Mk4 Golf oil pressure and auto transmission questions

[PSk]

Okay I have some questions if you have the time

I have purchased a 1998 VW Golf Mk4 1800cc, for my daughter as her first car. I have replaced the whole automatic transmission/diff transaxle with one from a wrecked car because the my cars original diff was toast due to what appears to be a cracked casing causing oil loss. Other than horrid diff noises this car drove well and if the odometer is to be believed has traveled only 130,000 km's. The excellent condition of the seats and other areas of the car make me think that this is valid.

To replaced the transaxle I had to disconnect and remove the battery and all the wiring plugs connected to the transaxle and starter. The transaxle swap has been completed and I have taken a short test drive. I have the following issues:

1. At around 2000 to 3000 rpm the engine oil symbol flashes and beeps. This did not happen before I pulled the transaxle. I have had the sump off to get at the flex plate nuts and did not note anything blocking or otherwise impeding the oil pick up, and obviously put new oil in and replaced the filter.

2. Also on the test drive if I accelerate and the revs get high-ish the transmission slips (I think) and the engine revs flair. This could be because my replacement transmission is worn, but I have also read that the transmission is sort of intelligent and learns how the driver drives. Now of course I have a different transmission and I've read that the computer might need to relearn or be reset. To clear/reset the computer I've read that you need to turn the ignition on, but not start the engine, and press the accelerator to the floor. I have done my best to confirm the oil level is correct and pretty sure it is now right. Note the oil in my original transmission did not look or smell good, and I reused the original torque converter without draining it of oil, but I have since the road test drained some of the transmission oil and put in fresh oil. The oil in the replacement transmission looked and smelt good. Part of the deal for the replacement transmission was that I could not have the torque converter unless I paid heaps more. I also have ensured the separate diff area has the correct oil ... and pleased that everything was quiet on the test drive

I have not test driven it again as I need to solve the oil pressure issue.

I have read that it could be oil pickup, stuffed camshaft(s) ... usual engine wear problems, but the engine is as quiet as mouse. It of course could be the oil pressure sensor, and I've also read that:
- the engine speed sensor can cause exactly the same symptoms,
- earth connection issues,
- maybe related to disconnecting the battery. Is there a proper way to reconnect it up again?
- maybe I've damaged a wire??

Any ideas and knowledge about these cars and this area would be greatly appreciated.
Thanks
Pete

[crsmp5]

ahhhhhh you changed the oil... you put 10w-40 in it not some #w-30 correct? if not put some 10w-40 in... #w-30 gets too thin when warm and will kick oil light on over 2200rpm and hot..

thats how those trannies fail... slip slip.. no such thing as a good used one...

you do not need to remove oil pan to get to the flex/torque converter nuts... by the axle flange is a little plate held in place by a 10mm headed bolt... removing it accesses the nuts..
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[PSk]

Yes I put in 10w-40 (but I admit my first test drive was with old oil so maybe was too thin/stuffed). Thanks for the tip re the flex plate nut removal!

But I have solved the oil pressure warning issue, by:

1. Pressing the accelerator to the floor with only the ignition on. This is supposed to reset the automatic transmission "driver learnt" settings.

2. I pulled a couple of wiring plugs apart on top of the transmission as I wanted to confirm the multi-pin one was connected properly. Confirmed. I had to pull the other plug off to get this multi-pin one off, ie. to get my hand around it.

3. I located the oil pressure sensor and confirmed that the wire was connected properly.

4. I cleared the "Inspection required" and "Service required" warnings.

I do not believe there ever was an oil pressure issue, but instead I was getting error codes that if I had a proper diagnosis computer I would know the exact issue.

Unfortunately the transmission still slips, so will have to pull the plates out of the other transmission and transplant. Bit of a pain as not the easiest transmission to remove, but I've discovered it is easy to remove the suspension sub-frame (leaving steering rack behind) and this gives you a lot more room, and means you to do not have to rotate the diff up. Much better.

BTW: I've read that these auto transmissions are sealed and there is no oil filling point. On mine above the auto-tran sump guard at the front is a plastic spout. Pop the lid off that and you can pour oil in there. At first I thought it was a breather but it is not, and it definitely has a lid. Anyway, worked for me
Pete

[crsmp5]

back in the day it had a dipstick tube and stick there... but ill be honest why vw took it away.. the only 3 300k ones ive seen/driven have never had the fluid touched.. every 80k-150k bad one has... so well never touch the fluid.. drive it like granny and never try to hurt it... and dont think/touch/worry on the fluid...

they also had a spin on oil filter on top of the oil cooler on top the tranny... they took that away first.. then the dipstick..

id also remove the axle flange under the turbo for room..
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[PSk]

I have found the reason for the replacement transmission slipping. The low/reverse clutch diaphram spring was broken into 2 pieces.

Nearly finished the rebuild and re-install so will soon know ...
Pete

[PSk]

To aid others I thought I'd post an update. It has taken this long to get to this point through delays, etc.

Anyway after putting the auto all back together it still slipped. My next step was to swap valve bodies and the solenoid wiring loom.

Now coincidentally we had visitors and one of them is an electronics wizard and he decided to check the solenoid wiring loom out. What we discovered is the one in the car had a direct short between the black and black and white wire. Now the black and white wire controls the oil pressure solenoid!!

This electronics wizard took my spare loom away and repaired it as it had become damaged during all my work and maybe was before anyway.

I have just fitted this repaired and confirmed good solenoid wiring loom and also spent half a day trying to get my computer and an Italian car connector to connect to the cars transmission control unit with no luck (I have an Alfa 156v6 and it works on that) hoping to be able to clear any error codes ...

Anyway my first test drive proved that there was no slip ... great but it was in limp mode. Sigh.

Now service manual docs that we found indicated that you need to do full throttle and kick down tests, etc. for the transmission control unit to relearn, so I did this and now it changes beautifully. So smooth, quite impressive.


So the lesson learnt is:
1. If you are getting nowhere with a 01M transmission, replace the solenoid wiring loom. It is poorly designed and VW have 3 versions of it so had a few goes at getting it right ... It stupidly runs under the transmission cooler meanly it gets hot and also is immersed in hot oil inside the transmission, and has very fiddly connectors which break easily.
2. You need to do a thorough road test to allow the control unit to relearn.
3. I also learnt that after market radios can affect your ability to connect a computer to the car, and can damage the connector through too much voltage ...

Anyway just thought that might help
Pete

[PSk]

Solved the apparent oil pressure issue; the terminal connector was loose on the pressure sensor. Tightened and solved.

Pete