Oops, brake fluid reservoir ran dry due to a leak, pedal now goes to the floor.

[BobandWeave]

So I ran my brake fluid reservoir dry and I'm guessing I introduced air into the brake lines because now the pedal goes to the floor and there is no more braking. (Fortunately, this was discovered in the driveway.)

Could there be another reason why the pedal goes to the floor? (The reservoir is indeed empty.)

I've never experienced a brake fluid leak before. I did not notice any stains on the driveway indicating a fluid leak of any kind, which threw me off the scent of a brake fluid leak in the first place (I thought it was just the pads wearing down).

I was planning to flush the brake fluid soon anyways (at winter tire swap-over time next week), which was why I ignored the brake warning light (indicating a low fluid condition). Unfortunately, the leak ran faster than I thought.

Anyhow, is there anything special I have to do now, now the lines are perhaps full of air?

 

[ChrisMU]

Likely a rear wheel cylinder or leakage from a rusty brake line. Find/fix the leak and bleed the system. Note: brake fluid damages paint and tires. Are both parts of the reservoir empty (assuming this is a newer than 60’s vehicle)?

 

[BobandWeave]

Likely a rear wheel cylinder or leakage from a rusty brake line. Find/fix the leak and bleed the system. Note: brake fluid damages paint and tires. Are both parts of the reservoir empty (assuming this is a newer than 60’s vehicle)?

Thanks, I will look for the leak first then (though I thought I'd put in some fluid first so that it can leak some more).

Re: both parts of the reservoir, I don't see more than 1 part to the reservoir (it's a Gen 5 (2011-2020) Dodge Caravan)).

 

[dishdude]

Usually if you run the reservoir dry you need to bench bleed the master cylinder.

 

[Accent Abuser]

So I ran my brake fluid reservoir dry and I'm guessing I introduced air into the brake lines because now the pedal goes to the floor and there is no more braking. (Fortunately, this was discovered in the driveway.)

Could there be another reason why the pedal goes to the floor? (The reservoir is indeed empty.)

I've never experienced a brake fluid leak before. I did not notice any stains on the driveway indicating a fluid leak of any kind, which threw me off the scent of a brake fluid leak in the first place (I thought it was just the pads wearing down).

I was planning to flush the brake fluid soon anyways (at winter tire swap-over time next week), which was why I ignored the brake warning light (indicating a low fluid condition). Unfortunately, the leak ran faster than I thought.

Anyhow, is there anything special I have to do now, now the lines are perhaps full of air?

If you have abs it may need to be bled using a scan tool, only way to find out is to fix the leak, fill it back up, bleed it out and see if the abs light comes on.

 

[michaelluscher]

(it's a Gen 5 (2011-2020) Dodge Caravan)).

Take note of this
May not be your problem, but still might be a problem

 

[BobandWeave]

Usually if you run the reservoir dry you need to bench bleed the master cylinder.

Thanks for the note. Is this mandatory or is just a time saver?

 

[BobandWeave]

Take note of this
May not be your problem, but still might be a problem

Thanks. I'll look closely. When we changed to winter tires, the brake lines that were visible during the tire changing process looked fine. That video shows that there might be rust hiding further along the line.

 

[kschachn]

Thanks. I'll look closely. When we changed to winter tires, the brake lines that were visible during the tire changing process looked fine. That video shows that there might be rust hiding further along the line.

A couple of years ago I ended up replacing all the brake and fuel lines on my old Accord, as you mention they looked fine in the wheel well areas and even a bit further down under the car. But a brake line up and above the fuel tank popped open during heavy braking and it was badly corroded for a long ways that wasn't visible. There was also significant corrosion on the five lines inside the plastic protection cage that ran the length of the car. Of course my vehicle was a bit older but it's worth a close inspection.

 

[BobandWeave]

Update: I found the leak. It was coming from the piston of driver's side rear brake caliper. A lot of fluid leaked out there. There was indeed a stain on the driveway but it was under the car just inside the rear tire so it was hard to notice (though admittedly, I didn't know to look there).

I'm going to get the car towed to my mechanic who I've asked to replace both rear calipers with better ones. The one that leaked is from a pair of low-end aftermarket calipers. He was probably thinking he was doing me a favor by getting me cheaper parts last time.

Having said that, the reason the cheap calipers were installed in the first place was because something seized in the original factory caliper causing that one wheel's brakes to overheat. So OEM calipers can have problems too.

It's interesting but my guy says that parts of any kind are hard to get right now. I may have to accept what's available.

 

[eljefino]

Thanks for the note. Is this mandatory or is just a time saver?

It depends, but if your service manual (or the box the part comes in) tells you to do it, you need to do it.

Reason is, many cars have firewalls that tilt back from vertical. So the forward end of the MC is higher and can get airlocked with a bubble if it's not tapped there for a line. Of course if there is a line, there's a decent chance you can shoot that bubble all the way down your hard lines and out your wheel bleeders.