Air in brakes, brakes failing and ABS?

[Krystal18]

Hello,

I'm posting on here because I've had a few issues with my 2008 Mitsubishi Lancer ES (base mode + extra airbags; no other mods). It's done 112,000km.

For the past 8-9 months I've been driving and suddenly the brakes don't respond unless I push it to the floor (usually I just tap my brakes and they respond). This continued as I drove and I called my local repair shop as they'd only just done a service a few weeks before (it's outside of warranty so I no longer go to Mitsubishi for serving).

They bled the brakes, found nothing wrong and all was good - for about another 2-3 months. Then the same thing happened. Again, they bled the brakes, inspected and all was good.

It happened again a few months later and I had lost control of the car and almost had a serious accident. I took it in and insisted they have a more thorough look at it. Again, they bled the brakes, did more of the same tests and couldn't find a problem. I took it in again that week and they had suggested replacing the master cylinder. They weren't confident but I agreed to have it replaced - about $800 including labour.

Again, even after the master cylinder was replaced, the brakes have failed again. The repair shop has gotten advice from 2 brake specialists (who suggested the master cylinder and were stumped that didn't fix the issue) and have now gotten advice from Mitsubishi who've suggested replacing the ABS module - for $3,000 plus labor! However, the repair shop isn't confident it'll fix the problem because the air in the brakes shouldn't have anything to do with the ABS, they said.

Someone else has suggested replacing the booster, but that's also going to cost $1,000.

Obviously, I'm hesitant to replace such expensive car parts because the car is really only worth about $5,000 according to Red Book. An expensive experiment if neither option works!

I know next to nothing about cars. The repair shop has been awesome for years and are very honest. I trust their advice and they've been extremely helpful. I'm hoping someone here can help me!

My questions are:

A) has anyone else had a similar problem in their Lancer?
B) if so, did replacing the ABS module or the booster work?

Thank you!

[aspir3]

There are many things that could be the problem. Some members on here have had to replace their ABS unit as it throws up a CEL for being faulty. It is very costly to replace.

The best advice I can give you is never trust the advice received on the internet. Stick with your mechanic as he is trained/qualified and has viewed and inspected the car.

Brakes are important so take them seriously.

[himynameisdaniel]

brakes are a closed system.

there should be no leaks. and no air in it. Water will seep in over time but that is only because the fluid is designed to absorb moisture from air. this is fixed by flushing the fluid every so often.

The brake system in our car requires a glycol based brake fluid and not silicone.
using silicone based fluids will damage practically everything.

try the following.

+check for leaks.
+check for vacuum leaks (the entire system of assisted braking relies on there being a vacuum generated when the engine is on.)
+take it somewhere else to be re-bled
+using two people have one person depress the brake pedal fully while the other watches to see how far the brake fluid travels down. if it vanishes completely and then comes back up slowly after the pedal is already returned you probably have air in the master cylinder and that needs to be bench bled or failed booster.
+while the engine is off your brake pedal takes about 2-4 pumps and should be incredibly firm afterwards and almost impossible to press down.
+inspect caliper pistons and ensure that they can move and seals are not damaged.
+there should be no play with the braking system and the workshop will need to 100% tell you why they think replacing the ABS unit or booster will resolve the issue. if they don't know then take it somewhere else.
did they do any troubleshooting on the ABS unit or the booster?
ripping and replacing parts is not a smart troubleshooting method.

honestly I'm pretty sure you can run the entire system with the ABS\ASC fuses pulled, its just those components wont work. The brake lines just go through the ABS unit regardless of its status of operation.

take it somewhere else first. and get them to ensure that is generating a vacuum.
Also do a search on here for lancer workshop manual.
There is a wealth of information on how to troubleshoot our braking system and the design and specifications as well as acceptable thresholds for service.

[Lancer1993]

This sounds like a scary problem since it's not there all the time, so hard to diagnose and fix.

With the ABS some here have had issues and got a rebuild replacement which is a lot cheaper, not sure on the details but it could be worth a check if you decided to do that as it will cost less than the dealer replacement part.

[Krystal18]

Thank you to everyone who replied I didn't expect such quick responses! Thanks!

The place where I take my car has been excellent. Keeping in contact and following up way beyond their duties.

They are wary of changing any parts because they can't guarantee new parts will fix the problem. They're definitely not trying to rip me off. They're just not convinced without some evidence (I.e. Confirmation from someone else they replaced the ABS module and it fixed the problem).

I guess my options are to replace the parts or to buy a new car neither option is cheap. Of course I want to exhaust all avenues first before spending a lot of money.

Thanks @himynameisdaniel for the thorough instructions. I'll ask my dad or my brother to take a look and do what you've suggested and see what happens.

Thanks @aspir3 - definitely agree that the mechanic is best because he's there and has looked at the car - a bit like a doctor! The mechanics from 4 different shops haven't had experience with this issue (one has, but the issue has never been successfully resolved) so they're not confident in replacing so many parts nor such expensive parts! That's why I was hoping someone here may know of this issue and how they resolved it successfully.

Thanks @richyo for the recall information. My brother suggested the booster might be problematic (not the mechanic, but my brother knows his way around cars for sure). I never got a recall notice and my dad has the same car and neither did he. I wonder if it didn't affect the 2008 model, although it seems from the recall notice it may have? Might be worth some follow up with Mitsubishi myself. Thanks!

Thanks @Lancer1993 - I'll have a search for a rebuilt ABS. Haven't had any luck finding a second hand one just yet, but will definitely continue to look. I was advised any second hand part must be from a 2011 model or later because of known issues.

Thank you all again!

[Krystal18]

@aspir3

What's a CEL?

Thanks!

[himynameisdaniel]

CEL = check engine light.

[Krystal18]

Thanks @mynameisdanirl!

I'll learn all these things eventually

[toc]

Are you saying that the physical pedal touches the floor when you push it when the fault is present?

An easy check is the vacuum lines, if you have a vacuum leak it can affect braking.
When the issue presents itself and you take it to them, is the issue still present at that time, or is it a one time only and it comes good?

[Krystal18]

Thanks @toc

The pedal almost touches the floor before getting any response and therefore the braking time is much longer. The problem occurs suddenly without warning and then remains until the brakes are bled. With the exception of last time, when after about 20km it resolved itself, the problem is there when I've taken it into the mechanic. Bleeding the brakes fixes the problem but only for 2-3 months. They can't work out how the air is getting in nor can they actually get air in there.

Does that sound like the vacuum?

[burfadel]

I believe a vacuum leak would only make the braking more difficult, not such that the brake pedal goes to the floor. The only likely place for a vacuum leak would be inside the brake booster unit where the vacuum line attaches, as the vaccum line itself is pretty heavy duty (pretty much like this on all cars).

What happens when you pump the brake with the engine off? Like if you went now, opened the drivers door and pumped it?

[Krystal18]

Thanks @burfadel and @mynaneisdaniel:

I went and pumped the brake 3-4 times as suggested with the engine off. The brake pedal does become stiffer (but with force I could still press it down to a certain degree).

I'm assuming that's healthy? Maybe it's normal because the brakes have been bled and it's all okay for now?

I will have someone check the fluid levels toothed I compress the brake pedal when I get the chance and let you know.

Thanks!

[DORA_ANNE]

Hi Krystal , Might be a idea to go to Mitsubishi & ask them about the recall for the brake booster as I have a 2008 VR & Mitsubishi replaced mine & I didn't get a letter from them " Probably because being a second owner "

I have always had my Lancer serviced at my local Mitsubishi & they told me the booster had to be replaced under recall .

[Lancer1993]

IMHO when you take you car in to the dealer for service or any work they should run the VIN to check on any outstanding recalls, better still if they did this at the time you book it in then the parts needed could be ordered so you wouldn't have to make a 2nd visit if things needed replacing. They don't even need your VIN as they can use the rego number to get the VIN.