Walt, the reason I started helping the top by putting mild upward pressure on it when lowering the top is that a couple times when I tried to lower it, it moved up a fraction of an inch, never cleared the latch, then was brought back to home position by the latch. All while the button was pressed to lower the top. It has worked perfectly every time I give it this little bit of help.

I assumed (not sure this assumption is right) that since I have lowered the pressure with the device, I am right at the margins of acceptable pressure. I don't know.

Also, (get ready - I am not an engineer and should know better)... just because the measured pressure was highest at the peak of the lift may not mean that that is where the most pressure to operate the top is required. Does the pressure change because the system "knows" when it is needed? Does it change because there is a "program" that controls pressure. Do you know the answer to any of this? I don't. Does any of this make any sense? Like I said, I am not an engineer.

Thanks Walt. Thank you for producing the Pressure Reducing Valve.
In addition to real measurable benefits, it has reduced (not eliminated) my "topphobia".

Jack

 

Remember that the hyd system on this car is a push / push system, that means all hyd operation to move a hyd device (roof latch or lifts) is a push of hyd pressure from the pump on an open and close operation. Along with the push / push system you have a host of switches in the header and rams that must be satisfied in order for the roof to operate properly. Now along with that you have 2 control modules (security and body control module) that read the position of the roof by way of the switches in the system. I can go on and on but the bottom line is that the roof will operate properly as long as the devices controlling it are working properly and this is with the PRV installed, remember that the valve kicks in only to eliminate the excessive pressure at the end of the close operation of the roof latch and the rams. When all is working properly the latch cylinder will open allowing the roof to lift away from the switch at the latch to tell the control module to tell the pump to now retract the rams resulting in the roof opening. If for example the latch is sticking it will not open all the way and the roof will not clear the switch to begin the next sequence. Your gentle push up allows the roof to clear the latch and the roof opens. Could additional pressure allow the latch to open better YES, however, it should not be necessary all the time all you need to do is first try to use a dry lubricant on the ram of the roof latch and switches if necessary.

Reading this might help http://www.jagrepair.com/HydRoofManualOperationxk8.htm

 

My top operates with the exact same requirement as Blk Cat's, that is needing a push to clear the latch in order to lower the top.

On lowering the top, the latch opens and releases the catch, but then it needs an additional push to clear the latch itself. Without that nudge, the motor strains for about ten seconds, until it reverses the opening sequence and closes the top.

My diagnosis is that the top latch switches which signals the latch has been opened is failed... so even though the latch is open, the controller thinks it is still closed and therefore fail-safes the sequence back to closing it. My push upwards, bypasses or overrides the switch function and sends the mechanism into the next sequence and whereupon everything thereafter operates properly.

PS. Without a push, while the motor strains, the cylinder piston seals will leak fluid under the ever increasing pressure. With a quick shove into the next sequence stage, the cylinder do not leak under the normal pressure as limited by Walt's device.

 

I often see this problem and what should be taking place is that the latch piston is being pushed to open that latch it is also driving the locking slide to release both end roof stays. As it is doing that it is releasing the center stay and at the same time it is pushing the roof open and at that time it will clear the switch that tells the pump to go to the next step. Proper lubrication helps the travel of the piston and slide! I have also identified a few roofs that have over time operate a little freer causing the roof to sag resulting in this same issue. I have also seen where a little tweak of the PRV allowing it to work better but I feel it should not be the first thing you do to correct the problem you need to find out WHY it is not working properly. I have not had the problem yet but when I do I will find out why. I should mention I do have the PRV installed and had no reason to adjust it yet.

 

Guilty

Doug

 

Having to give the roof a boost is not the end of the world, but as Gus mentions it is a signal that something else is going on. A subset of roof systems have this problems but most don't. One good outcome of taking the cover off for an inspection is you open the mechanism for a good lubrication. When you see how that is constructed you will understand why it is prone to hanging up.

Blkcat's question about pressure is easy. The pump puts out flow. The pressure that results is directly related to force x velocity. If the mechanism moves fast the pressure is lower because the flow is filling the increased volume created when the cylinder piston moves. If it moves slowly the pressure is high for the opposite reason. Maximum pressure occurs when nothing moves at all which is called dead-head. Therefore the pressure is an indirect measure of how much work is being done.

If your roof doesn't move then the pressure goes up to the maximum the pump is capable of, which appears to be around 1650 psi. This is what the relief valve is there to do, cut off the over pressure that results. The relief valve is a band aid for the symptom not the cause. In properly operating systems there is a pressure spike because the roof controller holds the pump on for an extra 1-2 seconds after the latch switches signal it is finished. Protecting against spikes caused by mechanical problems is a side benefit.

 

Gordo,

I think your diagnosis about the latch switches is the likely cause, but (maybe you already know this) this symptom doesn't indicate any problem with the top mechanism because the top is not being pushed open until after the system sees that the latch is raised.

The pump direction has to be reversed after the latch is raised in order to open the top. The system is never trying to raise the latch and open the top at the same time.

So the straining you're hearing doesn't have to do with getting the top to open. Until the system sees that the latch has raised, it's not even trying to open the top. If anything, the pump action while trying to raise the latch would act to close the top further were it not for the top solenoid being set to prevent flow in that direction.

 

Thanks. I get it.

I am going to spray Sailkote over everything visible without taking things apart this afternoon. The top works fine without "help" most of the time. I just started "helping" it all of the time to insure it would work. I wonder if it will work all the time after Sailkote? I will see.

When I get some time I'll unscrew stuff. I have not removed any of this stuff. Then I'll spray more Sailkote. And see the condition of the hoses.

Never dealt with this stuff with the manual top on the Miata.

Jack

 

Hi,
I have a leak from the hood latch area and need to make sure whether it is the latch cylinder or the hoses that leak. What is the simplest way of getting access to see where the leak is? I have not been able to find the answer among the enormous amount of entries on the popular subject of the leaking hydraulic system!

 

You can write a book on this issue (and some here pretty much have). I am not an expert (Gus is the guy) but my guess would be the hose fitting rather than the latch itself. Presumably it is pretty easy to remove the header piece to take a look and likely Gus will weigh in.

Doug

 

+1 Doug mine were leaks at the crimp that connects the hose to the fitting. There are several excellent videos list in DIY section. I used them when I replace mine 3 years ago.

 

You will need to check the hose and latch assembly from of the top of the header and I have photos and info on how to access it from the top. As for the leak the percentage of most failures are related to the hoses and not to the latch seal. I am attaching two links to my page that should help you.

Link JagRepair.com - Jaguar Repair Information Resource
Link JagRepair.com - Jaguar Repair Information Resource

 

Hi Gus,
Recently sent a request for a quote on the convertible pressure reducing valve to your website but so far no reply. (I have been having some email issues).
Did anyone suggest installing an accumulator in the system to reduce pressure spikes?
Thanks,
davem99

 

Sorry! I am on a long vacation and I guess I over looked your request. I presently have 10 units on order. Please send another request to my email and I will get back with you

 

Attn. Gus, XK8,
Hi Gus, You may remember last year I purchased and installed the hydraulic relief valve. No doubt by unlucky coincidence one of the top hoses has now failed resulting in the inevitable green shower. So, what replacement hoses do you recommend? Do you sell them? Saw something about braided hoses. Your website description of how to replace is terrific, I think I can do.
Thanks, davem99

 

Was the hose that failed one of the original factory hoses?

Gus

 

Dave, I've deleted your email address, to avoid you becoming the target of spammers.

 

First thanks to Gus and everyone for the excellent instructions. A couple of comments:
Bought the new hoses and rebuilt latch cylinder from Top Hydraulics, excellent and quick service.
I had difficulty putting enough pressure on the top of the ram cylinder toggle mechanism, so rigged up a 2 x 2 lever and using the rear seat belt to restrain was able to release and open the top.
To facilitate pulling the new hoses into the trunk I held the top about halfway open. Also reach in and snip off all the wire ties etc. that you can find.
Had difficulty down through the fuse box area, so removed the brown cube relay , reached in and removed the white plastic twin hose clamp to make more space for the connector to pass.
Hope the attached photos help.
Took me 3 or 4 days in between rounds of golf, it's a time consuming project but doable for most Jag owners.

 

My Saturday morning project was to install the hydraulic pressure relief valve kit. Thanks to Gus and LSI for quality parts and great instructions! The only difficulty I had was in rotating the lower elbow fitting on the inboard side of the pump so that I could insert hose #1. I couldn't get a wrench on the fitting because of the adjacent petcock. I removed the hydraulic line from the fitting and attached a "sacrificial fitting" to the elbow. Then, with vice grips on the sacrificial fitting, I was able to rotate the elbow fitting about 10 angular degrees clockwise. That was all I needed to insert hose #1. The rest of the installation was a breeze, and I am now much more comfortable with the top operation. Thanks again to everyone for the great information!

 

Gus is "the man" for taking a project on like this. I installed the kit on my 2003 XKR which still has the original hoses. No leaks after a month. My experience was similar to PatB's. On the up side, I was able to get familiar with the NAV and CD changer which is likely the next project for me.