Hello again everyone, just wanted to post a recent bag cleaning I've done. Thanks to Matt (TheMiniMan), I have another chance to get my car on the road for the first time in 30 years… more excitedly, the first time for us to drive the car since acquiring it alittle over 8months ago.
Second hand bag:
First thing I like to do is pull the skirt dust boot off if its still on. There is no use in keeping these on if the bag is in storage… They hide rust and new boots are cheap. I use a small flat blade screw driver and filet the rubber away from the lower piston shaft. Some of these almost feel glued on.
Rusted tapered cylinder… bummer! But not to fear, I don't believe this is will hinder performance or safety. I could eventually, but hopefully by then I will be able to repair or replace them.
Inspect all over, here is some rust starting on the ferrule and inner cone neck:
Don't forget, the drain hole should be at the bottom on the rear bags!
Cleaning the inside of the bags, I made these two items from an old shock body and a 5/8"UNF bolt. Nice to have a lathe, but you could do this with just a drill and vice. Drill the center of the bolt with a small drill first, 3mm, then 8mm. Use a deburring tool in the drill on the threaded side to make an angle seat for the bag connection to seal against. On the other side, drill and tap a 1/4BSP. For the beaker, you can use some PVC tubing and a cap from any hardware supply. 50mm (2") tube should work, 200mm long, glue a cap on, drill and tap 1/4BSP and join it to the bolt. I used about 250ml (1 cup) of methylated spirits each pour.
When I cleaned my first batch of bags, I recycled the fluid. From the first pour, I would drain the cloudy liquid into a bigger bucket and wipe the sediment in the trash. Leaving it to sit for a while, you can start to see the water and other fluids separate from the spirits. Pour or better to siphon the cleaner fluid for re-use.
Flushing tools
Fill it up buttercup!
Grab piston and move it around… I like to push and pull up down and sideways to get as much of the spirits in and flushing around to help brake up the gunk.
Drain:
First drain close up:
First drain spirits starting to separate from gunk:
First drain sediment:
Forth drain:
Last flush, fluid much clearer with less sediment:
Now we inspect the inside of the tapered cylinder. It was obvious that there was rust from the edge, and looking deeper we see nice chunks of layered rust.
I glass bead blast the bodies, I start with a light blast to reveal any color markings to help identify previous bag types… This has a green band, which confirms makes this a later "normal" 21A1477/21A1804. This will probably be the softer type bag with larger bleed hole.
Green band:
Blasted bag:
Rusted inside of tapered cylinder:
Clean inside of tapered cylinder:
While being most careful to not damage the skirt, I've sanded down some of the thin rusted metal and die grind the sharp edges to a blunt edge. I like Galmet ionize rust converter, with an acid brush, try to get down in the side of the bladder and tapered cylinder.
Pushing piston/skirt with tool, or any 1/2" diameter (12.7mm) shaft, you can use a long M12 bolt if you don't have anything else.
Galmet
Whoops, I've popped piston out! First time this has happened, but I'm sure it won't be the last...
Pushing piston back in with an arbor press. Not much pressure was needed, standing on it probably would have worked.
Pressure testing bag setup. I'm using a weak dilute of coolant to water. Pulling fluid from this bottle and draining it back in.
Gauge pressure, 300psi holding for a couple hours… probably should have taken it to 400psi for shits and giggles, and safety. I'll do that when its in the car under "normal" factory conditions. I probably won't go to 450 as the factory suggests as this is not a new bag.
Finished bag. I taped up the rubber flex shaft and tried to cover most of the rubber as the solvents in paint degrades rubber much faster (like the window rubbers and seals that crack quickly after a quick/cheap tap and paint body job)
In the car tonight! Holding at 300psi on its own (too dark to take a pic, was doing it all by torch). Thanks again for the hustle Matt, happy to have our car on her own four shoes!
Cheers, d
