How to recondition a VCU yourself.

Alibro · Dec 18, 2016

I guess in theory loosing 20 or 30kg plus the small amount of drag it causes should have an effect on mpg but as said it seems to be pretty minimal.
If you don't loose the weight then probably not worth doing.

jonaf · Dec 18, 2016

Kayos said:
I've actually calculated it, reset trip and fill up and I get 26mpg with or without a prop

Which proves your wheels are the same diameter and the VCU is healthy

Kayos · Dec 18, 2016

jonaf said:
Which proves your wheels are the same diameter and the VCU is healthy

I like your thinking, the tyres are identical but I removed the prop during the clutch change and left it off as my repair was leaking

Alibro · Dec 18, 2016

Kayos said:
I like your thinking, the tyres are identical but I removed the prop during the clutch change and left it off as my repair was leaking

Put your VCU in a vice and crank it round until the leak(s) show(s), mark them then turn the VCU over so the fluid can settle.
Clean it up as best you can and weld it again, watch the mini volcano's grow in front of your eyes as the fluid bubbles through the welds.

Grind it back a bit and repeat until it stops erupting, test again on the bench, leave it for a few days to ensure it doesn't drip out, refill and it should be OK to refit.

Then after a few days test it with the OWU test and adjust the fill level accordingly.

Nodge68 · Dec 19, 2016

Kayos said:
I've actually calculated it, reset trip and fill up and I get 26mpg with or without a prop

I did extensive economy testing with and without the VCU on my V6. I ran for 5K miles with and 5K miles without the VCU. I used a spreadsheet to do the maths on fuel usage. The V6 gained 0.29 MPG when running without the VCU. I suspect that most of that gain was down to the loss of 30Kgs of wait from the vehicle.
So removing the VCU does improve economy, but not by much.

Kayos · Dec 19, 2016

Nodge68 said:
I did extensive economy testing with and without the VCU on my V6. I ran for 5K miles with and 5K miles without the VCU. I used a spreadsheet to do the maths on fuel usage. The V6 gained 0.29 MPG when running without the VCU. I suspect that most of that gain was down to the loss of 30Kgs of wait from the vehicle.
So removing the VCU does improve economy, but not by much.

Mine wasn't extensive, one tank with it fitted, did the clutch and left the prop off and got the same result, however 0.29mpg is very minimal and as you say, probably the weight

rob_bell · Dec 19, 2016

I suspect that those who do see a measurable improvement in fuel economy without a VCU have a cream-crackered VCU (and possibly IRD), and are driving more economically (whether consciously or not).

Nodge68 · Dec 19, 2016

rob_bell said:
I suspect that those who do see a measurable improvement in fuel economy without a VCU have a cream-crackered VCU (and possibly IRD), and are driving more economically (whether consciously or not).

Interesting point. With the V6 running 2wd. You have to remember not to give it to much throttle when pulling out of junctions, particularly in the wet. It spins it's wheels very easily, which results in TC intervention. This more gentle acceleration could account for the slight increase in economy. But I still put it down to the wait loss, more than anything. At least with the way I drive!

Andy_J · Dec 19, 2016

Going to give this a go over Christmas, as I have 3 VCU's that are shot. Got a couple questions

1. how deep does the hole need to be/how thick is the metal on the VCU?
2. How do I know when I have drilled deep enough?

Thanks

Nodge68 · Dec 19, 2016

Andy_J said:
Going to give this a go over Christmas, as I have 3 VCU's that are shot. Got a couple questions

1. how deep does the hole need to be/how thick is the metal on the VCU?
2. How do I know when I have drilled deep enough?

Thanks

The end plates are around 10mm thick.
I set my pillar drill depth stop to 9mm. Then just kept nipping a bit more metal until the drill broke through. You'll know when it has, as the fluid bubbles out. The second end is more guess work after 9mm. Take is slow and you'll get there

Alibro · Dec 19, 2016

Andy_J said:
Going to give this a go over Christmas, as I have 3 VCU's that are shot. Got a couple questions

1. how deep does the hole need to be/how thick is the metal on the VCU?
2. How do I know when I have drilled deep enough?

Thanks

Keep drilling until you're through.

As Nodge says around 10mm but don't worry about hitting the first plate. It is connected to the outside casing of the VCU so the marks you make on it will always stay in the same position.
I heard a tip, to put a load of grease in the hole when you get nearly through to hold the swarf but it should come out with the gunge anyway. In anycase you'll make more swarf tapping the hole so make sure you do it asap after drilling the holes.

Do us all a favour and try filling them with different methods and report back which is the bestest.

GrumpyGel · Dec 19, 2016

Andy_J said:
Going to give this a go over Christmas, as I have 3 VCU's that are shot. Got a couple questions

1. how deep does the hole need to be/how thick is the metal on the VCU?
2. How do I know when I have drilled deep enough?

Thanks

Did you ask Santa for some Polydimethylsiloxane?

rob_bell · Dec 19, 2016

GrumpyGel said:
Did you ask Santa for some Polydimethylsiloxane?

He said he'd rather have a mince pie

Andy_J · Dec 19, 2016

What's Polydimethylsiloxane? asked Santa for some 100,000 silicone oil.

Well drilled it with two 8mm holes and got the first disk, can't see any goo trying too ooze out yet, will see what it is like in the morning

Going to try the grease pump method of filling first.

Will report back once I have some results or problems, silicone oil has delivery of date of 8th January

Alibro · Dec 19, 2016

[QUOTE="Andy_J, post: 3887880, member: 55876"]What's Polydimethylsiloxane? asked Santa for some 100,000 silicone oil.

Well drilled it with two 8mm holes and got the first disk, can't see any goo trying too ooze out yet, will see what it is like in the morning

Going to try the grease pump method of filling first.

Will report back once I have some results or problems, silicone oil has delivery of date of 8th January

[/QUOTE]
S'what it says on the tub.

http://www.ebay.co.uk/itm/Silicone-...637557?hash=item360e914d75:g:ToYAAOxyJX1S~Ufp
I used an M10 extra fine tap so drilled a slightly bigger hole 8.8mm I think but would need to check. The fluid should start to ooze out immediately as it's normally under pressure. If it doesn't then the VCU will be really tight and you might struggle to crank it round initially to mix whatever cleaning fluid you plan to use.

Andy_J · Dec 20, 2016

Alibro said:
S'what it says on the tub.
http://www.ebay.co.uk/itm/Silicone-...637557?hash=item360e914d75:g:ToYAAOxyJX1S~Ufp

Yep that's the stuff

Alibro said:
The fluid should start to ooze out immediately as it's normally under pressure. If it doesn't then the VCU will be really tight and you might struggle to crank it round initially to mix whatever cleaning fluid you plan to use.

Tiny dribble of stuff oozed out, going to give it 24 hours upside down and hope. Was 7 minutes on the VCU test so I expect it is nearly seized completely.

Alibro · Dec 20, 2016

Andy_J said:
Yep that's the stuff

Tiny dribble of stuff oozed out, going to give it 24 hours upside down and hope. Was 7 minutes on the VCU test so I expect it is nearly seized completely.

You may as well start injecting white spirit or whatever it is you intend to use. My first one was like that but I cut it open so can't comment on how hard it will be to flush out.
If you had a syringe with a needle you would have a better chance of getting the white spirit into the gunge.
I'm surprised the car didn't tear itself apart (or did it) with a VCU that solid.

Andy_J · Dec 20, 2016

Alibro said:
I'm surprised the car didn't tear itself apart (or did it) with a VCU that solid.

Destroyed the IRD, half the teeth stripped off the driver side output and end casing split into 2 pieces

Alibro · Dec 21, 2016

Andy_J said:
Destroyed the IRD, half the teeth stripped off the driver side output and end casing split into 2 pieces

I think congratulations are in order here, (that sounds wrong somehow, can't think why

) you might just be the first person to do the OWU test on a VCU that has actually trashed a drive train. What weight and length of bar did you use? I normally use a 5Kg weight on a 1.2m bar but some folk use other weights. Also do you know what mileage was on the car?
This is important as we have previously only guessed at how bad a VCU has to be to do harm, however it is also true that there are other factors like tyre sizes and pressures that can speed up the issue.

Andy_J · Dec 21, 2016

It was 5kg at 1.2m, was 126k miles. VCU was on an L series. Tyres were all identical and pretty much same tread depth. Was on a vehicle I bought at auction for £300 so expected something knackered. Tested the VCU once I had replaced the IRD

Can just about turn the VCU with a 4' bar on it so should be able to get the old goo out of it. Going to leave it to drain for a couple of days before I put white spirit into it

How to recondition a VCU yourself.

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