Suspension woes. Hard, crashy skittish ride.

[DylanGreene]

Hi everyone.
I'm looking for a little help with my MG F I've just been silly enough to buy.
When I bough the car the suspension was rock hard, but the ride height looked low. Now I'll be honest I made all of the mistakes, I bought the car without researching anything, I bought with my heart, and I didn't test drive for very long. After I bought it I looked around online for the symptoms, thought that the suspension would just need a pump up, so I took it to a local MG specialist, and they let all of the air out and re-inflated it. It made no difference, so we did it a couple of times to make sure, it was still rock hard.
Now here is the problem, my first thought was that it would need all new spheres all round to fix, my guess being that that they have lost nitrogen.
The MG garage think that it's like err a valve controller or something behind front wheel arches? I've been looking for the part they are referencing, but as yet I have no idea as to what it is. They have second hand parts to fit, and the cost of parts is reasonable, but as with these places, labour is at the top end of the garage market, It going to be about £5-600 to have these parts fitted.
I'm worried about shelling out, only to have to fit new spheres anyway, which would work out at another £600 of labour cost alone I would think.
Should I ask them to just replace all of the spheres, or trust their instincts and my lack of knowledge?
Any help would be appreciated, even with all of the problems the car has grown on me quite quickly.

[cath's mg]

Hi Dylan, welcome to the Register.
I am not by any means an expert but from what I have read there should be tell tale signs if the spheres are leaking, a Green residue on the spheres.
I am sure one of the Techie guys will be on soon to give you a better diagnosis.

Good Luck

Gary

[mgfsoldier]

No valve controller. the left pair are linked and the right pair are linked. Did the pump have a vacuum mode or did they just let the liquid out. When pumping what PSI did it get to on the pump? Was there no movement at all.

Changing a sphere isn't a particularly long or hard job only a couple of hours and second hand pods are around £100 a pair.

[DylanGreene]

Hi Dylan, welcome to the Register.
I am not by any means an expert but from what I have read there should be tell tale signs if the spheres are leaking, a Green residue on the spheres.
I am sure one of the Techie guys will be on soon to give you a better diagnosis.

Good Luck

Gary

Hi Gary, I cannot see any weeping or leaking around the spheres, they look a little crusty and old, but not leaking.

No valve controller. the left pair are linked and the right pair are linked. Did the pump have a vacuum mode or did they just let the liquid out. When pumping what PSI did it get to on the pump? Was there no movement at all.

Changing a sphere isn't a particularly long or hard job only a couple of hours and second hand pods are around £100 a pair.

No liquid, they let all of the air out and the car visibly dropped in ride height. Then they manually pumped it back up, I don't know how many psi too, but they did check the ride height against the wheel arch. But even at normal ride height, the suspension is rock solid, feels like riding on the bumpstops though it isn't. I didn't know that the liquid could be changed?

[robbie1003]

No liquid? The pump up requires the correct liquid after vac the system,there should be no air in it.

[DylanGreene]

No liquid? The pump up requires the correct liquid after vac the system,there should be no air in it.

Are we talking about the same thing? I'm sorry I'm very new at the mechanicals of this car. They had like a big box with a lever on it, pumped up the suspension to the correct ride height. When it didn't work first time around, they vented it all to the atmosphere, so I guessed that it was just air.

*edit* Thinking about it more, it must have been a fluid, and I wasn't paying enough attention, I got confused as the chap said that if not done correctly "air" could get caught in the system and mess up the ride. As for if it had a vac controller, they where able to I guess take fluid out, as they dropped it to the lowest ride height and then introduced it again.
I'm sorry if my description of this is rubbish.

[mgfsoldier]

The car is not riding on Air it should be pumped up with a hydrolastic fluid pump not Air. Find a garage that knows what they are doing with the equipment and it will probably pump fine. Find a garage from here
http://www.hydragas.co.uk/

[mgfsoldier]

Potentially all of the nitrogen has leaked out but I struggle to see it would have done all 4 pods. 1 or 2 I would believe but all 4 is unlikely.

[DylanGreene]

Potentially all of the nitrogen has leaked out but I struggle to see it would have done all 4 pods. 1 or 2 I would believe but all 4 is unlikely.

It is definitely rock hard on all four corners. Yet sitting currently at the correct ride height.

[diesel destroyer]

Is it possible the car has lowering pins? and said garage are trying to get it to standard height?

If you pump the spheres up to max they go solid

How about taking all four shockers off.. just to see if its any different then..

[DylanGreene]

Is it possible the car has lowering pins? and said garage are trying to get it to standard height?

If you pump the spheres up to max they go solid

How about taking all four shockers off.. just to see if its any different then..

Yeah, the garage did get it to standard height. How would I know if it has lowering pins on it?
When they let the fluid down, it was equally as hard as when it was at the correct height.

[Dell]

If you pump it up to 400psi it should be fairly close to the correct height whatever that may be ie about 10mm lower if it has lowering pins fitted at least that way you will know that the system is not over pressurised. Air in the system should not cause it to go solid it would tend to have the oposite effect & make it feel spongy.

[Rob Bell]

Dylan, firstly welcome to the forum!

Now, to suspension. The pump and lever you saw is pumping hydragas fluid, and it sounds as though the garage has done everything correctly.

If the car is at the correct height, the suspension should be supple not rock hard. If rock hard, there is something wrong.

One potential is that the hydragas units have become depleted of their nitrogen springing medium. The other is that someone has driven over speed pumps at speed and have ruptured the internal rubber membranes!!!

So the question is what is the ride height measured from wheel centre to the wheel arch lip for all four corners?

Hope you don't mind, I'll move this thread to technical

[DylanGreene]

Dylan, firstly welcome to the forum!

Now, to suspension. The pump and lever you saw is pumping hydragas fluid, and it sounds as though the garage has done everything correctly.

If the car is at the correct height, the suspension should be supple not rock hard. If rock hard, there is something wrong.

One potential is that the hydragas units have become depleted of their nitrogen springing medium. The other is that someone has driven over speed pumps at speed and have ruptured the internal rubber membranes!!!

So the question is what is the ride height measured from wheel centre to the wheel arch lip for all four corners?

Hope you don't mind, I'll move this thread to technical

Hi Rob, thanks for the welcome, you guys have been very kind! Sorry about posting in the wrong forum, and thank you for moving it to the correct place.
My ride height in mm is:
Front
O/S 344
N/S 350
Rear
O/S 332
N/S 352

That's measured (badly) with a tape measure to the edge of the arch, give or take 5 mil for my eyesight.

[Rob Bell]

No worries Dylan

Actually your suspension is still quite low. If the suspension is still standard, then the correct heights front and rear are 368 and 358mm +/- 10mm (@17C - there is a 0.4mm correction for every degree difference in temperature).

Knowing the pressure is actually quite useful: although you don't set ride height according to pressure, the nominal heights noted above equate to a line pressure of 400psi. The pump your garage used sounds like a Liquid Levers device, and should therefore have a pressure gauge, so the mechanics will know the pressure they pumped your car to. If the current ride height was attained with a pressure of 400psi, that means one of two things:
1. the suspension has been modified by someone in the past - either with lowering knuckles, or with cut down taper pistons.
2. the hydragas units have failed with nitrogen depletion +/- ruptured internal membrane

If pressure is not being maintained, and the height is dropping over a period of days, then a fluid membrane has failed, and one of the spheres need replacing.

Looking at the numbers you've provided, and not knowing the line pressure, I'd take a stab that the OSR hydragas unit has a fluid leak. Unfortunately it is a common problem with age, but replacement is easy enough.

Have a read through these pages, and you'll soon be up to speed on things Hydragas! http://mgf.ultimatemg.com/group2/suspen ... _index.htm

Good luck!