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How do I test a clutch master cylinder?!


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I've been having issues with my fairly new Tilton 3/4" clutch master cylinder..

 

When I press the pedal down I have firm pressure all the way down to the floor. I've noticed while I'm sitting at a stop light I am loosing pressure and after lets say 40 seconds the master cylinder will loose almost all pressure.

 

I can let up on the pedal and you can hear brake fluid being sucked up into the cylinder and then I have full pressure again!

 

I've tried bleeding the hell out of the setup without any changes.

 

 

I've also noticed I can press the pedal to the floor and slowly slowly slowly let up on the pedal. About 3/4 on the way UP I can hear the same noise. The noise of brake fluid being sucked or squeezed in/out of the master cylinder.

 

 

Any ideas?!

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No leaks anywhere? You've pulled the boots at the master and slave? Checked around the hoses and fittings? If that's the case, then I'd say replace the master again.

 

Also, if you're sitting at a light for a minute, it's a good idea to put it in neutral and let the clutch out, especially if you're running a stiffer than stock clutch.

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Did you bleed the master cylinder before bleeding the lines? You can actually bleed it in the car just make sure you get something like fish tank air hose or some small tubing like that and bleed it into a cup with some paper towels shoved in it.

 

Also some times parts we buy are rebuilt and not rebuilt very well. If you pulled apart the mastercylinder you might discover that the two seals on the shaft were installed incorrectly or possibly are defective.

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  • 2 years later...

Hi, I just found this forum. This thread could have been written by me!

 

Here's copies of the emails I just sent to Tilton:-

 

"I have recently finished my long term project - pic attached.

 

I fitted the Tilton clutch kit:-

 

61-601 Hydraulic unit

 

61-612 T-5 bearing retainer

 

75-875U 7/8†bore master cylinder

 

The car has done about 1,500 since rebuild and after about the first 1000 miles I noticed the clutch giving difficulties in clearing. It was difficult to select gears from cold, but after a few minutes and a few gear changes it seemed OK. Also, on occasions when reversing or travelling slowly forward the car would stall as the clutch had completely let itself out even though my foot was still depresssing the clutch pedal.

 

I have bled the system and there was little or no air in the system.

 

Yesterday the clutch would not work at all. No gears could be selected at idle. There was 'pressure' or resistence at the pedal but clutch would not clear. Then the pedal suddenly went weak with no pressure or resistance.

 

I noticed there was a lot of gurgling coming from the master cylinder (mounted on the pedal box of the car.

 

I removed the metal output connector and put my thumb over the nozzle. Pressed the pedal and no fluid wanted to come out past my thumb pressure.

 

I removed the m/cylinder and when operating the puch rod I noticed that the fluid was in fact coming right up into the reservoir and not out the output nozzle.

 

Can you please advise as I wonder if:-

 

1. the seals have failed or

 

2. There is some other issue.

 

The system has only done about 1500 miles from new."

 

Also added this:-

 

Just thought I'd add more info.

 

The attached pic is of the master cylinder - dismantled view ( I just had to check after taking 3 hours to get the darn thing out of it's mounting).

 

Anyway, as I gently extracted the piston I noticed that the rubber seal ( arrowed in red) remained inside the cylinder and had to be shaken out.

 

The other seal (blue arrow) was intact.

 

I noticed the red seal seemed very flimsy and didn't even have a snug fit on the end of the piston??

 

I am in need of some advice really:-

 

1. Do these Tilton master cylinders have a failure rate that you knw of?

 

2. what might cause the cylinder to fail (if that's what has happened)?

 

3. My set up seemed correct in terms of the push rod etc - but can always re-visit that if you think there's an issue.

 

4. I am almost loathe to have a rebuild kit for this as it's only been in and working since July last year and done about 1500 miles total.

 

So, any help gratefully received."

 

I wonder if there's an update to the original post in this thread? Seems a common factor here.

 

cheers Chris U.K.

 

PS - Pics attached.

post-17480-046892100 1298218704_thumb.jpg

post-17480-049532700 1298218818_thumb.jpg

post-17480-019984800 1298218828_thumb.jpg

post-17480-063204900 1298218837_thumb.jpg

post-17480-097129200 1298218848_thumb.jpg

post-17480-088431400 1298218882_thumb.jpg

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Update.

 

Sent my master cylinder away to Tilton reps in UK. Both seals were like jelly. Something in the fluid had made the seals swell and fall off ( well the end seal fell off )

 

Know idea what could have done this. Used Dot 4 Carlube fuid.

 

Had a new seal kit fitted and will install next Monday after a good flushing through, hoping the slave hasn't got the same plague!!

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