11 replies to this topic

[3VILC]

I know its not really the done thing, but I have seen lots of posts filling the bags themselves with air under water to check for leaks as with a tyre, but would it do any harm to fill the whole system with compressed air just to see if it holds pressure (for static testing purposes only, not to be driven on)? I don't have access to a hydrolastic pump but dont want to go buying a heap of stuff for it to find out the system is knackered anyway and loses pressure in a week.

 

Thanks, Clive

[Spider]

Could be dangerous to do with air, given how compressible it is.

I'd suggest using straight water if you want to test the system for leaks etc, if it's all good, then drain, put it under vacuum and then fill with the correct fluid. The vacuum would remove a fair bit of the water, but not all of it, the small amount that remained would mix in with the Hydro Fluid as it's around 50% water.

[3VILC]

No problem, I shall have to continue searching for a pump to borrow or parts to make one. Figured now harm in asking since I already have a compressor. Just trying to minimize the outlay on parts that will be otherwise useless if I end up converting to a dry system.
Does anybody know, roughly, how often a good system would need to be pumped up? As far as I know, the car has been sitting for the best part of 22 years so could just be normal pressure loss? Drivers side has a little height, passenger side is sitting on the bumpstops

[cal844]

There are new pumps available on Facebook but I don't know how good they are

[mini13]

this might be handy.

 

http://www.elevenhun....com/pumpup.php

as mentioned the pressure is high, not sure what minis were, but metro's were 300ish psi on the front, so your looking at 200psi +  you dont want a sudden gaseous escape at that pressure!!

[Ethel]

My first thought was air would behave entirely differently -  liquids aren't compressible, so the pressure comes from the rubber (or gas if it was hydrogas) at the top of the unit. Just pumping one full of compressed air would force the "piston" part of the displacer in the opposite direction to normal use and could cause a failure, rather than detect an existing one.

 

I've seen plans online for converting a grease gun in to hydro pump & some of the retail units I've seen look suspiciously like a clutch slave cylinder in a box with a plastic tank & valve or two.

[mab01uk]

From Mk1 Performance website: Make your own Hydrolastic Testing Adaptor:-

http://mk1-performan...tic_testing.pdf

 

IMPORTANT !
It has been pointed out that inflating a hydro unit to relativity high pressure using air is not without risk. The compressible nature of air makes the amount of stored energy in such a unit potentially dangerous.
A safer alternative would be to use water or hydro fluid to inflate the unit.
Anyone choosing to pressurise units using the method described in the article, do so at their own risk!

 

This thread may also be of interest:-

https://www.theminif...it-gold-plated/

Edited by mab01uk, 09 December 2020 - 01:58 PM.

[mab01uk]

From Mk1 Forum: This won't evacuate, it only pumps up. You can use it for "draining the system. Connect it up, turn the red knob & the fluid drains out. Turn the knob the other way & you can pump the system up.
If you don't have a vacuum facility just pump & drain a few times, this works nearly as well as vacuuming the fluid out.
These are the best value units currently available:-

https://www.ebay.co....HMAAOSwY3tbR4ap

 

[Spider]

I made my first Hydro Pump from a Clutch Master Cylinder, mounted in a frame, with a hand lever. It was slow and the Reservoir needed regular topping up, but it did the job. Later, I made a 'Vacuum Pump' using an old LPG Gas Cylinder that I fitted 2 pipes to, one juts went in near the top, the other, also coming in through the filler, went near the bottle. The one that went to the bottom was connected to the Hydro System, the one near the top, to the Inlet manifold of my trusty Mini Van. As the fluid came out, it would store in the Cylinder. I needed to keep a check on the Cylinder as I never wanted it filling right up ! I always started with it empty.

[3VILC]

Just as an update for anyone interested. I ended up making a pump out of an old bottle jack. The result, at least 1 displacer leaking where the hose connects. Looks like it will be a dry conversion and pass the good displacers on to someone in need.

[DomCr250]

I made my first Hydro Pump from a Clutch Master Cylinder, mounted in a frame, with a hand lever. It was slow and the Reservoir needed regular topping up, but it did the job. Later, I made a 'Vacuum Pump' using an old LPG Gas Cylinder that I fitted 2 pipes to, one juts went in near the top, the other, also coming in through the filler, went near the bottle. The one that went to the bottom was connected to the Hydro System, the one near the top, to the Inlet manifold of my trusty Mini Van. As the fluid came out, it would store in the Cylinder. I needed to keep a check on the Cylinder as I never wanted it filling right up ! I always started with it empty.

We did exactly the same in the 80's - it worked very well.  Only thing I remember struggling with was getting a Schrader valve fitment that had a barb long enough to take the plastic delivery tube.

 

We never worried about the actual system pressure, just pumped it up till the rear ride height matched the measurement in the factory manual!

 

I've got two full 5L  bottles of hydro fluid still sitting in the garage, my old 1275GT used to leak a decent amount so I just kept topping it up and these must have been left over.

[Spider]

 

I made my first Hydro Pump from a Clutch Master Cylinder, mounted in a frame, with a hand lever. It was slow and the Reservoir needed regular topping up, but it did the job. Later, I made a 'Vacuum Pump' using an old LPG Gas Cylinder that I fitted 2 pipes to, one juts went in near the top, the other, also coming in through the filler, went near the bottle. The one that went to the bottom was connected to the Hydro System, the one near the top, to the Inlet manifold of my trusty Mini Van. As the fluid came out, it would store in the Cylinder. I needed to keep a check on the Cylinder as I never wanted it filling right up ! I always started with it empty.

We did exactly the same in the 80's - it worked very well.  Only thing I remember struggling with was getting a Schrader valve fitment that had a barb long enough to take the plastic delivery tube.

 

We never worried about the actual system pressure, just pumped it up till the rear ride height matched the measurement in the factory manual!

 

I've got two full 5L  bottles of hydro fluid still sitting in the garage, my old 1275GT used to leak a decent amount so I just kept topping it up and these must have been left over.

 

 

I fitted a Y piece and used the same Check on the Valve, either side of the Y piece, I had small Ball Valves fitted. I did this mainly because while the Schrader Valve is great at holding pressures, they aren't so good at holding in a Vacuum, and that's what I always saw as a issue with the factory pumps, in that when going from Vacuum to Pressure, you had to swap hoses and in doing so, usually the system would suck some air back in after pulling a Vacuum on it that seemed counterintuitive. It's the Air in the System that causes them to rust from the inside out.