How to recondition a VCU yourself.

andyfreelandy said:

Allowed to settle overnight, left about 10ml in pipe and it almost disappeared into the VCU overnight. When pipe unions removed, took out about 5ml to allow plug fitting. With ally washers. Sump plugs actually. The 150ml quoted was the total input give or take 5ml - an odd drip here and there !

Click to expand...

andyfreelandy said:

So - done this now. Thanks to all above particularly Alibro for the info. Thought I'd share the learning !!!
View attachment 118158 Bought VCU for refurb, bench tested at 45 secs, marked out and drilled / tapped VCU - opposite each other for balance.
View attachment 118159 Drained most of gunk overnight.

View attachment 118160 Pressure flushed with solvent until every trace removed and fluid clear.
View attachment 118161 Fitted 'vent pipe' and pressure filled with 150 ml of 100,000 ctu silicone. Vent allowed silicone to pop and fart up to heights of about 12" and allowed pressure fill in about 20 mins. Fascinating process. :0
View attachment 118162 Allowed to settle overnight, left about 10ml in pipe and it almost disappeared into the VCU overnight. When pipe unions removed, took out about 5ml to allow plug fitting. With ally washers. Sump plugs actually. The 150ml quoted was the total input give or take 5ml - an odd drip here and there !

View attachment 118163 Rub down, coat of smoothrite and Bob's yr doo dah!!
Bench tests at around 15 seconds (1m 5kg) which, according to my calcs will be around 25 secs at the wheel.
New GKN Fag bearings to fit.
Will fit to car and report back.

Now will do the old one which I took off the car and cannot turn even with a breaker bar - see thread on rear tyre wear !!!

Only change I would make is that I have now bought a HSS tank cutter drill to prevent worrying about drill break through damaging the first disc - the point of the drill touches it. Also a tank cutter would not leave a slight burr inside - I drilled it increasing the size by 1/2 mm each time to reduce burr left to negligible.

Click to expand...

htr said:

The I read that article about recon'ing a VW VCU the article suggested an air quantity of 7 to 8% iirc. Has anyone measures the VCU's volume?

Click to expand...

andyfreelandy said:

Had time to tidy up after the VCU refurb and have the following 'vital statistics' that may be useful. I did some maths and took away the weight of teh bottles etc and can conclude:
200ml of NEW 100,000 ctu fluid weighs in at 217g so 1ml = 1.085g.
Old VCU liquid removed which I estimated was around 160ml by measurement only weighed in at 119g and so I think that the 160 figure was flawed. Maybe nearer 110ml or it gets lighter with use?!!?

I inserted to full, but not brimmed to top, what I measured in as 150ml. By weighing the remainder from my 200ml bottle (still with me?) i concluded that I had inserted 167g into the VCU which at 1.085g per ml gives a volume of 154ml. This agrees with my 150ml measured. What is a teaspoonful between friends??

Haven't had time to fit to car yet - well, clearly I have had time as I have done the faffing about above, but not had the motivation to get underneath again !

Anyone else on this route to refurb???

Click to expand...

andyfreelandy said:

Had time to tidy up after the VCU refurb and have the following 'vital statistics' that may be useful. I did some maths and took away the weight of teh bottles etc and can conclude:
200ml of NEW 100,000 ctu fluid weighs in at 217g so 1ml = 1.085g.
Old VCU liquid removed which I estimated was around 160ml by measurement only weighed in at 119g and so I think that the 160 figure was flawed. Maybe nearer 110ml or it gets lighter with use?!!?

I inserted to full, but not brimmed to top, what I measured in as 150ml. By weighing the remainder from my 200ml bottle (still with me?) i concluded that I had inserted 167g into the VCU which at 1.085g per ml gives a volume of 154ml. This agrees with my 150ml measured. What is a teaspoonful between friends??

Haven't had time to fit to car yet - well, clearly I have had time as I have done the faffing about above, but not had the motivation to get underneath again !

Anyone else on this route to refurb???

Click to expand...

Alibro said:

I thought I'd post my experience here of reconditioning a VCU by flushing it out. I don't believe this can ever be as good as cutting the top off and properly cleaning every disk but my experience so far is extremely positive. Many of us don't have a welder or the skill to use it so without spending hundreds this is your only other choice, this is copied from other threads so may be a bit disjointed.

1. Drill two holes in the end the appropriate size for the tap and bolts or grease nipples you intend to use. I used M10 Extra fine as I hoped the extra number of threads would make it stronger. I think the drill was around 8.9mm but it's easy to find tables showing the correct drill size for your tap.

2. Leave it overnight for some of the gunge to ooze out

3. Tap the holes now so that any swarf will come out with the gunge as you clean it (use a 1/4" extension bar from a socket set to extend the tap).

4. Clamp it in a vice and using a syringe or a small funnel pour in as much white spirit as it will take.
5. Put the rear propshaft onto the splines and stick a long crow bar (or similar) through the UJ and start turning to mix the white spirit with the fluid still in the VCU. Note, this might be hard work.

It might be a good idea to tidy your bench before taking photo's and posting them on the internet.

6. Repeat points 2 through 4 many many times over a week or so until there is more white spirit pouring out than gunge and the VCU is quite easy to turn.
7. Once happy it is as clean as your going to get it then leave it to drain for a few days turning repeatedly to try and get rid of as much white spirit as possible.
8. Once drained start injecting new fluid in with a big syringe. You'll need to keep turning the VCU to get the fluid right down and in between the disks. You might find the fluid wants to come back out so screw in the bolts to stop it.
This process can take several days.

9. Repeat until you have approx 150mls of 100,000 cst fluid in the VCU. This bit is easier said than done due to the amount that spills.
10. Screw in your bolts, refit to the car and drive for a few miles to really mix everything up.
11. Do the one wheel up test and if too slack squirt in a wee bit more fluid (easier said than done) or if too tight let some out then drive for a bit more and test again.
Note, It might be worth putting in a little more than 150mls of fluid as it will be much easier to let excess out than put more in. I plan to add another 10 - 20mls on top of the 150 for that reason. Also a little ends up spilling out so it's hard to measure exactly how much made it into the VCU.

Tips
If using grease nipples they are very shallow so no problem but if using bolts you'll need to cut them down to approx 9mm. I cut mine to 10mm as I'm using a copper washer which is probably unnecessary but I have them so why not.
Drill the holes as near centre as you can (half way between the shaft and the edge) Too near the edge and you'll hit the side wall and too near the shaft and your bolt head will foul the curve at the shaft.
Buy a good quality tap and tap handle. I have a cheap tap which is useless and a reasonably good one which is great. I used metric extra fine M10 but fine or even normal would be OK if using bolts instead of grease nipples. Grease nipples are very shallow so don't have much thread to grip and if your tapping isn't perfect you could easily strip the threads.
Get a good big syringe with a large nozzle.
Weigh the fluid before you start and at the end to confirm you have the right amount in.
Pour the fluid into the syringe. Trying to suck it into the syringe will introduce so many air bubbles you wont be able to use the markings on the syringe to measure it (and its painfully slow).
Both cleaning and filling are very very messy jobs. Be warned and have appropriate gloves and cleaning materials.
To find the silicone fluid go to ebay and search for 100000 cst

Disclaimer
I'm not claiming this is the correct method or saying this is how you should do it. I'm only posting this to show how I did it and to show it can be done.

Edit
VCU is back on the car and giving a OWU time with 5kg weight and 1.2m bar of approx 20 seconds. This is pretty close to OEM I believe so happy it isn't too tight. As pointed out by others, the OWU test cannot confirm the VCU works as a VCU so I tested it in a muddy field and happy to say all four wheels were spinning at the same time. Also tried to spin the wheels pulling away on a wet road and no wheel spin. Still to test on a steep stony hill so can't confirm how much torque will be transferred to the rear wheels but the three VCU's I reconned before worked perfectly for over a year before I sold the cars. If this one is as good as them then we can say this is a valid method for reconditioning your VCU virtually to OEM.
The only concern I have with using this method to refurb your VCU is that there is bound to be residual old fluid mixed with white spirit which is now mixing with the new silicone fluid. This may or may not have an effect on the performance or useful life but it seems to work just fine for now. BTW I went with the grease nipples in the end as they are smaller, lighter so less likely to cause vibration also makes it possible to inject more fluid if necessary with a grease gun.

Click to expand...

Nodge68 said:

I will do mine in the summer. I try to avoid grovelling on the ground when it's cold and wet.

I'm going to try a simplified method first off. I plan on drilling two holes in the can opposite each other. One at the top of one end and one at the bottom of the other end. I'll thread them to take 6mm grease nipples and fit one nipple, which I'll orientate at the top. I'm then going to inject 30,000 fluid into the nipple, which I'm hoping will expel the old fluid from the opposite threaded hole. I think I'll need to rotate the VCU occasionally to get most of the old fluid out. This is all very experimental so results will be interesting. I'm opting for 30K fluid because of the mixing that will take place with a quantity of old fluid. I'm hoping this will give a working mixture.
If it works, it'll make VCU maintenance much easier to undertake. Possibly even allowing fluid changes without removing the unit.
I'll report my findings later in the year.

Click to expand...

PopRivet said:

Hi. How did you get on with filling the VCU with 30000 fluid? It's of great interest as I'm preparing to do the job myself.
Thanks.

Click to expand...