Topic

Hello I great and wise collective brain, i seek enlightenment.

I have (and love) a 1998 F with just over the 100K on the clock. Bought a year ago having been garaged for 18 months. Very low suspension when bought that was re-gassed (fluid) and ride and handling were fine. The car went into my local MG specialist (who are honest enough to admit they don't really understand the F suspension) for a fair amount of work for one reason and another last month. Garage fitted 2 new lower suspension arms, 2 rear top ball joints 4 nylon lower shock bushes and pumped her up to 368mm.
The car rode so badly that my better half was reluctant to get in it (my chest hurts...and no she wasn't laughing). Having done some basic forum snorkling I thought it worth bleeding a little fluid to see if that would help. What came out was foam not fluid. Took the car back to the MG boys who drained it completely while scratching heads about the foam. They have said they think they may have used the wrong fluid (one hydrogas pump used for one thing only...how does it get the wrong fluid?) Anyway pumped up again and running at 368mm the car was long legged and bouncy and just not as comfortable as when I bought her. Ride height has dropped a little since I collected last week.

Theories

1/ Lowering knuckles have been fitted by a previous owner and the ride height is therefore set too high ( I have no idea what PSI they pumper her up to )
2/ Sphere failure

I have read various strings and many people mention "changing spheres" but not which ones. The car sits level, it bounces once when pressed on each corner but clearly something is wrong and I have no clear idea how to be sure if its front, rear or all four spheres that need replacement.

I have seen a lot of info on the "schrader valve weld in to re gas" option but is anybody with the skills and the tools now doing this with second hand spheres to create "reconditioned" units? I can get 2nd hand from Martin Smith but again no idea how to know if the units are any good.

Is there such a think as a simple step by step diagnostic process that can be followed in order to be sure of the fault and where it lies?

Any help, hints, photos and biscuits gratefully received

Plenty of the F owners will give you good advice on this topic. I'll just say 'welcome'.

Hi and welcome.

Sounds like they pumped air in rather than fluid.

Whereabouts are you.

James

James

All the foaming fluid was drained out, the garage has the standard hand pump but not the vacuum option. Once drained they threw all the fluid in the pump reservoir away, cleaned it out, and restocked with new fluid. It was then re pressurised and on draining 5/10ml from each side it is now clean and green fluid not foam. The ride is however still harsh and bouncy.
I live in Somerset. I contacted the nearest garage listed on the Hydrogas register (John Spencer at Hatch Bauchampt near Taunton) and although he has a pump with vacuum the vacuum element isn't working very well. I was hoping to be able to have the system properly pumped out rather than just drained under its own pressure and then re pressurised from scratch just to be sure all the air and crud have been removed but cannot locate anybody nearby with e vacuum system.
It still suggests reduced nitrogen but as I said before I have no idea which sphere and how to test to be sure.

Thanks for the response so far

In all probability all four spheres are suffering varying degrees of nitrogen depletion.

That seems to be the most obvious, and expensive answer. I have been quoted £45 a corner for second hand spheres locally which seems to be about par. If somebody is "reconditioning" spheres with the Schrader adaptation then perhaps that cost can be mitigated slightly with the donation of the removed spheres.
I assume that the replacement suspension components have stiffened up everything else and highlighted the nitrogen depletion problem. I also wondered if the nylon bushes fitted should be taken out and replaced with rubber. I know nylon lasts longer but its much firmer and could this make all the difference?
Coil spring conversion just doesn't make financial sense given the cars value

The coil spring conversion available in the UK, is by all accounts, useless anyway!
There is a different conversion kit sold here in Oz, this is said to very good, but expensive, and you loose the excellent ride characteristics of the Hydragas set up.

I've done autopsies on knackered spheres all either had nowhere near the required 240psi of nitrogen gas left in them or none at all.
I've even found supposedly working spheres with severe gas depletion.

The ones that have ruptured diaphragms contained no gas at all (yes a ruptured upper diaphragm would cause the loss of gas, but this isn't the case where the lower diaphragm is the one that's ruptured)
I suspect when the gas gets depleted more fluid is pumped into the system in an effort to maintain ride height until, with no nitrogen gas to act as a spring, something has to give and the diaphragm ruptures.

I know that spheres have been regassed for other Hydragas equipped models, but I've not heard of anyone successfully regassing MGF spheres yet. I suspect that this is because the spheres used in the MGF are smaller and as such vulnerable to the effects of heat soak from welding.
As time and $$$ allow I've been doing some experimentation with regassing spheres, trying to come up with a method of controlling the heat soak from brazing or Tig welding in fittings to take schreader valves.
Yes, I know Mig welding would enable more control of the effects of heat soak, but if I'm offering reconditioned spheres they need to be properly engineered, as these are a pressure vessel, I prefer the idea of a good weld strength for durability and safety.
Remember the upper diaphragm is close to the area that is being welded and as such may be affected by heat soak.
I've built a water bath in which I weld the fitting to the sphere, it still gets hotter than I like, so I'm looking to circulate the water.