Preset - Good to know. I agree that, in my case, 11 year old hoses are bound to fail no matter what. The pressure valve is good insurance against failure in the other components - ram seals, etc.

I am surprised to learn that the top controller system is less integrated than that of other manufacturers of the era. Especially since the convertable model was envisioned at the outset and the XK8 was an important milestone for Jaguar. Must have been a cost issue. Another reason to install the relief valve...

 

Agree. And beyond the distributed nature of things, there is NO control of the pump voltage, and therefore pressure. It's on or it's off.

PWM (pulse width modulation) is often used (I know you know this) to control fuel pump voltage and pressure in fuel injection systems, and I bet the same technique is used in many ragtop ECUs.

The voltage reduction system you and I use is in effect a poor-man's ECU.

 

Yes, use the hose kit from Gus's link. The quality of the hoses and fittings are impressive. It also installs without any issues. My Jag mechanic had never seen this kit, was impressed with the hose quality and the retrofit did not take any longer to install than a factory kit would have.

 

I suspect the reason the top function is distributed across multiple systems is because it not only controls the top but also has to communicate with the speed sensor, rear windows, chime, etc. I can see where it could be considered a more elegant solution to communicate over the bus to these existing controllers than work around/override them.

Sure makes me appreciate the rock solid manual convertible top in my 2001 Corvette! Unlike the soft tonneau cover of the XK, the hinged fiberglass one is also a thing of beauty, actually enhancing the look of the car with the "waterfall" element. Of course it's easier to do that on a 2 seat car than a 4 seater, and my wife definitely prefers the power top in her XK8 (even though I, too, cringe every time she hits the button, though the voltage reduction system gives me some peace of mind).

 

I am sure I posted this previously but the best solution for the XK8 (either as part of the original design or possibly as a retrofit fix) would be for the top to be hydraulically powered (as it now is) but for the latch to be manual. It seems like virtually all of the leak problems occur with the hose that connects to the latch. It would be great if that hose could be blocked off so that manual opening and closing of the latch could be performed via some handle. I realize that this would be a difficult/impossible retrofit due to all of the microswitches that sense what is going on with all of the components in the system (including latch status). But it certainly could have been part of the original design. I cannot imagine that owners would have considered it a burden to manually open and close the latch as long as the top itself raised and lowered automatically.


Doug

 

HA! That is exactly the way I feel. I just dropped the top on my Corvette after mopping up Pentosin from inside the Jaguar.

I'm hoping that after I install Gus' armored hoses and with the pressure valve I can stop holding my breath every time that pump whines into action...