Hydrolastic

Is there a right and wrong way to release the pressure in the hydrolastic set up in preparation to stripping it?

i just remove the dust cap from the valve, push in the central valvey bit with a screwdriver or similiar (like you'd let down a tyre), and try and catch the fluid as it comes spurting out (goggles!)

had no problems doing it this way in the past

Thanks for that, is the fluid reusable?

You'll most likely realize the answer to that question when you see what comes out. Use new stuff.

ditto!

I actually have a hydrolastic pump for mine, works a treat because it catches the stuff if you lose it but can pump more in as well. Just need to know the trim height (centre of a wheel to the centre of the wheel arch...somewhere round 33 or 34cm I think)

is it possible to hire these pumps ?

I think you can you know but don't hold me to that. I aquired mine from a friend who used to do a lot of work on MG's cos they have a similar system. You may well find one fairly cheap you never know

Does anyone know if it is possible to make a hydrolastic pump?

If you Google it there are quite a few ways of doing it. The cheapest way apparently is using a grease gun, but the succes rate is not very good.

Very easy to make a pump. I've replied to a previous thread with a diagram, have a search, and I'll see if I can find it.



Found it

https://elf-hornet.forumotion.com/t1251-liam-s-1966-mk2-elf-restoration-thread

My cost less than £20 to make and has made it's money back already

many thanks will give it a go!

I don't see any way for the grease gun to evacuate air from the system; i.e., create a vacuum in the line.

You're right, it doesn't create a vaccuum so won't be much good on a brand new / empty system.

But for topping up it works brilliantly.




Having thought about it, surely if you can hold the purge valve open somehow (which I think is just a schrader valve near the front displacer) then surely you could use the grease gun to pump fluid through until no more air comes out, then close the valve and keep pumping.

There are a couple of hydro pumps for sale on Ebay, but be warned, they are not cheap.

The hydro pump as used by BMC dealers was the best thing, but you can make something equivalent in performance without spending a lot of money. While I was trying to do this
hydro hose repair I found an old Cars and Car Conversions article where they used a manifold vacuum tank to evacuate and recharge the hydro, a copy of the article is on the MK1 Performance Conversions site. So they didn't even need a vacuum pump, they just used engine manifold vacuum. I copied the idea, modded a vacuum tank with a hose and Schrader no-loss fill valve, but I did not try to use the engine vacuum as my vacuum source like CCC did. Instead I borrowed a generic vacuum pump and plumbed that to my tank.

I own a genuine BMC Hydro pump. The vacume side of it I only use when I need to replace a ball & cup in the front of a Mini/Austin 1800 etc. When Vacume is applied it retracts the bag enough to get in there easly. I have found over the years the best way to remove all the air from the fluid is to pump the system up to the required pressure, release it all, and repeat, again & again. Each time you release the pressure it seems to remove the air trapped in the fluid untill on the last release there is no more air. Then just pump up to the req pressure. This method works very well. And when releasing pressure from a hydro system, if your going to stick somthing in the valve wear safty glasses, 450 psi fluid can make you blind very quickly.

Jono_h, I've never seen a Mini with a purge valve near the front displacers.

850man, if you have a BMC pump, why not use the vacuum side of the pump instead of multiple fill/purges? On a Mini, at least, it works well.

The modified grease gun might work OK for a minor top up, but for systems way down or having been evaculated (like the original post on this thread), one ends up with too much air in the system and an ineffective hydrolastic system. Sort of like brakes with air in the lines.

i can only say that i have used my own little "grease gun" pump to refill, from empty, my own car's hydro system about 3 or 4 times and have had no trouble at all

cheleker wrote:Jono_h, I've never seen a Mini with a purge valve near the front displacers.

Cheleker,

Where does the vaccuum pump connect to? I thought you connected the filling bit to the valves on the rear subframe, and the vaccuum pump to a valve at the highest point (which I assumed to be the front displacers)

Thanks,

Jon

Big_Al
I wonder how much better the car would ride by drawing the proper vacuum on the system first to get all the air out. Brake systems will work with air in them, too. Just not as well.

Jon,
All the work is done via the rear subframe valves. That's why the factory pumps had the vacuum set up built into them. If the hydro systems were like brake systems with openings at both ends, the process would be different and the "grease gun" set up would work for evacuated systems as well as for top ups.