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MG ZT / Rover 75 - VIS Valve Motor: How to?

126K views 108 replies 30 participants last post by  sjbso2000 
#1 ·
Right this is swiped from the Xpower forum
original Author Sheddist so all credit to him as it a damn good howto
lets grow this into a Vis Valve and Manifold Howto

Sheddist Said

"Thanks to Aldon, who donated a dead actuator to the cause. Here is what this is all about:
[/IMG]

These are a bit of a pain to get apart and is about the longest part of the process.
First, ease back the clips
[/IMG]
Then using a thin, wide blade,
[/IMG]
gradually prise the cover away from the housing. It will not come off at this stage
[/IMG]
Cut a suitable piece of wood or metal to fit right inside the electrical connector
[/IMG]
Then push the connector blades and cover apart. This requires a fair bit of force and don't worry if a blade bends or pulls out of the circuit board. When the cover is off the motor internals with the worm gear removed look like this
[/IMG]
One or both of the two black limit switches is likely to be loose. This is due to poor location resulting in broken soldered joints. The next stage is to remove the circuit board. First, prise out the worm. Take care not to loose the washer off the end of the worm shaft. Use a wide flat blade to spread the load and unclip the worm, bringing the motor and PCB with it.
[/IMG]
At this stage the switch terminals can just be resoldered and the actuator put back together, only to fail again. You can improve matters by screwing the swtiches down. You will need a 1,8mm drill, 8BA tap and 8BA by 1/4 inch screws. Or use 2mm if you prefer metric! These can all be obtained from http://www.mainlytrains.co.uk/acatalog/index.html
Just do a search for 8BA and then for the drill.
Drill out the switch pegs with the 1,8 drill
[/IMG]
Tap the holes
[/IMG]
and fit the screws. TAKE CARE TO ENSURE THE SCREWS DO NOT SHORT OUT 2 PCB TRACKS. FILE A FLAT ON THE SCREW HEAD TO AVOID THIS.
[/IMG]
Once the screws are fitted, resolder the switch terminals.
Remove the old sealing bead from the case joint and apply new sealer. I use blue Hylomar
[/IMG]
Reassemble the parts, taking care to clip the motor and worm in together, not forgetting the washer.
Fit the worm wheel so that neither switch is operated- both white switch plungers are not pushed in by the cam, then fit the cover.
I have a test box to test these things - another "how to" coming for this.
Before refitting, plug the actuator into the wiring harness and turn on the ignition- dont try to start the car. This will reset the actuator. Align the actuator output to the manifold slider, and secure with the 4 screws. Start up and check for air leaks, the screws need to be tight and you may have to add a bit more sealer around the actuator joints.
Take a test drive"
 
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11
#2 · (Edited)
Yuk look at the state of that!

Inside a KV6 inlet manifold, this is one Mucky piece of plastic

Pictures courtesy of lates who said :-

"Afternoon gents,
In my quest to unwind and get ready for me holidays I came across an old gopping inlet manifold I just had to get to bits.

I do not recommend anyone taking theirs to bits "just to look" as it involved a bit of bashing and there are no servicable parts inside.So curiosity got the better of me. I do not think this car had a good service history or higher quality oils judging from the amount of gunked up goo inside.


Anyway here goes, 56k apologies.....
























Thats ya lot folks, outcome is if your manifold rattles throw it away.

edit see here for descriptions and original sizes.....
http://s30.photobucket.com/albums/c3...es600/?start=0
"
 
#90 ·
Inside a KV6 inlet manifold, this is one Mucky piece of plastic

Pictures courtesy of lates who said :-

"Afternoon gents,
In my quest to unwind and get ready for me holidays I came across an old gopping inlet manifold I just had to get to bits.

I do not recommend anyone taking theirs to bits "just to look" as it involved a bit of bashing and there are no servicable parts inside.So curiosity got the better of me. I do not think this car had a good service history or higher quality oils judging from the amount of gunked up goo inside.


Anyway here goes, 56k apologies.....
























Thats ya lot folks, outcome is if your manifold rattles throw it away.

edit see here for descriptions and original sizes.....
http://s30.photobucket.com/albums/c3...es600/?start=0
"


Help!

Mine rattles, would a check and possible fix of the Vis recify this..

I checked one once before and it was fine, the other at the back, I didn't..

Or is it the big costly job of the lot on top? Any advice would be appreciated as im considering a new car otherwise.. :-(

Thanks in advance..

V6 2.5 160 ZT 51 plate..
 
#4 ·
Stereo - Keith, I have tried to be nosy and take a unit apart before now to look at the motors and switches, how much does it take to separate the cover and housing? That was the point where I called it a day.

Also, recently, took manifold off and sprayed through with carb cleaner which is a dirty experience - try not to let the small flap valve from side of manifold fall out whilst this is going on.

Immediately after, I thought I had created a VIS valve problem as on start up things were a bit clattery, but a 70 mile drive appeared to cure it and no noises since, so I guess a bit of oil does no harm.
 
#70 ·
I had exactly the same thing, the rattling was worse when i started it up, i drove for a while and the problem has never returned. The carb experience was messy and i also suffered from a sticky throttle. Some oil is needed just to keep it running, i guess its just a case of how much and its quality. That oil gets into the VIS motors as well.
 
#5 ·
I have had the lid off the front motor but not the back one they are a wee bit tight but the feeler gauge method above looks ok

The rear butterfly valve can go in any way round so I took mine out to clean it. I can't see that one ever causing a problem itself it will just be the back motor unit

The front valves are a different story what a silly idea sealing it all up that sort of thing we were taught to reject during the first months of my engineering apprenticeship. as it makes it impossible to 100% indentify if all six are ok or not

As for the front motor I took apart it looked ok but that was before I found the above howto so I did not however check the soldering to the switches though, I will next time I am in the mood as the above mod is a good one, most components over a certain weight subject to heat and vibration should not be secured only by solder as it will fail over time

I would like to disect a failed inlet manifold one day when I get the chance and post the photos here same as I am doing for the rad fan motors

Hence the two place holders above

Anyone got an old one lying around? If not next person to get one changed don't leave it at the garage please lets put it to good use on here.
 
#7 ·
Thanks I will send you my address as I am terminally curious about all things that fail prematurely

btw look up I have pinched your post for posterity or until something more sticky comes along :)

Assuming nothing is broken is that manifold actually worn out or could one be revived in a cleaning bath?
 
#8 ·
The difference between pics 8 and 9 show where the spindle goes through the throat and one of them is completely oval. I think it is only fit for the wheelie bin. I will send it so you can see how it all works.All of the bits are there but not pretty as brute force is required to get it into bits.You could put it all back together with plenty of hot glue and sealant I guess ?
 
#11 ·
I agree although I haven't got the one Lates is sending for a close up yet but they do look terminal.

I wonder, are the butterflys and their pivot points plastic or metal?

It will be interesting to see how the valves are actually fitted I wonder if out of desperation they could be rebushed using PTFE or something
 
#13 ·
Beg to differ!
I recon these can be fixed.
My plan is to fabricate new butterfly valves and slider out of brass. Just need the dead manifold to play with! May just need to ream out the holes to take the spindles.

With respect to the state of the disected unit, then looks like the oil catch tank is a method to reduce this.
 
#16 ·
Thought you could hide on the 75/ZT section?

No offence 1955 diesel

Agreed about the expansion issues. These can be allowed for when considering clearances. PTFE will be fine for bushes, provided the bushes cannot fall out! The existing system may have expansion issues. The plenum is glass filled PA or PBT. The slider and butterflys look unfilled and will expand more rapidly. This could lead to the hot weather problems suggested by Parsec

My main concern is the ability to get the cover off and refitted/replaced and maintain a seal. If a plenum does darken my door, first job will be to make a mould over the cover to stand a chance of producing a replacement. Will also, given the chance, try splitting the weld using a hot blade. The walls look thick enough to refit a cover with a row of proper screws.
 
#19 ·
Well after my tour around the Midlands yesterday looking at various tourers during a hi speed blat home I gained the impression something was not right!

definate feeling of power fluctuations through the gears

I put testbook on it this afternoon and sure enough Vis valve fault looged in ECU so off it came and as expected one micro switch with a dirty great big dry joint

Both switches are firmly fixed and resoldered to the board now so that won't happen again
 
#20 ·
Help please

Hi i have a MG ZT 190 a few things are going on but cant find the answers except for this forum thread i may be wrong though.
1) around 2000 rpm and then again at around 3500rpm i get a rasping sound, it sounds roughly like a loose heat sheild vibrating.
2)power seems pretty poo until around 3000 but only sometimes
2)and this is where i am gonna sound really thick i can only find the front spark plugs where are the other three im guessing below the manifold (black) does this have to come off? and is there a how to do.

Hopefully somebody can help and sorry if im a pain.

Thanks

Ian
 
#21 ·
Maybe easier to begin a new thread for your issues but in the mean time...

1) around 2000 rpm and then again at around 3500rpm i get a rasping sound, it sounds roughly like a loose heat sheild vibrating.
Time to check underneath to make sure everything is secure.Can this be reproduced under the bonnet ?

2)power seems pretty poo until around 3000 but only sometimes
Maybe worth getting it plugged in to a diagnostic, maybe related to issue #1 if the plenum is faulty.

3)and this is where i am gonna sound really thick i can only find the front spark plugs where are the other three im guessing below the manifold (black) does this have to come off? and is there a how to do.
Remove the centre bulkhead clips and 8mm bolts to help with access to the plugs, it is possilbe without removing the plenum.

Hopefully somebody can help and sorry if im a pain.
Don't worry about it :)
 
This post has been deleted
#25 ·
My throttle is "lazy", it needs a half of a second for the motor to get the revs when pressing the pedal (I know that it can't be instant but mine is really slow) and about a second to go back to idle when I release it.
Hi Fidel,
My V6 does the same. If anything mine takes even longer than a second to go back to idle. I find it makes smooth gearchanges very tricky. I mentioned it to my local dealer when I had it serviced and they put it on the T4 but didn't find anything unusual. It seems to be a function of the emissions control strategy in the ECU, which opens the IAC valve when the throttle closes. I'd be interested to know if there is any way to sharpen up the throttle response as I find it very frustrating.

MJT.
 
#27 · (Edited)
I just wanted to post here and say a HUGE THANKS to Sheddist for his informative pictures of the VIS Motors at the top of this thread (and to Keith Alexander for bringing them over here from the XPoiwer forums).

Really, I would never have had the courage to venture near these beasties without having such clear piccies and the benefit of Sheddist's disassembly notes. I'm not frightened of a bit of work, but I would probably have stopped at the point where the top covers appeared not to want to come off, for simple fear of breaking the PCB or something inside. With Sheddist's examples, I had the bottle to carry on!

And boy, was it worth it? You bet! In spades. My late father had been told by his main-dealer garage that his inlet manifold needed replacing because of a rattle, and that it would cost circa £864 (plus VAT) in 2005. Unfortunately, he wasn't using the car much then anyway, and passed away from cancer late last year, so the job never got done (and the car never accrued many more miles anyway, so he would never have seen the benefit of the nearly-a-grand he would've spent either!)

The car came to me in November '07 as a bequest after his death, and I have done my level best to make him proud and keep it in fine fettle. Everything's been pretty fine until last night, when presumably the power-valve VIS motor finally gave up the ghost. I thought I had fuel starvation or something - the car was seriously down on power, laboured, misfired, and felt really, really worrying for the last ten miles (at midnight, of course) up hill and down dale on the the shortcut around A36 to home which avoids the new roadworks there. I really didn't think we'd make it, but we limped home (pregnant wife and all) and breathed a sigh of relief. I checked under the bonnet with the engine running, before I shut it down - and the VIS rattle was there in earnest. It sounded much louder than usual - like a bag o' spanners - and my heart sunk. :(

Today, I spent the afternoon stripping down BOTH VIS motors, cleaning them up, resoldering the switch connections, and resealing and refitting them. Both switches in the power-valve motor had dry solder joints, and were flapping about sufficient to completely 'miss' the cams on the worm-driven gear). Re-solder and glue to the PCB with superglue before resealing.

The balance valve motor seemed basically okay (no dry joints, and the switches were still tight to the PCB) - but I stripped them down anyway and re-soldered and reglued them to the PCB, too. The motor did seem very oily, so I cleaned that up and tested it (a nine-volt PP3 battery across the terminals works fine for this, by the way. You can even pop off the motor from its contacts at the 'plastic end', and test it separately from the PCB - it's a clip-on fitting, it seems. Another note to anyone attempting this - be very careful when removing the back (balance valve) VIS motor... the plastic valve itself (just inside the manifold) is not firmly fixed into that manifold, and can be pulled out either when removing the VIS motor itself, or (as happened to me) when removing the cloth that you have stuffed in there to keep the dust out while you go away and fix the motor! If the balance valve drops, it will fall under the engine, and require a very obedient and brave wife with thin arms to gingerly slide an arm down there to get it! Be warned!

I've since put everything back together again, and since then, run the engine in situ (haven't taken it for a run yet, because it's about to get dark and I don't want to get stranded if it DOES still have a problem)... but immediately, the absence of ANY VIS rattle was noticeable - real 'stand out' noticeable'. Even my wife spotted it - the engine is now purring like a cat, and there is not one single moment during the whole rev-up to about 6K that sounds even the least bit like George Formby playing the spoons! :)

I can barely wait to take her for a spin tomorrow (because presumably, it's never been so 'tight' as this, in all the time I've had the car - so I'm looking forward to an improvement in the mildly-laggy powerbands I've experienced in the past).

But whether it solves my main 'misfire/power' problem or not (I'm fairly sure it will) I just wanted to say that big thanks to Sheddist, for helping me to sort this one out for myself, rather than letting the garage rip me off. Many, many thanks indeed! :)
 
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