Periodically, you will find yourself pumping up MGF suspension systems to get the correct ride height. There are explanations and “how tos” but this is my experience documented to assist others. It’s relatively straight forward. I was apprehensive about it but received great help and advice.
Pump Required #
To be able to do the pumping up MGF suspension task, you need a pump. This topic has already been covered separately. So, please review the MGF Suspension Pump knowledge base article.
Hydragas Fluid #
In the USA/Canada this is not a simple thing to obtain or order. Fortunately, for those of us in North America, Mark Jones has figured out a “home brew” recipe that very closely matches the consistency of the official hydragas fluid. Mark’s home brew recipe is as follows:
- 45% denatured alcohol
- 45% water
- 10 % antifreeze concentrate/glycol
So, how do you get this ready and mixed? #
My approach was to use a (US) gallon jug, do some calculations and mark up the jug. A US Gallon is is 3.74 liters. So, 45% is 1.7 liters. So I poured into my jug 1.7 liters of water and made several marks. I then added an additional 1.7 liters and marked this second level on the jug as 90%. Finally I added another 170 ml of water to get me to 100% and marked the jug again.
Where do you get these items? Well the denatured alcohol is readily available from boating stores (as Mark had advised). This alcohol is used as fuel for some stoves on boats. I was able to find a gallon fairly easily at a local West Marine store. The antifreeze concentrate should be readily available at your favorite auto supply store. Mark recommended Prestone and that’s what I got. Lastly, I decided to use distilled water and this should also be readily available at grocery or other stores.
You can pour in the distilled water up to the first 1.7 liter / 45% mark. Follow this with the denatured alcohol up to the second 1.7 liter or 90% mark. Lastly add the neat antifreeze/glycol to the top mark for your 100% level mark. Shake and mix well.
To store this, I checked into safe containers for denatured alcohol. From that research, containers made of HDPE or marked with a number 2 recycle symbol are OK. My gallon milk jugs are HDPE and I noticed that my spare antifreeze containers were as well. So, I am using 2 old antifreeze containers to store the remainder of my hydragas home brew fluid.
Suspension Height – Workshop Manual #
So, what is the correct ride height for an MGF with hydragas suspension. Well, consulting the workshop manual we get a value of 368mm +/- 10mm on the front wheels and 363mm +/- 10mm
Adjustments for Air Temperature #
Although not mentioned in the workshop manual, I found several references to these measurements being based on an air temperature of 17C which is approx 63F. If the temperature is below this it is noted that you subtract 0.6mm for each 1C that the air temperature is below 17C. When the temperature is above 17C/63F you add 0.6mm to the values.
The Measuring Points #
As the workshop manual notes, you make this measurement from the bottom edge (underside) of the wheel arch to the center of the wheel. Use an appropriate measure. If you don’t have a tape measure in mm, do a conversion using an online tool. The height affects the handling and ride of the car, so is important. So get the right value for whatever measuring tool/tape you are using. As a starter, 368mm is approximately 14.5 inches. Alternatively you could do a calculation to measure from the ground to the underside of the fender.
Pumping Up Process #
Having done the process, its nowhere near as scary as it might seem. I was able to get clarifications from Mark on the functioning of the pump I have which helped enormously, and prompted this article. Additionally I watched several videos. This one from Rimmer Bros I found very useful. They have a different pump with only one valve.
Preparation & Force Required #
You may be surprised at how much force on the pump will be required. I was. You will want to have the pump on a very sturdy surface. This is why I extended the hose on my pump. I wanted to have the pump on the floor.
Remove air from the pump hose by pumping some fluid. Just put the end of the hose/schrader valve into the fluid containment area. Then pump until fluid is coming through.
I put about 1 gallon (US) of the hydragas fluid into the pumps tank/tray. This is sufficient for a pump up of both sides. I was using the provided plastic tube that extends the pickup point for the fluid from the tray/tank.
Connection To Car #
Make sure the schrader valve coupler is open. On my setup this means turning the top anti-clockwise (counter-clockwise). Do a visual check to make sure the pin is fully withdrawn and not protruding into the fitting.
The suspension schrader valves are located behind the black plastic cover, so remove this in advance. The plastic covers on the schrader valves are like the dust caps on tire valve stems. Unscrew one and put it somewhere safe and that you will remember where you put it! Now you can start to thread the pump coupler/schrader valve to the car.
The coupler and schrader valve must be absolutely aligned. You do not/should not need a wrench to attach this. If the coupler on the pump won’t screw on by hand, reposition and start over. You may need to apply a little pressure to the top of the coupler while screwing the nut fitting to get the threads started. Once you get the threading started keep tightening by hand. When the coupler is fully in place, a final snug down on the wrench is all that should be required.
As an aside, this is similar to brake pipes. If you can’t get the fittings threaded by hand, something is wrong. You do not want to cross thread this. Walk away and come back if necessary, but the attachment should only be done by hand until that last snug up. Watch the Rimmer Bros video if you haven’t already.
The right side of the car (Driver’s side on RHD car) I found easier to attach. There’s more room to get the alignment right. On the left side (Passenger side on RHD car) this was more tricky. I tried various positions before getting one that worked as shown in the picture.
Pump Valves & Schrader Valves #
With the pump I have, close valve number 2 and have valve number 1 open. You can then close the coupler on the end of the pump’s hose to make the connection to the suspension system. You should hear a little “fizz” sound as the final twist on the coupler opens the car’s schrader valve. Check for any leaks. If any, you may need to snug the coupler up a little more with a wrench. But don’t go crazy.
Once the connection to the car is OK you should also see pressure shown on the pump’s gauge. My car was sitting at about 335mm height and I had approximately 325-350 PSI showing on my pump gauge. From the Rimmer Bros video the target pressure is about 450 PSI but the ride height is more important. You can use the pressure gauge on the pump as a guide, in between making measurements.
Use the pump handle to add fluid/pressure to the suspension system. As mentioned earlier I was surprised about the effort required to move the pump handle. Especially at 400 PSI and above. By making frequent measurements, and having a rest, you should not find you have too much height/pressure.
At the correct ride height you should undo the top of the pump coupler fitting to allow the schrader valve on the car to close. You can then release pressure in the hose by opening valve number 2. Follow this with opening valve number 1 slowly and all pressure should be released. Check the pump pressure gauge. Now you remove the pump coupler from the car’s schrader valve. Some fluid will leak out so be ready to wipe this up.
Pump Pressure Readings #
In case helpful, here are the pressure readings on my pump gauge. One is as I got started and the other shows the pressure once I achieved the ride height I wanted.
Repeat the process for the other side of the car. Don’t forget to get any air out of the pump hose before making the connection to the 2nd schrader valve on the car.
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