Twenty years ago I used about an 18" section of flared steel line which I picked up at the local auto parts store. The hydrolastic factory fitting was used on the flared end and a compression fitting on the other end.

I figure plain old anti-freeze has all the propeties required by the system. Plus, we're dealing with 40+ years of development with anti-freeze whereas nothing has been done with hydrolastic fluid chemistry since the systems were new. I use straight anti-freeze. I have a can of the original factory fluid as a great conversation piece for display purposes. 

I have a modified grease gun and one of the original factory "robots". I use my modified grease gun because it's easier to get to, set up and use than the robot. While you can't totally evacuate the system with the grease gun, you can easily get most of the air out of the system by bleading. As opposed to the braking system, it's not as critical that you get every single air bubble out of the hydrolastic system. 

My America's had bleed valves in the front hoses under the bonnet. It was easy to pump them and get the air out.

You can buy a cheap venturi vacuum pump from harbor freight that you hook to an air compressor. You'll have to figure out some plumbing config that both the pump and vacuum can connect to with shut off valves for each side. Shouldn't be too hard. I might make one myself with some ball valves and pex tubing.

We use straight 5 year antifreeze. No water nothing added. My 1967 was a frame off restoration in 2005 and we have the BMC machine also. Just pumped it off and measured to make sure that both sides were the same height. 

When we had Austin Americas we used the modified grease  gun. Then we found a brand new machine at a British car fleamarket. 

Deb

Suprisingly less than you would think.  I have a very slow leak in one of the bag fittings and have pumped up to >300 psi (from almost nothing) about 5 times in the last 3 years with less than a gallon.  I have the BMC shop tool so it's become a 20 minute job including all the prep work start to finish. I've always used the genuine hydrolastic fluid like you said but understand that if you use anitfreeze that most dilute it with water at some ratio.  Remember that air in the line is your enemy so you may want to try and purge as much (all) from the line before you refill.  

Thanks for all the input.  I'm feeling better about it already.  I've got a grease-gun pressurizer tool put together.  Anyone know about how much fluid I'll be refilling?  I've got most of a can of genuine hydrolastic fluid (over a gallon or so).  If I need more I understand antifreeze is an acceptable alternative.

Thanks again.  This forum and you guys are great!

I repaired the line on my first Elf using central heating fittings.

It saw some serious abuse as the 20-year old me went through a hump-back bridge yumping phase and it held up fine.

The Australian workshop manuals mention using compression fittings to repair damaged pipes.
Note, These are from the 1100 manual, the pipe size is larger

I second the idea of using compresson fittings. If the brake/leak is between the subframe and body, replace a section of pipe using steel brake line of the same outside diameter.

If it's just a small leak, just cut the pipe back enough for a compression fitting to rejoin the two ends. When you go to the hardware store, ask them to explain how to install it. One of the easiest jobs you'll ever do.

I like to paint brake lines and hydro lines to prevent rust, road salt damage. Paint it up after your repair.

Use jack stands when you get under the car. Do just use a jack. Not safe.

Then you'll need someone with a pump to recharge the line.

Any shop that makes hydraulique hoses can fix it for you.

You can buy replacement lines.

Think big tractor and bull dozers.

Deb

When I bought my hydro car in 1994 the suspension appeared to be completely depressurized and it was sitting on the bump stops. I drove it home a distance of about 30 miles, on back roads, hardly exceeding 30 to 35 mph. What I found was a cracked right side hydro line just forward of the dog leg near the schrader valve. We cut out about a 12" section of the old pipe and replaced it using compression fittings and a new copper line purchased at the local hardware store. It has held up fine to this day. 

That will work. 

In the old daze the manual stated that you could drive the car at up to 30 mph with the suspension deflated to get it to a shop for service.  Having done this, I would be more conservative with the speed. I used several pieces of plywood between the body and bump stop to generate the required tyre clearance.

Cheers, Ian

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My 1966 Cooper-S has sprung a hydrolastic suspension leak in the interconnecting pipe where it passes over the rear subframe (left side).  I am hoping the pipe can be cut and coupled onto a new fabricated pipe by maybe a brake line shop?  The wheel arch rests on the tire, so I wedged a big socket on top of the rubber bump stop so the car could at least roll onto a flat bed to tow it into a shop.  

Anyone have experience with this kind of repair?  Am I heading in the right direction?  I'd really like to keep the hydrolastic as the displacing units seem to be intact and I like the ride.

Thanks in advance for any advice.

Todd