Gearbox/transmission module fault

Gaygle said:
Then this is nothing to do with your gearbox. If your car continues to move forward despite you having full pressure on the brakes - it is your brakes at fault. Your brakes are *easily* able to win the battle between your engine/gearbox wanting to go forward and your brakes trying to stop you.

When you said your brakes are "flat to the floor" I'm assuming that was just a turn of phrase, and your brake pedal feels firm, consistent and with no dead spots at the top of the pedal?
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I went to the garage today and they said the brakes are absolutely fine. I spoke to a transmission place and he said the same, that the brakes would override any gearbox transmission fault.
The brake pedal feels a lot more ...effective? I don't know if thats the right word, on the left hand side than the right. as in when i was testing it after the garage today, when I had my foot down on the left hand side of the brake pedal, it was like emergency stop, on the right hand side, the side I normally put my foot down on, its a more gradual stop.
 
tacticalx86 said:
I went to the garage today and they said the brakes are absolutely fine. I spoke to a transmission place and he said the same, that the brakes would override any gearbox transmission fault.
The brake pedal feels a lot more ...effective? I don't know if thats the right word, on the left hand side than the right. as in when i was testing it after the garage today, when I had my foot down on the left hand side of the brake pedal, it was like emergency stop, on the right hand side, the side I normally put my foot down on, its a more gradual stop.
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A brake pedal should not feel more effective one side or the other, so either it's your braking technique, i.e. the way you are pushing the pedal down, causing this sensation, or you have a mechanical fault in the brake pedal.
 
radderfire said:
A brake pedal should not feel more effective one side or the other, so either it's your braking technique, i.e. the way you are pushing the pedal down, causing this sensation, or you have a mechanical fault in the brake pedal.
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Really at a loss what to do. I'm already booked in at another place friday, just a standard garage which did the brake pads for me, ironically these issues didnt' start until they'd put the new ones in. But if they say there's nothing wrong with the brakes too, I don't know.
 
tacticalx86 said:
Ok so I've noticed two times in the last few weeks including tonight my car has had issues slowing down. This is where I start breaking and brake but the car continues to shift forward. Tonight it was at a set of red lights, thankfully no other cars around. Can a bad TCM cause this? The brakepads both front and back were replaced recently.
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ok from limited experience ,having had mainly autos for the last 20 odd years. when you apply the brakes press the pedal in the centre , (it should make no difference at all as the brakes either work or dont, its one rod working the hydraulics)
when you say the car tries to shift forwards when braking, do you mean that when stationary its trying to move forward almost surging?.
we have this with our new c max auto where at lights it tries to move forward against the brakes, never had it before on autos but when approaching a auto gearbox specialist they stated its common with the newer type boxes ? meh.
doesnt really bother us.
as folk have said the error code was probably and old code never cleared, whenever the family get a newer car i always read all codes and clear them, then re read them a month later to see if any reappear. more often or not they dont, with modern cars the state of batteries can cause all sorts of spurious codes to appear.
i wonder if you are braking to a stop at the lights and then letting your pressure off the pedal slightly allowing it to try to move forward. i always keep my left foot tucked across the front of the seat and just use my right foot either brake or accelarator, it was how i was taught when i started driving autos for a large private hire company, and i have kept doing it.

these sort of problems can really start to annoy you and eventually spoil the car for you ,i hope you resolve it good luck.

just a after thought and maybe leading up the garden path, but you have a abs system and i suppose it could be a pressure fault or imbalance that may want checking out,. got a friend with a ford and he recently changed his pads and discs all round, he then had random brake problems , calipers locking on others releasing.
in the end i took a scanner to him and he rebled the brakes using the scanner to allow the abs to release air trapped in the system.

turns out that a small amount of air had got in and was causing havoc with the brakes, still ideal time to change the fluid:)
 
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gc123 said:
ok from limited experience ,having had mainly autos for the last 20 odd years. when you apply the brakes press the pedal in the centre , (it should make no difference at all as the brakes either work or dont, its one rod working the hydraulics)
when you say the car tries to shift forwards when braking, do you mean that when stationary its trying to move forward almost surging?.
we have this with our new c max auto where at lights it tries to move forward against the brakes, never had it before on autos but when approaching a auto gearbox specialist they stated its common with the newer type boxes ? meh.
doesnt really bother us.
as folk have said the error code was probably and old code never cleared, whenever the family get a newer car i always read all codes and clear them, then re read them a month later to see if any reappear. more often or not they dont, with modern cars the state of batteries can cause all sorts of spurious codes to appear.
i wonder if you are braking to a stop at the lights and then letting your pressure off the pedal slightly allowing it to try to move forward. i always keep my left foot tucked across the front of the seat and just use my right foot either brake or accelarator, it was how i was taught when i started driving autos for a large private hire company, and i have kept doing it.

these sort of problems can really start to annoy you and eventually spoil the car for you ,i hope you resolve it good luck.
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No I don't mean that, it is trying to move when my foot is down on the brake. It is not getting to the point where its stationary. I brake and brake but it continues to move like it's got a mind of it's own
 
tacticalx86 said:
The brake pedal feels a lot more ...effective? I don't know if thats the right word, on the left hand side than the right. as in when i was testing it after the garage today, when I had my foot down on the left hand side of the brake pedal, it was like emergency stop, on the right hand side, the side I normally put my foot down on, its a more gradual stop.
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I probably wouldn't say this to the garage as they may just dismiss it as all in your head because this is impossible. The pedal pad your foot touches is connected to the metal rod which is connected to a single rod.

There's a possibility that there could be air in the system but this would result in a sloppy pedal which would firm up temporarily when it had one or two pumps to it. The fact you're saying that you've got your foot flat on the brakes as hard as you can and the car is still going forward is 100% an issue with the brakes. No matter what hypothetical fault is with the gearbox, the brakes should stop your car without breaking a sweat and keep it stopped. Also, it seems very coincidental that you had work done on the brakes and now the car sometimes doesn't stop.

How often does this happen?

Does it only happen as you pull up to junctions or traffic lights or does it happen when you're driving along and you sometimes feel the brakes aren't effectively slowing you?

When you are in the situation where you've got your foot hard on the brake and the car is creeping forward, what do you do to stop the car? If you release and reapply the brakes does it cause the car to subsequently stop?

Do you ever feel the pedal is inconsistent? For example, does the top of the pedal sometimes feel a soft, but other times it feels firm and sharp?
 
Gaygle said:
I probably wouldn't say this to the garage as they may just dismiss it as all in your head because this is impossible. The pedal pad your foot touches is connected to the metal rod which is connected to a single rod.

There's a possibility that there could be air in the system but this would result in a sloppy pedal which would firm up temporarily when it had one or two pumps to it. The fact you're saying that you've got your foot flat on the brakes as hard as you can and the car is still going forward is 100% an issue with the brakes. No matter what hypothetical fault is with the gearbox, the brakes should stop your car without breaking a sweat and keep it stopped. Also, it seems very coincidental that you had work done on the brakes and now the car sometimes doesn't stop.

How often does this happen?

Does it only happen as you pull up to junctions or traffic lights or does it happen when you're driving along and you sometimes feel the brakes aren't effectively slowing you?

When you are in the situation where you've got your foot hard on the brake and the car is creeping forward, what do you do to stop the car? If you release and reapply the brakes does it cause the car to subsequently stop?

Do you ever feel the pedal is inconsistent? For example, does the top of the pedal sometimes feel a soft, but other times it feels firm and sharp?
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I've noticed in general the brakes don't feel that good when slowing down when driving along but failing to actually come to a complete stop has only happened twice , when coming up to junctions. I try and use the handbrake and it still moves, eventually after keeping my foot down the car does stop
 
tacticalx86 said:
So I took it to the specialist. They're saying one of the calipers (rear) is getting stuck, and the brake fluid level is too high and of low quality
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I wouldn't have thought any of that would make the car completely incapable of being stopped at low speeds. The fronts do most of the work, too much fluid in the res is really here nor there and you could replace your fluid with cooking oil and it would still "work" for a time at least.

You mentioned in your coolant thread that you didn't know if it had ever had a major service so if the fluid hasn't been changed in over a decade then it's worth getting it changed anyway but again unless you're cooking the brakes and heating up the fluid until the moisture in it starts to boil I'm still not so sure it would be the root of your issues.
 
tom_e said:
I wouldn't have thought any of that would make the car completely incapable of being stopped at low speeds. The fronts do most of the work, too much fluid in the res is really here nor there and you could replace your fluid with cooking oil and it would still "work" for a time at least.

You mentioned in your coolant thread that you didn't know if it had ever had a major service so if the fluid hasn't been changed in over a decade then it's worth getting it changed anyway but again unless you're cooking the brakes and heating up the fluid until the moisture in it starts to boil I'm still not so sure it would be the root of your issues.
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It's the only thing I really think it could be and the fact its only happened since getting the rear brake pads done
 
tom_e said:
I wouldn't have thought any of that would make the car completely incapable of being stopped at low speeds. The fronts do most of the work, too much fluid in the res is really here nor there and you could replace your fluid with cooking oil and it would still "work" for a time at least.

You mentioned in your coolant thread that you didn't know if it had ever had a major service so if the fluid hasn't been changed in over a decade then it's worth getting it changed anyway but again unless you're cooking the brakes and heating up the fluid until the moisture in it starts to boil I'm still not so sure it would be the root of your issues.
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Do you have any theories then?
I'm getting conflicitng advice about the transmission, one mechanic thought it could be as could someone on another forum, another mechanic said it wouldn't be and the brakes would override etc as did someone on here. Maybe a cylinder leak? But I'm sure it would have been found.

I will get the repairs done anyway, but assuming this issue continues and remains undiagnosed, what is the best way to stop the car, as I recall I tried using the handbrake but it still kept moving.
 
tacticalx86 said:
Garage says copper grease was put on the front brake pads which shouldn't be used, whichb
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Yeh that ain't going to be it unless someone put copper grease on the pad faces or disc. It's not good to use copper grease because of it's effects over time on rubber such as the brake piston seal, but we're talking years to deteriorate the rubber and even then that wouldn't make the car not stop.

If this started with the rear pads I think you should be looking at that. What brand are the rear pads for a start? Are they Eicher or some dumpweed like that? The reservoir was probably overfilled because the garage who fitted the brake pads pushed the caliper pistons in to accommodate the new thick pads and didn't drain off the excess brake fluid. Nothing more than that.
 
Gaygle said:
Yeh that ain't going to be it unless someone put copper grease on the pad faces or disc. It's not good to use copper grease because of it's effects over time on rubber such as the brake piston seal, but we're talking years to deteriorate the rubber and even then that wouldn't make the car not stop.

If this started with the rear pads I think you should be looking at that. What brand are the rear pads for a start? Are they Eicher or some dumpweed like that? The reservoir was probably overfilled because the garage who fitted the brake pads pushed the caliper pistons in to accommodate the new thick pads and didn't drain off the excess brake fluid. Nothing more than that.
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I'll get them to clarify but they said something about copper not mixing well and when it was getting heated the brakes were seizing jon

I've got no idea.

The technician who diagnosed it was the same one who did the rear pads, he said the brake fluid needs changing and the front brake pads and discs need replacing. He also said if the other garage had said about getting the caliper replaced we could but he didn't see anything obviously wrong with it
 
From another forum https://frenchcarforum.co.uk/forum/...uld be ABS related.,it would be working again.


"Could be ABS related. Intermittent wheel speed sensors have been known to cause momentary complete loss of braking at very slow speeds around 5-10 mph. It usually only lasts for a fraction of a second so by the time you released the pedal and pressed again it would be working again.

I'm not so sure about whether it could happen at 70 mph though. Have you ever had the ABS system read for fault codes ? If it happens very rarely it could be a challenge to pin it down."

"The wheel sensors just generate a certain number of pulses per revolution which the ECU counts to determine the wheel speed.

The road speed is determined by the wheel(s) with the greatest rotational speed at a given instant, and any wheels deemed to be turning drastically slower than the fastest wheels (or not turning at all) when braking are assumed to be locking up and the brake for that wheel is momentarily released, with the ECU watching to make sure the rotational speed of the wheel increases again. (Consistency checks) Some cars tie the operation of the rear wheels together for ABS, but front is always independent.

So what happens if a wire to one of the sensors goes open circuit due to suspension movement flexing a broken cable ? As far as the ECU is concerned that wheel has just suddenly locked up as its no longer receiving pulses from it, so it will release the brake on that wheel.

However if after a certain time the wheel speed doesn't increase then the ECU will know that the lack of wheel speed signal is bogus because if the other wheels are doing 50mph and it released the brake on the wheel and it still says 0 mph half a second later it knows something is wrong and most likely the fault light will appear and it will start ignoring that wheel sensor.

There are a ton of consistency checks that the ECU does so they're not easily fooled, but a brief intermittent loss of connection to or short on the sensors triggered by suspension/cable movement can confuse the ECU momentarily.

On my previous Xantia every time the rear wheels went over a large enough judder bump at a slow speed of around 5-10mph if I had my foot on the brake as it hit the bump I could feel the pedal rapidly pulsate due to the ABS kicking in. (It never lit a fault light) I never did fix that but it was probably a broken wire to one of the rear sensors. My current Xantia doesn't do this"

ECM is related to the gearbox/transmission module isn't it, which had the error code?

One of the items on the invoice for repair was for a new front wear wire - is this related?
 
tacticalx86 said:
ECM is related to the gearbox/transmission module isn't it, which had the error code?

One of the items on the invoice for repair was for a new front wear wire - is this related?
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I'm assuming you mean ECU. ECU refers to any module that controls a function of the car. The ABS will have its own ECU and is unrelated to the transmission.
If you had any kind or ABS fault I would expect the ABS fault light to be illuminated on the dash.
The "wear wire" will be a brake pad wear sensor. Standard to replace when replacing pads.
 
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