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Are there any Jaguar mechanics on this forum? My coolant level sensor keeps setting off the low coolant level warning light. When the engine is cold, the light is off. There is plenty of coolant, no leaks. The car only has 19,000 miles. What causes this sensor to fail? Is there a way to fix it or do you just replace it and the tank as a unit? The car is under warranty for 6 months. I don't want to have to address this fault again! Is there a better sensor available now?
Paldi, 2 things can cause what you are seeing. The less obvious one is if you run too much water in the coolant system, the density of the coolant is not high enough to make the float be boyant. So, the float sinks and triggers the low level alarm. As you warm up the coolant, it expands slightly and this causes the density to go down, which in your case is enough to cause the float to sink. So, if you know you have the proper ratio of water and concentrated coolant, then all is good. But, if this has started after you topped up the tank with just straight water, you may have introduced the problem yourself.
The more likely scenario is that the float has become flooded. This causes the float to get heavier and simply not float at all. The only fix I have seen is to replace the tank. Some members have pull the tanks apart and dried out the floats and fixed it themselves, but that is a fair amount of work and if you are still under warrantee, I would let the shop deal with things and give you a brand new tank so you don't have to deal with it again for another 10 yeras or so.
I had the same problem on my '12. The tank was replaced under warranty. It appears that the float in the tank can become saturated (poor manufacturing by Bosch), and sink. You will get the warning because the float is sat at the bottom of the tank (the safest scenario), even though the tank is full.
The only remedy is to replace the tank hopefully, yours is still under warranty.
Thanks for the explanation. Since I am a new owner (only 1,000 miles) I do not know what the prior owner may have done. The car was manufactured June of 2019 so is only 5 years old. It was fine for my first 1,000 miles of ownership and then I took a high-speed, 100-mile round-trip on the turnpike. The issue cropped up the following day. I believe the tank was over-filled. I pumped out a quart and refilled 2 cups to bring it to the MAX line when the coolant was cold. The light went out but came back on when the temp warmed up. It goes out when the engine is cold. I wonder if the mechanics at Jaguar will want to replace or test the coolant as a precaution along with the tank/sensor.
Paldi, 2 things can cause what you are seeing. The less obvious one is if you run too much water in the coolant system, the density of the coolant is not high enough to make the float be boyant. So, the float sinks and triggers the low level alarm. As you warm up the coolant, it expands slightly and this causes the density to go down, which in your case is enough to cause the float to sink. So, if you know you have the proper ratio of water and concentrated coolant, then all is good. But, if this has started after you topped up the tank with just straight water, you may have introduced the problem yourself.
The more likely scenario is that the float has become flooded. This causes the float to get heavier and simply not float at all. The only fix I have seen is to replace the tank. Some members have pull the tanks apart and dried out the floats and fixed it themselves, but that is a fair amount of work and if you are still under warrantee, I would let the shop deal with things and give you a brand new tank so you don't have to deal with it again for another 10 years
or so.
Here's the float (I think). It was sunk to the bottom of the tank. I gently coaxed it up. The coolant was warm, not hot. Light out when I started the engine. Will do a test drive tomorrow.
I have the same problem all the time. Have not got around to replacing the tank, as in real terms it is arguably not as relevant as the following: - As Paidi you may want to bear this in mind, the float / tank is the least of your problems with the X351 coolant system. The coolant pipes are not much better than tissue paper over time. And by that I mean, not very much time... Over time they will leak. And catastrophically. The temperature gauge will also not tell you you are over heating (and killing ) your engine. So..., two recommendations. 1) every time you go for a drive, pop the hood and check the coolant level (I do it every time - and it has saved me). And carry a gallon of distilled water in the trunk (and a couple in your garage) and some coolant. A very minor hassle to avoid a blown engine and just and a small mark of respect for owning what is a real driver's car; 2) replace all the coolant pipes with metal ones (and definitely replace that horrific seamed one up front with a newer version of OE if it has not been done already), and make sure the water pump is JLR's 7th edition version of that pump, as the first 6 attempts were crap (leaked). It's about the only weak point on the X351's other than valve cover gaskets which when they leak will kill your alternator, battery etc etc. Get that done and you will have Lexus like reliability, maybe other than weak front shocks, that the S class owners will be very envious of.
Thanks! I'll keep an eye on things that can leak. My XJL was manufactured in June 2019, hopefully with the newest parts on hand so I hope I have the better coolant pipe and water pump! I don't know how to find out, but certainly concerned that float is bad after 19,500 miles. It's possible the prior owner added water rather than the proper 50-50 mix. The tank was a half-quart over full.
Back on again. In the morning it's off but back on after about 8 miles. No leaks, the coolant tank is holding steady at the MAX line when the motor is cold. Off to the dealer tomorrow for a new tank and fresh coolant.
Given your build date, you should still be under warranty. Your warranty starts the day the car is/was delivered to its first customer, not when it was built. The standard Jaguar warranty is 5yrs/100,000 miles. If it is a CPO car you can extend that by 1 year. You should also get free services for the first 5 years.
Even though you know what's causing your low fluid caption, the car is not driveable.
There are way too many horror stories of AJ engines detonating due to lack of coolant. The temp gauge really doesn't help you. It will go from its nice happy mid point to full deflection in seconds. Without the pre warning of low coolant you will have very little time to react to a serious problem.
It's not CPO, but I was told the warranty is good through December 2024. It's going to the dealer tomorrow. It's about 10 miles from me. I expect the low coolant light will pop on after about 7 miles.
In future keep fluid level bit bellow max, because then you have more air to scqeese in expansion tank, equals bit less pressure on the system. (pressure are known to push seams and seals)
In future keep fluid level bit bellow max, because then you have more air to squeeze in expansion tank, equals bit less pressure on the system. (pressure are known to push seams and seals)
Good advice! Mine is now slightly below max when cold. (I pumped out a half quart (2 cups) to get to that level.) It's possible the prior owner overfilled it, perhaps using water. Who knows? It's at the Dealership now. Hope to get it back tomorrow. On the way to the dealership, the light came on again after about 8 miles. They said they will do a pressure test of the system.
Dealer has evaluated the situation, and they are going to replace the coolant tank and sensor and drain & replace the coolant. Hopefully will pick it up tomorrow. They gave me a loaner. 2024 F-Pace. It's too tall!
In future keep fluid level bit bellow max, because then you have more air to squeeze in expansion tank, equals bit less pressure on the system. (pressure are known to push seams and seals)
It's back from service with a new tank and new coolant, the light is out. However, it looks like the tank is over-filled. Should I pump out enough to bring it down to the MAX line?
It's back from service with a new tank and new coolant, the light is out. However, it looks like the tank is over-filled. Should I pump out enough to bring it down to the MAX line?
05-31-2024, 11:35 AM
Coolant expansion tank sensor bad
