Clutch engagement changing after 30min, then maybe slipping (Page 1/1)
RustyTech JUL 07, 10:21 AM
I have Two Fiero's, both 1986 SE's with one being a 5sp and the other a 4sp; both 2.8v6, Each has about 120K miles on them.

I've replaced the clutch master and slave many times over the past 30 years of ownership. I remember in the early days the clutch would engage around the middle to upper releaser of the pedal. Now both engage in the upper inch or two of the releasing the pedal.

The 5sp appears fine and i have no problem shifting and accelerating.

On the 4SP i find that after driving for about 30 min, The clutch engages in like the last inch or less of letting out the pedal. it appears as if the vehicle does not have as much power as it did when it was cold and i'm wondering if the clutch disc's are actually slipping.
I've been able to slowly engage the clutch in 3rd gear from a stand still and slowly accelerate without stalling. I don't smell anything burning smell or anything out of the ordinary.
You can see the Slave pushing the piston to disengage a inch or two, same as on the 5sp.
I tried adding multiple washer even making a custom (short Rod) and that works great for another 30 min or so, then were back to square one.
If i remove the slave, the leaver moves another inch or so to engage the clutch, thats were i got the idea to shorten or shaft or use washers to move it farther away.
I've tried the Bleeding procedure where you pull the rod back into the slave and open and close the bleeder valve. This also works for about 30min or so before it starts acting up again.

I bought the slaves from Rock Auto and i think the 4sp uses the LUK brand while the 5sp uses the Centric one. (different design)

I would like to find a way to permanently fix this; even if i have to replace all parts again.

Anyone have ideas on what you think is causing this?

Many Thanks.
Patrick JUL 07, 11:07 AM
The clutch hydraulics are used to disengage/engage the clutch. The clutch hydraulics have nothing to with the clutch slipping when engaged.... unless you've totally buggered up the system by changing the length of the slave push rod to the point where the clutch can't now fully engage properly.

The single seal slaves are useless. They let air in.

[This message has been edited by Patrick (edited 07-07-2024).]

RustyTech JUL 07, 05:15 PM
Ya i know that, i'm trying to figure out why the point of engagement changes with usage and requires another bleeding to get back to (what i call) normal. Everything is good for about 30 minutes of driving before it appears to slip. I got a steep hill that 3rd gear handles without a problem, no chatter when accelerating in 4th gear either.

I've heard a bit about glazing and im wondering if this is happening after 30 min of use?

I don't think its the clutch itself and i wonder, although both clutch arms appear to be in resting in the exact same place, is the older design (4sp model) more prone to not fully engaging allowing partial slippage.

The fluid has been fully flushed and is clear with minimal residue and no leaks under the dash or in back.
cartercarbaficionado JUL 07, 06:10 PM

quote
Originally posted by RustyTech:

Ya i know that, i'm trying to figure out why the point of engagement changes with usage and requires another bleeding to get back to (what i call) normal. Everything is good for about 30 minutes of driving before it appears to slip. I got a steep hill that 3rd gear handles without a problem, no chatter when accelerating in 4th gear either.

I've heard a bit about glazing and im wondering if this is happening after 30 min of use?

I don't think its the clutch itself and i wonder, although both clutch arms appear to be in resting in the exact same place, is the older design (4sp model) more prone to not fully engaging allowing partial slippage.

The fluid has been fully flushed and is clear with minimal residue and no leaks under the dash or in back.


the 4 speed is less prone to slipping and if you think it's glazing then you need a new clutch as it's refusing to grip properly (or your roads got oil on it) but it's sounding like your slave cylinder is also picking up air so it likely needs to be replaced again since the new and reman stuff is garbage these days. I've heard that Rodney's one fixes alot of issues but I've been getting away with rebuilding my oem stuff since the aftermarket garbage on both my fieros has broken before the oem stuff did
Patrick JUL 07, 08:38 PM
IMO, you've got two separate issues occurring with your 4-spd Fiero.

1) Your single-seal slave is sucking in air.

2) Your clutch disk is toast.

A possible third issue is screwing around with the length of the slave push rod. All you'll accomplish by attempting that is making a bad situation worse.

[This message has been edited by Patrick (edited 07-07-2024).]

jelly2m8 JUL 09, 12:06 AM
To add to what Patrick said, you have multiple separate problems by the sound of it.

If you want to see if your clutch is slipping, get it to a medium speed in 4th gear like 60-70 kph and then STAND on the gas pedal, you will know then if the clutch is slipping or not.

The difference in clutch pedal height from 30 years ago till now could be bent clutch pedals.
longjonsilver JUL 09, 07:31 AM
Every stick Fiero needs Rodneys double seal slave piston and an adjustable clutch rod for the master, also available from Rodney. As mentioned, some people have had a bent clutch pedal. Clutch pedal shud sit about 1" higher than the brake pedal.

------------------
Astronomy says we will find a coded signal from outer space. Then we'll KNOW that life exists there, for coded signals aren't by chance.

Biology says there are coded genetic signals in every cell, but we KNOW that no intelligence created life.

I'm the original owner of a white ' 84 2M4 purchased Dec 10, 1983 from Pontiac. Always garaged, no rust, 3800SC, 4-wheel drifts are fun!

longjonsilver JUL 09, 08:05 AM
Then again, is your clutch line rusty? Fiero Store sells stainless replacements. i fixed a friends clutch and the problem was that the line was rusty under a bracket holding the line in place beneath the drivers door. Salt and dirt had gotten caught by the bracket and rusted a pinhole allowing air to enter. The clue was a tiny spot of oil on the driveway. We patched the line, bled the system and voila! no more problems.

------------------
Astronomy says we will find a coded signal from outer space. Then we'll KNOW that life exists there, for coded signals aren't by chance.

Biology says there are coded genetic signals in every cell, but we KNOW that no intelligence created life.

I'm the original owner of a white ' 84 2M4 purchased Dec 10, 1983 from Pontiac. Always garaged, no rust, 3800SC, 4-wheel drifts are fun!

RustyTech JUL 15, 09:45 AM
Thanks everyone so much for you feedback. It's giving me a few ideas to look out for and some ideas to test.

I've order a new Slave from Dickman; actually he said it was the last 4sp slave he had, no more all gone.
I should get it in just under 2 weeks as im shipping state side, then to canada.

I'm going to take some measurements and photos before i make the swap out, along with the end result. I'm hoping this is what happening as it sounds like the more its used, the worse it gets.

Thanks again,

Will post more soon.

Rusty
Patrick JUL 15, 07:50 PM

quote
Originally posted by RustyTech:

I've order a new Slave from Dickman; actually he said it was the last 4sp slave he had, no more all gone.

I'm going to take some measurements and photos before i make the swap out, along with the end result. I'm hoping this is what happening as it sounds like the more its used, the worse it gets.



This is an excellent choice for a replacement clutch slave. Don't mess around with the length of the push rod.

Keep in mind though... a new slave cylinder will do nothing to correct a slipping clutch.

[This message has been edited by Patrick (edited 07-15-2024).]