Syncro Decoupler on the blink

[nohabusguy]

Recently acquired an 89 Syncro with the decoupler (middle knob) and rear locker (right knob) set up. The syncro has the solid shaft now with the VC removed. I have noticed recently that the decoupler switch isn't engaging and disengaging without driving for a long period of time. There isn't a lot of rhyme or reason to when it works properly or not, except that its been very cold and snowy out in Massachusetts where I live. For example, I might push the middle switch back in to turn off the front wheel drive and the green light won't go off for at least a few miles of driving. Same way when I pull the switch, it will take a while to engage. If I drive for 20 plus miles, then it might start to work normally where pulling and pushing the switch causes the light to go on and off pretty quickly. The four wheel drive is definitely working when the light is on, as I am getting normal traction.

I will likely take it to my local VW guy to have it checked out. But he doesn't work on this type of set up too often (as he told me over the phone -- I could hear him thinking "I don't want to get involved with this"). Any thoughts on whether this is a minor/major problem, and what might need to be repaired? Thanks!

[jakebayless]

If I had to guess (which I'm doing ) I'd say that there is most likely a vacuum leak somewhere.

The control knob in the dash is merely a valve turning vacuum on or off to the actuator mounted back on the decoupler. (same actuator as the rear locker - exactly same system)

If you or your mechanic can verify adequate vacuum in the lines to & from the triple lobed vacuum canister under the drivers side frame rail, you are well on your way.

Two other likely scenarios I've seen are either a rusted acutator shaft (if rust is prevalent in your part of the world) or a sticky actuator itself.

I'd be willing to bet James (Dogpilot) can give you more specifics... Probably even has schematics!

I've been fortunate enough to have a troublefree decoupler for only a year or so... (still would LOVE to get my hands on a front locker!)

cheers,
~jake

[silversyncro]

My 91 syncro westy had what sounds to be the same issue earlier this winter. The problem turned out to be the vacuum check valve located under the van next to the vacuum resevoir. I just went down to napa and bought a generic valve for like three bucks, and it works like a charm again.
You just need to get the motor running, pull or push the knob so that you are asking it to do something...then crawl under there and start pulling vacuum lines off starting at the decoupler till you find either a blockage or a leak. Syncro.org has a great trouble shooting guide for your difflock if you need more info

[nohabusguy]

Thanks for the leads. I will check those out.

[silversyncro]

jakebayless has a few good points too, but the rear difflock, and the the de-coupler are not controlled by the same actuator in exactly the same place, they are in two totally different locations. That doesn't mean that a vacuum leak at, or on the way to your difflock wouldn't effect your de-coupler though.
Just didn't want you going on a wild goose chase.
Good luck

[nohabusguy]

Finally got around to crawling under the Syncro and troubleshooting this problem ... pulled off the check valve, and shot it with wd-40 and then compressed air (the stuff I use to clean my keyboard). I put the check valve back on and now everything works fine. Decoupler engages and disengages as it should. Thanks!
_________________
1967 Double Cab
1967 21 Window Deluxe Bus
1989 Westy Syncro (Subaru 2.5, dreaming of installing a NAHT)
1990 Doka Syncro (WBX 2.1)

[buspor63]

[Sodo]

[MTV1960]

Hi there, hope you can help trouble shooting an issue with my decoupler as it is not engaging. was working fine when parked 5 months ago. van is located in costa rica and was parked during the rainy season. rear locker works fine! a bit slow bit comes on in a min or so when pulled. What ive done so far.: Pulled off the check valve and sprayed it with WD40 and blew it out with compressed air. Has flow one direction. I can hear pressure at the dash switch when depressed. Then i pulled off the tubes at the actuator and sucked on both. one was holding and the other one was not until i pulled the knob then is was holding a seal one direction. could it be the actuator is bad by just sitting for 5 months? was going to remove it to inspect and clean it but thought i would ask a pro if that is possible to clean and reinstall or a waste of time. I dont have a backup part here in Costa Rica and would have to wait for some one bring one from the states. What do you suspect the problem is and if there is suggestion to try something now? pain to take down the rock guard if i dont have a new part or if that is that is te actual problem at all.
Thanks Michael V
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86 Wolfsburg Weekender
87 Syncro Westy

[davevickery]

They do get stubborn from lack of use. Maybe you can try working the actuator back and forth multiple times with a couple pieces of spare hose. Jack up a front tire and turn it slowly while sucking on the tube. You will know as soon as it engages as it won't turn any more. It does not take a lot of mouth pressure to activate them so if it does you know it is probably gummed up and you might have to take some of it apart to grease it up.

Every time my locker or decoupler started to give me trouble it was a crusty hose with cracks right at the nipple on the actuator. I cut off a bit of the end and back to normal. In one case I replaced a small section with some silicone hose. But mine are well greased underneath and I exercise them regularly.

[gears]

For me, it's always been the check valve ..
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[MTV1960]

Ill give it a try. What would be the procedure for that? Suck on the top or the bottom? guess i need a length of hose thats long enough to work the front wheel at the same time. Would the knob need to be open of closed at the same time ?
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86 Wolfsburg Weekender
87 Syncro Westy

[MTV1960]

Regards to the ck valve. i can move air one direction only but it not super open feeling. not sure if thats normal. Requires a bit to pressure to blow air past the valve. could that be restricting that system? I Do have a working rear locker and i think they share the check valve right?
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86 Wolfsburg Weekender
87 Syncro Westy

[davevickery]

You should be able to suck and blow through just one but take both hoses off the actuator then it doesn't matter the position of the dash button. The "suck to engage" is the inner blue nipple on the spare I just checked.

Gears may be right about the check valve. You could remove it and see if it is working. I don't think you even need the check valve, there is always suction in the cannister so it doesn't ever get pressurized. But you could remove it at least temporarily.

[clift_d]

Check it's not the decoupler indicator sensor before you go much further. This is similar to the reverse gear indicator sensor in that it is switched by a groove on the actuating shaft moving past the sensor. You should have the access to pull this sensor from the nose of the gearbox without too much difficulty which will then allow you to see whether the actuator shaft is actually moving or not. We had a similar issue a couple of years back when we were in Iceland, in that we thought our decoupler was sticking but it turned out that the indicator sensor was failing.
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1988 LHD T25 1.6TD Westfalia Club Joker syncro

[MsTaboo]

Van-Cafe:
http://www.van-cafe.com/diff-lock-actuator-check-valve

And lots of other goodies:
http://www.van-cafe.com/diff-lock-actuator
_________________
Currently:
'90 Syncro Westy 3 knob w/Zetec

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[MTV1960]

Right, so your saying that you were engaged but the sensor was not sending so the light was not on?
Im pretty certain im not engaged at all. I dont here or feel any grinding on the gravel when making a turn. I have zero access to parts here in Costa rica. I know of a syncro club in Nicaragua that could have parts but its too far. Im going to drop the Rock guard and remove the actuator and see if i can clean it. All the tubing looks fine.

This country is harsh on everything made by man. Syncro is headed back north for a refit in April. FYI think twice about bringing down your Vans to this part of the world unless you have at least one spare part of every part on the van, and every tool you can think of. List of parts replaced since 2014:
-2 wheel bearings
-2-rear CV's
-Power steering rack
-front claiper
-multiple bulbs
-Shure flow faucet
-Aux battery
-Subi oil pressure switches
-Subi SS header
-head light adjusters
-fuel filter
-prop shaft yokes
-wiper arms
-Front control arm bushings
-Coolant expansion tank

Pura Vida! Good surf though!
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86 Wolfsburg Weekender
87 Syncro Westy

[MTV1960]

Any one headed to Costa Rica that can bring me a check valve and an actuator?
_________________
86 Wolfsburg Weekender
87 Syncro Westy

[clift_d]

[gears]

If you can suck air through the check valve in one direction only, it's OK (it's supposed to seem semi-restricted).

Leaky hose somewhere would be my next guess.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com