So today saw the long awaited second bleed of the brakes having finally snaffled 4 litres of DOT4.

Everything was going by the book until the second bleed of the fronts with ignition on when a growing pool of fluid was spotted underneath.

It appears to be coming from under the pump yet both high and low pressure lines seem fine. This is the one part of the brake system that has not been touched throughout the overhaul.

Before I rip into it anyone got any similar experience i.e., what the cause may be and is there a likely solution, rather than a new pump?

Thanks in advance.

Having finally got in there, it appears that the o-ring between the pump and motor is goosed.

Went and found an o-ring shop up Binondo and they gave me one that looked close. However, it's still leaking and I think the one I've got is too thin. It looks to me that when it's in position, it should just stand proud of the pump body.

Anyone know the actual dimension of the ring?

I don't know the actual dimensions of the o-ring unfortunately. Doesn't feature on my parts catalogue either.
In the absence of a proper gauge (would have thought the o-ring shop would have one?!), try measuring the original ring using this:
https://www.imperialsupplies.com/pdf/B_O-Ring-Charts.pdf
I find it surprisingly accurate (needs printing to actual size, not scaling to fit page) and with a combination of inside/ outside diameters and measured thicknesses across cross section, together with a bit of maths (cross sectional area will be constant even though old ring is squashed into an oval), you should be able to get pretty damn close to the size

Thanks OB. I've got 3mm and it looks to me like I need 4mm. Getting one shouldn't be a problem

The other issue is that there's as small double lipped and sprung seal on the end of the motor shaft. It looks like that's leaking slightly as well and could be a little more difficult to source (once I've worked out how to remove it, that is!).

I've got one that was on the pump motor that burnt out and that is still round and not squashed. Assuming you are talking about the big one that goes around the end of the motor, measuring that with a ruler (as I've put my dial caliper down somewhere and can't see it at the moment) I'd say that it is just over 2mm thickness. Definitely not as big as 3mm and certainly not 4mm. I can dig the pump body out later and get some pictures if you need.

Hmm, interesting. Thanks for that. A pic or measurement would be really useful.

I used the 3mm but it still leaked, so I assumed I'd need bigger. Perhaps I'm wrong. Unfortunately I left the old one at the shop after the guy measured I/D and O/D behind the counter and didn't pass it back. My fault.

The ones I have are O/D 56mm, I/D 50mm and (obviously) 3mm thick. Again, if I actually need 2mm, it shouldn't be a problem to source. Especially now I've found the part of Manila given over exclusively to o-ring shops, but which cannot be found anywhere else in the city!

GeorgeB wrote:

The other issue is that there's as small double lipped and sprung seal on the end of the motor shaft. It looks like that's leaking slightly as well and could be a little more difficult to source (once I've worked out how to remove it, that is!).

---

Too much to hope for that it's got a part number on the closed face I suppose?
The problem with removing them (unless you can get to the back and drift them out) is that it almost always results in their destruction, so you go from leaking slightly to: omigawd now I have to measure the shaft and housing diameters and spend days in the O Ring Quarter which is hopefully the same as the Seal Quarter.

Dunno, the closed face is on the bit still attached to the motor that the top of the pump housing bolts to, and I'm wary about butchering things taking it apart. I'll have a good look at how it goes together in the morning and see what can be done.

If I do get it apart, I just hope it's not Wabco specific.

The O ring is definitely 2mm but the recess it sits in is slightly deeper. It's a nice fit on the motor though.

Thank you, Sir.

I was thinking more is better but obviously, less is more.

Just sent my chappie to the O-ring Quarter (like that!) for 2mm ring.

Going to replace that first and see, before I start worrying about the other seal.

Will report back.

Thanks all!

Sorry guys. Zero report.

I forgot that when a Filipino says, "Later" he does not necessarily mean the same day, so I'm still awaiting!

GeorgeB wrote:

I forgot that when a Filipino says, "Later" he does not necessarily mean the same day, so I'm still awaiting!

Same as in Spain, when they say 'mañana' they don't mean tomorrow, it's just not today.

France is much the same too, everything will be ready tomorrow but by the time tomorrow arrives, it's today.

But, why is the country, The Philippines, spelt with a Ph but a native is a Filipino with an F (and only one p)?

Gilbertd wrote:

France is much the same too, everything will be ready tomorrow but by the time tomorrow arrives, it's today.

But, why is the country, The Philippines, spelt with a Ph but a native is a Filipino with an F (and only one p)?

Ah, my Dear Friend, I wish I had an easy answer but, like so many things in this mighty Republic (Manila taxi drivers for example. What are they for?) it is one of life’s imponderables, I’m afraid.

Here they have embraced the spirit of mañana, as bequeathed by the Spanish and developed it into a true art form. Still, it keeps the watches simple. “Soon”, “Later” and “Tomorrow” are all the times needed and, as we’ve seen, “Later” can double for “Tomorrow” which, as you so rightly point out, becomes today, and thus falls into the category of “Soon” or “Later”. And so on…

More to the point, I've still no bleeding o-ring!

"Later" actually meant 7 days in this case!

Got the 2mm ring now (and a spare) and will fit it later. If it still leaks, then it'll be the motor shaft seal, so my fingers are crossed.

One little bit of light on the horizon if it is the seal, is that it doesn't appear to be a proprietary part and that SKF, who have a branch here in Manila, may be able to supply one.

Yup, it's the shaft seal.

Good-ish news is that the old one pulls out without any further dismantling.

The real good news will be if SKF have one in stock!

For those of you who have a leaky brake pump, the o-ring is 50mm I/D and 2mm cross section.

The shaft seal calls itself 16x8x6, SC/SF, NBR, SOG.

Both together cost around 1.20.

And job done!

Oh, and the seal came from the same place I got the ring from, so it's nowt special.

I'll call that a win.

Came down this morning, ignition on, found a small weep from the high pressure hose to the pump and nipped it up. Then bled the modulator, switched off, depressurised the system, fired her up and the light went out in 3-4 seconds (I don't need to move mine first!).

Light flickered when I gave the pedal two good stomps, then never reappeared for an hours test drive.

Pedal is nice, high and very smooth now, so it looks like I can finally put the brakes to bed.

Oh, and thanks a lot for the info 😊