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MG MGF Technical - Riding Height

I was wondering if somebodey could help me with a question about the riding height of my mgf. I took the car to the dealer and asked if they could set the car at the proper height. When I went back to collect my car they told me that they couldn't get it at the proper height. The height now is as follows:
front 335mm
rear 342mm
It is possible for them to get the front a little higher, but in that case the back comes up way to high. Does anybody know what the problem could be.
P.S. The car went to the dealer because it suffered from a HGF, broken lambda sensor, broken connector behind steering wheel for the airbag and some other small items.

Looking forward to receive an answer about the problem with the ridng height.

G.J. Wiegman
Gert-Jan Wiegman

Hi Gert
>they told me that they couldn't get it

I'm afraid but this seams to be standard answer of several so called garages.
I suppose they do not know how the system works, which is unfortunately also a standard for modern car works.
I know about a german chap who got the complete system changed under warranty all around including the pipes, cause his dealer was not able to find the failure. ;-)

Anyway, having built my own pump and also changed hydragas units myself twice and at last researched the internals with a hacksaw (thats true)..
http://mg-f.purespace.de/cut_unit/index.htm

Possible failures. (My guesses)
- air in the system: depressure to -0,6bar and pump the fluid back to app 400psi (app 30bar)
- not right bumped at rear and front while the pump sequence.
- nitrogen sphere broken. Can be found by individual high-pressure test.
- Units internal valves corroded (fully open or blocked)
- rear knuckle bolts not right inserted to the Hydragas unit
- Hydragas unit slipped out of the assembly position

May be there are some more possible or I'm total wrong, sorry I can only guess.

335mm at the front is crap, if the car has not got lowering knuckles. The spring does not work in right manner at the related low pressur of only 20 bar!! Your tyres will wear at the inside and the suspension behavior gets aweful at higher speed.
I suggest to ask your dealer for a written permission that you will not get tyre wear and everything is OK with car ;-)

If possible the go back to that dealer and ask for a new try.
They should do exactly what the workshop manual states and check also the position of the individual hydragas units fixture and that the knuckle bolts come right into the hydragasunits aluminum pistons.

- release fluid and evacuate to -0.6 bar
- refill and pump careful until the car starts to lift. From this moment the front and rear should be strong bumped once or twice after each 20 to 50psi pressure increase. This equalizes the pressure and fluid amount in both units. Also the knuckle bolts get centered to the pistons.

Here some more links with pictures:
http://members.tripod.de/MGF/defects/blownhydra.html
http://members.tripod.de/MGF/defects/blownhydra2.html
http://mg-f.purespace.de/pump
http://members.tripod.de/MGF/hydragas.htm

etc. etc...
all to find at
http://www.mgf-net.de

Regards
Dieter
Dieter Koennecke

Hi Dieter,

I talked with the dealer and he admitted that it could be air in the system. The only problem is that this dealer only has the equipment to fill up the hydragas system. So in other words he can not depressurise the system. Maybe this is the problem!?
He said that he can put the riding height at the front at the proper height, but in that case the rear is to high. In one of the threads I have been reading that you only have to look at the front and that the height of the rear is not that important. I don't know if this is true, but I need to get it right, because next Saturday I have an appointment for new tyres. Goodyear Eagle F1 195/50 front and 205/50 rear I hope this will be a good choice.
Okay thanks already Dieter for the info.
Gert-Jan Wiegman

GErt,

this must be a really poor dealer. The hydragas pump with suction function must be a standard tool at MG-approved dealers.
(Says also the Workshop-Manual)

Look asap for another one and leave out the tyre purchase until the hight is stable at 368 at the front.
http://members.tripod.de/MGF/ebhoe.htm
from http://members.tripod.de/MGF/technik.htm
(under construction)

Look at the table with temperature corrections.

The reason why you often read about 'look for the front hight only' is that the rear hight follows the front hight in relation of pressure increase or decrease as standard.

Standard is also a hight difference of app 5 mm between front and rear. But this is the opposite at your MGF. Reason can only be any additional weight of 50kg or hat in the front bonnet ;-) or any failure as I tried to analyse above.

BTW. you can try to check yourself wether the system contends air.
Park the car in a silent area. Surface should be flat. Don't pull the handbrake. Open the bonnet and the boot. With a strong grip to any strong part at the front, lift the car upwards and dive/press it downwards and hear for noises from inside the bonnet at the area where the hydragasunit is located. If you 'hear the fluid flow' with a slight 'sputtering' noise, then airbubbles are in the system. The same can be tried at the rear, but best place to hear it is at the front.

Also you can check yourself at the wishbones all around wether the hydragas-pistons are in place to the insered knuckles. No gap should be there between aluminum piston-pipe an the washer just above the dust protect rubber of the knuckle.

Lift the car with a jack and remove the wheels (sequence one after the other).
Look at this picture. The position of the hydragas pistons position should look this way:
http://members.tripod.de/MGF/mods/compare.jpg
(front drawn)

BTW another one can be the reason for the opposit hight difference... It can be that at the front is no washer between piston and knuckle installed. About 1mm washer at that lever position results in about 4mm right hight change.

HTH
Dieter
PS. Sorry for my non-polite sounding description. It should'nd, but you know the germans ... :o)
Dieter Koennecke

Gert-Jan,

Hi, Sorry I did not call you as I was on Holiday and have been sick since I got back, I have your number on my hotmail. I would at least park my F on some flat ground and measure it myself. This is because I have no trust of Rover dealers anymore.

To check it yourself see the instructions in the FAQ. If you were talking to a Rover dealer he will have a proper hydragas pump which will allow you to depressurise the whole system. If this is a Rover dealer he aint very good.

Try the Rover dealer in Zoetermeer, he aint MG but he is ok IMO. Get him to depressurise the system and pump it up again. One other possibility is that the garage is parking it on a hill after pumping it up or is measuring it with the handbrake on.

To get the correct height. Get a rover dealer to pump it up to over correct. Find a flat bit of level ground. Take the hanbrake off and bounce the front an back a bit. Leave the car to settle for two hours to allow the temperature to even out. Roll the car forward around a meter to avoid any tension in the suspension. Now open the Hydragas (tyre valve) caps and let some of the fluid out using a rag to mop up the escaping fluid. It only takes a little fluid to lower the car. Lower each side 5mm at a time until you get to the correct height. Remember that wherever you set it it will no doubt drop a little more as everything evens out. I set mine to around 360mm and it now sits at around 355mm.

I will send you an email...

Tony Smith

Hi Dieter and Tony,

I went to a different deale. He depressurised the whole system and after that he pumped it back up again. The mystery why the car was always a little to high at the rear was dicovered by him within 10 minutes. I bought the car secondhand and the other ownwer has put some "extra" washer/spacers at the rear. Why I don't know, but according the dealer those extra washers sould not be there. To take them out the dealer has to take apart the rear suspension. For the time being we found a compromise. The riding height at the front is now okay and the back is 8 mm to high, but still within the limits. If the car stays like this I will buy new tyres next saturday.
Gert-Jan Wiegman

Gert Jan, can I get your car details for the MGF HGF hall of shame? Dankuwel!
Dirk

Gert,
guess your hint on someone who added or removed washers wil enlighten the case.

This washers are not equal thick at every MGF. Some have none some have 1.5 mm washers, others I saw have 4mm washers.

The important relation for calculating the right washer depth is the wishbone length and the point where the ball joint (knuckle) meets the wisohbone.
This lever relation is 1 to 4 !
If you add 1mm then the ride hight increases by 4mm under same hydragas pressure.

If nothing else can be found, then I would work out the problem as follows.
- Remove all loads which are not Standard (tools, spare fuel tank etc) from the boot and the bonnet to get as near as possible to the MGFs specified weight.
- Fill the fuel tank

The measure the ride hights as Tony and I already stated in a very sensible sequence. Make more the one measures and calculate the average.

You should then be able to verify the front to rear difference at each side and this can be used to select the right washer hights.
Base is any rear side then with a washer of 1.5 mm.

If the calculation results in 3 or 4 or 5 or 6mm washers then let them add to the front.

You wrote actual is
>front 335mm
>rear 342mm

If this is 'true' then you need 7+5=13mm
13mm/4= 3mm washer(s) added at the front and it should be OK then.

Best Regards
Dieter
Dieter Koennecke

This sounds to me like previous dealers using extra washers to bodge the suspension when they could not solve a problem. Now all you have to do is get used to living with hydragas, it's given Dieter hours of fun :-)
Tony Smith

I need to make some minor adjustments to my suspension as currently one side is slightly higher than the other, but I'm not sure how much fluid to remove at a time. Could someone tell me approximately how much fluid would need to come out to lower one side by, say, 5mm.

Thanks

Richard.
Richard

Richard,
The answer is very little.The fluid is under considerable pressure and it is very easy to let too much out.Place an old cloth over the valve and just press it for about half a second.Let it settle, and chack again.MUCH better to this a few times than to let too much out.
By the way,if you do let too much out and are near Potters Bar I have a pump.
Good luck,
Tim
H10 VVC
Tim Sanders

>and just press it for about half a second. Let it settle, and chack again. MUCH better to do this a few times than to let too much out.

Hi,
agree with Tim's comment. Doing it in several steps is vital in my opinion. Release a little and wait some hours or go for some miles ride and do the next step one day later.

A little is IMO not more then 5 ccm (5cl). Can be about 5 to 8 psi pressure, but not approved this data.

HTH
Dieter

Dieter

Dieter, isn't 5 ccm 5 ml ?
(5 cl is 50 ccm, am I right ?)
Fabrice

1litre = 1000 CC =1000 ml = 100cl
Ian

Tim, you say you have a pump, is this the official Hydragas pump as sold to garages? If so how much does it cost, where can I get one and what is the part number. I have asked this question several times on this BBS and have never had an answer.
Tony Smith

Tony,
The pump is made more for amateur use than for garages but is quite adequate for the task.
Look at www.minispares.com you will find the details and even a picture of the pump.
From memory mine cost just under £300 complete with a gallon ( sorry 5 litres) of fluid.
Regards,
Tim
H10 VVC
Tim Sanders

>The pump is made more for amateur use than for garages

Tim,
beeing a bit sarcastic (as ever).
The professional pump in the garages is of no use if anones work with it :)
I like what you do. I make it also with my much more 'amateur' looking 'self-made-pump' and helped already some chaps here with a pumpjob.
> quite adequate
Of ccourse it is. Special the connector to the MGF-hydra system.
BTW I still have got only a poor connector. Tim, is the connector valve availiable as spare part ?

Tony
the pump that Tim got looks OK IMO, but 300GBP is a lot of money. :( I still cannot beleave that no MINI garage in Holland has'nt any.
Here is a picture that I took from 'minispares' some month ago. I just surfed the site, but did'nt find it again.
http://members.surfline2000.com/mgf-net/pump/tooll01.jpg

Regards
Dieter
Dieter Koennecke

Dieter,
Very sorry to hear of your accident.Glad you are OK, that is the main thing.
I will phone Minispares and ask if the valve is available as a spare part. If not I have the pump makers name at home and will enquire from them.
Will let you know here if I get any joy.
Regards,
Tim
H10 VVC
Tim Sanders

This thread was discussed between 01/10/2000 and 16/10/2000

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