Hydraulics troubleshooting on Vang/Backstay

[Paul Kekalos]

Hey all-

Boat was launched this week. As I was setting up the sails, I noticed that the Backstay/Vang Hydraulic panel (by helm) was not responding to any pumping- the pumping handle was going back and forth with no pressure whatsoever. I went to check the hydraulic fluid reservoir (in my case, located in port cockpit locker) and it was really low on fluid. I suspect that there has been a slow leak in the system (I traced the system and so no discernable leaks or puddles of hydraulic fluid). Any tips pr knowledge is welcome here. Is it as simple as filling the reservoir with new Hydraulic fluid? Or do I need to bleed/prime or otherwise "reset" the system?

Thanks in advance.

-PK

[Chris Leo]

Paul, 

This isn't much help other than to say on my J/40 vang:

1. this happened to me last year and I had the tech remove and rebuild it offsite, cost a few hundred but fixed the problem (broken O ring, but fully drained and visible on deck)

2. it's pretty weak on the prime again this year, instead of responding in 5-6 pumps sometimes it takes 20. No visible leakage, will check resevoir and see if I can refill

We're in Annapolis so this is after two cold winters.

Chris 

J/40 "Cowbuoy"

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Chris

(703) 677-4314

[Anthony M Iacono]

PK, I’m no expert, but I’ll pass along what has worked for me over the years on my J/42, I’ve sometimes improved the operation of my hydraulic backstay by using a bicycle tire pump to add a little air in the cylinder located in port cockpit locker when it wasn’t working properly.

While it has worked for me I understand one cause may be an air lock. In that case, the fix is usually to bleed the system: fully extend the cylinder, open the release valve if your unit has one, and pump slowly for about a minute. The goal is to remove air from the hydraulic system, not add air or fluid to it. Others may know much more, so Im sharing my experience.  Tony I Affinity

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[Sam Foster]

Had that happen last year and it was the vang seals. Our local boatyard has a guy that rebuilds Navtec and they had it fixed in two days and ready for Wednesday evening. Telltale sign was the sag on the boom. One side of the ram is gas filled (pushing the boom up) and when it leaks, gas leaves and/or hydronic fluid crosses over. Possibly where your “missing” fluid went. A few weeks later the backstay ram started leaking.. Amazingly consistent! The only other piece of the puzzle is the panel and pump at the helm (and reservoir (port lazerett for us). You’ll want to inspect in back of both panel (deep aft) and reservoir to ensure no leaking there.

Good luck! 

Sam

Cahoots #44

Sent from my iPhone

On Apr 29, 2026, at 2:32 PM, Paul Kekalos <pkek...@gmail.com> wrote:

Hey all-

Boat was launched this week. As I was setting up the sails, I noticed that the Backstay/Vang Hydraulic panel (by helm) was not responding to any pumping- the pumping handle was going back and forth with no pressure whatsoever. I went to check the hydraulic fluid reservoir (in my case, located in port cockpit locker) and it was really low on fluid. I suspect that there has been a slow leak in the system (I traced the system and so no discernable leaks or puddles of hydraulic fluid). Any tips pr knowledge is welcome here. Is it as simple as filling the reservoir with new Hydraulic fluid? Or do I need to bleed/prime or otherwise "reset" the system?

Thanks in advance.

-PK

[Chris]

Apparently I'm much lazier than the rest of you, because when I had a similar problem (no pressure, reservoir empty) I just filled the reservoir and pumped until I had pressure again and carried on my merry way. I expect there is a small leak somewhere, but I don't have an issue with fluid anywhere that I can find, and the system has worked for the two seasons since I topped it up, so I'm unlikely to do much more about it for now. Perhaps I'll add more fluid this spring to be on the safe side, good reminder. Part of the reason I'm not tempted to have the cylinders serviced is that when I had the autopilot ram serviced it came back with seals so tight that I have to disconnect the ram to have any feel in the system for racing, and am shopping for a new drive (planning Jefa DD1). So I'm a little wary of hydraulic service, perhaps unjustifiably so, but there you go.

[John Plominski]

If its been more than  4 or 5 years since you last rebuilt it, then the cause is likely what Sam is saying.  The rebuild is straight forward for someone who knows how to do it and relatively inexpensive as far as boat stuff goes.  Same for the backstay adjuster, a few hundred bucks to totally rebuild it.  

Drew

[Wayne Cassady]

An added thought for backstay adjusters and, in particular, the Navtec model. We had a couple of rebuilds and then someone told us that UV damages the top o-ring and is often the cause of leaking on our model. Made a cover for it about ten years ago and have yet to rebuild again so far.

Sent from my iPhone

On Apr 30, 2026, at 8:53 AM, John Plominski <drew.pl...@gmail.com> wrote:

If its been more than  4 or 5 years since you last rebuilt it, then the cause is likely what Sam is saying.  The rebuild is straight forward for someone who knows how to do it and relatively inexpensive as far as boat stuff goes.  Same for the backstay adjuster, a few hundred bucks to totally rebuild it.  

To view this discussion visit https://groups.google.com/d/msgid/j4x-owners-group/b5b270f5-42ba-4343-8056-6a4a07cded90n%40googlegroups.com.

[Paul Kekalos]

Thanks for the reply. No sag in the boom- in fact, the opposite- seems like the gas pressure in the vang is fine as the boom is getting pushed up with no problem- i just can't get it down. I did have the backstay cylinder rebuilt last year after a very noticeable leak. Didn't find any leaks at reservoir. We removed the panel and saw verrrry light evidence of what MIGHT have been leakage at some point, leading to the suspicion that there is possibly a very slow leak in the system that has only now become evident. I refilled the reservoir and still no luck. Currently troubleshooting against the idea that there is air in the system. We are going to try bleeding the system. I will update with findings...

On Thursday, April 30, 2026 at 7:22:23 AM UTC-4 Sam Foster wrote:

[Jay PA]

On the subject of hydraulic backstay cylinders, I just had my J/42 Sailtec backstay cylinder rebuilt for the second time in four years (Precision Marine, Tiverton RI).  New seals.   I was advised to NOT overtighten the knob on the side of the cylinder. That valve uses a soft brass pin with a cupped tip that seats on a ball.  If overtightened, the tip deforms and won't fully seat, causing loss of pressure over seconds or minutes -like mine.

When I had a Navtec vang/backstay hydraulic panel on my J/160, I had to pump it back and forth at the beginning of the season to work air out of the system.  I never had to bleed the system or change the filter, but those are described in the online owner's manual.

Jay P-A

J/42 Cirrus

[June Kendrick]

We had the pump go on our system.  Sent the whole panel & both cylinders off for rebuild at Oyster Bay Boat Shop. Been working fine since.