I’ve read more than once on this Forum about guys with reasonably low mileage (35,000 + -) pre-2010 XKs doing such things as replacing their transmission fluid, replacing differential fluid, replacing brake fluid, flushing cooling system, new water pump, new aluminum thermostat housing, new fuel pump, etc.

Since my 2009 XK daily driver now has 32,000 miles, I’m wondering if I should have one or more of these things done this year or next. Don’t get me wrong, I’m all in favor of proper maintenance … and sometimes even preventive maintenance … but one or more of these sound premature to me considering the comparatively low miles.

Since I’m sure that 99% of you know more about Jags than I do, I’d appreciate hearing your thoughts on this matter. Thanks in advance for taking the time to comment.

 

With some things mileage is the enemy. In some others time is.

At 49k my 07 trans fluid looked awful. Depending on duty (city driving much harder on fluids than highway) I'd say 50k at the latest. Do the diff when you do the trans.

Brake fluid. I think every 2 years is recommended. I do every three.

Coolant neck/thermostat housing. It's plastic on the non-supercharged engine. Heat cycles kill it. If you can find a metal replacement, do it. If not I'd change it out every 4-5 years. This is a known failure point that can leave you stranded. This is when you change your coolant.

Water pump. We have the 4.2 NOT the 5.0. Don't worry about it.

Fuel pump. Never heard of a failure.

I'm sure others will chime is.

 

Here is some transmission info From ZF website: "Regular maintenance intervals will substantially increase the automatic transmission's service life. ZF recommends a regular oil change at between 80 000 (50K miles) and 120 000 km (75K miles) or after 8 years depending upon the stress". If you run it with a lot of hard acceleration you may be in the ballpark based on age.

Oil change kits for a fast repair - ZF Parts

The fuel pump is interesting to me. On the X100 (including my 01 XK) a lot of them seemed to quit at around the 10 year mark regardless of mileage. I haven't seen many people with issues yet on the forum here (but we are barely to 10 years and/or I may have missed them?). That is the only thing with 3 Jags that ever stranded me and required a tow.

Brake fluid: every two years just for condensation/water removal for me. Without looking it up I think that is a Jag recommendation as well..I am pretty sure it was on my '01.

 

Does Jag make a metal replacement coolant neck-thermostat housing or is it an after-market item? Any idea where to get one if it is after-market? Thanks.

 

How long are you planning on keeping this car, do you want to keep it another year or for a very long time? That makes a difference you know. Let's go through your list...

transmission fluid - Manufacturers try to tell you it is a lifetime fluid. For other cars with the same ZF tranny they have experienced hard shifts at higher mileage (100k and above) and noticed a significant improvement in shifts with fresh fluid. However, waiting until very high mileage to replace has caused reports of transmission failure, the consensus opinion in other models is that the sudden change in viscosity was the cause and that at some point a flush is counter-productive. So the lesson is that an earlier change is better.

replacing differential fluid - In my Jeep this is something you do regularly. In standard passenger cars I never see much discussion on this so have no input. Personally I have never changed differential fluid on any passenger car at any mileage so don't plan on changing. If you plan on keeping the car forever then do it at some point.

replacing brake fluid - Brake fluid is Hygroscopic, it absorbs water. The system is vented so not a perfectly sealed. Because of this it is recommended to change every 2 years. Will your brakes fail if you don't, no. Folks say it will degrade the system over time. So if you plan on keeping the car long-term it is definitely on the to-do list. I asked friends who are car guys and friends who are not car guys, not one person in that list on either side has done a brake flush. And they have had many cars since they were kids. They rather scoffed at this one, however I always flush my brake fluid in my vehicles.

flushing cooling system - Up to you, don't have much input on this subject as I have always had a "if it ain't broke don't fix it" attitude to the cooling fluid. Contaminant build-up will supposedly degrade the system, so a flush at some point could be beneficial?

new water pump, new aluminum thermostat housing, new fuel pump - If they are working why do anything with them? There are a lot of parts in a car you can replace prior to failure, but you may be replacing something that has a lot of life still. If you could pin an exact mileage to when they will go bad then have at it, but for these you cannot.

 

Transmission - the X350 uses the same transmission as the XK150. There are numerous threads on the transmission fluid replacement, as well as endless debates on the cost and substitutes for the liquid gold as it's known in that forum.

Originally, ZF intended them to be sealed for life, hence no dipstick. They now recommend every 50k miles. So while your owners manual will say one thing, ZF has subsequently changed its mind.

Their recommended procedure doesn't actually fully flush the fluid. It leaves about 3.5 -4 liters in. If you follow their procedure, which should be OK as long as you adhere to the mileage.

Coolant - Jaguar uses Organic acid antifreeze which is orange and sold as Dexcool here in the U.S. This is different than ethylene glycol (green)and the two shouldn't be mixed.

The recommended flush cycle is 5 years or 100k miles whichever is sooner. Dexcool can and will gum up and cause problems. Again on the X350 forum, there are far more issues with the heater core than on this forum. Perhaps the XK has a different core design or fewer miles, but flushing the system is both easy and cheap.

There are myriad of lawsuits with Dexcool. Enough to tell me flushing every 5 years is the way to go for me.

FYI, Dexcool also doesn't play well with additives such as stop leak.

 

Very good point, whenever a flush is discussed it is the fluid available in the transmission housing, the torque converter holds about 3 to 4 liters out of the 9. I would see that a shop has the necessary equipment to get it all. With other brand cars with the same tranny some have gone so far as to change the fluid several times in a short period to flush out the old fluid, but this is for folks who are doing it themselves. Regardless, even if you have the 6/7 liters flushed the results are better than not changing the fluid!

I guess if we are talking about the OP doing the flush himself then it would be a different discussion than if a shop is doing it. I just know that the ZF 6HP26 fluid replacement procedure is a major pain in the rear and takes an assistant. Car has to be up on lift or all four corners on stands, open the hold, wait for the tranny to get up to temp (use a temp gun on tranny), fill the hole until it runs out while running it through gears. I paraphrase as I never have done it but have read a hundred threads discussing the particulars.

 

Unless you have an easy way to fill the transmission or you have a removable plug in the torque converter it is very difficult to do a complete flush. I have an old (89) volvo where the normal maint. is to do a flush every 50K miles along with a belt change. Car has 360K miles on it so I've done a few flushes. It takes me about 3-4 gals to do the flush and the method is to drain the pan , replace the filter , disconnect one of the trans. cooler lines start the engine and start putting TF in and watch it pump out into a container. Usually by 9 qts it looks pretty clean . Based on the way the Jag is set up this would be a tricky way to do it so the best that you can do is just a drain and replace. Also you would need to measure what you drain and make sure you fill the same amount. Not so simple in my opinion but doable.

 

Does Jag make a metal replacement coolant neck-thermostat housing that would fit a 2009 XK or is it an after-market item? Any idea where to get one if it is after-market? Thanks.

 

I've only seen them for the earlier XK100 (pre 2006) Snide. I'm of the camp that if it aint broke... but definitely flush and change your coolant and your thermostat.

If you're hell bent on changing the housing, CAR ID has the plastic ones for $160, including the stat. I'm guessing Rock Auto can beat that price.

 

There is no aluminium replacement part for the water outlet on the 4.2 litre unit. The plastic outlet, which contains the thermostat should be replaced each time the coolant is changed.

The JLR part number for the water outlet is AJ811793.

 

One thing I can vouch for...differential. at 30k miles, I noticed mine was "noisy" during very low speed corners, like parking lot. changed the fluid with correct LS type fluid, and it got totally and completely quiet. Made A Difference.