I notice a small leak from the low coolant level sensor on the bottom of the tank. It will drip onto the manifold causing a puff of white steam. Is there any way to tighten that sensor or use a new seal?

 

It is probably not the sensor as it is inside a tube within the reservoir completely isolated from the coolant. The reservoir is famous for tiny leaks.

Pressure test the cooling system and I will bet that you find a fine spray coming from some place that makes no sense. Most large auto parts stores will 'rent' a pressure test kit for free.

The plastic reservoir is difficult, if not impossible to seal with epoxy type stuff due to the surface of the plastic. I roughed up the plastic at the identified leak with 80 grit paper until it had 'fuzz' standing up and then used JB Weld to make a quarter sized patch. It has lasted for more than a year so far.

Heloise

 

Well it is leaking (dripping) from the coolant level sensor probe at the bottom of the tank. I can see it drip. Is this sensor probe a press fitting or screw on? Hard to tell when it is still installed. Is it just a matter of buying a new probe and inserting it?

 

As Testpoint said, the sensor is isolated from the coolant. Even though it is leaking from the probe area, it is the resevoir that is leaking, not the sensor or fitting.

 

To more specifically answer your question: the sensor snaps into place under the plastic fingers of the reservoir. It is not sealed to the reservoir.

I can absolutely, positively guarantee that the sensor and its connection to the reservoir is not the cause of the leak.

Also, be careful trying to remove the sensor with the reservoir bolted in place. It is a fragile tube easily broken. Ask me how I know.

 

Gotcha. Now I get it. So options are try to find some novel way (unlikely) to seal it as is or purchase a new tank.

 

I had a fine spray and leak from an invisible place on the expansion tank in my '03 XK8. Decided just to go ahead and replace the whole tank and glad I did. Also replaced the bleeder hose/line from the tank to the thermostat housing (when I loosened the old one it just broke in half, it was so brittle!). I got the tank from PartsGeek.com for about $150. It was very easy to replace, with minimal coolant loss (I put a wine cork in the hose connecting to the bottom of the tank during the exchange); just topped it off when it was all done.

 

I just replaced the thermostat housing with an aluminum one and that bleed hose you mentioned. It is very brittle. Nice idea with the cork.

 

I knew I should not have mentioned that my JB Weld repair had not leaked in over a year. Today it started leaking. Ordered a new tank.

I checked around on the net and specifically asked if the pressure cap and sensor were included in the sale as the pictures depicted both. Two vendors told me 'no, the cap and sensor are not included'. I went to Nalley Jaguar in Atlanta, a forum sponsor, and ordered the tank after the parts guy had a tank in hand and declared that the cap and sensor were included. Total price was $177.55 including shipping and Georgia sales tax. Ordering from out of state would have made the transaction $158.30, cheaper than Gatlin by $13.

Tight Wad Tom

 

Just be sure to drink the wine AFTER the job is complete, a well-deserved reward.

 

My apologizes to JB Weld.

In a post above I assumed that the year old JB Weld repair to the coolant tank was the reason that I now had a leak. The old repair held perfectly, the NEW leak was at a totally NEW point.

After installing my new 'came in a Jaguar box' tank I took a couple pictures to describe the discussion in this thread.

The sensor is held in by 'plastic finger' without any seal. The sensor is isolated from the tank coolant. If you were to remove the sensor entirely there should be no leak unless the tank just decided to leak there.

The sensor is removed by gentle pressure to 'snap' it out of place. Very difficult to do without removing the tank.

The sensor tube is a single sheet of kraft paper soaked in epoxy protecting a glass enclosed micro switch. VERY fragile!

The year old JB Weld repair to tank was not the source of the leak. It was clean and dry.

A completely new spot, near the bottom hose nipple just decided to start leaking.

The new tank came with the sensor and pressure cap installed. The sensor still was held in place by the 'plastic fingers' but the Jaguar vendor had sprayed an adhesive on the connection that will make future removal difficult.

The old tank is toast but the sensor is fine. Free to anyone that has a confirmed sensor failure.

. . . and, yes, I had replaced the original tank with a wreaking yard one a year ago. It came with the leak that I fixed with the JB Weld.

Tight Wad Tom

 

I can use the sensor! Please send me a PM. Thanks

 

My leak has baffled me for a long time. Dealer wanted $800 to replace several hoses that were said to be leaking. I replaced them myself, but still have leak that I cannot see but i smell coolant burning and my car needs an inch of coolant every week and I get coolant low message. Need a new tank.

 

A pressure test kit, available at your local auto parts store for free, will clearly identify the leak location and allow you to work on the system cold.

 

Well to my Joy .. Mine was not the reservoir,but actually the float in side the reservoir that was stuck. I took the reservoir out of the car and found that when you turn it up side down .. it was not making any noise at all. washed it out with water.. then blew it out with air.. shook it .. fingered it to touch the float and move it .. and she liked it.. the float is free now.. blew it out some more .. Now when you turn it up right .. then up side down you can actually hear the float moving up and down .. also found on the port where the hose leaves the reservoir to the thermostat riser.. it was broke off in side the hose.. I dug that out .. then cut the hose and re clamped it on the reservoir, no more light on the dash board that says "engine coolant Low" and also wanted to report that the rpms on the motor get there much quicker now then when it did before I found that cracked plastic inside that hose.. I assume air was getting in there and maybe putting car in to limp mode.. Any way .. just a note .. that because we get this warning on the speedo .. it dose not mean that the float can not be fixed.. unlike what the dealer will tell you .. to replace the unit at $300.00

 

xk8florida mentioned about a float inside the coolant reservoir. My mechanic recommended changing the sensor, not cleaning the float. Now I am not certain about his recommendation.

Because of the magnetic operation of the sensor & float, as long as the float is able to move, a dirty sensor should not cause a problem. But a dirty & stuck float should cause a problem.

Gus has excellent photos of the float inside the coolant reservoir.(See DIY Repair thread)

 

Just an FYI I had a coolant leak similar to the one OP described, and it was fixed with a new reservoir ($150 online).

I also now have a spare coolant level sensor if anyone wants it, worked well when it was removed. (PM me if interested)

 

Mine has just starting leaking! It appears Nelly Jaguar is gone and Geekparts.com is out of stock. Any other places to acquire this?

Thanks!

 

You can try Gaudin in Las Vegas you will get a discount as a forum member Direct JPLV Porsche Parts.com

Nalley are operating now as Greenville Jaguar and Hennessy took over the Atlanta operation.

 

I got one from RockAuto