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MG MGF Technical - Hydragas leak: Front left unit

A few days after pumping up my F hydra system I noticed a drop of fluid on the garage floor, apparently leaking from the front left unit. At present there are more than just a few drops and the car has "settled" too low, standing at 31cm from the wheel arch.
I have not had the time to examine carefully the unit yet but I am afraid that the front left unit might have gone kaput. I must say the hydragas units are all original -except one rear changed a few years ago- and the car is a 1997 MGF 1.8 mpi with only 40 k on the clock.
And now a question to the experts. A few month ago received two spare units from Andy Jennings -one rear, one front-. How difficult is to replace the front left unit (which in my car is the driver side unit)?
Many thanks. Mike

JM Vega-P.

Hi Mike,

great to see you are still online with your MGF :)

A broken front unit appears not so often. Did you check the interconnections pipe and the filler valve below the black cover ?

Anyway, the change is a straight forward job, but you need the vacuum function at your hydragas pump.
http://www.mgfcar.de/pump/Mvc_901f.jpg > yours if I recall right.

The air must be removed after the change. Otherwise the replaced unit will get damaged soon from inner corrosion.
You can reduce trapped air if you pre-fill the units and pipes with fluid while you put all together.

Any options to get hands on a pump with vacuum ?
Dieter

Hi Dieter,

Great to have news from you again!

No, I have not had the time to check the connections yet, but thought about. However, how often do they leak?
And no, I donīt have any chance to get a pump with the vacuum option. Just the "yellow thing" in the photo that you kindly included in your site. Nevertheless that pump -assembled according to your instructions- has been performing quite well, again and again, not failing once. The fact is that at present I have to overinflate the units -38,5cm from wheels arch- as they tend to "settle" 2,0 or 2,5cm in the following 48 hours after the procedure. Cold weather -and it is getting very cold around here- also very much afect the height. May be that there is no gas left in them, and only hydra?

Best wishes
Mike
JM Vega-P.

...Dieter....?

Do any of you know if Dieter is still around?
JM Vega-P.

Yup, I'm here :)
How sure are you that there is no air bubbles in the system ?
I think there is....

However, no gas (nitrogen) in the top sphere may be, of course.
But you also need the vacuum function for a final fix.

Anyway. a simple test for a broken upper sphere is as follows.

Disconnect the unit from the other one. So it is independent. Get the pump direct connected to the single unit and spot on the pressure gauge while pumping in the fluid. You will need a special adapter to link the unit thread to the Schrader female connector from the pump, or make someting else to fit the single unit to a pressure pump with gauge.

Pump continous and see the pressure raise until you read about 320 psi. Now the pressure increase per pump stroke should stay for a while at about 320 psi until ist starts raising again. (max 425 psi is enough)
In this case the unit is fine.
You pumped fluid into the lower sphere until you reached the upper diaphragma with high pressure nitrogen. (Starting at about 320psi)

It is not fine in case the pressure increase has no break at about 320 psi, but you can see the pressure increase constantly until it suddenly raises against a kind of block.
It means you have had not any back-pressure from the nitrogen gas sphere, cause it wasn't there any more.

This process is written to the workshop manual somewhere.

Hope it makes sense.

Regards
Dieter
Dieter

Very useful indeed, as always I must say. I will check the unit.
Grateful Dieter.

Mike
JM Vega-P.

This thread was discussed between 14/05/2011 and 02/06/2011

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