My daughter drives a 2006 Mitsubishi Eclipse. About 6 months ago, she noticed that occassionally when driving over a bump in the road her brakes lose pressure. The pedal goes nearly to the floor and the car is harder to stop. After a few days/weeks, the brakes return to normal. I was skeptical at first, but drove the car after one such incident and confirmed the lack of pressure. However, a Mitsubishi dealership couldn’t find anything wrong with the brakes while a specialty brake shop wanted to replace the master cylinder. Any suggestions?
If the pedal gets really soft and goes to the floor then this is a loss of hydraulic pressure. That will be from a leak, whether internal to the master cylinder or external someplace. There is also some possibility of a some substantial degradation of the flexible brake lines at the wheels - but I’ve never heard of that producing a pedal to the floor.
I can’t tell you why this is related to going over bumps in the road.
Is it safe to assume that the brake fluid level has been checked? That the brake fluid has been changed recently? That the brake system has been bled?
Was the brake specialty shop a corporate chain operation or a locally owned, independent shop? There is generally much more expertise and experience in the latter kind of place. Were either of these shops able to reproduce the symptoms?
Is this truly a sinking pedal? Or is it a pedal that gets kind of stiff and you have to push really, really hard to get any braking power out of it? Are both of you familiar with what it feels like when the ABS system kicks in? If not, is the weird pedal feel accompanied by any kind of noises (buzzing, groaning, grinding) or any vibration feel in the pedal?
Thanks for the insights. The brake fluid level has been fine and doesn’t seem to be leaking. The brake shop was one of the chain stores and I was skeptical of the quick (and expensive) diagnosis. The brake fluid was changed and bled at that time and I was hoping that it solved the problem, but it just happened again this week.
The pedal does seem soft when this is happening–it goes almost to the floor. My daughter says the brakes ‘whine’ when it’s doing this, but I haven’t noticed that aspect of it.
I’m going to make the WAG that there is a speed sensor problem, especially so if the speed sensors are integrated into the wheel bearings/hubs. The bearing/sensor isn’t so bad right now, but a bad bump will send things out of whack and the ABS system will kick in. ABS activation feels really weird if you’re not used to it.
Thanks! I’m going to check that out–I appreciate your thoughts.
I have a 08 Eclipse with the same issue master and booster have been replaced and still have the issue. did you find a sensor problem?
I think the shop is probably right, it needs a new master cylinder. They go bad in 5-8 years usually, and now is about the right time for an 06. The other place I’d check is the brake vaccuum booster if it has one. Sometimes they can develop an air leak. A shop could test it for you with their hand held vacuum gadget.
Offhand, it sounds like a failing master cylinder. Since another poster on this thread has the same complaint I took a look at ALLDATA and found there are Recalls out for this problem.
One Recall is SR-05-003 for the master cylinder.
The other Recall is SR-05-002 for the brake booster.
Both Recalls were issued in 2005 so apparently there was a problem with them from the get-go.
If these Recalls have never been performed previously then head to the closest Mitsubishi dealer and get it resolved free of charge; both parts and labor. Hope that helps.
Im a former mechanic that owns a 2006 eclipse with 60,00 miles on it, and just recently I hit a pot hole with the front right tire and my brakes did the same thing- went to the floor. When I got in the car to return home from work 8 hours later they were back to normal. A few weeks later my ABS kicked in when braking in the snow and my brakes did the same thing except they will not return to normal.( No warning lights on ) If I pump them one more time they feel good, on the first push they almost go to the floor. They act like they have air in the system. I bled them twice with no change.Going to try changing all the fluid to see if there is air trapped somewhere.If that doesn`t work I think there is something wrong with the ABS actuater/manifold . I done tons of brake jobs and have never seen anything like this! ( I hate ABS ). I Will Post when I figure it out!
Update to my brake problem. I fixed them!!! I was correct in thinking it had something to do with the ABS actuator. After driving it for a month or so with the pedal almost going to the floor I came home one snowy day and decided to make the Anti lock brakes actuate in my driveway, which has plenty of sliding room. I got going fast enough to make the car skid and actuate the ABS about 15 or 20 feet. I did it in forward and reverse about 8 or 9 times then I pumped up the brakes hard and shut off the car. The next day I took it to work and the brakes were normal (finally). That was over a week ago and they are perfect better than when I first bought the car with 52,000 miles on it (61,000) now. My thought was the ABS actuator was stuck in between cycles, probably from never being cycled before or not in a long time. I hope this helps other people because you can spend alot of money if you bring it to a mechanic that isn`t that familiar with ABS and starts throwing new parts at the problem!
I hope other people read this, sure you can throw a lot of money at parts, but every now and then there is a simple fix to a complex problem. Thanks from all of us.
Same problem, 2006 Eclipse soft pedal that didn’t really engage until 3/4 of the way down; whistling when the pedal was released, and seemed to “pump up”. Thought for sure “air in line” as soft pedal that pumps up is the classic symptom of air in line & I had recently replaced pads (but didn’t have a noticeable problem right after).
I was a very skeptical that the “skid fix” described above could help, but thought I would give it a try before I started to bleed brakes, check master etc.
It absolutely worked… pedal is fine now !
When I started messing with cars 30 years ago I had to rely on the old, crotchety
but helpful old school mechanic at my local shop … no way he could know everything about every car. The 'net is amazing for ‘obscure but important to you’ titbits… thanks Jeff H for sharing !