AAAGH Power trim again, 2nd installment

whisper said:
Hi,
Dealer has re-fitted rams (pistons). Problem becomes apparent - after tests dealer suggests new pump.
We fitted new pump - problem still apparent.
Dealer had boat lifted and checked system out - found "debris" in one cylinder - cleaned/refitted - problem still apparent.
Dealer at a loss to know what the cause is - neither he nor we understand what can be causing the "spring back" effect described earlier. Suggested we remove and replace both rams/cylinders.
I just worry that having forked out another £2k to do this job, it won't provide a cure, in the way that all previous attempts have panned out.
Click to expand...

Perhaps sounds like a second opinion from another dealer is required, or do you have a friendly donor boat that you could swap and change units with, although if there is debris in your system be careful. If a seal has broken up or there is swalf in the system you could contaminate your donor boat.

I would take the rams to a hydraulic ram specialist, maybe one from the construction sector, get them to strip and check the cylinders, rods and seals and report on the oil contained within the rams, get the rams resealed. A ram specialist will be able to tell you whether the rams were serviceable when you took them to him. He can also send the oil for analasis.

So if the rams were OK look at the pump, actuation valves and relief valve. When you lift, lower or set your drive one assumes it holds on the actuation valves. The relief valve operates as a weakest link in the system, when excessive load or the extremities of travel are reached, for example, when the leg come to the top of travel, you will note the pump keeps going and the sound changes, this is the relief valve dumping the oil to the reservoir, no relief valve and something bursts or cracks, weak relief valve and the system is inoperative . if the actuation valves are not holding or the relief valve is operating to low then perhaps this could be causing your problem
 
Thanks very much for the comprehensive reply.
We have tried very hard to avoid having to take the rams off completely. It's apparently a pig of a job to do and will mean the engine will probably have to be moved out of the way to allow access to the retaining pins.
I expect that we will do as you suggest, when we lift the boat out for the Winter.
 
I am just in the middle of trying to repair my DPE rams. They are spring loaded. There is a spring in each which would pull the leg in.... Not a very strong spring, but it's there. Trouble is, this is the wrong direction to your problem...
Second, There's a white plastic 'shut off plate' that fits over the end of the spring and has small protrusions that must fit back in the oil bypass holes. If they don't, then it will leak.
Not sure whether these are supposed to be there, but if mis-aligned.....
Lastly there is a ball bearing and a spring in approx 6 holes (I'll call them bypass holes).
Are you sure there's a ball bearing in each, with it's push rod, with its spring?
May be your hydraulics place lost a few bits?
BTW the white plastic plate on both of mine has taken a hammering. The spring looks as though it has contracted to its limit and smashed the top of the plastic.....

Hope I can get mine to work again (was gradually lowering itself going forward under power).
 
Are there any flexible hydraulic hoses on that set up , could they be knackered and swelling under pressure and then squeezing fluid back with no load , or as previously said could be air in there somewhere .
 
Couldn't see any problem with the pipes but it was a bit rough to go putting one's head into the engine comptmt. Will try again when/if it gets flatter in the next few days.

Our latest possible course of action is to bite the bullet, buy new rams/cylinders. We'd then take the rams from the new cylinders and put them in the old ones, thereby avoiding the cost of getting the old cylinder off the transom. Wonder if this is feasible/sensible?
 
I took my rams to a pretty local hydraulic chap yesterday. Says he can get all the bits....I'll let you know. The only bit that's cracked up in mine is that white plastic bit over the end of the spring that shuts off flow through the ball valves....
There aren't any external oil leaks.
The outer 'water' seal had a carbon steel seal, rather than stainless......original fit by VP....
 
jparham said:
I took my rams to a pretty local hydraulic chap yesterday. Says he can get all the bits....I'll let you know. The only bit that's cracked up in mine is that white plastic bit over the end of the spring that shuts off flow through the ball valves....
There aren't any external oil leaks.
The outer 'water' seal had a carbon steel seal, rather than stainless......original fit by VP....
Click to expand...

Good luck - hope it's a success.
 
I'll take some piccy's of 'before' and 'after', so others can see what to do (if it works).

FYI the outer (water) seal is a standard NAK seal, type VG1 16x24x4.
Would be easy to replace, but of course, if you are seeing an oil trail in the water, the inner scraper seal needs replacing aswell......which again is easy to do once you know how to get it out...
I'm getting all my parts from Pirtek - www.pirtek-europe.com. Supposedly on a 1-2 day delivery.
The inner white plastic sleeve thing is the thing I think is causing my problems, rather than the seals themselves..... This is a non-replaceable part, according to Pirtek, but anyone with a small lathe could make them up. I'm going to try to 'retrieve' mine. This is the 'bypass' valve when the ram is fully extended/contracted and the emergency tilt when the drive hits that unseen obstacle. Pretty sure this plastic would take one hell of a belt if the drive did swing up with any force.....
 
Sorry to bump up an old thread, but I wondered what the outcome of this was?

My DP-E drive drops over a course of 10 minutes when at speed. Dealer has found one stuck valve in the pump and fitted a new set over the winter, but now the boat is back in the water, it still has the same problem.
 
Update

Just to let you know, we repaired and polished rams, re-fitted them with new seals from Pirtek. Job cost not £250 as mentioned in previous recent thread but £80 all in. As against £000s quoted by Volvo engineers.

Result is perhaps a complete success ,though this may be in some doubt as we are getting a very slow drop of the leg. It goes down by 2-3"units" over about 30-60 mins. We are also getting some "bounce" - goes from 0 to -1 when fwd gear engaged and -1 to 0 when reverse is engaged. This situation is nevertheless a huge improvement over last year's position.

I'm not sure whether some slow leg drop is "normal" or not. Didn't get much response when I asked this on here last week.

Hope this helps.
 
First are you sure that you have all the air out, you have to drive the tilt up and down fully 5-6 times to do this, then drive up the tilt and leave it overnight and see it it sinks down.
It shouldn't not even if you stand on the drive which we do to test the valves in the system.
We have boats that have been in winter storage for 6 mths and the drive hasn't dropped an inch.
If you have a new pump (complete) then the valves that hold the drive at the selected position are new and should not allow it to float. Which then sounds like you have an internal leak in the crlinders, the white plastic part with balls and springs is the 'shock valve' which lets the drive kick up if you hit something instead of ripping the drive off, and only works in one direction i.e. up.
But if the cylinders are worn or that valve is damaged you can get the float you describe.
But I would do the static test first, if it doesn't sink overnight then you need to look at the trim sender for wear/damage.
 
Thanks for that.
We've done the fully up and down trick about 10 times to try to ensure that the air is all out. The noise the pump makes is as it should be - no gurgling etc.

When left overnight there is no downward movement of the leg - just as well as we are on a drying mooring!!

As mentioned earlier the problem is so much reduced on the situation we had last year that we are content to put up with it for now. It may possibly get worse again and if so it will then be "back to the drawing board".
 
You must log in or register to reply here.

Share this page

Top