Easier ways to replace Master Cylinder?
Thread Starter
Pro
Joined: Jun 2001
Posts: 509
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From: Edmonds WA
Easier ways to replace Master Cylinder?
I noticed the brake fluid was low on my 87 and that the master cylinder is leaking at the back and all over the booster. Looking at archived posts, it seems replacing the master cylinder is straight-forward except for the PITA it is to swap the reservoir/cup.
Can I get a replacement master cylinder that already has a cup installed to avoid that hassle? Do I need a vice to hold the master cylinder while pressing the cup in? Some people mentioned a c-clamp or the like to get the cup to seat. Is a tool the best way to go? Or, do you just have to lube it up well and press with a lot of force by hand?
Thanks for the help... I'm looking to avoid the exasperation others have mentioned :-)
Can I get a replacement master cylinder that already has a cup installed to avoid that hassle? Do I need a vice to hold the master cylinder while pressing the cup in? Some people mentioned a c-clamp or the like to get the cup to seat. Is a tool the best way to go? Or, do you just have to lube it up well and press with a lot of force by hand?
Thanks for the help... I'm looking to avoid the exasperation others have mentioned :-)
Last edited by K87ZZ4; Apr 22, 2009 at 11:43 AM.
Safety Car
Joined: Feb 2000
Posts: 3,771
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From: MANDEVILLE, LA La
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Getting the old cups out is easy you just pull, rock and twist a little...putting them in the new unit...not as easy. It is best to use a shop press to get the cups in the new unit. Press work can range from $5 - $25 if you don't have one in your garage.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
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From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
cups
The reman units come with new rubber bushings to screw the fluid cups into.
BUT:
manipulating the cups into the rubber bushings can lead to you cracking or breaking the cups.
If you use a hair dryer, or heat gun, and soften the bushings with heat, the cups go in easier, and plus, the heat transfers to the cups, and makes them a tad bit more pliable.
Don't over heat the parts, if heated too much, the cups can melt, and the bushings can distort and leak.
BUT:
manipulating the cups into the rubber bushings can lead to you cracking or breaking the cups.
If you use a hair dryer, or heat gun, and soften the bushings with heat, the cups go in easier, and plus, the heat transfers to the cups, and makes them a tad bit more pliable.
Don't over heat the parts, if heated too much, the cups can melt, and the bushings can distort and leak.
Pro
Joined: Feb 2009
Posts: 589
Likes: 1
From: PA
If he has a vice that might work. I never had to mess with mine on my 85. If I did, I think I'd put some oil on the rubbers and cups and press them in the vise squarley and evenly. I think that would work too.
They do look like buggers to me, like others have said here. Now I know they are, hahahaha. But where's there's a will there's a way.
They do look like buggers to me, like others have said here. Now I know they are, hahahaha. But where's there's a will there's a way.
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Thread Starter
Pro
Joined: Jun 2001
Posts: 509
Likes: 5
From: Edmonds WA
I moved not too long ago and my vise isn't even mounted on a bench. Thanks for the tip on using heat--I may try the hair dryer approach.
I have a reman unit on hand, but discovered it's half the best price of a new one. So, I'm thinking I'll take a shot at swapping the reservoir/cup. If I just can't get it, I can always get a new master cylinder instead... or maybe try the local machine shop.
Thanks... and any other tips are most welcome!
Thread Starter
Pro
Joined: Jun 2001
Posts: 509
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From: Edmonds WA
Update
On my 87, I have a single reservoir with a connector to the front port. I could not get either cup to fit over the rubber seal, with the seal on the master cylinder (as it was in the box). So, I took the seal off the front port and put it in the connector/cover first, then the front connector/cover went on fairly easily... I was surprised.
I tried that with the big cup on the rear port, but couldn't get the seal to seat right. Finally, I tried a socket (3/4 I think) with an extension to put just a little bit of pressure on the seal from the top and it went on. This seemed like a backward approach based on what others have said, but it seemed to work well. Of course, I'll keep an eye on it should it start leaking or anything. Just thought I'd put that out there in case it helps anyone else.
I also found it *really* easy to misthread the plastic pieces that screw into the master cylinder (the electrical connector especially)... I had to clean up the threads quite a bit and be extra careful to get it started just right (which is tough with a spring putting pressure on it at the same time).
I tried that with the big cup on the rear port, but couldn't get the seal to seat right. Finally, I tried a socket (3/4 I think) with an extension to put just a little bit of pressure on the seal from the top and it went on. This seemed like a backward approach based on what others have said, but it seemed to work well. Of course, I'll keep an eye on it should it start leaking or anything. Just thought I'd put that out there in case it helps anyone else.
I also found it *really* easy to misthread the plastic pieces that screw into the master cylinder (the electrical connector especially)... I had to clean up the threads quite a bit and be extra careful to get it started just right (which is tough with a spring putting pressure on it at the same time).
Racer
Joined: Oct 2006
Posts: 457
Likes: 0
From: Cincinnati Ohio
Me too..Why mess with putting those dingy yellowish looking cups back on when you can get nice new clean ones that are already installed?? I think mine was about $140 shipped.. Last year...
Burning Brakes
Joined: May 2006
Posts: 857
Likes: 1
From: Morrisonville Illinios
On our 87' I went and bought 2 new cups (from GM) for an 88' so I would have different resoviors to fill. On the original one it had a small crack in it that was on the back side and I wondered why It would loose fluid after a while. It was not that hard to put bouth of them on just used the deep well socket trick and then wiggled and jiggled. No problem's now.
wro87
wro87
Thread Starter
Pro
Joined: Jun 2001
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From: Edmonds WA
Racer
Joined: Oct 2006
Posts: 457
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From: Cincinnati Ohio
Well, for me, there were two reasons: 1. I got laid off recently and so I'm trying avoid spending any extra bucks I don't really have to. 2. I already had the remanufactured unit in my hand and could get started. If I had the bucks, I would have ordered a new unit with cups ready to go
Last edited by Blak Z06; Apr 27, 2009 at 04:33 PM.
Thread Starter
Pro
Joined: Jun 2001
Posts: 509
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From: Edmonds WA
Brake Bleeding Order - Early C4
BTW, while searching early on for lessons learned in replacing the master cylinder, I remember some mention of the proper bleed order for a system with ABS. Today, I couldn't find that post, so I looked it up in my FSM.
In section 5, under "Manual Bleeding", it says the bleed order/sequnce should be: right front, right rear, left rear and left front. Basically, start at the RF and move clockwise around the car.
Thought I'd post that in case it comes in handy for anyone with an early C4. I did see a post that mentioned a different bleed order, but that was for a 94--and may have been the traditional "start farthest from the master cylinder" approach, anyway. I remember reading that the reason for the different-than-traditional order has to do with ABS module.
In section 5, under "Manual Bleeding", it says the bleed order/sequnce should be: right front, right rear, left rear and left front. Basically, start at the RF and move clockwise around the car.
Thought I'd post that in case it comes in handy for anyone with an early C4. I did see a post that mentioned a different bleed order, but that was for a 94--and may have been the traditional "start farthest from the master cylinder" approach, anyway. I remember reading that the reason for the different-than-traditional order has to do with ABS module.
Thread Starter
Pro
Joined: Jun 2001
Posts: 509
Likes: 5
From: Edmonds WA
If I already had a good part without the cups.. I'd be doing it the same way you are.. Actually, when I bought mine i thought they all came with new cups. By the way I think I still have my old one, so if you did damage the cup while trying to press it in, let me know I'll give it to you...Sorry to hear about the lay-off
As far as I know, it's sealing properly now. I noticed that the 'lip' on the front port was less pronounced than on the rear port. I suspect that's why the front cup went on so much easier than the rear--don't know why the lip would be any different on one than the other
Oh, and one other thing... when it was all finished and I was ready for a test drive, I released the parking brake, but the red brake light in the dash didn't go out as I backed out of the garage--uh oh!
But, as soon as I put in Drive to pull back in the garage, the light went out--whew!
