Here's one for the brain trust...

I hopefully have experienced the first Jaguar miracle of 2020 and wanted some comments on my theory... mainly from those understanding the 86 SIII front suspension and power steering setup.

When I got the car back in July, the maiden voyages were smooth although I did not have many higher speed highway miles due to crusty tires.

Got new tires a few weeks ago and after about a week of driving I discovered that at certain times/speeds, the front end would wobble, shake and sometimes I had to really slow down to alleviate the issue.
I parked her with the plan to fully evaluate the front mounts, bushings, ball joints etc. Rotors OK and tires OK, so ruled those out.

But yesterday I finally checked the P/S fluid level and it was wayyyyyy low. Neglected to check since my other "old cars" don't have power steering. I filled to spec and to my amazement, the car no longer shows any signs of the shimmy, shake, wobble at any time during my 45 minute drive to work and through all ranges of speed.

I will run another "test" driving home today, but.....now to the question / theory.

Could very low P/S fluid levels cause the rack to more or less lose control of the tie rods and steering linkage such that the front wheels would flop around? I am not sure exactly how the P/S pump and pressure lines interact with the actual mechanical motions of the rack and rods, but it seems in the realm of possibility.

Anyway, appreciate any comments and I want to look at parts diagrams and do some more reading tonight on the workings of power steering.

Randy

PS - Oh yeah... and also, my A/C and broken radio started working when I topped off the P/S fluid...

OK, just kidding on these points.. I will take one possible Jaguar miracle at a time

 

Yes, a bit strange, because normal driving straight ahead on the highway would not need power for the power steering, it is only when turning at relatively slow speeds that assistance is given. PS fluid is continually pumped around the system, so passes through the rack and back to the pump. Only when the torsion bar in the PS valve at the steering column connection loads up is the return restricted on one side, thus creating pressure to assist the driver. The only thing I can think of is that there must be a slight pressure on both sides of the rack piston in the unassisted state, so if the fluid is very low, air can pass one side or the other and thus force the steering one way or the other.

 

Got to love those miracles. I never rush into minor repairs because I've had things fix themselves just as mysteriously as they broke. But a wobbly front end would be worrisome. Hopefully the top up of the fluid takes care of it permanently.

 

The fluid acts as a damper on the rack to a certain extent.

 

Well... I remain a believer. Two more 45 minute drives from 50-80 MPH and smooth as can be. Rides like a totally different car on the highway.

I will keep an eye on the fluid level and perhaps something else is amiss in my rack and P/S setup that makes this a one-off problem and cure. But for now I will accept the lucky fix.

Thanks for your replies

Randy