Engine Overheating Logan 1.4 GLE Petrol

I happen to be a proud owner of a Logan.  She's 4 yrs and 9 months old with 70000 kms on the odo.  Never faced any issues till date apart from the minor nuances of owning a car.  In fact have been recommending the car to anyone who's asked my personal views about it.  Being a mechanical engineer myself I am more than aware of the technology going into making this car.

Now I am facing a very peculiar problem.  The temperature gauge of my car starts displaying over heating (albeit 4 bars is acceptable).  Last year just as the winter was approaching (which can get quite harsh in New Delhi) I had faced this issue.  Showed it to some local mechanic who after checking it out suggested removing the thermostat valve.  I did and when it was removed I noticed that this valve had turned black (as if burnt out) instead of the usual color of brass.  Also, it would be imperative to mention that I did contact the dealer workshop and the mechanic replaced the fan fuse from the existing 60 amps to 80 amps

Anyhow, after this the car car behaved perfectly well till yesterday.  I started it after a gap of about 15 days (it had been parked at the same place over the fortnight) and while on my way to work noticed again that the temperature was heading upwards.  I opened the hood this evening and much to my horror the coolant reservoir was empty.  As dry as the desert! I topped it with approximately 7.5 liters of water (since the nearest parts shop is a distance away) and tested it for a good 1 hr after starting the engine.  I kept it running for the entire hour with various rpm levels and found that the temperature was within limits (of 4 bars as I said earlier).

Now the big question that still needs to be answered.  Where did all the coolant vanish?  Had there been any leak then it would have been visible to the naked eye the moment I started my car yesterday.

Can anyone help me zero in on the culprit?  Have been talking to a lot of my friends and have been listening to the issue of a faulty "cylinder head gasket".  I am pretty sure these gaskets don't give in easily.  Never have faced this issue with any of my cars in the past and present.

7 .5 ltrs of water  the coolant does rise and fall ! have a look when the water is cold and then look when it is hot ! That is the nice news from me ! Now pull out your oil dipstick and look for a yellowish gunge also take off the oil filler cap and look for Gunge in the cap itself maybe you have blown the Cylinder Head Gasket and the oil and water mixes and you need major repairs ! The stuff you said before about over heating falls into place with a blowing Gasket !!Also your car is due a New Timing belt and water pump so get it all done together
also after removing the  thermostat valve did you put it in boiling water to see if it worked or not ?

Approximately 5.45 ltrs is the capacity of the water system

http://wiki.answers.com/Q/What_are_the_signs_of_a_blown_head_gasket

and now you have pure water in your system !!! So you need to drain it ALL out and add antifreeze But this will all get done for you while changing the timing belt and water pump which like I said is now due to be changed

Thanks a ton Martin!  Checked the fluid levels this morning and found the reservoir to be "dry".  Also looked for the gunge thing you mentioned about and did'nt notice any.  So guess I will have to take it to the workshop for an investigation.

If you are losing Water Then check the Pipes ! Maybe you have a Rat ! They seem to enjoy Rubber ! But do not drive it without water and you will not be able to burn off all of that water So have a look round for it ! Try putting your heater on ! and look inside the car near your feet ! That is where the Heater box is ! Left of your left foot ! The water cannot Vanish

also look here at this German Translated Page !   http://translate.google.co.uk/translate?sl=auto&tl=en&prev=_t&hl=en&ie=UTF-8&u=http://www.dacianer.de/forum/motor-getriebe-kupplung/9842-wasserverlust-beim-1-4l-loesung.html&act=url

That's precisely what I am also perplexed about. The water cannot simply vanish. Checked all around the vehicle. Surprisingly no signs of leakage detected as well. I am utterly confused. Also putting my engineering qualification to the test. Frankly it's mote of an academic pursuit now!! Anyway stay tuned for more updates from my end. Thanks once again.

I am perplexed at the amount of water you claimed to have filled up with because it is over One and a Half ltrs more than will go in ! and if it was all in the engine it would not start because of the pressure of the water in the Engine