Clutch master cylinder - whats going on?

**steveG** · 26th February 2013, 09:40 PM

From reading the many posts on the subject I know that Defender clutch master cylinders only last on average about 3.768 months before failure

I've done OK then, as I put a seal kit in mine when I did the Isuzu conversion nearly 2 years ago and its only just crapped itself on the weekend.
Thing is, this one was a stainless sleeved PBR one (fitted by the PO), so I wasn't expecting it to die yet.

Even more puzzling is why the gunge inside it looks like this when flushed out with some brake cleaner:

You can see the liquid separation between the gunge and the clear brake cleaner, so I'm assuming the gunge is water with suspended metal particles that look like a fine flake metallic paint.
Before I removed the master I sucked all the fluid out via the bleed nipple on the slave to reduce the mess, so that's all that was left in the bottom of the master.

There was no leakage past the main seal, and the symptom was that the pedal would go almost straight to the floor, and you'd get a bit of "clutch" feel for about the last 30mm. I could see the level in the reservoir rise as the pedal was pressed, so I'm guessing the small seal inside that closes as the pedal is pressed wasn't doing its job?

Whats the go with the water? Has it just absorbed that much from the atmosphere in 2 years, or is it more likely I've managed to get some in the cap vent while washing the engine bay?
And where is that metallic stuff coming from? Could it be from the stainless sleeve?

Steve

**goingbush** · 26th February 2013, 09:59 PM

Looks to me like Raspberry Jam !!

have tried Jeep M/C on mine & that failed,
now Ive got a stainless sleeve OEM, Im running Toyota Dot3 in mine so far so good.

Toyota recommend Dot3 in their hydraulics because of failures using Dot4 , so fingers crossed, ( altho the experts will tell you 4 is better than and replaces 3)

**steveG** · 26th February 2013, 11:57 PM

Originally Posted by goingbush

Looks to me like Raspberry Jam !!

have tried Jeep M/C on mine & that failed,
now Ive got a stainless sleeve OEM, Im running Toyota Dot3 in mine so far so good.

Toyota recommend Dot3 in their hydraulics because of failures using Dot4 , so fingers crossed, ( altho the experts will tell you 4 is better than and replaces 3)

Looks more like Vegemite than raspberry jam to me!

I just can't work out whats caused the discoloration and metallic as there doesn't seem to be any obvious sign of wear like you'd see on an aluminium cylinder.

I'd read your previous posts about the Dot3, and noticed that Bursons have Bendix Dot3 on the shelf when I was in there recently. I've got to get some more fluid anyway so think I'll give it a go. Ordered a new TRW master cylinder to fit and will rebuild my current one as a spare.

Steve

**Bearman** · 27th February 2013, 06:42 AM

Sounds like the bucket seal on the piston was bypassing to me Steve. The colour of that gunk is interesting. It look like rubber residue to me. Have a close look at the inside of the sleeve when you dismantle it for rough spots particularly around the fluid inlet hole. I had a sleeved brake m/c fail prematurely some years ago on a series due to this. It appeared that they did not clean up the inside of the sleeve properly after the hole was drilled through it and small burrs were left there.If the gunk is metallic the only other place the metal could be coming from is the piston (apart from the sleeve which shouldn't wear).
I must be lucky as my county one hasn't been replaced for 18 years now and is still going fine (touch wood). It is a stainless sleeved one that I fitted when I did the build up in '94.

**rick130** · 27th February 2013, 08:19 AM

Hmm.

Had a PBR 3/4" MC for 4 years now and it's been OK ?

Slave is still original and it's a Nov '98 build (have I just put the mockers on it ?

)

**460cixy** · 27th February 2013, 12:53 PM

Originally Posted by goingbush

Looks to me like Raspberry Jam !!

have tried Jeep M/C on mine & that failed,
now Ive got a stainless sleeve OEM, Im running Toyota Dot3 in mine so far so good.

Toyota recommend Dot3 in their hydraulics because of failures using Dot4 , so fingers crossed, ( altho the experts will tell you 4 is better than and replaces 3)

Toyota seals are not compatible with dot4 why Toyota went down this path one will never know. So your jeep master failed? I haven't fitted mine yet haven't had a chance. How did the jeep cyl fail? Most landy masters I replace are chock full of metal particals like the push rod is cocking the piston and wearing the bore

**goingbush** · 27th February 2013, 02:39 PM

Originally Posted by 460cixy

Toyota seals are not compatible with dot4 why Toyota went down this path one will never know. So your jeep master failed? I haven't fitted mine yet haven't had a chance. How did the jeep cyl fail? Most landy masters I replace are chock full of metal particals like the push rod is cocking the piston and wearing the bore

There was a seperate fault with my Jeep M/cyl , a faulty valve ??- a one off issue I think I just got a dud one. After each clutch activation the pedal height would slowly increase to the point where the clutch would start to flare, after about 30klm (city driving) I'd have to crack the slave bleed nipple to release pressure and the pedal would go back to normal, about 10 cycles of this I'd have to top up with fluid.

I had to fix it in a hurry so just bought a stainless sleeved oem mc from Fred Smith LR

**steveG** · 27th February 2013, 03:58 PM

Originally Posted by 460cixy

Toyota seals are not compatible with dot4 why Toyota went down this path one will never know. So your jeep master failed? I haven't fitted mine yet haven't had a chance. How did the jeep cyl fail? Most landy masters I replace are chock full of metal particals like the push rod is cocking the piston and wearing the bore

I've read a few posts about modifying the piston to fit an o-ring near the push rod end of the piston. Personally I can't see that lasting well as it would always be dry and I'd think the o-ring would wear out pretty quickly.
Fitting a teflon backup ring instead of an o-ring would be a better option if piston cocking/wear is the root cause of the failures. Would be a nice simple mod.

The piston in mine definitely shows signs of rubbing on one side. Might give my pickup magnet a swim tonight to see if the gunge contains ferrous material.

Also makes me wonder if the squeaking clutch pedal I had for quite a while was the piston and not the pivot bushes like I thought it was.

Steve

**rick130** · 27th February 2013, 05:24 PM

Originally Posted by 460cixy

Toyota seals are not compatible with dot4 why Toyota went down this path one will never know.
[snip]

What the hell is the deal with this ?

They're both glycol ether fluids, but I've heard old Series Landy blokes say the same thing

**steveG** · 27th February 2013, 05:39 PM

I did a bit of searching last night and found a few Nissan guys reporting the same thing with older Patrols etc.

Doesn't the Dot4 have something else added to give the higher rating? Maybe its that causing the issues?

While we're at it, why do we use brake fluid which is designed for high temperatures in clutches which don't see high temps. Why aren't we running mineral oil like other hydraulic systems?

Steve

Thread: Clutch master cylinder - whats going on?

Thread Tools

Clutch master cylinder - whats going on?

Bookmarks

Bookmarks

Posting Permissions