This article is to walk you through refreshing the oil in your hydraulic shocks on the MGB. I have done the front ones for the photos and descriptions but I am sure you can take the information and apply it to the rears also. I found significant deposits of zinc from the years of use that I rinsed out with the flushing of oil as Peter Caldwell directed. Hopefully this will cushion your drive a bit!
Refreshing your MGB hydraulic shocks.
Written by: Michelle Pierce
Material contribution: Peter Caldwell
In order to complete this process, you will need to remove the shocks from the car. In my steps I am refreshing the front shocks, the shocks were removed while disassembling the front suspension for a rebuild.
- Oil drain pan
- Phillips screwdriver
- 7/8” socket and driver
- 20w Motorcycle/ATV oil (or whatever you choose to use)
- small funnel
Step 1: Find a clean worktop area or set up a spare piece of plywood on a couple of sawhorses if you don’t wish to cover your workspace permanently in oil. For my purposes I used a spare piece of plywood tucked into some extra garbage bags (to preserve the wood) and placed on top of two sawhorses.
Step 2: Remove the 8 screws (front, 6 rear) and carefully remove the gasket.
You'll want to save the gasket. Since you will be reusing it during the reassembly process.
Step 2: Remove the valve assembly, using a 7/8" socket. You will have the threaded plug, an inner valve assembly/spring/pin thing, a larger spring, and likely a shim washer or 3.
Here is a photo of the valve / piston assembly courtesy of Peter Caldwell:
Step 3: Hold over your oil drain pan, invert and drain everything.
Rinse in fresh oil. Use engine oil, it is cheaper than shock oil (barely now a days). You should NOT use any type of solvent for rinsing the chamber. Most likely you will notice significant deposits of zinc along the shock base near the gasket. I rinsed mine until the majority of the zinc had passed through.
Step 4: Next you are going to refill the shock chamber using (in order of preference) 20W motorcycle/ATV fork oil, hydraulic ram oil (for snowplows, etc.) (or from farm stores AWE68 oil), hydraulic jack oil, straight 20W engine oil. For this step you should not need a funnel but for the topping off later on you will want one handy.
With the shock gasket surface uppermost, add oil to just below the gasket surface. To hold the gasket in place prior to reinstalling, use a little bit of RTV on the gasket, and install the lid with the screws. DO NOT MOVE THE ARMS.
Step 5: Now, invert the shock so that the valve opening is uppermost. You'll want to practice how you'll hold the shock beforehand, as it is at an odd angle. Add oil into the hole moving the arms slowly through their full range always keeping the opening full.
You'll note bubbles, when they finally disappear, you are done.
Step 6: Insert the valve assembly, big spring first with shim(s) between it and the little valve body. Don’t worry if some oil overflows from the shock when you insert the valve, it is normal and is only removing what needs to go. Tighten valve assembly.
Step 7: Invert the shock to its normal in-use position, and you're done. Wipe everything off. Use your brake cleaner. Dry and paint.