why wont your gearbox go into any gear"

so symptoms:

clutch fluid under the car
the shifter wouldnt go into any gears.. wouldnt even make a grinding noise in any gear but reverse..
when we switched the car off we managed to move it..
when the car is running it wont go into any gears..
when the car is off, i can get the shifter into whatever gear i want..

what i did:
checked the slave cylinder- seems to be working ok.. no leaks etc..
checked the master- leaking from main external seal.. (i've since had it rebuilt)
pulled off inspection plates and had a look inside.. no clear evidence of anything failing..
suspecting that the friction plate may have gotten fused to the flywheel we unbolted the pressure plate and pushed it back.. luckily the friction plate is moving freely..
got my bro's snap on peep camera and had a good look inside.. nothing looks broken...

so:
could a rooted master cylinder account for these problems?
what else could cause this- would have to be a problem within the box itself...
thoughts?

cheers

Stomps

[midnight_purple_GA70]

so after the rebuilt slave you have put fresh fluid in and bled it all up properly?

pedal feeling normal still?

tried starting it in gear with clutch in to see what happens? if it starts trying to move while in gear with the clutch pushed in ide suggest you have a clutch issue...

if not ide see how releasing the clutch go? does it start to drive normally? will at least rule out gearbox failure

[Stomps]

hey..

we didnt rebuilt the slave.. we rebuilt the master..

havent bled it out again yet.. we wanted to see if there was any other issues before..

Im hoping that refitting the master, bleeding it all etc.. will solve the issue..

its more of a hypothetical to see if it doesnt... then what??

Stomps

[lexsmaz]

You mention the slave clyinder seems to be working, did you look at the amount of movement / throw it has ? & as asked how does the pedal feel, not to much slop / play at the top of the travel ? & is the pressure to depress the pedal the same as it has been ? ..

If it goes into gear well with the motor off & the clutch slave travel appears to be normal, i would suspect pressure plate has a cracked diaphragm or even maybe a cracked clutch throw out fork, which is not allowing the clutch plate to fully disengage & so causing the clutch plate to drag ...

( Takes me ages to type, saw your reply after i posted mine, hopefully a bled clutch will fix it ) ..

[Stomps]

You mention the slave clyinder seems to be working, did you look at the amount of movement / throw it has ? & as asked how does the pedal feel, not to much slop / play at the top of the travel ? & is the pressure to depress the pedal the same as it has been ? ..

If it goes into gear well with the motor off & the clutch slave travel appears to be normal, i would suspect pressure plate has a cracked diaphragm or even maybe a cracked clutch throw out fork, which is not allowing the clutch plate to fully disengage & so causing the clutch plate to drag ...

hmmm, interesting.. especially about the cracked diaphragm... i couldnt see any clear damage, but ill get the camera in again and have a better look..

re: slave cylinder... to be honest it's hard to say.. there was movement but it was hard to see if there was a full range.. (as we discovered the master failure quickly and didnt get a chance to try it further)

come to think of it.. there probably wansnt a full range of movement, because when i moved the slave manually yesterday it seemed to move a lot more than it moved with the clutch being pressed..

Stomps

[lexsmaz]

You wont see a cracked diaphragm by looking at it still assembled, normally when sitting on a bench after dissasembled you will notice quite a difference in finger heights from one side to the other if it has a cracked diaphragm & if you inspect the diaphragm closely, inside the clutch cover you will then see a crack in it as well ..

On hind sight what you could possibly do is before you remove the box etc is depress the clutch & turn the flywheel & see how much lift the pressure plate has off from the flywheel in one spot compared to another, all depends on how much you can see though, ( won't be easy or possibly to accurate, just a thought though ) ..

[Stomps]

hmm... no worries..

ill bolt the pressure plate up again and bleed the system... if the slave moves more than last time, HOPEFULLY ill be on a winner..

if not, its only a few mins to unbolt the PP again.. so no time lost..

cheers mate..

Stomps

[LeeRoy]

I'd be changing and bleeding the fluid before doing anything else, then checking fork throw.

[Stomps]

I'd be changing and bleeding the fluid before doing anything else, then checking fork throw.

yeah, we sort of did..

initially we bled the system and found that the master was rooted.. i guess we could have installed it, bled it and hoped for the best.. but then if it still didnt work, we would have had to release all the fluid anyway and re-bleed later..

so we decided to have a look at the mechanical gear for any obvious damage..

in hindsight, we prob should have just fitted the rebuild master and tried it out..

Stomps

[midnight_purple_GA70]

i think you will find what has happened if no mechanical damage was a failing master cyl progressively getting worse then as your mate drove it and not known how it should feel/drive its gotten so much worse to the point of not working...

drain the system and put fresh fluid in with the rebuilt master and i think you will be fine...

if not i think you will have the above pressure plate/clutch fork issues rather than a blown box.

[Stomps]

yeah, the blown box was a way out there chance.. its a r154 after all ffs..

the bloke that rebuilt it mentioned that the seals looked like they have been affected by a shitload of heat..

given it sits right over the top of my dump pipe... i may need to look into better heat shielding...

the master was fairly old but.. so hopefully this will solve it..

Cheers guys, ill let you know what i find.. prob wont get a chance to look at it until next wed though...

Stomps

[LeeRoy]

i think you will find what has happened if no mechanical damage was a failing master cyl progressively getting worse then as your mate drove it and not known how it should feel/drive its gotten so much worse to the point of not working...

drain the system and put fresh fluid in with the rebuilt master and i think you will be fine...

if not i think you will have the above pressure plate/clutch fork issues rather than a blown box.

Agreed, and it's one of the simpler, cheaper, and easier things to do.

Removing R154's is a pretty unfun job.

Edit: Stomps, i'm sure the box heat would be mostly from it's actual use, not radiant exhaust heat. Plus - there would be lots of air passing it that the exhaust would limit the effect of the heat.

[midnight_purple_GA70]

lots of clutchwork will also heat up the fluid which i would suggest thats the kind of heat they were refering to damaging the master cyl... over time though...

[Stomps]

Agreed, and it's one of the simpler, cheaper, and easier things to do.

Removing R154's is a pretty unfun job.

Edit: Stomps, i'm sure the box heat would be mostly from it's actual use, not radiant exhaust heat. Plus - there would be lots of air passing it that the exhaust would limit the effect of the heat.

Sorry, i meant the heat to the master cylinder itself, not the box..

yeah, im hoping to avoid dropping the box, but even so, its not that bad.. my bro and I did my entire manual conversion in 6 hours total.. drive in drive out..

TBH the fluid did look very cooked.. and smelled bad..

the car has had a fairly hard life.. especially since the manual went in.. new 400ish hp motor, big clutch, lots and LOTS of skids.. 2nd gear dumps etc... its entire life as a manual basically consisted of track days, motorkhanas etc...

Stomps

[BlackSupra]

Do you have a push/pull convertor for the clutch?

My factory one snapped at a bolt head and was allowing for plenty of flexing in the fork. Get someone to depress the clutch pedal and look at the slave to make sure it is moving the clutch fork.

I had the same symptoms with my R154 and it had glazed syncros after running redline shockproof and a few hard launches.