2004 XJR, 75K miles. I have rudimentary knowledge of mechanics but little familiarity with modern cars or the X350.

I have had a coolant leak for many months. When the coolant is low, the engine cooling fan runs and continues running after I turn the car off. (Normally, the fan does not run at all. I had no idea what it was the first time it started running.)

On occasion I notice tiny pools of water when I leave a parked space. (I have not tried to get under the car to place where the coolant is coming from.) Usually, there is no sign. Also, I can often smell a strange smell from the hood area after I stop the car or if I just open a window while at a stoplight. The smell is like burning plastic material but not as intense. It could be coolant burning off, but I'm not sure what coolant smells like.

I have been topping the coolant off with distilled water. Sometimes the car will run for a week or so before the low coolant warning comes on. Also, this might be bad but I put so much distilled water in it that I probably could have drank the coolant. I am never in below freezing areas, but maybe this is bad due to the anti-corrosive properties of the correct coolant.

Three days ago the car was just getting repaired for brakes last week, and the mechanic found codes for bad thermostat. (I did not mention the leaking coolant because I forgot to mention it because it had stopped leaking.)

He replaced the thermostat. This did not surprise me because I had been watching the water temp carefully because of the leaking coolant situation. The water temp would always rise to the midpoint and then stop right there. I started to become suspicious that there was something wrong. The thermostat should not have quickly risen and then stopped dead at the same point each time.

According to the write-up, the mechanic apparently but new "antifreeze" in the coolant system as well as replace the thermostat. I do not know if it was flushed or not.

After driving about 100 miles since the repair, I had to put 1/2 gallon or more of distilled water into the reservoir to top it off again.

Question: how bad is it to keep using distilled water to top off the coolant? Even when using so much of it?

Question: is there a common culprit for coolant leaks such as this in the X350 or the R variant of the X350?

Question: Should my thermostat stop precisely at the midpoint or is this the sign of a problem? (The invoice just says that replacement of the thermostat "cleared codes.")

Many thanks to anyone that can help.

 

First i would always use antifreeze in my car because even though you are not in any areas that get cold enough to freeze water, antifreeze is still needed because it also has a higher boiling temp than water. Secondly, if your mechanic replaced the antifreeze without draining the system properly, its possible that there is still distilled water in your system. Additionally, if he did not let the car adequately warm itself up before topping off the anitfreeze, it would probably show a low reading after you drove it and would require more. I had to replace my coolant tank because of a small hose line on the top that had cracked. other than that, i have never had a coolant leak issue so i wouldnt know the common areas to look for. I am sure someone else will chime in.

 

Long story short, get your cooling system pressure tested and fix whatever is causing your cooling leak(s). Failing to do so is likely to cost you a very expensive engine. You have no way of knowing when a small leak will become a big leak.


The thermostat is computer managed, and does not serve much more use than an idiot light. It will peg in the middle (normal) regardless of the temperature, so long as it falls within what the computer thinks is a normal range of temperatures. If the needle ever swings above or below normal after the engine has warmed up, you have seconds in which to turn the engine off to save the engine.


Use only the correct antifreeze, unless you are in a dire emergency, in which case water is better than nothing.


It doesn't sound like the shop knew how to bleed the cooling system of air, hence why you had to add so much coolant afterwards. Air pockets in the cooling system do not offer any cooling properties to the engine, and the thermostat does not read the temp of air.

 

Your Temp gage is a "makes the owner feel good" gage. It is designed to stop at the halfway point, unless your engine over heats, then it will jump to HOT. If that happens, stop ASAP.
Adding distilled water is Ok to use, but be aware that if you need to add just water long enough, you will get to a point where you have more "just water' in the system and the smell off coolant on shut down will go away, giving you a false sense of security that your leak has gone away also, thus letting you drive away with no coolant at all.
Because of the underpinning on your car, looking for puddles of water under the car is useless. The leak can pool on these pans, then run out completely away from the where the leak is. Keep in mind also, that water from your climate control unit (A/C) leaves puddles under the car also.
No reflection on you or your ability, but it sounds as if you have little or no automotive skills, so if this is the case, a dealer or a private repair shop skilled in JAGUAR repair is your best bet to fix your problem. Also, your last choice may not meet that standard. ASK as many Jaguar related questions as you can of any repair shop you choose. In your area, there should be plenty.

Cheers

 

Thanks! Sorry for not responding sooner. Log in issues. I'm going to take it back to the shop (a dealership).

This is good to know about the temp gauge. I'm surprised that it is designed that way.

This confuses me a little: "Additionally, if he did not let the car adequately warm itself up before topping off the anitfreeze, it would probably show a low reading after you drove it and would require more."

I was worried about topping it off when it was cool because I thought that the liquid would expand when heated and over-pressurize the system. I thought maybe you have to top it off when hot. (But then there is a warning graphic on the filler cap that looks like you should not open it when pressurized.)

 

[QUOTE=rhankey;1340249]. If the needle ever swings above or below normal after the engine has warmed up, you have seconds in which to turn the engine off to save the engine.

Why do you think you need to turn the car off if the needle dips below the midpoint

My car is throwing the coolant code and as i was driving it the needle would go from half to about quarter

I assumed ( may be the problem) that it simply meant the thermostat was stuck open and the coolant was cooling to much

I didnt think lower temps would kill the engine?
Spiking higher of course is a no-no

 

[QUOTE=slownlo;1341715]Could his concern be that if the temp is too low then this must mean that there is no fluid in contact with the thermostat? You are so low that the thermostat is measuring the air temp where ever the thermo is housed?

 

#1 Yes.

#2 ????

 

Sorry for the delay in responding. If the temp guage drops to 1/4 from 1/2 while the engine is running, it almost certainly means the guage is measuring a pocket of air. As a couple of others have indicated the temp guage can only accurately measure the temp of water not air. Air pockets do not wick away any engine heat, so you are flirting with destroying a very expensive Al engine in short order. My prior GM made car had chronic cooling system problems, and every time a hose blew, the water temp guage dropped while the block temp guage rose rapidly (that car had 2 separate gauges) - on 3 separated occasions it warped the heads even though I shut the engine down fast.

 

Well that makes perfect sense. Especially combined withthe coolant low code and the fact the coolant resevoir was suddeny very low


The resevoir was just changed when i bought the car and i bet they never bled the system

So best bet would be to perform the bleed function even when just topping off in case it did suck a little air