Clutch Problem

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Dec 21, 2015 | 06:59 PM

mapache

Thread Starter

5th Wheeling

Joined: Jul 2012

Posts: 31

Likes: 1

From: Virginia

Clutch Problem

My son brought his '89 f-150 (4.9L, Mazda 5-speed) home last weekend with a little clutch problem. Just a little hard to get into gear, but still driveable. So we started out to bleed the slave cylinder. Master Cylinder is full, opened bleeder screw, no fluid flow, as indicated in the Haynes manual. So we Googled and found a thread that said to bleed it like you bleed brakes (open, pedal down, close, pedal up...). So we tried that. Got a small amount of fluid, I'd say less than 1/4 cup, , then nothing. On the first 'pedal down' the pedal stayed on the floor. MC still full. Realized the diaphragm was still in the MC, took that out, MC was dry. Put fluid in, opened slave cyl bleeder, still no fluid flow. Pumped pedal, still nothing.
Replaced slave cylinder. No change.
Looked under dash, push rod appears to be working, at least from what I can see.

Anyone got ideas?

Dec 21, 2015 | 08:09 PM

ArdWrknTrk

pedant

Joined: Jan 2008

Posts: 23,576

Likes: 40

From: EXTREME southwest CT

If I had to guess when the MC ran dry the O-ring on the piston was rubbed raw and is no longer sealing.

Do check for firewall flex by observing the master while someone in the cab depresses the pedal to the floor..

Dec 21, 2015 | 08:19 PM

mapache

Thread Starter

5th Wheeling

Joined: Jul 2012

Posts: 31

Likes: 1

From: Virginia

Would that o-ring trouble cause the fluid to stay in the MC and not drain down to the slave?
This is not the first time I've read about looking for firewall flex. What am I looking for and what would it mean?
Thanks

Dec 21, 2015 | 08:21 PM

bashby

Post Fiend

Joined: Nov 2005

Posts: 7,437

Likes: 4

From: Charles Town, W bygod Va

They can be a pita to bleed. Try pumping the pedal 3-4 times, hold it down, then crack the bleeder. Repeat untiil you get a pedal.

Dec 21, 2015 | 08:27 PM

ArdWrknTrk

pedant

Joined: Jan 2008

Posts: 23,576

Likes: 40

From: EXTREME southwest CT

Quote:

Originally Posted by mapache

It wouldn't pump if the piston didn't seal.
If you had said there was fluid I wouldn't suggest it.

Just look to see how much the MC tips up as someone steps on the pedal.
If the firewall is coming apart you need to install one of two different reinforcement plates.

Dec 21, 2015 | 08:32 PM

ArdWrknTrk

pedant

Joined: Jan 2008

Posts: 23,576

Likes: 40

From: EXTREME southwest CT

Yeah, pain to bleed.
I usually just put a hose on my bleed nipple and let gravity do its work.
(Advantage of having a metal slave cylinder)

If I can get the clutch to work at all I will drive it.
It will work itself out from driving around.

Jan 8, 2016 | 07:07 PM

mapache

Thread Starter

5th Wheeling

Joined: Jul 2012

Posts: 31

Likes: 1

From: Virginia

Thanks to all for the replies. Firewall did not appear to flex. We bled it both with gravity and with the brakes-style bleeding. No pedal. So we replaced the MC and the hydraulic line. After bleeding, there was enough pedal to drive it some. After working with it a couple times and driving it a little, had good, solid clutch. So he went home. After a few days, he called me to say that it was feeling soft again. When he gets back to town, I'll get him to try @Bashby's suggestion.

@ArdWrknTrk, when you do the gravity bleed, do you get a good flow? When we've done that, it's been just a real thin stream, not much at all, just enough to keep a stream together and not be a drip.