Hello - My 1998 XJ8 developed a slow coolant leak a few months ago. I would get the low coolant warning message every 100-150 miles or so and would top off the coolant. I could not identify where the coolant was leaking from and except for one occasion, I never saw any coolant on the garage floor under the car. The one occasion was when I found a puddle of coolant on the floor under the engine. The puddle was large enough that I could not tell exactly where the leak was falling, but it appeared to be on driver's side (not certain though). Then I continued to have a slow coolant loss requiring occasional topping off, without seeing any sign of the leak or any more coolant on the garage floor. Then, several weeks ago, coolant loss completely stopped. I've driven roughly 600 miles and the coolant level is right where it was when I last topped it off. Does anyone have any thoughts on the source of the leak and why it would stop on its own? Is it possible it was "self-correcting" and I don't currently have a problem? I'm a little reluctant to take it in to shop when there is currently no coolant loss. Thank you.

 

When you say drivers side, which side do you mean? If you have a RHD car, that would make a little more sence because the Norma connector does fail on the RH side of the engine and the coolant drips straight on top of the catalytic convertor which in turn burns off right away. Check that regardless of LH or RH drive vehicles. What happens on most cars regardless of brand or make is that if the coolant leak is small enough, sometimes the silica portion(?? I'm no scientist) of the coolant actually turns into a gel and dries up which seals the leak. I know they say if it ain't broke, don't fix it. However, I'd seriously look into getting it fixed because there's a lot of plastic coolant components on this engine that fail.

 

Find and fix the leak before it really finds you again and leaves you stranded....

 

Ken since you don't have a location listed we are all guessing RHD or LHD. If it is a USA vehicle your problem is most likely the cooling system pressure cap going bad.
As the coolant expands under pressure the excess is sent to the overflow tank and as the system cools it is drawn back into the system. The overflow tank is mounted in the left wing (fender) once overfilled from a bad cap it will spill out.
Caps are cheap. I would get a new one and keep a check on it.

 

Thanks for the comments, everyone. Have to say I did not consider the international nature of this forum! I am in the San Francisco Bay Area and vehicle is LHD. As mentioned, because of the size of the coolant puddle I saw on once occasion, I'm not completely certain which side the drip was coming from but it seemed more to the "LHD side". My knowledge of mechanics does not go beyond the very basic but I will definitely replace the pressure cap, which I know is easy and cheap. I will also look more closely at all of the hoses and connections and will have the matter checked out by the pros when I take it in for service very soon. (I'm not familiar with the Norma connector or whether I can see it looking down at the engine vs. having to go underneath, but will plan to check it out.) Thanks again.

 

Check the T in the heater hose on the driver's side (LHD) where the under intake heater hose connects to the heater plumbing and the small hose of the T goes to the throttle body. You will have to remove the center rear engine cover. The T gets brittle and fails. Look way down in between the throttle body cable attachment and the coolant tank.

It starts as a very small leak that drips onto the exhaust, hence no drips on the floor or other evidence. It would just leak coolant slowly and have a slight coolant smell. Didn't find it until it got really bad one day and left a puddle. Ended up doing the heater hoses too because I couldn't remove it w/o pulling the blower and intake manifold (XJR).

-Mike

 

98 jag leaking coolant driver front side and overheats is it a hose or is there a tank,any suggestions,is there website with a diagram of coolant system and other settings such as plug gaps, compression of cylinders,general overview of drivetran.