The brakes are some of the most essential parts of your car. And as such, must be handled with every sense of importance.
If your brakes are getting mushy, you might have air in your brake line and you need to bleed the air out.
Sometimes this procedure goes smoothly but on some other occasions, you might notice there’s no brake fluid coming out when bleeding.
But not to worry. In this post, I’ll be taking you through the possible reasons why brake fluid would refuse to come out when you bleed your brake.
Before we jump right into it, let me explain why you even need to bleed your brakes in the first place.
Table of contents
Why Would You Want To Bleed Your Brakes?
Let’s say you’re installing brand-new brake calipers on your car because the old ones are going bad – they’re leaking, and you don’t want to flush the old brake fluid into the brand-new calipers. You’d need to flush out the whole system with a new brake fluid first.
Beyond that, brake fluid should be flushed every 2 to 3 years because it’s hygroscopic – meaning that it likes to absorb water.
The problem with water in the brake fluid is that water has a really low boiling point compared to brake fluid. The boiling point of brake fluid is around 400 degrees Fahrenheit while the water boils at around 212 degrees Fahrenheit. So it’s not very high. And the brakes get hot. They could easily exceed 200 degrees Fahrenheit.
So if that happens and you have water in your brake fluid, the water will boil and evaporate. This would create a void when you press on the brake. That void is compressible, so it’ll feel like you don’t have any brakes, which is bad. And in reality, you won’t have any brakes.
How To Bleed Your Brakes
To bleed your brakes, you need the following tools:
- An open-ended wrench
- Brake fluid (check your owner’s manual to see what brake fluid your car uses)
- A small bottle
- A hose that fits over the bleeder valve
Another thing that’s optional but really helpful is a turkey baster because the first thing you’re going to do is to remove as much brake fluid as you can from the master cylinder.
You want to make sure you clean your master cylinder with a paper towel before you open up the cap. This is very important in order to avoid having any contaminants getting in there.
With that cleaned off, open it up and set the cap aside. Now use the turkey baster to suck out as much fluid as you can and put it right into the small bottle.
The reason why you want to do this first is that when you’re flushing your brakes, the brake fluid will be coming out from the reservoir. You want to be pulling new clean fluid through the brake lines instead of the old dirty fluid.
If you spill any brake fluid in the process, you should clean it up immediately. Brake fluid is really caustic. It’ll eat through paint and cause corrosion on metal. You really don’t want brake fluid touching anything.
Please note, while sucking out the dirty old brake fluid from the master cylinder, ensure you don’t go too low. You don’t want to get in air through the master cylinder.
Once you’ve sucked out a good amount of old fluid with a little bit left in the master cylinder to prevent air from getting in, pour in your new brake fluid.
You can overfill the master cylinder with the new brake fluid because when you bleed the brakes, you’re going to lose a lot of fluid as it bleeds out of each brake.
The good thing about emptying the master cylinder first is that now you have some fluid that you can use to prevent air bubbles from getting into the container while you bleed.
Put the tube into the bottle, screw tightly, and make sure the tube goes all the way down to the bottom. So now, any air bubbles that come out will get forced into the air. Any sucking back will be sucking back brake fluid. It’s old brake fluid but it’s going to get pushed out anyway so it’s not a big deal.
When you’re bleeding your brakes, it’s always best to follow the rule that you’re supposed to do the farthest wheel from the master cylinder first, and then, go in order – so the second farthest wheel, 3rd farthest, and 4th farthest.
So in this case, it should be – the passenger side rear, driver’s side rear, passenger side front, and driver’s side front.
To bleed drum brakes at the rear using this two-person method, move the wrench counter-clockwise to open the bleeder valve. Once you open it a bit with the tube attached, you’d need to ask your buddy to press the brakes. At this point, you should notice brake fluid coming out through the attached tube. After some seconds, close it and ask them to release the brake.
Make sure you check the master cylinder every 10 times you press the brake because you don’t want to run dry.
After a while, you’ll see through the tube that the brake fluid coming out is clean. At this point, you move on to the next wheel.
Read: Service Brake Assist
No Brake Fluid Coming Out When Bleeding? Here’s A Fix
This is usually caused by your car’s proportionate valve. The proportionate valve works in such a way that the master cylinder brings pressure into the two ports on both sides of the valve and then it comes out the top to all four wheels.
For a vehicle without ABS system (which was what we worked on), the proportionate valve will look like a split diagonal system.
If you run into a problem where brake fluid is refusing to come out while you’re bleeding, you don’t need to hit your head on the wall. Just go to the proportionate valve, have a buddy step on the brake for you, and see if you’ve got pressure coming out of all the ports on the valve.
If you don’t have pressure coming to any port going to whatever wheel you’re having a bleeding problem with, then you’ve found the problem. Proportionate valve.
In addition to what I’ve just explained which is the failure of the proportionate valve, there are other failures you need to watch out for in proportionate valves, particularly if all the fluid was gone from the system.
Older General Motor vehicles in particular have a valve inside the proportionate valve that has a special clip you need to put on to it in order for fluid to flow through it. So that may be why it’s not bleeding out.
Also, in today’s modern vehicles, sometimes, you may have to use a scan tool to bleed your brakes.
So, instead of just using a buddy and their foot, you can just plug in a scan tool and bleed it out that way.
Read: Popping Noise When Braking
Conclusion
As I mentioned, the no brake fluid problem while bleeding is caused by your proportionate valve not allowing enough pressure to pass through any of its ports to a wheel.
I hope this information was helpful to you and saved you a headache trying to figure out the reason for no brake fluid coming out when bleeding.
