Roof hydraulic diagnosis help

[Brendon]

My T6 is in the garage again due to a dropping roof on the offside. Originally, we had a problem with the roof dropping in November 2019. Unfortunately, it seemed to 'fix' itself on the way to the garage and they were unable to recreate the fault. The vehicle was under warranty at the time. Since then we have had no issues with the roof until our two week trip to France in August where the fault came back. This was a bit of a bind as we were hoping to use the roof space for sleeping etc. so it put a bit of a dent in the holiday.

Anyway, I've spent a bit of time going through the various threads covering roof issues in an attempt to self diagnose the issue. Not that I was planning to undertake the works myself, but I wanted to make sure the roof fault was correctly identified, that I didn't get a re-occurence of the fault, and that I don't end up spending a fortune whilst the technician swaps out multiple components without applying any thought or logic.

Currently, the garage wants to replace the offside ram as "80 to 90% of roof faults are due to a faulty ram." Personally, I'm not convinced: here's my reasoning....
1) The ram is a passive device. Oil is pushed in at one end and the ram goes up. A faulty ram seal would cause the roof to drop over time. However, once the seal fails it doesn't then fix itself for 9 months before going wrong again.
2) When you raise the roof fully and then lower it immediately the faulty side drops much more quickly. A leaky ram seal would not have had time to leak so the roof should lower on both sides equally.
3) Regardless of how long the roof is up, or whether you jack it up prior to lowering, the dropping side lowers more quickly.
4) The roof drops quite quickly. About half way in under 30 mins.
To my mind, all of this points to an error with the hydraulic pump/valve set inside the cab. As I understand it, there are two valves and actuators that control the flow oil hydraulic fluid into and out of the rams. If one of these valves was not working correctly, perhaps not shutting down properly, fluid would leak back out of the ram and the roof would drop on one side. Also, if the valve was more open on one side than the other, the roof would not lower on both sides evenly.

Does any of this resonate with anyone, or am I talking rhubarb?

As the vehicle is only just over three years old I am angling for VW to take the bulk of the cost of repair under warranty, particularly as the fault had already occurred under warranty. Am I being too optimistic?

Any thoughts gratefully received. Thanks.

 

[Alan Andrews]

Your reasoning looks ok to me.

Likewise if 80-90% of faults are attributed to a faulty ram then it makes sense to replace this first. This is a very high probability number.

And if the fault is the same as before and VW have records of it, then yes I'd be looking to ask for a contribution to the repair.

How much you push for is down to your and your diplomacy skills.

Do have one of those vehicle stethoscope devices - with a long metal probe? I wonder if you would be able to hear the back flow of oil.

They are cheap and I have found them useful with our collection of cars to help identify noises.

 

[westfalia]

I think @TripleBee had a similar issue and replaced one Ram
but then the problem went to the other side so he had to replace
the pump and it did the trick.

 

[Brendon]

Your reasoning looks ok to me.

Likewise if 80-90% of faults are attributed to a faulty ram then it makes sense to replace this first. This is a very high probability number.

And if the fault is the same as before and VW have records of it, then yes I'd be looking to ask for a contribution to the repair.

How much you push for is down to your and your diplomacy skills.

Do have one of those vehicle stethoscope devices - with a long metal probe? I wonder if you would be able to hear the back flow of oil.

They are cheap and I have found them useful with our collection of cars to help identify noises.

A stethoscope is not yet in my arsenal of gadgets, but having a listen would be very useful.

 

[Brendon]

Your reasoning looks ok to me.

Likewise if 80-90% of faults are attributed to a faulty ram then it makes sense to replace this first. This is a very high probability number.

And if the fault is the same as before and VW have records of it, then yes I'd be looking to ask for a contribution to the repair.

How much you push for is down to your and your diplomacy skills.

Do have one of those vehicle stethoscope devices - with a long metal probe? I wonder if you would be able to hear the back flow of oil.

They are cheap and I have found them useful with our collection of cars to help identify noises.

SMG Tonbridge are quoting just under £900 to replace the ram. If I don't get much goodwill assistance, that seems quite a bit of expenditure to find it doesn't fix the issue. Of course, if VW is willing to cover the whole cost, then that's a different matter

 

[EddieEagle]

I had similar sometime ago. Swapped rams side to side which proved it to be the valves plungers or whatever in the pump.
This was at a VW dealership who fitted new pump under warranty.

 

[vwsween]

4) The roof drops quite quickly. About half way in under 30 mins.
Any thoughts gratefully received. Thanks.

At first I thought 30 mins a bit slow rather than quick for half way down! But I assume a typo. But then if you meant 30 seconds for halfway down, thats surely too slow. I have not timed it but surely the roof is normally fully closed in 30 seconds. I just wonder if this may be a clue to the problem.

 

[Monty-Wilf bus]

My T6 is in the garage again due to a dropping roof on the offside. Originally, we had a problem with the roof dropping in November 2019. Unfortunately, it seemed to 'fix' itself on the way to the garage and they were unable to recreate the fault. The vehicle was under warranty at the time. Since then we have had no issues with the roof until our two week trip to France in August where the fault came back. This was a bit of a bind as we were hoping to use the roof space for sleeping etc. so it put a bit of a dent in the holiday.

Anyway, I've spent a bit of time going through the various threads covering roof issues in an attempt to self diagnose the issue. Not that I was planning to undertake the works myself, but I wanted to make sure the roof fault was correctly identified, that I didn't get a re-occurence of the fault, and that I don't end up spending a fortune whilst the technician swaps out multiple components without applying any thought or logic.

Currently, the garage wants to replace the offside ram as "80 to 90% of roof faults are due to a faulty ram." Personally, I'm not convinced: here's my reasoning....
1) The ram is a passive device. Oil is pushed in at one end and the ram goes up. A faulty ram seal would cause the roof to drop over time. However, once the seal fails it doesn't then fix itself for 9 months before going wrong again.
2) When you raise the roof fully and then lower it immediately the faulty side drops much more quickly. A leaky ram seal would not have had time to leak so the roof should lower on both sides equally.
3) Regardless of how long the roof is up, or whether you jack it up prior to lowering, the dropping side lowers more quickly.
4) The roof drops quite quickly. About half way in under 30 mins.
To my mind, all of this points to an error with the hydraulic pump/valve set inside the cab. As I understand it, there are two valves and actuators that control the flow oil hydraulic fluid into and out of the rams. If one of these valves was not working correctly, perhaps not shutting down properly, fluid would leak back out of the ram and the roof would drop on one side. Also, if the valve was more open on one side than the other, the roof would not lower on both sides evenly.

Does any of this resonate with anyone, or am I talking rhubarb?

As the vehicle is only just over three years old I am angling for VW to take the bulk of the cost of repair under warranty, particularly as the fault had already occurred under warranty. Am I being too optimistic?

Any thoughts gratefully received. Thanks.

I would definitely be perusing full warranty claim, the issue was identified whilst under warranty and not fixed by VW regardless of whether they could replicate it, the bill could soon rack up if they do ram and pump. Perhaps the intermittent nature is temp related which i am sure has been discussed previously on the forum. I hope you get it sorted and VW do the right thing.

 

[Alan Andrews]

Is this the ram?

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Assuming no movement with VW on claim, Swap out, test - if ok then leave in place. if not then remove and put on ebay or keep as spare.

 

[Wogga]

Its a pressurised hydraulic system, if there is no sign of an external oil leak then the oil is bleeding back into pump sump, assuming it has a sump. Sounds to me like one of the pump valves is passing intermittently, possibly due to a valve not seating correctly. Well that's what happens in the big world of hydraulics. Usual suspects are crap under the seal seat, faulty NRV;s weakened or broken springs faulty valve which could be either the up or down valve passing.

Your original assumptions are pretty good.

 

[Brendon]

I had similar sometime ago. Swapped rams side to side which proved it to be the valves plungers or whatever in the pump.
This was at a VW dealership who fitted new pump under warranty.

Interesting. The idea of swapping the rams around occurred to me in the night. One would hope it would be less expensive than just replacing one only to find it wasn't the ram. Probably labour cost is the killer though.

 

[Brendon]

At first I thought 30 mins a bit slow rather than quick for half way down! But I assume a typo. But then if you meant 30 seconds for halfway down, thats surely too slow. I have not timed it but surely the roof is normally fully closed in 30 seconds. I just wonder if this may be a clue to the problem.

Sorry, I meant to say that the roof, whilst in the up position, is dropping about half way in 30 minutes. This is not whilst I'm trying to lower it. So I'm saying that the leak in the hydraulics is sufficient to let the roof to drop one side about half way in 30 mins.

 

[Brendon]

Its a pressurised hydraulic system, if there is no sign of an external oil leak then the oil is bleeding back into pump sump, assuming it has a sump. Sounds to me like one of the pump valves is passing intermittently, possibly due to a valve not seating correctly. Well that's what happens in the big world of hydraulics. Usual suspects are crap under the seal seat, faulty NRV;s weakened or broken springs faulty valve which could be either the up or down valve passing.

Your original assumptions are pretty good.

Pleased I wasn't talking rhubarb. My somewhat limited experience of hydraulics on tractors, excavators and the like point in that direction. A schematic of the roof hydraulics would be a boon in diagnosis though.

 

[Brendon]

I would definitely be perusing full warranty claim, the issue was identified whilst under warranty and not fixed by VW regardless of whether they could replicate it, the bill could soon rack up if they do ram and pump. Perhaps the intermittent nature is temp related which i am sure has been discussed previously on the forum. I hope you get it sorted and VW do the right thing.

Thanks for that. The occurrences were in cold weather the first time and hot the second, so I'm not sure about the temp issue (though had seen it mentioned in previous threads).
I must say that I'm a bit flummoxed about the whole warranty issue. I find it odd that I must rely on the garage to plead my case with VW. Is there any way I can make my own representations? How do I know if the dealer is trying hard enough on my behalf? I understood that manufacturers have some kind of pre-agreed 'goodwill' table, but I don't know whether that's applied rigidly, or whether there's flex.

 

[Wogga]

Pleased I wasn't talking rhubarb. My somewhat limited experience of hydraulics on tractors, excavators and the like point in that direction. A schematic of the roof hydraulics would be a boon in diagnosis though.

Your average mechanic, sorry motor vehicle technician, doesn't have a clue either, hydraulics are the speciality of plant engineers. Bless them I suspect electrics and hydraulics don't feature large in their day to day workload and therefore experience will be limited, not their fault.

 

[oak]

On the pump, swap the left and right hydraulic hoses and see if the problem swaps side. This is the quickest and easiest way I can think of to determine if it is the ram or pump.

Sent fra min SM-G975F via Tapatalk

 

[TripleBee]

I think @TripleBee had a similar issue and replaced one Ram
but then the problem went to the other side so he had to replace
the pump and it did the trick.

Please don't twist my replies!

I changed the left ram, where the sagging was. And the problem stayed at the left side. That way I could conclude it was not the ram, but the valve block on the pump.
The cheapest way is to switch the hydraulic pipes on the pump left to right, but this involves dismantling the headlining (or just plug it out with the headlining in place, but this might cause damage to the headlining), and a lot of time.

But for €300 for a ram (without work) or €1400 for the pump, you can have a go and offer some of your spare time.

 

[westfalia]

Please don't twist my replies!

I changed the left ram, where the sagging was. And the problem stayed at the left side. That way I could conclude it was not the ram, but the valve block on the pump.
The cheapest way is to switch the hydraulic pipes on the pump left to right, but this involves dismantling the headlining (or just plug it out with the headlining in place, but this might cause damage to the headlining), and a lot of time.

But for €300 for a ram (without work) or €1400 for the pump, you can have a go and offer some of your spare time.

Thats me told, it won't happen again.

 

[TripleBee]

Thats me told, it won't happen again.

If the problem changed to the other side by changing rams from left to right, then the problem would have been in the ram.
I replaced the left ram with a new one, and the problem persisted on the same side (left), so it could not have been the ram. It could have been an oil hose, but I didn't see any leaks, so that concluded to internal leaking in the valve block.

Anyway, I had my roof open for one night, one day, and another night, and in the morning I had some sagging again on the left side. That side was in the sun. I thought I would have had more shadow than it really did.
When lowering and opening the roof again, I heard some hissing sounds again. But the roof stays good if I open it in the evening and during the night.

When I changed pitches, the right side was on the sunny side, and in the morning I had some hot sun heating up the right side of the van. When lowering the roof, I stopped at about 30 cm from closing the front, and the left side dropped quickly, making a flushing noise in the pump or hoses? When I opened it up the next evening, everything was still fine, and the roof stayed open good for the night.

Maybe there must still be some air in the system? Or the 5 year old ram has suffered from the old pump in the past?
The sagging (when it occurs) stays on the left side.