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MG MGF Technical - Suspension hight

Hi, I have a Mk1 MGF and the suspension is low all around the car. I have measured it and it is about 50mm below the specified ride hight. I guess the hydragas suspension needs pumping up. Is it worth investing in one of the pumps on the market and are they straight forward to use. Plus is it normal for it to need pumping up occasionally or is the drop in hight indicative of a problem that needs addressing. I guess the fluid must be leaking out some where but then the drop is even all around so why have both sides leaked by the same amount? All thoughts and advice most welcome and appreciated.
DW Staniforth

Hi DW Yes the gas needs topping up about every two years in my experience. If you don't you will start to get Tyre wear and handling issues. I don't think it is worth getting a pump, but again others may feel it is worth the investment. My local garage charge £60 for a full removal and to fill with new gas, as any air must be completely removed. On another thread one chap paid £20 for his top up, so you can get them cheaper.
aj harris

The Hydragas units are not topped up with gas but with a liquid, which is a mixture of antifreeze and Metholated Spirits.

Branko

Mine's booked in for a top up on Saturday at an ex MG Rover dealer. They've kept hold of the pump - £15 per side.

If you were to buy your own pump, the juice is almost a 50/50 split of Alcohol & Distilled Water with just a little something nasty added to stop you from drinking it! Not sure how cheap Supermarket Vodka n' Tap Water would fair though....
Graham Elleray

The fluid and the pump is exactly the same as used in the Metro for many many years. Any local garage will probably have a pump to do this job. The fluid is available from ALL motor factors and is simply called hydrolastic fluid, generally in gallon containers and green in colour.

The only difficulty anyone may have is to find the top up valves. It took me an hour to find them when I got my MGF. I have my own pump that I have had for 20 years and found the top up valves hiding behind a plastic cover under the bonnet at the front of the car.
Robert (Bob) Midget Turbo

Just got mine back from the 'pump up'. Had it pumped to 400PSI and it's levelled out at 360mm - guess the cold has had an effect.

Didn't expect the car to look so different, the 16" wheels now look tiny especially with 215/40's wrapped around them.

May have to look at having the lowering knuckles fitted as the gap between the wheel arch and tyre is just crazy - looks like one of the Utilities Land Rovers you see in the fields!!!

Lovely ride though!
Graham Elleray

Hi thanks for all the advice. I have now booked it in at a local garage for it to be pumped up next Saturday. How will the garage avoid introducing air in the fluid, are the bleed arrangements? I'm still curious about why it drops in height. I imagine the fluid must have leaked out but where from? And can we all expect to need increasingly frequent pump ups as the years go by due to the leakage rate increasing with time?

Dave
DW Staniforth

Hopefully the garage will have a full-monty Hydragas pump that has a vacuum mode as well as the re-fill pump mode, as official MGR procedure is to evacuate the system completely & then re-fill, as that guarantees no air is present.

The drop isn't necessarily due to fluid having leaked out, the nitrogen gas pocket in each sphere can begin to leak with age. Ambient temperature plays a part too, the ride height difference between summer & winter is noticeable.
bandit

I note Bandits comment, that the gas might be leaking. However if the gas is leaking each time it is pumped up the gas volume will get smaller. Eventually there would be no gas left. Surely this will affect the suspension response eventually. This is because the ride height will be correct but the amount of gas will be less than required to provide the normal spring action. Could it be that the bottom rubber diaphragm stretches over time needing extra fluid to be added. So therefore they need pumping up even though they haven't lost any gas or fluid?
DW Staniforth

It's possible the diaphragm could stretch a little, which would enlarge the fluid chamber and result in a drop in ride height, but the added volume would be very small I think, judging by the pictures Dieter has of a sphere post-mortem. Being rubber, the diapragm will harden with age and microscopic cracks will eventually develop and allow fluid to seep out, likewise with the membrane between the fluid & gas chambers. The net result is that each top-up only half restores the balance, and yes eventually when all the gas has escaped the suspension will be kinda firm...

I believe the Citroen system suffers the same issue, and originally they had a valve in the nitrogen chamber allowing it to be re-filled when required. Not particularly DIY-able, but in theory the same could be done to give an ageing sphere a new lease of life - I recall someone looking into it, perhaps Dieter (it usually is!)
bandit

Hi Again,

Quick word of warning!

After driving for a couple of days since the 'pump up', I started to hear a knocking sound coming from the front of the car. Had a closer look today and the front anti roll bar links have sheared on both sides!

Have a look here....

http://www.mgf.ultimatemg.com/group2/suspension/ARB_bush_replacement.htm

...mine are exactly the same.

I'd gone from a ride height of 300mm up to the factory standard - not sure if the increase was the cause but it seems very coincidental.
Graham Elleray

The coincidental element is probably less about the change in ride height and more about what went on in the process. The body tilt that will occur as the first side is evacuated or re-filled would be extreme, and is likely to have stressed the ARB drop links beyond usual working range. The drop links do get brittle, so much so I now regard them as a consumable item, so for what consolation it might be they'd have broken at some point in the not too distant future just in daily pothole duty.

I'll be putting some Trophy knuckles & pins in the Classifieds shortly, along with some other spare bits.
bandit

OK Graham and Bandit thanks for the advice. I'll try to look at mine tomorrow. I do sometimes hear odd noises from the front so it could be that mine have gone too. So if the bushes and/or drop links need replacing is it better to use uprated (eg Trophy) parts or are the standard parts acceptable.
DW Staniforth

Hi all, I have just returned from the garage who pumped it up. The pressure went to over 600 psi, the gauge didn't read any higher than that! The height is restored to the correct setting and the ride quality is much better. They charged £25. Details of the garage-

rmcservicestation.co.uk

DW Staniforth

600psi??!!?? Their pump gauge must be faulty, the usual figure for standard ride height is 400psi.

AFAIK the ARB drop links are no different for Trophy models, nor are the front suspension bushes, although one of the front wishbone bushes is inserted in a different orientation on the Trophy. If you are going to re-bush anything, I'd recommend polyeurethane, e.g. Superflex or Powerflex, and if a 4 wheel alignment check in the past has found the front wheel camber to be off, Superflex will shortly be offering camber-correcting wishbone bushes - the days of an MGF eating front tyres may soon be behind us - hurrah!
bandit

600! Surely not, I think the Hydragas unit limit is 500 - or maybe that's just the max 'safe limit'. Agree with bandit the pressure gauge may be a bit dodgy on the pump....

I'm loving having the suspension set-up as it should be. Much more relaxing to drive, def' worth the aesthetic trade off IMO...

BTW cost me £85 to have the links replaced today. Could have been a lot cheaper if I'd have had the time to replace them myself - the parts only came to £35 inc vat. Also had them change the x2 front bushes on the ARB whilst they were under there...
Graham Elleray

This thread was discussed between 10/11/2009 and 21/11/2009

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