MK IX Tire pressures and Coolant additives

OK Gents, Just purchased a very nice MK IX in southern Louisiana. Put a new set of Michelin X radials on it and pressured up to 30lbs. Just want your opinions on the proper air pressure for 185 R 16 on this car. Looks as if the tire is a bit low to me at 30lbs.

Also its hot as hell here! 96 degrees and I am traveling across Texas (100 degrees) and ultimately hoping to reach Utah. This is a dead stock original Mk IX. Any cooling tips wopuld be greatly appreciated. As I plan to renew the coolant in the system, is there any coolant additives that would be actually worthwhile.

Plan to document the trip and post it here with all the trails and tribulations of long distance Jaguar saloon motoring. Any and all prayers are welcome.

Sounds like a fantastic road trip. Looking forward to the write up.
As for coolant additives, my belief is that after a total engine rebuild, new rad etc. A standard 50/50 water antifreeze mix is sufficient.


I would never use water, as it contains calcium, that will build up inside your engine.
Most shops do not even sell antifreeze anymore over here.
Use ready to use blue coolant is my advice.

Peter Jan

I have Pirelli Cinturatos on my Mk9. They are also radial tyres. 2,2kg is 31lbs. Try various levels and see what you like. Depends on road evenness, cornering capabilities, comfort level and so on.
I love this car. So easy to enter and get out of. Love the sofa, and my 4 speed upgrade using a T700 GM box and the conversion parts by John´ s Jaguar in TX. 4th is OD, so low revs at speed.

I own a MKVIIM and a IX. I was surprised at the tire choice. No issue as long the load rating is met.

Tires for these are tricky. I have never done radials. I am of the belief that before changing to radials there are suspension rubber and other things that would need to be done to get the best ride and handling characteristics out of that type of tire.

The tires usually has a range 28-32 PSI, at least the one I’ve mounted.

You still can’t look at tires especially radials and tell if they are properly inflated. Radials still have a bulge.

Under no circumstance would it be advisable to exceed the manufacturers pressure!!!

I had MIchelin X’s on my Fintail Mercedes, not a fan. I’m sort of surprised as the MKIX is pushing 3 tons and I wasn’t aware those were able to carry that weight. Personally, I go check the tire and verify its load rating.

Regarding your excursion and high temperatures. I would bring extra hoses. They are now making a Kevlar substrate hose, I used to think those were overkill but with the limited numbers that the market services it no longer surprises me if they can’t make them competently and now have added Kevlar. There are a lot of problems with rubber parts, both in size and function. The vendors tend to opt for cosmetics than durability when calendaring the rubber for the process. All I know is my Father didn’t have issues like this when he drove them.

Racers use something called “water wetter” I believe its a surfactant that keeps bubbles from forming which negate heat transfer. A water and antifreeze mix is advisable and protects better than 100% of either.

I woukd recommend carrying extra hoses, a coil, cap rotor and a condensor, though condensors and rotors have been iffy as of late, hence the increase in electronic refits.

Have a safe journey!

I concur with much of the advice you have received. If you find that overheating, or near so, plagues you, a total replacement after clearing all water out, is to add Evans Coolant. This made a big difference in my 1966 S-type saloon. Evans is not water based. While trying different approaches over the years, I learned that water wetter is a rubbish product that made no difference at all. The Mk IX have more room in the engine bay and so you may do fine without any modifications to good old antifreeze. Remember when establishing tire pressures that the Texas pavement will elevate your pressures from cold by a fair bit! You’ll see on the order of 2 pounds increase in tire pressure for 80oF versus 90oF.

Not actually so: in dyno tests, I saw a 2-4 degree Fahrenheit difference: it’s no panacea , and will not help a plugged-up old, crusty cooling system, for sure.

In my racers (where antifreeze is verboten) it was worth that teeny bit.

Water wetter may or may not make any difference to the operating temperature.
It depends on whether your cooling system is working within its design range, meaning that the engine temperature is controlled by the thermostat. Under these conditions adding Water wetter or similar will probably make no difference.
If however your cooling system is marginal, say due to radiator plugging or similar malady, and the thermostat is running wide open it will NOT be controlling the temperature.
In this case the temperature will be a function of the heat capacity of the coolant system.
Since water wetter improves heat transfer from engine to coolant you should expect to see a temperature drop in a problem system.
I have seen a drop of 20F on one car that was very marginal and had a propensity to boil using basic 50/50 mix.
So the bottom line is for me “if the car is overheating, try Water Wetter but if the temp is OK it doesn’t matter whether you use it or not”

OK, but not a practical benefit in those saloons that so often have overheating issues.


Yes… that’s what I said.

Drain rad & block, flush with clean water (up to temp), drain again.

Unless in arctic circle 30% coolant to distilled water (sold in supermarkets for steam irons etc) and a bottle of water wetter. Water is by far the most effective coolant in transferring heat, and the coolant added is to prevent corrosion and prevent freeezing.

Even in good order the system can struggle with hurry up and stop; e.g. cruising then traffic jam or town crawl. I have fitted an auxillary fan that kicks in at 88’C.