I bought my Jag (2000 S-Type 3.0) a year ago with 89K. It now has 93k. Power steering started acting weird (noisy, lots of resistance at slow speed) during the drive home this weekend (400 mi. round trip) and the power steering fluid is well below the Min mark (never checked it before so I don't know if it's leaking or not).

My problem is, I don't know what kind of fluid was put in there before, and I don't know if it's OK to "mix and match" steering fluids. Don't really have a service history on it either.

The question is, should I take it to the shop and have them flush out the old stuff and put in new stuff, or can I top it off with the Mobil 1 synthetic that I've seen mentioned, then keep an eye on it for possible leakage?

Thanks in advance.

 

If the fluid looks old and is more of a blackish color and kind of a burnt smell, I would say to do a flush.

 

The power steering gear uses Dexron III fluid, which is easily found at most parts suppliers.

If the fluid is low, more than likely there is a leak in the system. Check the high-pressure fitting where it joins with the power steering pump for leaks along with the hoses to and from the steering rack and cooler. Also check the rubber boots at the steering rack ends to see if they show signs of fluid dripping or are swollen with fluid. If the rubber rack end boots show signs of fluid leaking or are swollen, the steering rack seals are worn and the rack must be removed for service or replaced.

 

The 2000 MY S-Type used ESSO 998 (JLM20772 up to L86901). It is the only S-Type that needed the special vacuum bleeding procedure if air gets into the system. The 2001MY onward used a different rack (ZF I think?) and is self bleeding. The PAS fluid changed to JLM21703 from L86902>

I have never tried to replace the fluid in the early cars with the newer fluid as I keep both in stock.

If you do drain and flush, be aware that air in the system will cause the steering to 'pulse/knock' until the air is removed from the system.

bob gauff

 

For reference, I recently drained and refilled the power steering system on VIN L35986 with Dexron III without any adverse affects or drivability issues.

 

The key word there is "recently". Sometimes the effects of a change will not be known until some miles down the road.

Now, if ESSO 998 (JLM20772) is similar to Dexron then maybe no harm, no foul. But, if it is not, then someone would be wise to research the chemistry before such a changeover.

The main concern would be the seals.

 

The fluids are quite cheap so why not use the right one...

 

I believe there is a substantial amount of misinformation and accompanying misunderstanding regarding power steering fluids in general. Manufacturers choose a fluid based on three or four main criteria: lubrication qualities, viscosity at different temperatures, detergent capability and of course as has been pointed out, compatibility with the various seals and hoses. If one takes the time to review the specifications of the fluids available, one will see that many of the specifications overlap or are exceeded in many cases.

Rather than be drawn into a lengthy debate, I will report back after several months or 20 000 miles on the condition of the power steering gear in the vehicle in question.

 

And that is exactly the point.

Either the substitution is safe or it is not.

Guessing is not really a great option unless one is willing to foot the bill for a bad guess.

Parts & Labour for replacing a pump and rack due to a bad choice is not a great tradeoff when it comes to the minor difference in cost.

It would seem that if one *must* guess, then the safest thing to do is to find out what fluid is used when that same steering rack is used in a FORD application, and at least use the FORD specified fluid.

Even then, one must check the approvals and recommendations of the vendor.

 

Or, one is willing to spend the time to review the specifications and choose a fluid that is compatible without the need for 'guessing' as guessing is not something one should do when it comes to vehicle maintenance. As previously stated, there is a wealth of misinformation and misunderstanding on the subject of fluids, not just power steering fluids.

If one is in doubt and not willing or unable to research the specifications, it is probably safest to stick with what the factory recommends when it comes to fluids and lubricants so there is no need for 'guessing'.

 

However, from reading the opening post, the OP is not exactly well versed in the ins and outs of power steering fluid. All he wanted was advice on the recommended fluid. For someone in that position, the recommended fluid particular to his vehicle year is the best option. Note that he did not ask for substitutes.

If you wish to argue the merits of substituting Dexron for the specified ESSO 998 (JLM20772), then it should be in its own thread and quote the supporting documents.

In the interest of keeping this thread informative and on topic, it is now closed.