After I did the brakes on the '88, at least one observant rennlister noted that the brake fluid should also be
flushed since it had not been flushed since 2004. Manual recommends every 2
years. Since I've never flushed the brake fluid before, I decided to buy a
power bleeder and give it a try.
Since there's bound to be one other Noob like myself out there, I took a few pics of the procedure I went through.
First, I would highly recommend getting the power bleeder (costs about $40). If you flush the brake fluid yourself every 2 years, it's well worth it. Get the 45mm cap version - it fit perfectly on the brake fluid reservoir with no leaks. Here's the power bleeder - it comes with a pressure gauge, fittings, hose, reservoir cap and gasket and extra hose connections. Everything you need - hose fittings were even pre-fitted.
Second, you'll need some clear plastic tubing for the flushing from the calipers to the drain bottle/container. I just went to Home Depot and got some clear tubing that was 5/16" outside diameter and 3/16" inside diameter. Fits nice and nug on the caliper bleeder nipples.
Third, make sure you have enough new brake fluid. The manual says the brake system holds about 1 liter of fluid. You will need that much plus more in order to flush the system (until you see your new fluid coming through the hose). Also, try to get a fluid that is a different color than your current fluid. Since my fluid was a dark gold color and the new synthetic DOT 4 fluid I got was clear, it worked great for determining when the old fluid was out of the line/system. I bought 4 12oz bottles for a total of 48 oz.
Next, I made a receiving container for the used brake fluid. I used a 64oz clear Gatorade bottle. Drill a 5/16" hole in the top of the cap so you can insert the plastic tubing through the lid.
Then, measure a length of plastic tubing. About 33 inches is what I used. This will reach from the caliper nipple all the way down into the bottom of the bottle (with the wheels a few inches off the ground).
Place the plastic tubing through the cap to the bottom of the container
You will need to connect the hoses that came with the power bleeder. One hose with the male end is attached to the cap that goes to the reservoir. The other hose goes to the power bleeder tank. I used teflon tape on the threads of the brass fitting.
Then tighten the connection....
If you haven't done so already, loosen the lug nuts on the wheels, raise the car and place it safely on jack stands and remove the wheels. Locate the caliper nipples (2 on each caliper for the S4, 1 on each caliper for the OB brakes) and clean the area around the nipple, remove the nipple cap.
Now you can connect the power bleeder cap to the brake fluid reservoir on the car. Hand tighten so it's snug - no tools required. I also recommend placing a towel (or baby diaper in this case) under and around the reservoir to catch any spills.
You will need to pressure test the connections BEFORE you put the new fluid into the power bleeder tank. Make sure the lid is secured on the power bleeder tank and pump the top handle.....
....pressurize to about 10psi. Watch the pressure gauge to see if it will hold pressure. I monitored it for about 3 minutes with no drop in pressure. After that, I was good to go. You need to de-pressurize the tank. To relieve the pressure, you slowly unscrew the lid on the power bleeder tank.
Next, set up the receiving bottle and tube. I started at the wheel farthest away from the brake fluid reservoir (passenger's side rear - outside nipple). After doing both inner and outer nipples on the passenger side rear, I did the driver's side rear wheel, followed by the passenger side front wheel and lastly, the driver's side front wheel last. You'll want to do the driver's side front last - explained later.
Now you can fill the power bleeder tank with the new fluid. I bought some synthetic, DOT 4 fluid -> 4-12 oz bottles.
Go ahead and pour all 4 bottles in the tank and put the lid on snuggly.
Then pressurize the tank by pumping the handle. At first, use about 12psi. If you need more pressure, you can pump it up more. I later found 15psi was about right.
Next, go to the caliper bleeder nipple and using an 11mm wrench, slowly loosen the bleeder fitting.
Continue loosening the bleeder fitting until you see fluid flow
through the tubing. I loosened the fitting just enough to allow a steady flow.
You can also monitor the fluid coming through in the container to gauge how much has been depleted from the power bleeder tank.
When you see the color of the new fluid (clear in this case) coming through, you can tighten the bleeder fitting back down. It took a minute or two for the old fluid to flush clear at the back wheel. All the remaining times at the other wheels were less since they were closer to the reservoir and had less old fluid to flush.
I used a rag placed around the nipple to catch any fluid that might spill when disconnecting the hose from the nipple. After placing the rag, remove the hose from the nipple and hold it up so the remaining fluid will drain into the bottle.
Snap the protective cap back on the nipple.
Check the pressure in the power bleeder tank frequently - at least once between bleeder fittings. Being a Noob, I was checking it about every 20-30 seconds! If the pressure gets down below 10psi, I would pump it back up to 15psi. Also, watch the level of fluid in the power bleeder tank. As long as you don't flush too much new fluid through the system, you should have plenty to finish out the procedure at the last wheel.
After you've repeated the process on all the wheels, you should end up at the last wheel - the driver's side front. When you've bled the last fitting. you're ready to complete the procedure. You're bleeder tank of new fluid should be pretty low. You will need to "push" air into the car's brake fluid reservoir if it is past the max fill line. This will allow you to get the right level in the reservoir before disconnecting the power bleeder. If the level of fluid in the reservoir is already at MAX, you can simply close off the last bleed fitting at the caliper, disconnect the hose at the caliper fitting and slowly open the lid on the power bleeder to relieve the pressure.
Otherwise, follow this procedure: while the caliper is still bleeding fluid, tilt the power bleeder tank so that the intake tube is no longer submerged in fluid. You will immediately see air flowing through the tube from the tank to the reservoir.
Carefully watch the level of fluid in the reservoir and when the fluid reaches the MAX fill line, tighten the bleeder fitting at the caliper to stop the flow.
Next, you can relieve the pressure in the power bleeder tank by loosening the lid slowly.
Then disconnect the power bleeder cap from the reservoir....
....and place your original reservoir cap back in place.
Here's the old fluid fill bottle when I was finished. You can see the old fluid that was displaced - I used nearly all 48oz of the new fluid
Now you can try out the brakes. I had my wife start the car and work the brake pedal while I checked for leaks before putting the tires back on. Everything checked out great and the brake pedal felt just right. Put the tires back on, lower the car, snug the lugs and take it for a test drive!
This was a painless procedure but I believe only due to the power bleeder. I've bled brakes before by simply working the pedal and monitoring the fluid reservoir when I added new brakes. That was tedious compared to the power bleeder. So, for my first complete brake fluid flush, I was very happy with the process. It took a total of about 3 hours because I was reading EVERYTHING and I had to manufacture the drain container. With this setup, I think next time it would go faster - maybe an hour or hour and a half.