bubble master cylinder jar (new one)

[MMDream]

Hi everybody,

I have a leaks on my old master cylinder, then I replace it.

But now after a good bleeding (4 drumb) the pedal still to sweet the first time and more hard when I pump.

I think it still air on brake system...bleeding again...

But infact when I pump slowly I saw the air bubble on master cylinder, just occasionaly.

goes through the hole before between the jar and the master cylinder coprs.

For be sure the master cylinder is brand new and I finish to suspect them.

What do you think.

Thank

[bmcecosse]

It is normal to see a small 'fountain' of fluid in the master cylinder - do not fill it to the top. Make sure the brakes are adjusted up tightly when bleeding - and start at the wheel furthest away from the master cylinder.

[MMDream]

Thank,

I know the rocedure to bleed the brake. It's not the first time I use but in this case same after long (relly long) bleeding it still have some bubble rising in master cylinder by first hole (towards the front of mog)

Ok fort the fountain of the brake oil, but this one come from the hole on the back of the master cylinder not the front one.

[MMDream]

I try to check the first sseal on master cylinder :
I put air pressure (blower) by compressor directly to close to this seal.
I take off the big dust procetion and put blower parallel to

But I didn't see any bubble again.

[MMDream]

In fact the bubble rise when I finish to push the brake or when I keep down.

Not when I start to push the pedal.

[MMDream]

Maybe find the trouble:

From Brakes / bleeding / faults and master cylinder replacement by Moderators

"If you press the pedal slowly and bubbles come up then you have a leaking secondary seal - fix this ASAP. Corrosion in the bore making the secondary seal leak is the most common failure of the Moggy master cylinder (it is more likely to happen in cold weather as the seals shrink just a fraction but it can happen at any time). If left unchecked you are likely to get a nasty surprise and no brakes one day."

[bmcecosse]

But you say you have replaced the master cylinder - I assume with a new one ?

[MMDream]

Yes it is.
Brand new, just received.

[MMDream]

Then, I change the master cylinder for second time (again new one) but there is exactly the same problem.

Just little bit less bubble.
...

[bmcecosse]

I don't see a problem - just bleed the system out properly!

[chickenjohn]

The problem here is that the Minor fluid reservoir is very low down compared to most cars so does not benefit from the hydraulic pressure from the gravity head present in a remote reservoir system pushing air bubbles out. So we have to try a different tactic. Try jacking up the rear as high as possible (support axle with stands!!) when you bleed the rear,, left first then right, then do the same for the front, again left before right. This will help the air bubbles to naturally rise in between bleed strokes, thus avoiding trapped air.

[MMDream]

Ok I'll test this technic

[MMDream]

Do you think the bubble can come from pipe?
It's strange because same when the back of the car is really high, I can't bleed any bubble. There is just brake fluid

[bmcecosse]

Which is perfectly normal as I pointed out ages ago.

[MMDream]

Sorry, Im not sure to understand.

What is normal? To see bubble? Or it's normal that bleeding is hard?
See the bubbles disturbs me, but the real problem is the soft pedal on the first pressing and then hardened by pumping

[bmcecosse]

I give up...last advice - adjust the brakes up properly...

[stag36587]

Actually I've got every sympathy with the OP - I have had persistently exactly the same problem, even with all brakes adjusted up hard, checked, double checked and triple checked and replacement master cylinder fitted. And I have bled brake systems successfully on other cars. I think in this instance chickenjohn's advice is definitely the most helpful - I'll be trying it over the weekend to see if it makes a difference because I am losing all patience with it but determined to persevere until I've found the answer. It would be a cop out to call in the professionals

[MMDream]

Hi bmcecosse, sorry if I have not succeeded but I already check the good adjustment of the break, I try also to much tight and also with hand brake on the floor - at midle and really tight....
But for the moment nothings.
I will try to check master cylinder on table (master cylinder with just 1 brake caliper - bleed it then test if I can do a good bleed & if it's properly work

I'll see...

[Sandun]

1st check brack oill - remove the filler nut then slowly push brack paddel u can see the pump oill bubbel , if yes ur master pump is fine work - 2nd off the master filling nut - jack ur car wheel then rotate wheel from ur hand next push brack if the wheel can not move the brack is fine -

[john newton]

just had lots trouble new m[cyl wouldnt bleed atall useless... sent it back. fitted another new one perfect. awaiting report...