Volvo DPH steering issues
I have searched the forums and find loads of information on steering rams but I have a different problem.
The port steering ram on my friends Jeanneau Prestige 34 HT (twin D4-260’s) was leaking and has been replaced, the system was fully bled and topped up with ATF in both the orbital unit and the high pressure reservoir.
After a high speed run of around 10 minutes the steering became lumpy and felt just as if the high pressure pump had failed and we were reliant on the manual orbital pump to steer. We slowed down and after another few minutes the orbital unit ran out of oil and steering lost. Running the boat back to the moorings at low speed and the steering returned to normal allowing us to place it back on the moorings safely. I then checked the system and found no oil in the orbital unit but the HP reservoir full to overflowing.
Any suggestions as to what is the cause, my thoughts lead to me think it might be a pilot operated shuttle valve bypassing but without access to a circuit diagram I am not familiar enough with the layout to be certain.
Thanks in advance for your help and look forward the vast knowledge on here helping to pinpoint the issue.
Hi seems strange only one ram changed, im sure it wont be long before the other fails which means another lift out.
If th boats around 18 months old id get your serial numbers , contact a dealer to see if it falls into the recent batch that requires replacing, you sould get that free but maybe not the lift out etc.
If the said system has been running with sea water in and around the system it has the kiss of death now as salty water has penetrated the system, the oil goes pink as it mixes with water through the whole system, sometimes the pump fails, seals on the shaft leak, it them dumps fluid out under pressure, the relief valve seizes open reducing pressure.
Dealers often just flush out the bad oil, for the problem to return shortly after costing more in the long run, there is no simple answer other than keep flushing oil through or remove every hose and pipe and clean out etc, a really costly job, or just keep changing the oil until it stays nice and red.
As you lost pressure at higher rpm id say there could be a relief valve problem as the valve will be bouncing on and off its seat many times to maintain constant pressure, the fluid does interchange in the system thats why the engine room reservoir oil goes milky as well as the steering helm oil.
Thanks for the reply.
I have been looking online for a circuit diagram but haven't found one.
A pure guess on my behalf is that the high pressure circuit exerts only upon one steering ram (S/board) and steers the other drive via the drag link leaving the second steering ram (Port) linked into the low pressure orbital pump circuit to facilitate manual emergency steering. Am I on the right track?
I think I located the pilot operated valve for the high pressure steering circuit but need to go on a crash diet before attempting to access it! Do you know if the HP PRV is located in the valve block or is it in the pump body?
Thanks again for your help,
Hi sorry no your theory is not correct, both rams are linked fluidwise via the same hoses so both rams do the work, the linkbar is to keep the drives pointing the same direction.
Valves are located on the transom shield area at the rear of whichever engine has the pressure pump on.
Thanks for replying. It was hard to see what was what yesterday by the time we got back to the moorings. It did look that the pipes from the steering unit split in the engine bay with one pair going to the steering valve mounted at the rear of the s/board engine and the other pair heading off behind the port engine but I was unable to see whereabouts they terminated hense thinking that the port ram was plumbed direct to the orbital unit as an emergency steerage system.
I must admit that following your description I am at a loss to understand what the port pair of pipes are doing. Is it likely that there are two steering valves fitted, one on each leg, although I don't quite understand why that would be the case?
To simplify the system.
The pressure pump, has a feed from the reservoir to the pump, no presure just suction.
The pump pressures oil to the valve body and shuttle valve system(too complicated to describe without a drawing) on the rear of engine, a bleed pipe returns oil to the reservoir so creates a full circuit through an oil cooler.
The steering helm pump has a hose circuit from the helm to the shuttle valve, which makes a circuit through the helm pump but directs oil whichever way is required dependent on which way you want to turn, this then diverts to open the high pressure valves oil from the pump to divert oil to the rams down one pipe , oil then returns through the other pipe from the ram, the 2 higher pressure pipes to the rams T off to both rams via a drilling in the transom shield at the top(looks like a big blank plug with 2 allen head screws) which port opens depends which way you turn the wheel.
Thats about the simplest way I can describe it.
It sounds like the preshure relief valve in the pump is stuck open. Remove the pump, remove the fitting where the high preshure pipe connects to and the valve should now fall out.
If not then a strong whack with a copper or nylon hammer usually shifts it. If it was stuck then the valve and housing need to be cleaned until it moves freely against its spring.
The reservoir shouldn't be able to overflow as it should be sealed when the lid was replaced.
Thanks again for your time and the description. I have a fairly robust hydraulics background so your post leads me to have a couple of additional questions:
Originally Posted by volvopaul
Is the orbital unit and low pressure circuit sealed and topped up via the bung on the steering hub or is it an open circuit and topped up by the returns oil from the steering valve?
On the circuit you describe if I have understood your description correctly there is no ability to turn the legs if the engine isn't running as the steering rams rely on the engine driven HP circuit, is there no facility for emergency manual steering on VP outdrives?
Thanks again. Sorry for all the questions but having just sold our yacht I am trying to get my boating hit by helping a friend sort out a few problems while waiting for our new MoBo to land in the UK just after New Year.
Hi yes top up the oil through the plug behind the wheel when the engine is off, fill up replace bung and turn left to right you will feel oil feed in then air air re enters it goes loose again, so top up, etc do this till the reservoir is full, beware pressure builds up so take care when removing the bung, have a cloth ready!
Originally Posted by onlyme
Yes the boat will steer without the engine running but very stiff to operate.