Performing a brake fluid flush on your BMW E30 is one of the easier jobs you can do to restore performance back to a critical system of the car.
The condition of our vehicle’s brake fluid directly affects how the brake pedal feels. Any air in the brake lines will make the pedal go soft and reduce braking ability. Water is also a detriment to the brake system. If any water is absorbed into the brake fluid, the fluid’s boiling point will lower. If the fluid boils, air enters into the system. Older cars, like the BMW E30, can have rubber components of the brake system that have not been changed since the car was new. Perished rubber is a common way air and water can get into the system, preventing the brakes from working correctly. To best negate any effects from old brake fluid, you should flush out the old with new fluid when the brakes are serviced.
Performing a brake fluid flush at home is something everyone can learn. The job will require some practice but only requires minimal tools. Having a friend to help during this process will help if you don’t have access to a power bleeder. While this DIY applies specifically to the BMW E30, the general method applies to nearly every vehicle on the road.
BMW E30 Models Applicable:
Symptoms of a when to perform a BMW E30 brake fluid flush:
- Soft pedal feel
- Reduced braking distance
- Brake pedal stays at the floor when depressed
- Dark-colored fluid in the reservoir
As discussed at the top, the condition of your vehicle’s brake fluid is vital in a properly functioning brake system. The brake fluid is what transfers the pressure put on the brake pedal to the brake calipers. If air enters the brake lines, it will compress under pressure giving little to no pedal feel as well as actual braking performance.
High-performance driving also plays a part in the condition of the fluid. If the brakes get too hot, the fluid can boil, leading to the degradation of the fluid and tiny air bubbles in the lines. These effects will only become worse over time if they are left untreated. If you plan on doing any high-performance driving, it’s a smart idea to change your brake fluid before and after your event. This doesn’t generally apply to autocross, as the brakes aren’t worked to that high of a temperature.
How long will it take to perform a BMW E30 brake fluid flush?
Set aside thirty minutes to do a full flush. Getting all of the bubbles out of the system can be a pain, so test the brakes after the first bleed to confirm that the pedal is as firm as it should be.
A pump or powered brake bleeding tool is a worthy investment if you foresee more driveway brake fluid changes. These bleeders will suck the air and old fluid out of the lines making the bleed, a one-person job.
How much does it cost to perform a BMW E30 brake fluid flush?
The price to flush the fluid on our E30 will cost about $12, the price for four 500ml bottles of fluid. If you want the pressure bleeder to assist in the job, that’ll cost just under $60.
A brake fluid flush isn’t a difficult job, and the charge for having this done by an automotive shop reflects this. It shouldn’t cost more than $100 to have this job done by a professional.
Tools required to perform a BMW E30 brake fluid flush:
Parts required to perform a BMW E30 brake fluid flush:
Steps required to perform a BMW E30 brake fluid flush:
Step 1: Jack up the car and remove the wheel
Starting on the rear of the passenger’s side, jack up the corner of the car. The rear jack points are located just in front of the rear wheels, where there are two hex head bolts. Support the vehicle on a jack stand if you have one.
Next, remove the lug bolts from the wheel with the 17mm socket and breaker bar, and set the wheel aside.
Step 2: Set up the pressure bleeder
Open up three of the brake fluid bottles and pour them into the pressure bleeder. Next, open the hood and locate the brake fluid reservoir. It sits on the driver’s side of the engine bay at the back, just to the left of the strut tower.
Remove the cap and screw on the pressure bleeder. Have a rag handy to clean up any spilled brake fluid. Brake fluid is extremely corrosive and will destroy paint with ease.
Once the pressure bleeder cap is attached to the brake fluid reservoir, the system can be pressurized. Manually pressurize the bleeder by using the handle on top of it and working it like a bicycle pump. Pump the bleeder until it reaches around 15 psi. Once pressurized, the pressure shouldn’t be slowly decreasing. If it does, there is a leak in the brake system.
Step 3: Flush the system
With everything finished under the hood, go back to the brake caliper. The caliper bleed screw protrudes from the top of the caliper on the backside. First, pop off the protective cover and move the sensor wire out of the way.
Put the boxed end of our 7mm wrench around the bleed screw, now that it is exposed. Next, connect the bleed bottle hose to the bleed screw. Once the hose is secure, open the bleed screw by turning it to the left.
Watch the fluid as it fills the bottle. Close the bleed screw when you see the change from the old, dark fluid coming out to the new, light-colored stuff. When new fluid starts to come out, that corner of the car is finished. Remove the hose and put the protective bleed screw cover back on. Next, put the wheel on and set that corner of the car back down.
Step 4: Repeat the previous step for the other three wheels
The process in step 3, covers each brake caliper. Periodically check the pressure bleeder during the bleed process. Keep steady pressure on the fluid, and never run the bleeder dry. Fill and pressurize the system as necessary.
When torquing the wheels, set the wrench to 108.5Nm, or 80 lb-ft.
How to bleed a BMW E30 clutch slave cylinder:
Bonus Step 1: Bleed the clutch slave cylinder
E30s that use a manual transmission use the brake fluid and its reservoir for their clutch fluid. To completely drain out the old brake fluid, you can bleed this too.
Looking up at the clutch slave cylinder from under the car, you’ll see a bleed screw on the bottom of the cylinder. Slip-on the box end of the 7mm wrench and connect the bleed bottle hose, just as you did with the brake calipers. Follow all of the same steps as the brake bleed after this.
Pairing this job with a brake pad change would make a great beginner DIY for anyone you might know who is looking to start working on their car. If you’re interested in more DIYs for your BMW, you can visit bmw.fcpeuro.com and subscribe to our YouTube channel.
Car and motorsports-obsessed writer/editor for FCP Euro's DIY Blog. Constantly dreaming of competing behind the wheel or searching for another project. Owner of a turbo Subaru Forester and a ratty Porsche 914, neither of which are running.