clutch master pushrod lenght

[Emma-Knight]

I had to renew all clutch hydraulics. The master cylinder pushrod that came out is 73mm long - measured middle of bolt hole to front half round tip. Brian Buckland writes 80mm from center bolt hole to rear of front push lense. My Elans pedals are both the same position and the cylinders seem original. I would take the shorter lenght (73mm) pushrod if, if not a 3/4 (instead of a 7/8 ) slave cylinder had been fitted. I have the correct 7/8 one to install now. With the 3/4, the clutch did only just separate, even well bled. So my fear: with the 7/8 slave the movement of the shorter master pushrod might be insufficient. Any ideas? Are there different lenght pushrods for, say, S1/S2 and later cars? I'd like to reinstall the original lenght pushrod though I have the longer one too.

Anna (has to be on the road on weekend to keep up with the Porsches)

[garyeanderson]

Hi Anna

I went looking for some examples last night but couln't find any. I went out this morning a found a pair that I removed from a crashed Elan S2 that I was given recently. There is a photo of those two push rods, the one with the elongated clevice hole is what I think is the brake but I don't think it matters as they are the same length. The other photo is of the ones in the box that I couldn't find last night, one of them is long and is probably from another crashed Elan S4 coupe that I was also given.The others are from other Elan's that are still disassembled. I think Brian's book has a lot of things right but he is not an S2 person and lots of suttle changes occured over the 11 year production run that were nessessary because of using up stocks of existing parts or re-engineering to use in later models.

[Robbie693]

When I bought new Brake and clutch master cylinders from Paul Matty they told me to use the old pushrod as the new ones were too long. This is for a Plus 2, don't know if the same applies the Elans...

[steveww]

The new clutch master cylinder that I fitted last year came with a separate threaded rod and U shaped bit with the holes in (no idea what the correct name for this bit is )

I just held the clutch pedal at its normal height and adjusted via a couple of lock nuts. I can take a picture if you want.

[garyeanderson]

All of the clutch and brake masters I have bought come with the wrong clevice fork as you decribed it Steve, but if it works, that great. Most of these push rods that I have seen are too long to adjust as you have done, at least on the Elan's I have played with, the Plus2 may be different. As Rob has said, just swap the old push rod onto the new master and everything is back to normal. I got the same advice from Don Tingle back in 1991 when I bought a replacement brake master.

Gary

[SADLOTUS]

http://www.nfauto.co.uk/master_cylinders.htm

These people do threaded master cylinder rods, but I couldn't find the U shaped metal bit for the end.

Rod end anyone?

http://www.nfauto.co.uk/rod_ends.htm

[Emma-Knight]

I fitted the very short "original" 74mm active length, as the brake pedal should have the same elevation. It does seem, my car has both rods too short and I will fit "80mm" rods both sides. Just not before week end, as the short lenght seems to work so far.
Refitting the old ones sometimes is bad because they are pitted and will ruin the dustcover and sooner or later, dirt will enter the bore and grind nice slots in the cylinder wall. That happened with my car. I am running the system on DOT 5 silicon fluid now and will report...

Gary, I like your car collection - they look so unmolested - especially the dark blue one. With such a car, I would have started from scratch. DPO's sometimes really create such a fuzz! The modifications could be called "Hardly Dangerous"...

Tomorrow we go places together with three Porsche 911, an Amphicar, some 70's "Yanks" and some Geman precious metal. They scheduled a suitable watering place for the Amphicar. If all works fine, I'll take some pictures.

Anna

[arendjankleijn]

Anna,

Watch out with the DOT 5 fluid, I renewed my clutch master and slave cilinder, and yes I lengthened my push rod from 73 till 78 mm because it was difficult to put the car in gear, and after a few weeks the fluid was black and there were very smaal parts of rubber in it. I dismenteled the whole thing again, went to the Girling shop where I was told that the rubber cups from 20 years ago couldn't cope with the agressive DOT 5 fluid.
They renewed the cups for free and gave me DOT 3 fluid with it. Until now, 3 months later, all seems fine!
AJ

[SADLOTUS]

Silicon fluid is marked as DOT 5 but it's not the same as ordinary DOT 5 brake fluid. I've had it in my system for years no probs... bit of indigestion but thats all!

http://www.automec.co.uk/pdf_files/brak ... answer.pdf

[Zlinster]

I'm just rebuilding a clutch master cylinder.

I've removed the one on the car. It was full of gunge and crud. I guess that's why I was having slight problems changing gear. Fluid was weeping from the push rod boot in the footwell.

I have several old brake master cylinders and one clutch master cylinder in the box of bits that came with the car. I removed the push rod from a clutch and a brake M cyl looking for a good condition pushrod.

Thing is, as shown in the picture, all the pushrods are a little shorter than the dimensions in the BB bible.

It's this a problem? If it is then what shall I do?

At least I found one pushrod that looks nearly new.

[lotusposition]

Be very careful. I spent an inordinate amount of time trying to construct an adjustable pushrod to conform to the BB measurement given in his book and it caused all kinds of problems.
I eventually reverted to my original pushrod that was only fractionally shorter and finally got a working clutch again.
Also found that the workshop manual 2mm for slave pushrod adjustment is incorrect. Instead of measuring to the tip of the semi circular end of rod I took the gap from the shoulder behind it. And after months of pain and frustration my clutch works again and disengages fully!

[Andy8421]

FWIW, the trick with pushrod length is to ensure that there is some free-play in the pushrod when the pedal is all the way up.

There is a small rubber at the end of the master cylinder that at rest needs to be pulled away from a drilling to allow fluid to flow back into the reservoir. The components inside the cylinder are sized so that this rubber gets pulled away just before the piston hits the retaining circlip at the mouth of the cylinder bore.

If the pushrod is too long, and stops the piston returning all the way to the circlip, then the rubber doesn't get pulled away and the master cylinder won't work properly.

The easiest way to make sure all is well is to have a little slop in the pushrod when the pedal is up.

[lotusposition]

Absolutely correct. This what I eventually discovered after much trial and error. Needs a little free play on the pedal itself.