Yesterday afternoon I discovered that my wife's 2006 XK8's coolant expansion tank has a pinhole leak, probably on its underside plastic nozzle since that is where I discovered a small amount of orange-colored wetness by feeling the area with my index finger. When the engine is hot, a single droplet of coolant oozes out underneath the tank every 60 seconds or so, falls to the hot exhaust pipe below, and instantly vaporizes into a sweet-smelling steam puff that visibly rises up through the drivers-side hood seam. That is how she first spotted the issue after pulling into the driveway, shutting off the engine, and remaining in the drivers seat while finishing up a phone conversation. Once the engine bay cools down enough, this pinhole leak stops....

I ordered a replacement tank (part no. MJD4400AB) from rockauto.com for about $58 including shipping and it should show up here early next week. Knowing the infamously lousy plastics used in these cars, I am surprised and pleased that her original factory tank lasted more than 12 years....

For those of you who have already done this job, any tips and tricks on how to replace the tank while minimizing the coolant mess created during the process would be much appreciated....

 

I am Sure you will get more expert help than me but here goes.
I had to replace mine when I bought my ''04 XK8 this spring. Took about an hour. I assume your replacement included a new sensor. The small fragile plastic return pipe is hopeless. I replaced it with a strong rubber tube of the same dimension. Don't break nothin'<g>.

 

Best trick I have heard is to use a turkey baster-type tool to get most of the fluid out of the tank first.

Second, I agree that the hard plastic pipe to the thermostat tower is a problem area. My broke just by "looking" at it. This is also 2 stub hoses and a pipe, so 4 interfaces instead of 2 for a simple hose. I replaced mine with a length of new coolant hose I had in the garage.

Best of luck, keep us posted.

 

The turkey baster idea is a good one. I have a cheap Harbor Freight hand pump left over from this car's coolant outlet pipe / thermostat assembly replacement job back in November 2014. I will probably try to use that, but the tank may prove to be too shallow for this pump to be effective....

When I did the coolant outlet pipe job I went ahead and replaced that fragile plastic breather pipe from the thermostat tower with a length of rubber fuel line hose. No problems with it since....

How many of you replaced the factory Norma-type hose clamps with worm drive-type hose clamps when you replaced your coolant expansion tank?

 

Release funny hose clamps with small flat blade screwdriver. Insert perpendicular to hose and twist to release. Buy new clamps and few extra.

I'd take entire plastic hose off very fragile, take to store to size proper hose. Buy 2 feet in case that plastic breaks.

Use channel lock to secure or loosen underside hose.

Electrical connector is secured with metal bracket need to slide it down, don't lose it (same concept as your puddle lights connector if you've seen that.

Easy 10 min job.

John

 

+1 on the turkey baster pretty simple job after that
Good luck

 

My two cents

The larger water hose on bottom can be stoppered with a wine cork. Stops most of the mess once you have siphoned out the tank itself.

(full disclosure: this idea was borrowed from another forum member)

 

Thanks to all who contributed to this thread....

I did the coolant expansion tank replacement job first thing this morning. Pumping out the contents of the old tank first leads to much less coolant spillage during the process. I was extra-careful with the small metal clip which secures the coolant temperature sensor electrical connector into place. Before removing the clip, I covered the area below it with an old towel so that if it did spring away from me, it was likely to be stopped and trapped in the towel. As I worked the clip loose with a small flat-head screwdriver, I made sure I had the top edge of the clip tightly pinched between my thumb and forefinger. Fortunately I never lost my grip on it during either the removal or the installation so I never had to go hunting for it. Once you have the clip pulled slightly out of its bracket you could run a section of fishing line through it and tie it off so that if the clip does decide to fly, it will remain on the end of your line. I thought about doing that but was confident enough that I would not lose my grip on it....

The 5/16-inch rubber fuel line that I had used back in November 2014 to replace the original lousy plastic breather hose between the thermostat tower and the coolant expansion tank had already baked into a hard, brittle, inflexible hose that refused to pull off of the two plastic nozzles it attaches to on either end. So I decided to sacrifice this hose, slit its ends with a box cutter, and easily pulled it off that way. Keep in mind that whatever you decide to use for that breather hose just sits there and bakes above the engine and underneath the engine dust cover - not an ideal environment for any component. In an effort to find something more robust that may tolerate the engine heat somewhat better, I made a quick run to Advance Auto Parts and came back with a 3-foot section of 5/16-inch transmission fluid rubber hose. We shall see if that also bakes into a hard, brittle line after just a few years. But since fuel runs through its lines relatively cool while transmission fluid runs through its lines relatively hot, I figured it is worth a try for the $6 it cost me....

After getting everything back together properly and double-checking my work, I started the engine and let it run for 10 minutes or so. No visible leaks. So my wife took off on her initial test run and returned about 10 miles later with no issues. I will leave the engine dust cover off for a few days and inspect all the fittings very carefully after each drive cycle to ensure that the new tank is functioning properly and all hoses are leak-free. I expect to have to top off a small amount of coolant each day through the weekend in order to bring the system back up to normal. Time will tell....

 

Jon,

Very informative notes. Thanks.

My leak appears to be identical to yours. Question: are you happy with the tank you purchased from Rock Auto? Their price is really attractive.

 

Dennis,

My rockauto.com replacement coolant expansion tank has performed normally thus far. It is made by URO - they make a number of various hoses and components for Jaguars and other European marques. I do not expect this particular tank to be any better or hold up any longer than the lousy OEM ones, but for less than $60 including shipping it was certainly worth a try....

 

Thought I was having a leaky reservoir situation as well, turned out to be a loose expansion tank cap thank God. I had checked the fluid level the prior week and had not completely tightened the tank lid; after a half turn it was secure, and stopped producing the coolant-steam cloud. I had noticed the fans running longer as well, and just plain coming on without having driven very far.

 

Same type of problem with my 97 XK8. I see coolant escaping from the bottom of the tank but I have not removed the tank to see if the problem is the hose connection on the bottom or the tank itself leaking. Any suggestions?

M. Thomas

 

If you see and feel coolant at the tank bottom's hose connection, 95% of the time it is indeed a leaking tank. Be sure to replace the top breather hose as well (the semi-plastic hose running between the top of the coolant outlet duct and the coolant expansion tank). Use a sturdier material such as a rubber transmission fluid hose or a rubber coolant hose. You can purchase them by the foot at any auto parts store. Buy 3 feet of hose and cut to fit....

 

Thanks for the response.
Yesterday I ordered a replacement tank from a place in California. It cost me $118, including delivery, all the way to Toronto, Canada. I will do the hoses at the same time. I will probably take the car to my mechanic and replace the coolant at the same time. It will be cleaner draining the system before replacing the tank and hoses. The tank will take a week to get here and I will respond with the results after the job is done.

Thanks

 

I have not found any information yet on how to drain the cooling system to replace the coolant. Any suggestions on best way to drain the out the old coolant?

 

I used this guide

 

Thanks to the great response by the forum members, the replacement job was done today and so far no leaks.
I still have more driving and burping to do, but all looks good right now.
Thank you all for responding so quickly.

 

Well done. Just be sure to keep checking the coolant level after your daily drive cycles and topping off more coolant as necessary. My experience is that it usually takes two to three days to finally get the coolant level in the new expansion tank to stay where it needs to be....

 

Just finished the expansion tank replacement this morning. Like, Jon89, I went with the URO tank at $55 delivered. Figured it's worth a shot. I also, used a turkey baster to remove the coolant and a wine cork to plug up the large hose that goes on the bottom of the tank. You will still lose 3-4 ounces of coolant but, not so bad.

The spring clip on the sensor connector took a little time. First, not to lose it, second, to get it back on without losing it. I found that starting the clip on the connector (before it clips into place) then plugging the connector into the sensor make things a lot easier.

Start to finish about 45 minutes. Hope this helps.

Cheers!

Andrew