Clutch reservoir cap breather hole

[Pianoman]

I am having problems with my clutch system. I had a new clutch recently put in but over the last few weeks first, second and reverse gears have been problematic in the time it takes the car to get warm. I have replaced the clutch reservoir and the rubber hoses.. Ive also lengthened the slave rod to get the maximum length, bled the system but the clutch sometimes still won't engage enough to get those gears. Ive also noticed sometimes when I have the clutch pedal fully pushed down,suddenly it lets go and will then travel all the way to the bulkhead.
Ive also noticed clutch fluid being pushed out of the small breather hole in the lid of the clutch reservoir cap.

Any ideas? Thanks

Series 2

[MarekH]

All the clutch does is disengage the bit sticking out of the front of the gearbox and the bit sticking out of the back of the engine from each other. It doesn't have anything to do with changing gears.

From your description, it sounds as though either or both of the pistons in the clutch master and/or slave cylinders do not always travel smoothly for some reason.

The slave cylinder piston pushrod travel is in a straight line, but is often plagued by having rusty sludge accumulate there as it is the lowest point.

The master cylinder piston pushrod travel is controlled by the pedal which pushes in an arc. If not close enough to being in a straight line, it can score the master cylinder bore and cause trouble that way. This is possible if your car has been converted from auto to manual using a hotch-potch of aftermarket parts.

As to forcing clutch fluid out of the reservoir, there ought not to be any fluid pressure in the system at all at the point where the path back to the reservoir gets re-exposed. That implies the two pushrods don't move back in sync, so either there is a partial blockage in the line between them or the master doesn't move as freely as the slave did OR you've overfilled the reservoir somewhat.

kind regards
Marek

[christopher storey]

All the clutch does is disengage the bit sticking out of the front of the gearbox and the bit sticking out of the back of the engine from each other. It doesn't have anything to do with changing gears.
Marek

Well , that is something of an oversimplification. It has everything to do with changing gears : clearly in this case as the system heats, some clutch drag is developing . I would dismantle and thoroughly clean both the clutch master and the clutch slave cylinders. If on inspection the cylinder walls are unblemished then I would rebuild with new rubber kits. If, however, either cylinder has scored walls than new cylinder(s) are required

[MarekH]

The oversimplification is justified - it is not the big diaphragm spring that is causing the problem. What was being described was the lack of smooth release of force from it.

kind regards
Marek

[lowact]

Aren't the symptoms, inconsistent clutch clutch activation (preventing gear change) and fluid being pumped back into the reservoir, exactly what you would expect if the master cylinder piston was leaking?

[MarekH]

There is no report of any leak nor of there being any fluid being lost. What has been reported is inability to push the pedal down far enough smoothly to the bulkhead as though there is a notch it has to get past and also that the return journey (powered by the big spring thing in the bellhousing) is not smooth on the way back either.

It also sounds like extending the pushrod length is a way of getting a bit more travel before this notchy bit is come across BUT the pushrod has to be adjusted so the correct freeplay is observed, otherwise premature wear can take place at the bellhousing end of the throwout bearing and/or clutch plate components.

(We haven't been told whether this is a hydrostatic slave or the conventional slave and with the former, the resting position changes with clutch plate/throwout bearing wear, whereas with the latter, the wear is taken out by periodically adjusting pushrod free play. We do know that the clutch plate has just been changed and that the car stood for 37 years - see Donal's other posts. We don't know whether the master or slave cylinders are original or not.)

I think both Christopher and I are expecting to see wear on the cylinder walls (or a ton of rust) inhibiting smooth movement of one or both of the cylinder pistons. (The only other way to get the same effect is the auto to manual conversion misalignment of parts as earlier described.)

With the pushrod disconnected and the line open between the two cylinders, each should be able to move each piston in and out all of the way in and out down the bore smoothly with little or no resistance. (Each cylinder has some small springs inside it which are easy to push against compared to the forces on either end of the hydraulic chain - the left foot at one end versus the pressure plate at the other.)

kind regards
Marek

[Allrand]

Sounds to me like the reaction valve seal at the front of the clutch master cylinder isn't holding pressure while the pedal is pushed. The strength of the clutch pressure plate is pushing back on the slave cylinder and hence fluid Is pushed back to the master cylinder and then past the reaction seal, thus back into the reservoir & out of the bleed hole. With the pedal depressed there isn't enough volume available in the master cylinder to accommodate the original amount of fluid, the only place to go is out of the bleed hole.

[Pianoman]

wow thanks everyone, Allrand might have it. I will order a rebuild kit for both master and slave and try to rebuild them both. This is the first car ive ever done any real mechanical work on ever and it really is making me stretch myself. Im not complaining, its a great experience but it also is really making me appreciate and respect the work and the knowledge that goes into maintaining these cars.

[mgcjag]

"Clutch reaction valve" ?.....the brake master has a reaction valve.......Steve

[johnetype]

Given you can get new clutch master and slave cylinders for £30 each I see little point in rebuilding/resealing the potentially rusty old units. If you need to change them, fit new ones.

[christopher storey]

I will order a rebuild kit for both master and slave and try to rebuild them both.

I would not order the kits until you have stripped and examined the cylinders . If the bores are in good condition, you can then order the kits . If they are not, then order new cylinders

[Pianoman]

Hi John,
where did you see the cylinders for 30 quid? I tried to find them on SNG and they seem to start at 134 and go up to over 350

[abowie]

Hi John,
where did you see the cylinders for 30 quid? I tried to find them on SNG and they seem to start at 134 and go up to over 350

Clutch master https://www.sngbarratt.com/English/#/UK ... 0master%60

Clutch slave https://www.sngbarratt.com/English/#/UK ... 20slave%60

[Pianoman]

Thanks so much Andrew, you are an E Type super-hero

[abowie]

Thanks so much Andrew, you are an E Type super-hero

More that I've spent too many hours ordering parts from SNGB

Just double check that the slave cylinder part number is correct for your car as there are a couple of iterations.

[Allrand]

Apologies, Steve is probably correct, I was speaking from memory of my restoration. I rebuilt my brake masters but bought a new clutch master because mine had a broken flange. Which means that fluid is still leaking past the main seal in the master cyl. If it's the slave cyl there should be some visible leakage at the slave, allowing the pedal to go all the way to the bulkhead, it wouldn't push fluid back to the master cyl.