Anybody,
My son's car seems to have a number of issues. He has about 110k miles. His brakes were going to the floor so we ordered new rotors, pads and calipers. We replaced them and flushed the lines (rt rear, lft rear, rt fr, lft fr order). He test drove it and nothing changed. Meanwhile, his battery light would go on intermittently. We replaced the master cylinder. Also, once he started his car and the starter would not stop until the fuse blew. The solenoid was bad so we replaced the starter. The starter seemed to work. Then it acted up again and ran until the fuse blew. We replaced the ignition switch. I was checking the alternator and noticed a cyclic voltage fluctuation from 14v to 16v. We replaced the alternator (that was fun). When we bled the brakes with the master cylinder replacement they were rock solid. When he test drove it the brakes went to the floor while the car danced over the road (right to left) so we decided the brake issue was the ABS pump/control module (the dreaded module). Then he went to start it to bring in the garage and the starter stayed on again. What do you think? Dare I mention ECU?

 

My guess would be something in ignition key "start" wiring is shorting causing 12vdc to continue when the key is released from starting to still continue feeding starter

Maybe pull wires from starter and meter them for VDC while someone turns the key to start then releases it (basically mimic a normal key on engine start movement with the key)

rare that 2 starters would fail the same way...possible but I would think wiring to starter being more the cause

Brake issue..did you replace booster or just MC?

 

I am wondering if the common denominator is the ecu. I would assume that the ecu cranks the starter until it (the ecu) gets signals (o2 reading, min rpm, min alternator voltage, etc) and runs the starter accordingly. Two starters with the same intermittent issue? Not likely. The wire thing, what would all the sudden cause a mechanical issue like that - and only fault intermittently during the start cycle. Did not replace booster. When I bled the brakes they were solid - no spongy feel - solid and not to the floor - just where the pedal should be. Wouldn't a bad booster have a vacuum leak or make braking harder? If it over-boosted I would think it would make it too easy to stop?? Isn't the booster isolated from the hydraulic lines - yes? Again, I am guessing the ABS works as follows: Each wheel has an encoder. All 4 encoders are wired to the ecu to monitor lockups, speed, and speed difference between tires. When the ecu detects a locked wheel it sends signal the the ABS to the control of that particular wheel to let up on braking - and the closed loop feedback continues in millisecond cycles. Again - the ecu becomes a common denominator in the odd behaviors. The nature of the brake failure is odd - it feels like each tire is responding independently - kind of like a regulated failure of each line separately not like a more centralized failure indicative of a common pressure drop.

 

My understanding is the ECU (and I think it is PCM, powertrain control module) does not command the starter. The ignition switch does. If the starter continues to run even if key is no longer being held in "start" position that signal to starter is not coming from ECU. There is likely a short in wiring between ignition switch or the ignition switch but you say that has been replaced. ECU would not be making the key stay in the "start" position to cause the starter to keep running....if I understand correctly that has happened o two starters until a fuse blew...what fuse?

IDK if ABS is entirely controlled by the ECU or if there is a control module separate like other cars on the Escape.

You tried pulling any codes with a OBD2 scan tool?

So on the brakes the initial problem was pedal went all the way to floor. You replaced calipers, pads, rotors, bleed brakes and then replaced MC and bleed brakes again....and pedal still goes to floor?

I was just asking if you had also replaced the booster.

 

We need to be a little careful because sometimes we make more problems when imagination runs wild.
Better way is to isolate the problem.
You can take the ABS out of the possibilities by removing the ABS fuse. If the problem goes away you have narrowed it down to the ABS. If not , then you move on to the next possibility. Not knowing where you obtained the replacement master cylinder , some are defective right out of the box. It would not be the first time we figured ,it can't be that part because I just replaced that. If the problem is still present with the ABS disabled there is a good possibility the MC is defective.

 

hanky and 09xcape,
Thanks for your response.
09xcape,
ECM, ECU, PCM, etc. they all can be applicable I think we know what the reference is to. You asked me if I replaced the booster - was there a particular reason? The fuse that blew is the high current (40A) started fuse. The ignition does not work like the old style where you turn the key to start and have to hold it there until it starts, and then you detect the engine started and you release the key. It works like a push button start except the button is the key just making contact in the start position. When the starter goes on you can release the key and it continues cranking until the motor starts and the car detects that the motor is running and turns off the starter. No lights are on when running - but I haven't hooked up an OBD2. I thought if there was a code it would light up a light - but I will look into that. Thanks.

hanky,
I replaced the MC with a re-manufactured one and there was no change so like you I thought it was defective so we replaced it with a new one. Again, it bled rock solid with the motor off. If the MC was faulty it would not be rock solid. If there was air in the line it would be spongy. Great suggestion on the ABS fuse. I will try that and the codes when I replace the bad replacement starter.

PS.
Forget that imagination thing and the "we" reference. I think you basically said that I have a reckless imagination and it could get me into trouble - but in a condensing way placing yourself above such a thing.
Thanks.

 

I asked if booster was replaced to know if it was. Outside of ABS it is the only part you did not replace regarding brakes so curious if you feel it is good

Your brake issue is the pedal goes to floor, right?

I have a 09 Escape and to start it you turn the key as far as you can and when motor starts you release it and it springs back from "start" position to "run" position. Maybe your model is different.

In any event, as you note, the starter continues until the fuse blows. IDK if the PCM is somehow commanding the starter to continually engage once key is in "run" position which is why I was suggesting a wiring issue vs PCM. Your thoughts are different so pursue what you feel you need to

It's a forum you ask ? and we have offered our thoughts.

All codes do not turn on the CEL which is why a scan tool is always helpful on these OBD 2 cars. Some are capable of reading ABS and transmission codes. I have the Actron 9680 but there are several and sometimes auto part stores have loaner scanners.

as Hanky posted, pull the ABS fuse to disable ABS and see if that resolves the pedal to floor issue

Dealership can scan your car and "re-flash" the PCM if needed or otherwise determine if the PCM is functioning correctly.

Good luck

 

Dear mgc1,
you are absolutely correct , I am placing myself above that because I have learned the hard way, we, meaning lots of folks with some dirty toes and burned fingers because we stepped into and got burned jumping to conclusions that we might have been better off if we didn't look for a reason to always blame "The old black box"..

I am going to pass a morsel of info on to you that might be helpful, and that is you CANNOT do a decent brake bleed on a vehicle that has an ABS without a capable scan tool operate the ABS valves.
Sorry if you took offense to my post , it was not intended and was a reminder for those of us that sometimes have a tendency to forget or overlook.
There are times when a booster can produce seemingly unrelated problems, but also a reminder that there is a continuous direct mechanical link between the brake pedal, the booster and the master cyl. If the pedal goes to the floor all the booster does is assist , it does not have any disconnect between the pedal and the rod going into the master cyl.

 

09xcape,
Again, thank you both for your input. Question: what does IDK mean?

 

IDK= I don't know