Last week driving my 86 2.8 5 speed, the clutch pedal went to the floor, and I was stuck in 2 cnd gear. Thankfully, made it home to the garage without incident. I assumed the line between the master and the slave had blown, and I was correct; a leak right where the line curves around the floor drivers side, about two feet from the master. I put in a line repair, and then tried to gravity bleed the clutch system. Nothing is getting through to the slave. So I undid the repair to check if it was blocked anywhere, and it is not. However with the master reservoir full, no fluid exits where the line is broken, even when I pump the pedal. The master cylinder is a new replacement less than 200 miles ago on the car. Everything looks normal, but the master is not doing what it is supposed to do. When I first cut the line, hydraulic fluid did come out of the line where it is severed. So????
No, the Clutch master cylinder should flow fluid freely. Did you flush the clutch line before the previous replacement? perhaps there's foreign mater that worked its way making a restriction.
You may have to pressurise the clutch master cylinder reservoir to get the fluid to move and correctly fill the slave cylinder. I do this with a homemade lid and a foot pump. Gentle pumps; not too much! I've never managed to bleed this system properly without having first chassed out all the air. Be carefull to refill the little reservoir often, if not you will just have to start again.
Regards, Rafe
------------------ "Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero https://youtu.be/hUzOAeyWLfM
[This message has been edited by Frenchrafe (edited 12-08-2023).]
I always start fresh by bleeding the master cylinder on the bench that removes air from the cylinder before it is installed in the vehicle.
This process can save time and effort compared to bleeding the master cylinder on the vehicle.
EDIT: IF you doubt the MC; bench bleeding will show you that it is working or not. Check out videos online that shows the steps if this is the first time......
------------------ Original Owner of a Silver '88 GT Under 'Production Refurbishment' @ 136k Miles
[This message has been edited by Vintage-Nut (edited 12-09-2023).]
Jelly where did you get the idea that bench bleeding the MC would damage it ? Not bench bleeding is more likely to damage the MC as you can get an air lock causing problems to bleed . sleek
There is all kinds of internet advice in general about bench bleeding the master, so I am going to assume I can try that step. The master has maybe 200 miles on it and worked perfectly before the line broke. I will check blockage in the line when I disconnect it from the master, but doubt that is my issue. Thanks for all the input!
Jelly where did you get the idea that bench bleeding the MC would damage it ? Not bench bleeding is more likely to damage the MC as you can get an air lock causing problems to bleed . sleek
From the GM Service manual, from 20 plus years on here seeing what works and what doesn't and 30 years experience sending happy customers out with a properly working Fiero Clutch system.
We are talking the Fiero Clutch master cylinder, not the Brake master cylinder
[This message has been edited by jelly2m8 (edited 12-09-2023).]
Jelly whether you like it or not bench bleeding will do no harm to a clutch master cylinder. Its just that you have to use your finger to act as a check valve to stop air from sucking back in while pumping the piston. It works very well and prevents that air from entering the line and slave. sleek
Jelly whether you like it or not bench bleeding will do no harm to a clutch master cylinder. Its just that you have to use your finger to act as a check valve to stop air from sucking back in while pumping the piston. It works very well and prevents that air from entering the line and slave. sleek
it don't matter if I like it or not, I don't give 2 fuks past what I know how it works and having satisfied customers and making a honest living.
Here are ways to purge air from hydraulic systems...
Fact My '88 GM Service manual has a clutch master cylinder bleeding procedure which is the two-person pedal method and DO NOT Warn about bench bleeding.
Like jelly2m8 said; I also use "that works and what doesn't and 30 40 years' experience" too......
In my world when a hydraulic system has been opened to air: Bench bleeding a MC is the fastest, easiest and visional way that the cylinder is flowing fluid, and all air has been removed before it is installed in the vehicle. Obviously, the line still must purge; I found vacuum is fastest, easiest and better than other methods which is my opinion.
Well, I pulled out the master, bench bled it, and blew through all the lines to confirm there was no obstruction. Reinstalled the master, topped up the reservoir, and depressed the pedal. Fluid disappeared from the reservoir. Lowered the rear of the car, and gravity bled the system, with help by sucking on a hose attached to the bleeder on the slave. Got a steady flow of fluid, initially with air bubbles, and eventually clear with no bubbles. I will do the final step of depressing the slave piston to bleed out any remaining air. I could get no flow through the master until I bench bled it, so with it working after I did that, I am a believer in bench bleeding. Thanks for all the comments; this forum is golden. Steve
Sorry guys, I was not aware of a double post, and really don’t understand how the second one got started. I am still working through this issue: master is working, pedal is moving fluid. I have no leakage in the line to the slave I can find. No air is coming out of the slave with the pedal depressed. Pushed the slave piston in to get the final air out. The pedal is high as it should be. But no movement of the slave piston when the pedal is depressed. .??? I have been on this for days now, and am stumped.
Sorry guys, I was not aware of a double post, and really don’t understand how the second one got started.
Steve, the funny thing is... this is the duplicated/second thread.
quote
Originally posted by stevep914:
The pedal is high as it should be. But no movement of the slave piston when the pedal is depressed. .???
What resistance are you feeling when you press the clutch pedal to the floor? If the slave isn't moving, the clutch pedal can't possibly feel the same as when the clutch was actually disengaging.
Patrick, I have decent pedal pressure. And the pedal is right up where it should be when not depressed. I spent several hours this morning, fiddling with this, and have found another small line leak right where the line goes up through the front trunk floor before screwing into the master. Although I was getting a clear line with no bubbles at the slave bleeder, the leak may have been just enough to not allow movement of the slave piston. I am HOPING that is my problem . So I will replace the whole line from the master down to about the middle of the car underneath, where the line appears healthy. I will update this when that is completed. There is no obvious problem with the Dickman slave so far.
And the pedal is right up where it should be when not depressed.
I forget whether we discussed this in your previous clutch threads... but do you still have the factory installed return spring on the clutch pedal in place? If you do, that might be the actual reason the clutch pedal is fully returning to its rest position. (Pontiac long ago recommended that the clutch pedal return spring be removed.)
Well guys, I admit I am stumped. I replaced the clutch line from the master to about halfway under the car. No leaks I can find. Bench bled master, gravity bled the whole system to the point of clear fluid no air bubbles. Clutch pedal sits up where it should. Depressed the slave rod and cleared the air out of the slave. Clutch pedal moves fluid through the system at the slave bleeder when I open it. But the slave pushrod does not move. It is a Dickman slave that worked perfectly until the clutch line blew. The overall principle is pretty simple. The fluid has to go somewhere. The master fluid reservoir goes down as the clutch pedal is depressed. Any words of wisdom? I have done this procedure before twice; when I replaced the slave, and more recently when I replaced the master. Got perfect results ultimately both times.
The master fluid reservoir goes down as the clutch pedal is depressed.
Does the fluid return to the previous level when the pedal is released, or does the level go down (and stay down) every time the pedal is depressed and released?
Ok, this morning, I depressed the clutch pedal slowly, with the slave bleeder closed, and got some air bubbles coming up through the master reservoir. Did this several times, and got a couple of bubbles each time. The fluid went down in the reservoir marginally, assuming the fluid took the place of the air. I now have partial slave piston movement. So I guess somehow there is still air in the system, even though none was coming out of the slave bleeder. Had to go to work, but will play with this again later today.
Clutch bleeding prodeedure You can do it your way, But this method always works for me. After checking to be sure there are no leaks in the Clutch Hydraulic system. Complete ALL of the following steps before test driving the car: 1) Install a helper in the drivers seat to push in and let out the clutch pedal on command. 2) Remove the cover from the Master Cylinder reservoir. 3) Top off fluid in the reservoir. 4) During the course of this procedure DO NOT allow the "helper" to "pump" the pedal. The "helper" is to depress and release the pedal on command only, DO NOT PUMP THE PEDAL. (See theory below) 5) You will be opening and closing the bleed screw on the slave cylinder as instructed below. CAUTION: During this procedure protect your eyes from squirting brake fluid. 6) (Helper) Press clutch pedal in fully and hold. 7) (You) Open the bleed screw to allow fluid to escape. 8) (You) Close bleed screw. 9) (Helper) Release pedal completely 10) (You) Top off fluid in reservoir. 11) Repeat steps #6 thru #10 no less than 5 times before going to #12 below. NO PUMPING! 12) You have now bled the Master Cylinder and the hydraulic line. YOU ARE NOT DONE YET!!!!! We must now bleed the Slave cylinder. (This is what the manual doesn’t tell you) 13) With no further action to be done with the clutch pedal, you can no remove the "helper" from the drivers seat and have him (her/it) help you do the following. 14) After topping off the Master Cylinder, completely remove the bleed screw from the slave cylinder. 15) Have the "helper" stand at the ready with the bleed screw and the appropriate wrench for installing the bleed screw. 16) PROTECT YOUR EYES! 17) With the bleed screw removed. With both hands grab the push rod coming out of the slave cylinder and push it into the slave cylinder as far as it will go AND HOLD it in. 18) Your "helper" will now install and tighten the bleed screw while you hold the plunger in. 19) When bleed screw is tight release the rod and as it comes out guide it into the proper position on the clutch arm. 20) Top off the Reservoir and the job is complete.
Theory: Why do I insist that you REMOVE the bleed screw when pushing the plunger in on the slave cylinder? This is simple hydraulics. Fluid or air will always go the direction of least resistance. When you are pushing the rod into the slave cylinder you will find that it is impossible to push it in at a slowly and steadily pace. If you push it in too fast with the bleed screw still in and just unscrewed a few turns some of the brake fluid and/or air in the slave cylinder will go back up the hydraulic line that you just bled, thus necessating your starting over. When bleeding your clutch....The biggest mistake or miss-conception a person can make is to pump the pedal. The clutch Hyd. system, unlike the brake Hyd. system SHOULD NOT BE PUMPED. The only thing that happens when you "pump" the clutch is that you make any large air bubbles in the hydraulic system into a bunch of small air bubbles. BTW these small air bubbles are harder to bleed out than larger bubbles. You cannot "pump up" a clutch. If you have to "pump up" the clutch to make a shift then you have a leak and you can bleed the system a dozen times to no avail. On the clutch, think about it now, if you could "pump-up" the clutch wouldn't the T.O. Bearing tend to invert the clutch diaphragm and travel toward the engine until it met up with something solid like the flywheel. On a braking system, when you "pump-up" the brakes you force the brake pads into the rotor until the line pressure builds up enough that the resistance you feel when pumping the pedal increases. Further, as you press harder and harder on the brake pedal the pads just increase their pressure on the rotors. GM Thought this through when they designed the system. To avoid "pumping up" the clutch hyd. system, GM put in a small bleed back hole in the master cylinder. (BTW not an original idea, all Hyd. clutches have it) This bleed back hole relieves line pressure every time the pedal is at the top of the stroke. Didn't you notice when you "pumped up" the clutch pedal that it doesn’t firm-up like the brake pedal does? The only thing you accomplish when "pumping up" the clutch pedal is to take any air bubbles that are in the system and atomize them into smaller air bubbles, thus making the problem worse. Remember when you were at the soda shop, as a kid, and your parents kept giving you hell about playing with you soda and straw? Same theory here! The more you move that soda through the straw the smaller the air bubbles become. BTW the "hand pumps" work ok but I’ve never needed to buy one yet. With the hand pumps you still need to ensure that the slave cylinder gets completely bled. v8archie
That is a great tutorial, and having done this before, I am following your procedure to the letter. EXCEPT, I did not remove the slave bleed screw when depressing the slave pushrod. I will have another go at this today. At present, I have about 1 inch of slave pushrod travel; not quite enough for clutch function.
Did the slave bleeder out, and slave piston push, got the remaining air out of the slave, and have full clutch function! I have done this enough times now, I should know better than to shortcut the last step. Bottom line: clutch did not work leaving the bleeder screw in doing the slave rod push, and did , removing the screw to do it. Thankyou everyone for your input; these cars have their challenges, but this forum and those willing to share their expertise, makes owning one of these cars worth the trauma!
