Ups, had the same problem as you describe just on my way to a mountain resort. I was driving for about 3 hours without any problems. Then I stopped at a gas station to refill. Just seconds after I turned off the engine, coolant fluid started to leak under the front left side of the engine... First I thought it was the plastic radiator cap (the one for draining the system) but when I touched it - it was dry. Then I disassembled the shield over the front left wheel and found the expansion tank. The coolant was leaking from there.

My main question is - should I have some kind of cap or plug on the expansion tank?! Because when I checked it there was just a whole on it (maybe this is some kind of overflow vent to prevent high pressure) and while the engine was working - no coolant was leaking. After turning the engine off it starts running antifreeze from this whole... and every time it's loosing about 1.5 liters of coolant.

Please give me some advices on how to fix this because right now I stuck in a cabin - 200km from the nearest civilization

P.S> I just had a look at the EPC... it seems that this is just a whole... but then - why the coolant is leaking from there?! The only two things on this expansion tank is the hose entering in it and this strange whole!

 

My bad I decided to read the entire thread once again and even when I was absolutely sure that all my hoses were connected properly to the header tank I went down to the garage (thanks god the mountain cabin we are at has a garage) and noticed that the two pipes are not crossed as described in the thread...

Maybe I did this mistake after I had my cooling system flush last week...

Well I disconnected them and reattached back the hoses crossed. I hope this is the reason why the car was "bleeding" it's coolant. We'll see tomorrow morning as it's getting dark, cold and snowy outside and I'm not sure if I want to make a test run right now.

I made a photo after switching the hoses - please, tell me if they should be connected this way!

 

Correct, you can also confirm that on your previous post image for the routing of the pipes and the crossover effect.

 

Yes that is correct -- the upper one above the first cap seal is the overflow.

 

After reading again and again I'm still afraid there is something I don't know how to check... Well I did fix the problem with the mistaken fuse places, but is it possible while driving the car on long trip (2h, maybe 250-300km) with not-crossed fuses on the coolant tank the engine could have overheated? The temp gauge on the dashboard didn't show any signs of trouble neither a Check Engine light or any message on the dashboard appeared... But still - driving for so long and increasing so much the pressure inside the system - could this have brought some kind of problem?!

Maybe I'm just overreacting but it seems like the engine's sound is different since this accident...

 

remember the temp gauge is setup to be halfway over a wide range of temps...so you cant rely on that...and yes your car could be running hotter but not in the danger zone...i was losing a little coolant over time and it was found to be a water pump that was dripping ever so slightly and a hose at the back of the engine doing the same thing...

 

I had this happen to me many times before I finally figured it out. It is very unlikely you overheated or caused damage. I only noticed the problem after parking the car after driving on very hot days (90+ F).

Kind of interesting how common this mishap is. Ironically enough I was at a local autozone the other day and a lady was there with the hood up on her ~1999 XJ8. Her coolant lines were not hooked up correctly either (not crossed) :-). I did tell her that they were wrong and noted that if she sees coolant underneath the front wheel well - that's why....... :-)

 

the pic of the bumper overflow tank you have circled in red, is that suppoed to be just an open hole?

 

Yes, I had the same problem. New water pump, thermostat and hoses when the timing chain was replaced. Had the float sticking in the expansion tank so the sensor replacement and wd-40 to the float was done. The stupid mechanic (who will remain nameless) switched the 2 hoses and then coolant was coming out of the lower overflow tank. The mechanic (no time to point fingers) replaced the expansion tank and it still was overflowing so I read this wonderful and informative thread then switched the hoses after I did not put the coolant lines in correctly to begin with. I wish I read this before I replaced the sensor and the expansion tank by myself......The coolant still looks like it is leaking a bit and hoping it is some settling going on with the system. I will keep an eye on it and see if it is fixed.............my wife is not happy so I hope it is fixed

 

Eleven year old resurrection: even so, it is important to remind newer members that something as simple as a badly aligned hose can cause lots of problems.

I keep this picture on my desktop. . .