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clutch master cylinder question

xplorernewb

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May 6, 2014
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City, State
washington state
Year, Model & Trim Level
91 ford explorer sport
so yesterday i installed a new master cylinder. after installing i bled the master cylinder with the plunger beneath the clutch pedal. i used the mityvac tool to bleed the line and it was a piece of crap and fell apart on me the first time i used it so i gave up and had it towed to the mechanic.

i brought it in with the clutch making a creaking sound and it also grinds when the clutch is released/pumped while shifting(which is the reason why i replaced it).

would air being trapped inside the master cylinder cause the throwout bearing to not seat properly or something, causing it to grind or make a screeching sound? the screeching sound happens when the car is off. clutch is less than 6 months old.. any ideas?
they say if this doesnt work than the throwout bearing is probably bad.. but wouldnt it squeak while releasing the pedal? cause it doesnt squeak...
 



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also i could not manage to turn the master cylinder in order to bleed it. which is another reason why i think theres just a bubble in the master cylinder. am i correct?
 






So your saying, you get the sound with the car off while depressing the clutch pedal?
 






so after further investigating, ive noticed a couple things. i noticed it will shift fine at 1/4 from the top, but as soon as i get close to the floor, thats when it starts making the grinding sound (with the car running). it will also make a clack sound when i release the clutch pedal (car running). so basically it will go from squeak (depressed) clack (clutch engaged). car running. but it will shift good, no grinding at all if i only use the top part of the clutch. it is also grinding. when the clutch is released and in neutral. still get a clacking sound in neutral. kinda sounds like something is broken inside. still think its the throw out bearing.?

the transmission is ready to be dropped, just need the jack now. any other ideas of what i could be expecting besides the throw out bearing?
 






Just look at the fingers on the pressure plate. Look for obvious issues there.
 






xplorernewb,

Sounds like you have a lot of stuff going on,
but with regards to your original repair;

When replacing the master cylinder, you need to bleed:

* the master cylinder

AND

* the slave cylinder.

Hope that helps :)

Also, don't know about the particulars of your '91 Explorer Sport,
BUT the "small detail" in the '98 Clutch Hydraulic System is the VERY TINY "O" Ring
between the Master Cylinder and the Fluid Line that is connected to the bottom of it.

By Design, when the Master Cylinder is disconnected from the Fluid Line,
the "O" Ring wants to fall straight down onto the ground (if you're lucky)

Available at Harbor Freight:
brake-bleeder-and-vacuum-pump-kit-harbor-freight.jpg
 






I bled both, used the bleeder tool as well. Brought it to a shop and the guy was familiar with these and went through the correct steps instead of following the manual. I asked to make sure and he said he was aware of that and did the job. No air in the lines. Pedal is great, shifts great right at the top of the pedal. Just grinding when applied at full pressure on the pedal to the floor. I noticed the squeek got louder after i removed th starter so th noise is definitely coming from inside. Having difficulties getting that damn y pipe off. Probably going to cut it off
 






So just for ***** and giggles i had someone pump the clutch slowly to avoid the squeak and it was fine but when they did it fast the slave cylinder would jump quite a bit at the hose connector but would stop moving as soon as i grabbed it but still squeaked. I don't know if it moving like that is normal but i don't recall it moving that easily after it was installed
 






xplorernewb,

You said you replaced the master cylinder - OK, we got that.

So, at the same time, did you also replace the slave cylinder?

If not - just for giggles, how many miles are on that old slave cylinder?

Both of them get the same amount of wear, and if anything, the slave also is exposed to more heat, since it's within the bell housing.

Here's where I am going with this; if you put a new master cylinder over an old slave cylinder, what it sounds like happening is that when you partially depress the master cylinder via the clutch pedal, the slave cylinder is holding the "partial" pressure & fluid volume put out by the new master cylinder.

BUT, when you fully depress the master cylinder via the clutch pedal, what is happening is that the slave cylinder cannot hold the full pressure and full fluid volume of the new master cylinder.

Without being there, all this is purely speculation.

BUT, I'm basing this on a long time ago, on my Ex, when I did the opposite of what you did.

At 100,000 miles, I replaced a clutch, flywheel, and slave cylinder.

I DIDN'T replace the master cylinder.

The result was the old master cylinder didn't have enough power to allow the slave cylinder to fully release the clutch, and made for some bad shifts.

I hope this helps -

PS: I re-read your original post.

You say the clutch is less than 6 months old.

Is the Throwout Bearing less than 6 months old as well or?
 






Yes the slave and bearing was replaced, flywheel was not. If the pilot bearing was included in the clutch kit i got then it was replaced too. Don't remember. Should have 5-7k on the clutch itself and it was doing this before i replaced the master since it wasn't replaced when the clutch disc and plate was. From the sound of it it seems like its coming from the engine side of the bellhousing. I read on a couple forums that had a few issues like this and it was fixed by replacing the pilot bearing. Similar ones were solved by replacing the flywheel but that one member wasn't able to shift (it was cracked) and would stall. Wouldn't the throw out bearing affect it when the clutch is engaged (pedal released)?
 






And the pilot bearing is in operation when the clutch is disengaged (pedal pressed)?
 






Wouldn't the throw out bearing affect it when the clutch is engaged (pedal released)?

The throw out bearing is only used/comes into play when the clutch pedal is depressed/pushed towards the floor.

The following is NOT directed towards you, just said from an engineering standpoint. The fastest way to burn up throw out bearings is to sit at stoplights with your foot depressing the clutch.
 






well i finally got the transmission down. havent gotten back underneath to check anything out yet but i did look at the slave cylinder. the bearing seems to have a lot of side to side and in and out play. i can spin it also and feels like its scraping quite a bit and binding when the play comes into effect. (still on the transmission if that makes any difference). kinda feels like a bad wheel bearing. looks all scratched up on the surface and redish color. not sure if thats from the clutch or what. i have the next couple days off so i can finish this tomorrow morning and crawl back under the damn thing but could this be the problem?
 






by the way i never hold the clutch down. i try to use it as less as possible
 






At stop lights, my dad always held the clutch in. He did this for 119,000 miles before I took the vehicle. It now has 137,000 and I've pulled the engine for an overhaul and to replace the clutch. Everything is worn even, due to be changed though.
 






by the way i never hold the clutch down. i try to use it as less as possible

Good - your clutch should wear out before your throwout bearing (not vice-versa) :)
 






So how is the throw out bearing supposed to spin? Is there supposed to be any play? I read its supposed to spin like a skateboard wheel but it stops spinning before i even let go of the bearing and will bind if i try to spin it while partially engaged and i can feel a click and a small woosh sound if i do it right but its not leaking at all
 






well i just pulled the clutch off and the pilot bearing is shot. didnt damage the shaft though so thats good. anyway thanks
 






getting a new clutch assembly for free as soon as i bring in the bearing :) supposedly it had a lifetime warranty on it
 



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well i managed to get the bearing out of the flywheel but noticed something odd.. there was another bearing behind the one in the flywheel. like the shop just didnt remove it and shoved another one in there.
i had to take the flywheel off in order to get the other one out. glad i did though because i noticed a couple cracks. anyway time to put it back together
 






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