I've been chasing down a Low Coolant message.

The message appears only when the engine is cold, not immediately at the initial start but after it warms up just a bit. The message stays on for about 5 minutes - until the engine is at full operating temperature - then goes off and stays off. It won't come on again at hot starts. However, once the engine returns to stone cold - overnight or after 8 or 10 hours - it will repeat the cycle on the first start.

So far I removed and cleaned the expansion tank, taking care to see that the magnet is properly located and moves freely. This had no effect.

Then I replaced the coolant level sensor. This had no effect and the situation remains the same.

Any further ideas?

Thanks!

 

My first answer would be you don't have the proper amount of coolant in the system. Have you filled the expansion tank with coolant? Symptoms sound like you are slightly low on coolant.

 

I should have mentioned that it is topped off fully...

Thanks

 

It MIGHT be the cap pressure valve is leaking so it dumps fluid into the overflow tank as it warms up.
When the engine cools the fluid will be drawn back into the tank so it looks full.
Have you tried looking at the level when the light comes on ?
The other possibility is an airlock - did you drain the coolant or just empty the expansion tank?

 

Steve,

I had not thought of the cap leaking...something to investigate.

I only emptied the expansion tank.

Here's an oddity. I siphoned off the coolant from the expansion tank and put it in two clear glass jars. When I returned 1/2 hour later the fluid in the first one I filled was orange-cloudy but the fluid in the second was second was orange-clear, like new fluid. There was evidently some sort of layering going on in the expansion tank. How much fluid moves through there anyway? Seems like it would just be a bit of back-and-forth between the expansion and overflow tanks. The fluid is 2 years old. The car has no cooling problems.

 

When the cooling system is drained, flushed and refilled, this doesn't remove or replace whatever coolant is held at the time in the Atmospheric Recovery Bottle. There will always be some old / original coolant left in there.

When you siphoned off the Bottle contents, this is probably the first time it had ever been completely emptied. Layering sounds a reasonable explanation for the separation as you had drawn all the old sediment off the bottom of the tank.

Graham

 

Scott, I have been experiencing this problem as well on my 97. When cold, no message. After it gets to 160-170 F, the message appears. It is driving me nuts!
I am going to try Steve's suggestion and pick up a new cap today.

 

A new cap is one of the few bits that isn't overpriced!
Let us know if it works.

 

Hey! Can you do the cup and ball trick as well?

 

Swapped the cap from my X Type but that didn't do it. At 160F got the message again.
Maybe I just need a new tank ouch!

 

hi, since youve already replaced the sensor the problem could lie within the expansion tank it self. believe it or not there is a float iside (i know because i disected mine when i replaced it) had i known i might have tried to pressure wash it using a water pic initially it was gummed up but after wiping it up it seemed to move freely. the best place for a replacement tank is parts geek.com 150.00 jag wanted 225.00 it comes with a new sensor and the whole job takes about a half hour. good luck

 

You are correct about the price, PartsTrain has it for $145 or so. They do become fatigued from many, many heat cycles and can split, so replacing it after 13 years is a good practice I guess.

 

Pay only about $150 for a new one, they are an easy internet find. Thanks for testing the cap theory.

I thought for sure that cleaning the tank would free up the magnet and solve the problem. If the magnet itself went bad I would expect a constant reading or no reading at all. Same with the sensor...

Sure seems to be temperature related.

 

I did clean the tank out with radiator cleaner and the magnetic float moved freely.

 

I checked last night and the price was $156, now its over $200. Too weird. If someone finds a link for a $150+/- price please post it.

 

Found one on eBay for under $150 new: Jaguar XK8 98-06 Expansion Tank MJD4400AB | eBay

 

Gaudin has it for $175 . So I went out to swap back the caps. Temp was 100 F. Then I let it idle. Went to 180F with no warning message. Go figure?? I have some errands to run tomorrow so I'll see what happens when I drive it.

 

Sorry my theory was wrong. Did you say you put the old cap back and it was OK?

 

Spurlee --

The temperatures in play here sound suspiciously like those where the thermostat starts to open. New thermostat recently?

How about this test: Cap off. Cold start. Note coolant level. Watch for low-coolant message to appear. Has the coolant level in fact gone down?

(We might spill a little coolant with this test, but probably not.)

edit: You can check free movement of the magnet thingy if your finger is long enough. Seriously. I can just barely reach it. Feel inside the tank at about the 7:00 position, where 12:00 = the nose of the car.

 

New OEM thermostat about 2 years ago. I can feel and hear the magnet move freely.

It looks like the jury may still be out regarding the new cap idea - see nearby post. That's a $9 solution. If that is a bust I will experiment with your test idea.

Thanks!