Clutch Master Cylinder Q's

[tomtom72]

Hi guys....I know, another clutch master cylinder Question. :rolleyes:

I need to know if there is any way to tell the difference between the M/C that came in my 90Z from the "new" one the dealer put in last yr. Would the OE/BG cylinder have a Date Code?? Is there a physical difference? The one that was in my car before I went to the dealer had a zip tie holding the reservoir to the metal body thru an "eye" on the reservoir. Any clues would be great!

Reason I'm asking: Last yr the M/C leaked into the foot well & dealer said M/C leaks, need to r&r it. I asked for the line + slave to be done at same time. They said you don't need those parts. I said okay just do the M/C and I bought a new slave + line from P&G and did them myself. Now a yr later I have same symptoms, T/O noise when I step on clutch...intermittant but still not good to ignore. I look up the "how to" section at the NetRegistry and notice a M/C r&r write up w/pictures...the replacement M/C pictured doesn't have the zip tie But it is a Wagner. My "new" M/C from the dealer has the zip tie...should I be thinking I got "hosed"???

I'm ordering a new M/C from P&G Chevy today....if the dealer stuck it to me I'd like to know for sure if I can tell the difference between the two "new" parts. Thanks!

:???:
Tom

[Tom]

I posted this reply in another thread about the hydraulic clutch system.

I have seen the clutch master and slave cylinders have bad bores when they come out of the box. You should disassemble any new master or slave cylinder and inspect the bore. The bad bores will have one or more depressions in the surface where there are no hone marks. The bore should have a uniform surface finish from end to end. The cylinders with this bore problem will last for several thousand miles before the seals wear enough to start leaking.

The cylinders are very easy to disassemble, pull the rubber dust boot back, remove the retaining ring and you can then remove the piston assembly. Reassembly is just the reverse.

[tomtom72]

Thanks Tom, I made a note of your findings from the other post & put it in my Helms manual! I was posting this because I was trying to pin down how to tell an original from a GM replacement part. Hopefully I'll know by the end of this week when my new stuff arrives.

If the bores have indents in them then the part is no good, right? Ya gotta chuck it & start again? The rebuild kit doesn't account for re-honning & using larger diameter seals??

Thanks for sharing the knowledge!:thumbsup:

Tom

[Tom]

The defective new cylinders I have seen would not be helped by honing. You would have to take out so much material you would need an oversize piston and seal and you would end up with thin cylinder walls. Just return the cylinder to where you bought it and get anouther if the bore is bad. I usually take them apart and inspect the bore while I am still in the parking lot of the place I bought them. They are easy enough to take apart you could do it at the counter.

Honing with the typical wheel cylinder style hone removes very little material and does not take out enough material to require oversize pistons and seals. If you did take out enough material to require an oversize seal you also need an oversize piston or the seal will not last very long since there will be excess clearance between the piston and bore. Here is a link with pictures showing what happens to seals with excess piston to bore clearance. http://www.parker.com/o-ring/Literature/10-5700.pdf Paragraph 10.1.1.2 shows extrusion and nibbling of o-rings but the same thing happens to lip seals. This is part of the Parker O-Ring handbook and you can find a lot of other seal information in other sections of the handbook.

I still have the leaking original I removed from my 90. I will dig it out and take a look to see if there is a way to ID the original. At one time the C4 Corvette clutch system hydraulic cylinders were made by Lucas Girling but I don't know for sure if they were still making them in 90.

[tomtom72]

Tom,
Thank you for your help and the links! Truly it is the people that I've "met" while owning my ZR-1 that make this a very enjoyable experience! The car isn't so bad either!

I will practice on my old stuff when the new stuff arrives. I may be blaming the dealer for something that is not of their doing as I have learned from you. If they did take a short cut that is related over at the NetRegistry site about just bleeding & refilling the fluid and then charge me for a new M/C + labor I will seek redress from them...if I can prove it. I'll not waste too much time on this as spring is coming & I need to fix my clutch system so I can enjoy the car. The heck with anything else!:mrgreen:

Thank you again for your help!
Tom

[Tom]

I took my original leaking clutch master cylinder apart to see if it could be saved with a rebuild kit before I ordered the new one. The bore in my original was bad and had a large depression which wore out the seal in one spot at around 8,000 miles. I would take apart the one you remove from the car and see if it can be saved with a rebuild kit. It might be something simple like an improperly molded seal or a seal that was somehow damaged when it was assembled. The seal lip could have been caught and cut upon assembly or there could have been a burr that was not properly removed which damaged the seal.

I dug out my original and the only identification I could find was on the pushrod dust boot where it said Girling and had a part number and on the reservoir which had a part number. I didn't find anything that looked like a date code. The reservoir was held on by a zip tie. I bought the replacement at a Chevy dealer and the box was marked with the GM logo and part number 10147953. I haven't had a chance to look at the replacement cylinder in the car yet but when I do I will let you know if it matched the original.

[John Boothby]

I just had my m/c and slave replaced by the dealer. The original (the one that came out of the car) had a black body with zip tie. The new one is cast and bare (not painted). The reservoir does not have the zip tie, but looks more secure. I can not see any markings at all.

Just how prevalent is the bore honing problem? I hope I got a good one!

[tomtom72]

Hi John & Tom,

Thank you Tom for all your effort!

John, I don't remember for sure if the one in my car had a black painted body or not. I know the one in there now is bare metal, I think... but has a black zip tie holding the reservior to the metal cylinder bore. Come to think on it I do tend remember my OEM one as black & not bare metal. Maybe I'm faulting the dealer wrongly. I will go look at the one in my car again. Makes me think I gotta pay more attention to what's there before I go replacing things!
If the dealer did right by me then I must have got either a bad M/C or slave...no matter I ordered a new M/C & slave this week. This could be a major PIA if the jobber for GM is gonna mess up the bores like what Tom described!:mad:

I will for sure take my old stuff apart and then the new stuff to see what's up! Maybe I'll try aftermarket if the new stuff doesn't check out. This could get expensive & tend to s#*k big time! I hope you got good ones!

Tom

[Tom]

It is probably only a very small fraction of the cylinders that have a problem, but I have seen enought bad parts and it is so easy to disassemble and inspect the cylinders that I would reccomend it before going to all of the trouble of installing the new parts and bleeding the system.

I also bench bleed the master cylinder before putting it in and when I replaced my master cylinder I did not have to do any additional bleeding at the slave cylinder. Just hooked up the new cylinder, moved the clutch pedal up and down a little bit to get the seal to go back and forth past the port to the reservoir, and the system was ready to go.

Changing the master cylinder is a pain since you spend time get the ECM out of the way, time to remove the lower trim panel and then contort yourself under the dash to get the pushrod retaining clip off and back on. Also you can't really see the one retaining screw for the trim panel at the top back edge that faces the driver's door.

[Tom]

I checked on the replacement I put in my 90. I got it at a Chevy dealer and it is the identical black painted steel cylinder with the zip tie holding the reservoir on.

[tomtom72]

Tom,

Thank you very much for all your help and info and the time you took to share it with me!:thumbsup:

My tracking # says I should have my new stuff this afternoon and then I can get to get'in something done. Now that I know what I should be looking for this should be a straight foward deal. I know the M/C the dealer put in has the zip tie on it I just don't remember if the metal is bare or painted. I should take back what I thought about getting hosed by them!:o I wonder if they will give me credit if the parts are in fact bad? I got the slave from the same dealer too, at their parts counter.

Thank you again!

:cheers:
Tom

[tomtom72]

Just an update. The stuff you buy from GM looks exactly like the stuff that was in the car from BG, complete with Zip Tie! My apologies to the dealer for thinking the worst.

I took apart the M/C and slave that was in the car and found no damage. What I did find was a bunch of rubber particles in both bores. In the M/C some were stuck in the holes in the piston. That is my fault because the dealer said that the M/C was leaking and nothing else. I asked for the line and slave to be done at the same time but they said "why? They are okay". I should have been more insistant. I took the car home & ordered the line & slave and should have not used the car till I installed all the new parts...I didn't and I think the hose was flaking or shedding particles and that started my occasional loss of system pressure. It took awhile to show up but eventually it did.

I learned to listen to zfdoc from this. He says "treat the system as one part". I did but not in the spirit he meant...don't do as I did! Get all the parts first and do it yourself it isn't that difficult...it's a PIA due to cramped working space but you don't have to be a genius to change out the parts. Just take your time and remove all the stuff you see that is in the way up by the M/C, it will make your task easier by a bunch! Yes the rocker + gill panel + battery and do the airbag sensor while you're there! then the line clamp on the fire wall. Then the slave, if you have a 13mm swivel socket & a line wrench you're set...the exhaust can stay put. It helps to bleed the slave and M/C before you puy them in. All the stuff comes with caps so use them to your advantage and you can even fill the line. I put the line in first, used the caps to hold fluid in it while I connected the slave to it and then refilled the line using a squirt oil can, then put the M/C in and connected the line after the M/C bolts were in abit, then do the clip was at the pedel, then tighten the M/C bolts. There shouldn't be too much air trapped so you can pump the pedel to get the rest of the air.

:cheers:
Tom

[tomtom72]

I finally got around to examining the slave that I removed from the car and I found something interesting...I can't get the piston out? I've applied a fair amount of force to it using expanding snap ring pliers in the depression for the actuating rod. I don't think where the piston is getting stuck has anything to do with the working range of motion of the slave though. It gets stuck way past the point at which the snap ring would limit it's travel but I can't get it out of the bore!

I would have thought that the piston would come out easier than this!:icon_scra
I didn't have any trouble taking the original slave apart so I don't get what I'm doing wrong with the replacement slave I bought after the dealer did the M/C. This is strange.