clutch slave hose wont fit. help - Alfa Romeo Bulletin Board & Forums

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post #1 of 16 (permalink) Old 03-19-2017, 11:11 AM Thread Starter
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clutch slave hose wont fit. help

I helped a friend replace his clutch slave which was leaking. we changed the hose at the same time.
However, at the clutch slave end, the new hose is about 5 mm too long... meaning the flare end will seat inside the clutch slave before the nut even approaches the body of the clutch cylinder.

I ended up putting some washers in ( like 5) but am not happy with it because I am not 100% sure the flare is 100% seated

Would I be better to seat the flare ends, then use an M12x1.0 nut on the male portion of the hose as a "lock" nut and lock it to the cylinder?

He bought the tube from someone in UK but the old hose clearly has a shorter fitting then the replacement.

Michael
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post #2 of 16 (permalink) Old 03-19-2017, 12:18 PM
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I would think you would want the flared end to seat before the "nut" bottoms against the slave. The hex head is just there for tightening purpose. If it strikes before the flare seats you may end up with a leak. Newer hose fittings may be different in order to use the hose on other applications. Assuming you have not reversed ends, however I believe the threads are different to avoid this happening.
Cheers, Jon
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post #3 of 16 (permalink) Old 03-19-2017, 01:20 PM
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Quote:
Originally Posted by not2old4toys View Post
I would think you would want the flared end to seat before the "nut" bottoms against the slave.
Agree. In other words, you probably have the correct hose, and it should be installed without any washers at the slave cylinder. The tip of the metal fitting on the hose seals inside the cylinder.

It would be helpful to know where you got that slave cylinder hose. If it is from an Alfa specialty supplier, such as Centerline, you can be confident it is the correct part. If it is from a general parts supplier, such as Rock Auto, then anything is possible.

Jay Mackro
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Last edited by Alfajay; 03-19-2017 at 01:58 PM.
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post #4 of 16 (permalink) Old 03-19-2017, 04:47 PM Thread Starter
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alfajay and jon
thanks for responses. he bought the slave from centerline, but for whatever reason bought the hose form UK at classicalfa i think. the only difference from the original part is about 5 mm extra length on the slave side.
If i seat the flare, but dont lock it with the "nut", isn't there a chance it would loosen?

Thats what I was thinking of putting a m12x1.0 nut as a lock nut to ensure it doesn't loosen,
michael

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post #5 of 16 (permalink) Old 03-19-2017, 05:01 PM
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Quote:
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alfajay and jon
thanks for responses. he bought the slave from centerline, but for whatever reason bought the hose form UK at classicalfa i think. the only difference from the original part is about 5 mm extra length on the slave side.
If i seat the flare, but dont lock it with the "nut", isn't there a chance it would loosen?

Thats what I was thinking of putting a m12x1.0 nut as a lock nut to ensure it doesn't loosen,
michael
Once both threaded ends are secured there is no way for it to loosen.
Jon

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post #6 of 16 (permalink) Old 03-20-2017, 05:44 AM Thread Starter
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jon
if the part going into the slave has exposed thread ( because the male portion is too long), and the hex nut isn't flush with slave, couldnt vibration etc cause it to loosen?.
its not like the other end secured by a clip, so this end could theoretically rotate and "Unscrew"

Michael
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post #7 of 16 (permalink) Old 03-20-2017, 07:14 AM
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Michael:

You're over-thinking this. Couldn't vibration etc cause the cylinder head nuts to loosen? The lug nuts that hold on your wheels could theoretically rotate and "Unscrew". But fortunately those things don't happen. And your friend's clutch slave hose won't come loose either.

Just tighten the hose fitting "enough" and it will be fine.

Jay Mackro
San Juan Capistrano, CA

'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L
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post #8 of 16 (permalink) Old 03-20-2017, 07:20 AM Thread Starter
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ok got it! will do.
LOL- as a cardiologist I probably do overthink things but usually to my patient's advantage

Michael
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post #9 of 16 (permalink) Old 03-20-2017, 07:29 AM
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Think of it this way:: when you removed the hose, you first had to loosen the union at the hard line from the clutch reservoir. If you had tried to loosen at the slave cylinder first you would have met resistance from the hose trying to coil up. There is no extreme pressure in the line that is going cause it to loosen. It will hold!!
Jon
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post #10 of 16 (permalink) Old 03-20-2017, 08:21 AM Thread Starter
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AHH, so the coil resistance of the hose is keeping it seated. got it. it makes sense but i guess mechanically it feels better ( to me) to have metal on metal tightened up at the hex portion.
i think i will remove the washers so that I am 100% sure the flare ends of hose and slave are snug
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post #11 of 16 (permalink) Old 03-20-2017, 09:16 AM
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Not necessarily, it prevents it from loosening.
Jon
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post #12 of 16 (permalink) Old 03-20-2017, 10:53 AM Thread Starter
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jon thats what I thought- just basic good mechanics practice- but jay disagreed.
the fact is the new premade hose has a fitting too long for the new slave. I till like my idea of a thin nut, m12x1.0, that cinches down on the slave, like a lock nut, but applied only after the hose flare is well seated on the slave flare inside the slave body. then it doesnt matter if some thread and the fixed hex of the thread is protruding.

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post #13 of 16 (permalink) Old 03-20-2017, 11:06 AM
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Quote:
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jon thats what I thought- just basic good mechanics practice- but jay disagreed.
I've lost track of what I disagreed with.

Jon is correct that the flex hose is secured to the chassis at the end where it connects to the rigid line from the clutch master cylinder. Since the flex hose resists twisting axially (or "coiling" as Jon puts it), can't rotate much at the slave cylinder end. However, its modulus of elasticity for axial twisting isn't infinite, so if you really want to worry about something, while the hose certainly can't turn enough to completely back out, it could back off a few degrees and cause a leak. But the point is, this just doesn't happen.

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I till like my idea of a thin nut, m12x1.0, that cinches down on the slave, like a lock nut
Well, I don't like that idea (and for what it's worth, I'm a mechanical engineer). As you tighten that lock nut on the threads, you're pulling the fitting outward. Admittedly there is only a minuscule amount of axial play in the threads, but your lock nut still decreases the sealing force between the hose end and the slave cylinder.

While some fittings are designed to use a soft, copper washer between the hose and cylinder, the Alfa clutch slave just wasn't designed that way. The surface of the slave cylinder where the hose enters isn't polished to allow a washer to create a tight seal. And using a stack of washers to create a seal is a definite no-no - lots of surfaces for a potential leak.

Jay Mackro
San Juan Capistrano, CA

'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L

Last edited by Alfajay; 03-20-2017 at 11:20 AM.
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post #14 of 16 (permalink) Old 03-20-2017, 11:16 AM Thread Starter
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ok i also was slightly concerned about the nut and the outward pressure, but u correct the axial play should be minimal especially since there are many 360 degree rotations of thread... so just tighten it and no washers, and it shouldn't come undone.... why dont they just make the correct size fitting? LOL. thanks for everyones help. michael

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post #15 of 16 (permalink) Old 03-20-2017, 11:24 AM
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Quote:
Originally Posted by mibi View Post
why dont they just make the correct size fitting?
It IS the correct size. It just has a few extra threads so it can be used for a variety of applications - the manufacturer would need to charge $100/hose if this part could only fit 40 year old Alfa Romeos.

Jay Mackro
San Juan Capistrano, CA

'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L
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