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.
I used a syringe last time


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. I also blasted it with compressed air and got a lot more out.
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.

Cor, that looks like sooo much fun

Has anyone ever told you, you've got to much time on your hands.

One day I'm coming over there and buying you numerous pints.

Mike

Edit on 31/3/18, I found a load of photos from the previous attempts where I cut the top off. I'm not going to spend any time writing about them as I've done that else where but I thought it might be helpful to post them here so that anyone thinking of refurbing a VCU will have a better idea what they're dealing with.

Cut to the inside (left here) of the weld line to avoid cutting into the lid of the VCU. With this setup the VCU will spin freely allowing you to make a nice straight cut.

Nicely.
If you use grease nipples as plugs, then why not use them to fill it too?
You can buy a brand new grease gun on ebay for a few quid. (or clean your old one if you can be assed) Hold it pointing downwards and pour the silicon fluid into its open end. You will then be able to pump the fluid into the VCU under pressure (leave the other plug out so air can escape).
This way you can pour the exact quantity into the grease gun and avoid much mess and fluid loss.

I use a clean grease gun to pump fluid into the hydrolastic suspension on my collection of Austin /Rover sh1t so its capable to dealing with very high pressure.

Edit - it will take a little thought....you will need to account for the quantity of fluid that will stay in the grease gun mechanism and nozzle - shouldnt be too hard to work out though and add that to the quantity you need to inject.

dave21478 said:

Nicely.
If you use grease nipples as plugs, then why not use them to fill it too?
You can buy a brand new grease gun on ebay for a few quid. (or clean your old one if you can be assed) Hold it pointing downwards and pour the silicon fluid into its open end. You will then be able to pump the fluid into the VCU under pressure (leave the other plug out so air can escape).
This way you can pour the exact quantity into the grease gun and avoid much mess and fluid loss.

I use a clean grease gun to pump fluid into the hydrolastic suspension on my collection of Austin /Rover sh1t so its capable to dealing with very high pressure.

Click to expand...

Great suggestion. Maybe someone will try this and report back.

dave21478 said:

Edit - it will take a little thought....you will need to account for the quantity of fluid that will stay in the grease gun mechanism and nozzle - shouldnt be too hard to work out though and add that to the quantity you need to inject.

Click to expand...

Every method will have pros and cons. This could be a good way to inject the white spirit (or your cleaning fluid of choice) too.

I soaked mine in diesel, its strange stuff to clean off

I used petrol the first time and heating oil 2nd and third times. But when cleaning the disks in a basin you can get away with using whatever you want. I used white spirit last time because it's very clean and drys without leaving a residue. Also slower to evaporate than petrol but I am sure there is better fluid available for the job.

Alibro said:

Great suggestion. Maybe someone will try this and report back.

Click to expand...

That's the way I'm planning to do mine Ali. I've got a new grease gun and 6mm grease nipples, for the task. I'm holding off on doing the job until my VCU shows 60 seconds on the OWUT.

I found this information on the web on removing silicone.

Any orange citrus cleaner should work or just orange juice if thats all you have.

Drycleaning Fluid

Sulfuric acid

Naptha can help with Silicone residue.

Isopropyl Alcohol

While many solvents abound...
Orange Glo (citrus based cleaning solvent)
Oxyclean
Tri-Chloro-Ethane
Pre-Kleano (Automotive product)
PST Silicone Grease Remover (PolySi Technologies)

Denatured Alcohol seems to be the best option for removing silicone lubricant, rubbing alcohol would probably do just as well.

Acetone

Automotive paint industry use Naptha to remove silicone contamination.

I was a bit concerned about using anything that might harm the bearings and seals.

...and lungs.

Nodge68 said:

That's the way I'm planning to do mine Ali. I've got a new grease gun and 6mm grease nipples, for the task. I'm holding off on doing the job until my VCU shows 60 seconds on the OWUT.

Click to expand...

Might be a while Nodge, i saw you saying yours is currently at 45 secs .

The guys that were trying to set up a commercial operation refurbing VCUs in Spain, weighed them and when adding the new silicon filled till they reached the same weight.

fredi250 said:

The guys that were trying to set up a commercial operation refurbing VCUs in Spain, weighed them and when adding the new silicon filled till they reached the same weight.

Click to expand...

My accurate scales only go up to 2kg so I would have to rig up something to weigh it accurately. Also I don't know for sure what the correct weight is as the 150g mentioned is only internet talk (although seems to be about right). Add to that the likelihood of old fluid mixed with white spirit is still in the VCU before you start adding the new fluid, and there are way too many variables to make this an exact method. That makes it more important to add a little more than you think necessary so that you can release some if it is too tight. Much harder to add more unless you go down the grease gun/nipple route.

Interesting reading.
Peeps need to be very careful of the cleaners they use. Use a ventilated area (preferably outside open air) and be very careful of acid content and how severe the cleaning chemicals are. The vapour off some of them is a big enough hazard to cause permanent damage to breathing.

I would be inclined to use a quick evaporating solvent such as alcohol or lacquer thinner for the last couple of rinses then blow the remainder out with compressed air.
Of course using this sort of solvent you should be wearing a respirator, safety goggles and nitrile gloves, and preferably do it outside where there is good air circulation, and no pilot lights or angry wives to cause an explosion.
I do think the grease nipples are an excellent idea.

I thought about using panel wipe for the last couple of flushes but like I said I was concerned about harming the seals and bearings so didn't bother. I did blast it with compressed air though to get as much out as possible .

Another great write up Ali