1.2TDI gearbox: stopped working

M

Miguel Silva

Member
Dear all,
My gearbox was working fine. I parked the car, removed the negative battery connector (I have a current leak since a long time and with the recent very cold weather, in Switzerland, the battery discharges too quick) and went home. A few hours later, I connected back the battery and when I tried to start the motor, it didn't, not a single noise. All display lights were OK, the battery has been charged recently, so I don't think that's the problem. But what I quickly noticed was the absence of the gearbox pump noise. I then realized I can't change any gears (note: automatic gearbox), the display indicates I'm moving a gear (like from P to R to N to D) but there's no gear changing noise. After a few minutes I heard the gearbox pump working but just for a few seconds, then it stopped. I opened the front cover and there's a constant low level humming noise near the gearbox accumulator (the accumulator was changed by me about ~3 years ago). I haven't yet checked the oil level (by turning the accumulator). The gearbox pump occasionaly start working for a very brief moment, like I described. Do anyone have an idea what could be the problem? Thanks in advance for all your help. Cheers. Miguel
 
Could be a few things. A scan with VCDS would help. What is the ambient temperature there? Is it possible that water has entered the reservoir? The scuttle drain is immediately above the reservoir and if this is blocked or separated, it is possible for water to enter the reservoir - as the reservoir level goes down, air is drawn in through the green cap. This would lead to an emulsion forming which might freeze. Other possible causes are low oil level, failed accumulator or failed pump. The hum is normal with the ignition on.

RAB
 
Hi RAB,
Thank you for the quick reply. I (still) don't have a VCDS and I know I should (you gave me that advice long time ago).
The scuttle drain (that's a new term I just learn from you) isn't separated. I can't confirm if it's blocked or not. My problem happened this last Sunday, the temperature must have been already above zero, the weather got better on Saturday, but it's true that we had snow last week and a very cold weather (below zero).
I read from one of your posts that to check the oil level, one needs to rotate the accumulator half a turn. Could you tell me at what level the oil should then be? I don't see any min/max levels indicated. If it's low, how do I proceed? Do you need a key to open the green cap? Do you have a suggestion for the oil to be used?
I'm almost sure that even without the ignition on, I have this hum. By the way, when I open the driver's door, the gearbox pump doesn't start either.
I'm guessing the motor doesn't start because there's isn't enough pressure in the gearbox actuator system (just like when all is OK but I still have to wait for about 20s until the gearbox pump finishes it's job and I can start the motor).
Thank you very much.
Best regards,
Miguel
 
Make sure that the drain tube is not blocked. Unplug the hydraulic unit electrically and rotate the accumulator half a turn. Then top up the reservoir with VW hydraulic steering oil until the level is within the inscribed rectangle. Then tighten accumulator and plug back in. If the pump doesn't run for long, there is either something wrong with the pump or there is little nitrogen left in the accumulator and it needs replacing. The green cap just unscrews.

Have you tried starting in neutral? This can be done without pressing the foot brake. If so, you either have a faulty brake switch or the clutch actuator is starting to fail.

RAB
 
That was quick! Thank you.
OK, I'm going to refill the reservoir following your instructions.
I can't move (physically) the gear to neutral with the selector: the display shows like I'm changing the gears (except in tiptronic mode) but I know they're not changing because I can't hear the usual noises. The brake switch is working, I can see it in the indicator next to the selector when I press the brake pedal.
Let's see if filling the reservoir helps.

Cheers,
Miguel
 
The brake switch is, in fact, two switches, one of which operates the brake light. You should be able to move the lever to neutral with your foot on the brake. If not it does suggest that the brake switch is faulty. Pressing the foot brake also opens the clutch and allows starting in P. If the brake switch is faulty, this won't happen.

RAB
 
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Dear RAB,

I guess I didn't explain myself clearly: I can move the lever to any position, and as I move I have the indication (in the front panel) that I changing gears (but I know that I'm not because I don't hear the usual noise of gear being engaged/disengaged). From what you just described, I guess that maybe the clutch isn't being open for some reason. Not enough pressure in the accumulator circuit would be my first guess. When all was working, every time I want to use the car, the moment I opened the driver's door I would hear the gearbox working (~20s) and quite often again when I turned the ignition key half way (i.e. before the motor started). Now there's nothing, so maybe there's isn't enough pressure to open the clutch. I'll see if during the weekend I find VW hydraulic steering oil and refill the reservoir.
Thank you very much for all your help.

Cheers,
Miguel
 
Could be a pump issue then. Even if there's no oil, the pump should at least start. Unplug the unit electrically and then re-connect. Is the battery OK?

RAB
 
Dear RAB,
I was wrong when I said the pump doesn't work : it does when I connect the battery but not for long. And then every few minutes but just for about 5 seconds. I've checked and refilled (just a tiny bit) the reservoir. I've also fully charged the battery. It still doesn't work, I can't started the engine, the electric starter motor doesn't even tries to turn. Maybe not the best post to ask this question : is there a specific model/brand you suggest for a vcds? Thank you. PS: is there a fuse you suggest me to check if it blow? I ask this because I was connecting/disconnecting the battery quite often before this problem showed up and I wonder if this might have destroyed something.
 
VCDS is only available from Ross Tech or its distributors: https://store.ross-tech.com/shop/cat/VCDS

This is a list of distributors: http://www.ross-tech.com/distributors.php

A scan would be essential to make any progress. Note that the software cannot diagnose a failed accumulator. A failed accumulator (little or no nitrogen) is consistent with a pump running for a short period of time (although not conclusive). How many km has the clutch done? It could be that the guide sleeve/clutch bearing has failed and is preventing starting. VCDS will assist in detecting this. Is the rubber inspection moulding present at the top of the clutch housing. If not, water may have entered and caused the clutch to seize.

With the bonnet off and ignition on, does the clutch move when the hydraulic station is unplugged and then connected? It should.

Fuses are listed in the car manual. Checking them all wouldn't take too long.

RAB
 
If you are reluctant to buy VCDS, it might be worth trying a new accumulator. Eventually, you'll need one anyway. If that doesn't work, you'll need VCDS! It soon pays for itself with a 1.2Tdi!

RAB
 
Apologies for asking/swerve, but it's been on my mind for a while. I'd like VCDS but the price for a good kit is substantial. On that link the professional kit is $899 and then there's the VCDS HEX-V2 enthusiast kit at $300 I'm confused as to what kit i would need? What is the cheapest way of doing this? Cheers Mark.
 
Vorsprung durch Technik said:
Apologies for asking/swerve, but it's been on my mind for a while. I'd like VCDS but the price for a good kit is substantial. On that link the professional kit is $899 and then there's the VCDS HEX-V2 enthusiast kit at $300 I'm confused as to what kit i would need? What is the cheapest way of doing this? Cheers Mark.
Click to expand...

I think it depends on how many vehicles you plan to use with it. When I bought my HEX-CAN it was about the equivalent of $300 and was not limited. If I was buying one now it would be a version of the HEX-V2 which is limited to between 3 & 10 vehicles, and priced accordingly. The function will be the same as the professional versions apart from the vehicle limits and features that are not essential.

RAB
 
RAB said:
VCDS is only available from Ross Tech or its distributors: https://store.ross-tech.com/shop/cat/VCDS

This is a list of distributors: http://www.ross-tech.com/distributors.php

A scan would be essential to make any progress. Note that the software cannot diagnose a failed accumulator. A failed accumulator (little or no nitrogen) is consistent with a pump running for a short period of time (although not conclusive). How many km has the clutch done? It could be that the guide sleeve/clutch bearing has failed and is preventing starting. VCDS will assist in detecting this. Is the rubber inspection moulding present at the top of the clutch housing. If not, water may have entered and caused the clutch to seize.

With the bonnet off and ignition on, does the clutch move when the hydraulic station is unplugged and then connected? It should.

Fuses are listed in the car manual. Checking them all wouldn't take too long.

RAB
Click to expand...

Dear RAB,
Thank you very much for the information and suggestions. I just ordered the HEX-V2 (limited to 3 cars).
I bought the car in second hand, but I would guess that the clutch is the original. The car has about 150.000 km at present.
I will try to see the state of the rubber inspection molding. I will see if the clutch moves by unplugging/connecting and also, why not, check all fuses.
Cheers,
Miguel
 
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Dear RAB,
When I unplug/plug the hydraulic station, the clutch (lever, connected to a cable that goes to the clutch slave cylinder(?)) moves but then goes back to its initial position, just after 1 or 2s. Practically every time I unplug/plug the hydraulic station, the pump works for no more than 5s.
I have replaced the accumulator with a new one but the problems remains (all same symptoms).
I have checked the 20A yellow fuse and the relay '373' (swapped with the other '373'), in the compartment beneath the driver's foot (I saw this on a post in the german forum back from 2012, with your participation in it!).
I don't know where's the rubber inspection molding (I haven't yet searched neither in the internet!).
I received the VCDS and I got the following report attached. I see that there's faults in the 'Transmission'. Could you comment on that, please? Thank you very much. PS: I haven't deleted any of the faults so it's probable that faults in other sections (ABS, etc, are from another time). Should I clean them all?
Cheers,
Miguel
 

Attachments

  • Log-VD539956-WAUZZZ8Z22N030480-158420km-98437mi.txt
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Hi Miguel,

All the transmission faults are consistent with disconnecting the hydraulic unit with the ignition on. Clear the faults with VCDS. With VCDS, 02 Transmission, Measuring Block 08, check Block 002. It should be between 1.8 and 2v with the hydraulic station disconnected and about 4v with it connected. Keep doing this and see if you get consistent results. If the lower reading is outside the lower limits, complete a basic setting as here:

http://wiki.ross-tech.com/wiki/index.php/5-Speed_Electronic_Manual_Transmission_(085)

Do everything and follow by the letter in the order given. If the lower readings are not consistent, you probably have a failed guide sleeve - VCDS cannot diagnose a failed guide sleeve unaided. A failed/failing guide sleeve will prevent starting.

RAB
 
Another possibility is that the spool valve on the hydraulic station is failing or has failed. This controls the clutch actuator. When the hydraulic station is connected or disconnected with the ignition on, the clutch should maintain the same position. Your test with VCDS will confirm this. If not, it does suggest a problem with this valve. There are instructions on the German forum for repairing it. Use Viton O-rings, not NBR.

RAB
 
Dear RAB,
Thank you very much for your replies. Unfortunately, I haven't had much time to work on the car. Once I have more news, I will come back here.
Could you tell me how to write spool valve in German? It's, of course, to try to inform myself as much as possible in the German forum. Thanks.
Cheers,
Miguel
 
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