HP Pump Leak - New 'O' Rings fitted

Over the last couple of months I've investigated - and hopefully solved - the leak from my HP pump.

With the radiator already off the car, I had better access to the bracing bars and hydraulic connections on and around the HP pump and so pulled it off. With the pump on the bench, I removed the pulley and this is what I found!

Not what I wanted to see!

It looks like the leak is coming from around the inner edges of the green closing cup rather than from around the shaft itself. Maybe like this?

Possible leak routes? (part numbers from catalogue 648)

Not sure what I mean? The deflector and its seal (part 37) fit on the shaft like this.

Deflector seal on the shaft

Deflector over the seal

And then there is a thin metal 'closing cup' (a dust cover?) over the deflector and bearing - but it doesn't fit around the circumference of the shaft. its centre hole is considerably larger than just the diameter of the shaft. Its job seems to be to keep dust and grit out of the bearing.

'Closing cup' over the deflector

The grease and hydraulic fluid seems to be oozing from under the closing cup edge - not from the shaft. So it looks to me as though the deflector seal (37) is doing its job but that the seal behind it (part 35) and the seal carrier it sits in, might be the culprit. 

Seal carrier and seal (labelled as 'part 35')

After some investigation, I'd bitten the bullet and over winter had bought expensive accurately sized seals (you can read about those HERE) and so set about stripping the pump. In fact I also stripped my spare pump - reasoning that if it was going to act as a spare, it might as well benefit from new seals. I could also use it as a point of reference to check my previous work. That other pump had broken mounting brackets - so I got a couple of secondhand ones from a D parts supplier. And another three-belt pulley.

I've rebuilt this pump before. I covered it HERE. Disassembly meant pressing the main pumping parts from the end plate and removing the bearing to access the seal carrier hidden behind.

End plate, bearing, spring, seal carrier and seal
(credit unknown)

I couldn't find anything obviously wrong. Yes - I'd fitted the seal carrier the right way up. And - yes again - it's surface was clean and flat to provide good contact to the bearing.

Surface looked good - no burrs

After cleaning everything, I very gently 'dressed' the surfaces of the carriers on some wet and dry paper and did the same with the inner part of the two bearings. I fitted my new, expensive seals to the carriers and fitted the carriers to the end plates.

When fitted in its recess, the seal carrier still popped out (as it had done on the first rebuild) due to the force of the spring behind it - but not nearly so readily as when I'd first rebuilt the pump. A tighter fit was an encouraging sign.

The consensus of opinion is that, as well as the rubber 'o' ring seal needing to do its job, pushed by the spring behind, the brass/ bronze seal carrier itself also has to fit flat to the bearing to create a metal-to-metal seal. As such the bearing and seal need to be flat to one another when fitted.

For that reason - and as before - I slowly and carefully pressed the bearing into the end plate. I used a large diameter socket so that I was pushing on the outer part of the bearing. And as before I stopped as I went and 're-adjusted' the position of the seal carrier from the pin-roller end to make sure it was correctly positioned.

Pressing the bearing into the end plate

This is the view from the pin roller end after the bearing was fitted. At the bottom of the hole you can just make out a sliver of the bronze/ brass seal carrier and the bearing right at the back.

Bearing and seal carrier in the end plate

Everything looked to be in place. Unfortunately pushing the shaft on the bearing from the pin roller end tends to push the bearing back out again(!) so that it needs to be re-seated. Eventually everything was back together.

As well as the special sized seals, I also bought two new replacement big seals for the cases. I'd recalled from when I first re-built my hydraulic pump that it was hard to press the large outer case back over the seals and onto the end plate. Based on a tip I'd tried using a leftover cardboard inner from a reel of duct tape, but it still moved around too much on the domed end when force was applied and wouldn't push the casing on squarely. To hold it steady, anything used to press the casing on needed to fit around the sides of the casing as well as the end dome.

This time I was ready! I bought some clear resin and took a mould of the end of the casing. I set the casing up so that it was level in my mould and about an inch or so deep in the resin - more than just covering the domed end.

Making a mould of the casing end

I left the resin to harden

New tool for fitting HP pump casings....

I used a block of wood to pad-out the shaft end and my new resin tool to press the casing on. The mould holds the casing steady and spreads pressure on it across a wider surface as it is pressed home.

Pressing the pump casing onto the pump

My mould worked really well and made quick work of refitting the covers. After that it was on to priming......

.....and painting

I'd already planned ahead and bought new tab washers for the pulley nuts. One of the pumps pump is back on the car and the other one is sitting on a shelf - just in case it's needed. Once I get the steering rack and radiator back on I can run the engine and find out....