DIY VCU service

matacaibo · Apr 1, 2014

Definative VCU thread

Wondered where I read this so I did a search & hey presto, info provided by our very own Mad Hat Man.
Look at the fluid characteristic & the fact it says it is patented

The Mad Hat Man · Apr 3, 2014

I still reckon that by the time yu have found and bought a suitable fluid and trialled and errord the amount (its critical) in the VCU, yu could have bought 4 or 5 replacements at least.

matacaibo · Apr 3, 2014

The Mad Hat Man said:
I still reckon that by the time yu have found and bought a suitable fluid and trialled and errord the amount (its critical) in the VCU, yu could have bought 4 or 5 replacements at least.

I hadn't realised the amount of fluid was critical until I re read your previous post.
Each to his own but personally I couldn't risk the VCU not working when it was needed offroad.....there might not be any trees around to attach the winch to

jonaf · Apr 4, 2014

jedi said:
Excellent!!! work Jonaf.....This is what I like to see, The thickness of the VCU casing looks quite thick? :biggrin1: looking at the photos you have posted, How far in does it go, before your reach the plates inside?

What sort of fluid did you use to refill them?

The end walls of the VCU are 10mm thick. The easiest - but also the slowest way to drain the unit is to drill out the steel balls and let the fluid run out by itself. This takes several days. Getting the last drop out takes weeks if you do it this way. Heating will speed up the process.
I do not think it is necessary to replace all the old fluid. Diluting the stale fluid with some fresh thin silicone will loosen up the VCU and make it work OK again. I did it this way with the first one I did and it worked fine.

Northern Irelander · Apr 4, 2014

jonaf said:
The end walls of the VCU are 10mm thick. The easiest - but also the slowest way to drain the unit is to drill out the steel balls and let the fluid run out by itself. This takes several days. Getting the last drop out takes weeks if you do it this way. Heating will speed up the process.
I do not think it is necessary to replace all the old fluid. Diluting the stale fluid with some fresh thin silicone will loosen up the VCU and make it work OK again. I did it this way with the first one I did and it worked fine.

Useful tips, have you tried vacuum pumps?

I was even thinking of drilling holes in the outermost edges, then add a suitable solvent and centrifuge the remaining fluid/diluent out the holes!
VCU could even be left in situ, take it for a test drive (or place on stands) and let the transmission/prop centrifuge out the rest of the gunk for you.

bugsb · Apr 5, 2014

after drilling and pumping out some of the fluid 8 weeks ago and replacing it with a silicon oil then re-welding the holes i got my vcu to pass the wheel up test
lucky i had x2 vcu's to play with it takes 40-50 miles for the silicon to mix with the old silicon
first attempt to little oil was replaced so 2nd vcu i removed and replaced with more silicon oil
it is trail and error depending how thick each vcu's oil has gone
i am in the process when i get time to re-do the first vcu
Ron

WilkoUK · Apr 5, 2014

Hi,

Just to add some info. The recon VCUs from Bell are cut at the top, cleaned out, refilled, re-welded together and re-sprayed. Nice neat job.

bugsb · Apr 5, 2014

bugsb said:
after drilling and pumping out some of the fluid 8 weeks ago and replacing it with a silicon oil then re-welding the holes i got my vcu to pass the wheel up test
lucky i had x2 vcu's to play with it takes 40-50 miles for the silicon to mix with the old silicon
first attempt to little oil was replaced so 2nd vcu i removed and replaced with more silicon oil
it is trail and error depending how thick each vcu's oil has gone
i am in the process when i get time to re-do the first vcu
Ron

i should add always measure how much fluid you remove so you replace it with the same amount
Ron

jonaf · Apr 5, 2014

bugsb said:
i should add always measure how much fluid you remove so you replace it with the same amount
Ron

With grease nipples it is easy to adjust the fluid amount. A few extra strokes with the gun makes the VCU stiffer. If it becomes to stiff, just press the ball valve with a thin crosshead screwdriver and let some fluid out.

Nodge68 · Apr 5, 2014

jonaf said:
The end walls of the VCU are 10mm thick. The easiest - but also the slowest way to drain the unit is to drill out the steel balls and let the fluid run out by itself. This takes several days. Getting the last drop out takes weeks if you do it this way. Heating will speed up the process.
I do not think it is necessary to replace all the old fluid. Diluting the stale fluid with some fresh thin silicone will loosen up the VCU and make it work OK again. I did it this way with the first one I did and it worked fine.

I'm sure I read an old thread of yours on another LR forum on this very thing.
Interesting reading. I've been thinking of trying it myself.

Nodge68 · Apr 5, 2014

bugsb said:
after drilling and pumping out some of the fluid 8 weeks ago and replacing it with a silicon oil then re-welding the holes i got my vcu to pass the wheel up test
lucky i had x2 vcu's to play with it takes 40-50 miles for the silicon to mix with the old silicon
first attempt to little oil was replaced so 2nd vcu i removed and replaced with more silicon oil
it is trail and error depending how thick each vcu's oil has gone
i am in the process when i get time to re-do the first vcu
Ron

Is the VCU fluid simple silicone oil? I don't think so.
As far as I know it's a non newtonian fluid. This fluid has special properties the make it thicken when agitated. It is more complicated than that. Agitation causes local heating of the fluid, this heating causes the thickening. Or the localised thickening causes heating. Which ever way it is, normal silicone oil doesn't behave like that. Silicone oil gets thinner as it warms up in the same way that mineral oils do.
Silicone oil is now used in radio controlled car shocks so is, cheap, easily obtained and is available in a wide range of viscosities, non of them much use in a VCU though.

bugsb · Apr 5, 2014

Nodge68 said:
Is the VCU fluid simple silicone oil? I don't think so.
As far as I know it's a non newtonian fluid. This fluid has special properties the make it thicken when agitated. It is more complicated than that. Agitation causes local heating of the fluid, this heating causes the thickening. Or the localised thickening causes heating. Which ever way it is, normal silicone oil doesn't behave like that. Silicone oil gets thinner as it warms up in the same way that mineral oils do.
Silicone oil is now used in radio controlled car shocks so is, cheap, easily obtained and is available in a wide range of viscosities, non of them much use in a VCU though.

the oil is mixed with the old fluid to water it down that is all
it is pure silicon oil
Ron

The Mad Hat Man · Apr 5, 2014

Nodge is absolutely correct.

The stuff you are using is not suitable for the application.

You are ****ing in the wind. It might help, but it ain't the correct stuff. It's like putting engine oil in a gearbox -" it's oil, right!" It might work, but it isn't as good and it won't do what is required long term. If yu don't mind checking yo VCU every weekend then that's fine, but it's a bodge. It cannot be recommended.

bugsb · Apr 5, 2014

The Mad Hat Man said:
Nodge is absolutely correct.

The stuff you are using is not suitable for the application.

You are ****ing in the wind. It might help, but it ain't the correct stuff. It's like putting engine oil in a gearbox -" it's oil, right!" It might work, but it isn't as good and it won't do what is required long term. If yu don't mind checking yo VCU every weekend then that's fine, but it's a bodge. It cannot be recommended.

not recommending it to any one it was a lets see if it works or put them in the bin but it worked fine i do check it every 2 weeks and am interested to see how long it will work for so testing in progress
Ro

The Mad Hat Man · Apr 5, 2014

Certainly worth a try, at yo risk. Be interesting to see your results.

bugsb · Apr 5, 2014

The Mad Hat Man said:
Certainly worth a try, at yo risk. Be interesting to see your results.

i will be keeping an eye on it for the next at least 6mths so far i have done around 2000miles but have not used the car much in the last 2-3 weeks as i needed the van
on a 100mile trip to work first thing i do is check the temp by hand so far its just been luke warm to touch one wheel up test is fine if it got stiff i have the tools with me to whip it off
Ron

DastardlyDan · Apr 5, 2014

All you've done is turn your car from a viscous 4WD, to FWD, with a rear end that just adds drag

It'll never "fail", and as has been said time and time again, the "rear wheel test" will only test if the VCU has totally locked up, it gives no indication of proper function

Either fit a new VCU, or just remove it and gain a smidge of mpg

The Mad Hat Man · Apr 5, 2014

Where did you get that **** info from?

VCU test is as good as we can get at the mo. You are talking bollox

jedi · Apr 5, 2014

Just freeing up the vcu a bit whether it be with silicon oil, new vcu fluid or even dog **** is a fix for me

You only gets 12 warranty from a reputable reconditioner anyway......what happens after that?

Has anyone had any problems with a recon one?

Hippo · Apr 5, 2014

DastardlyDan said:
All you've done is turn your car from a viscous 4WD, to FWD, with a rear end that just adds drag

It'll never "fail", and as has been said time and time again, the "rear wheel test" will only test if the VCU has totally locked up, it gives no indication of proper function

Either fit a new VCU, or just remove it and gain a smidge of mpg

It's the "one wheel up test" and it's a measure of the resistance across the vcu. It's give us an analogue reading which varies from vcu to vcu. There are some vcu's where it won't give a reading but that's because the owner is too lazy to perform the test. Other than the "turnip test" there is nothing betterer than the "one wheel up test."

Reconditioners may advertise the test is bollocks, but they forget what they said when they ask you to drop by so they can use it to convince you to part with yer money when they test yer vcu with the same test.

DIY VCU service

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