Coolant Loss

[Graham-W]

Car is Skoda Superb 1.9tdi 130psi. 130,000 miles on the clock.
I'm loosing coolant and can't see where it's going. On long journeys (when the engine is warm) I loose very little and can easily do 100 miles before topping up. Short journeys around town I need to top-up 1/2 litre every couple of days.
I've had all the covers off the engine and can see no leaks from hoses, radiator, water pump or anywhere else. No water in the oil and no evidence of fumes in the header tank.
Engine doesn't overheat and temp is rock steady at normal position. Can't see any steam from the exhaust.
I have my suspicions but any suggestions will be much appreciated.

[SlackAlice]

Radiator Cap? At 130,000 miles it might be getting a little tired and weak.

Might be head gasket minor leak, between waterways and piston bores. A compression test would show this and also might show as 'bubbling' in the radiator header tank.

[Graham-W]

Should have said, replaced radiator cap.
Also dosed a couple of times with Radweld. I suspect, like you, a minor leak on head gasket. Nowhere else for the water to go. Seems like it's nipping up when the engine is warm but leaking when engine is cold. No bubbling in the header tank though. Guess I'll keep running it and look out for a replacement car. Been quoted almost £1000 by my local mechanic for head gasket and much more if they find the head is cracked.

[jake-the-peg]

I had a similar situation in an Astra- finally resolved when the radiator was changed.

I guess what was happening was that there was a small leak somewhere in there that opened up when the eninge was hot but not enough to let off visible steam.

[mjwman]

I recently lost water in my 2005 Octavia 2.0TDi.
I could not see a leak either. However the sweet smell of coolant gave the game away. A bit of searching and we found a tiny escape from the radiator which I guess will be a siliar type to yours.
On replacement we found that there were in fact 3 tiny leaks on the radiator.
Follow your nose and sniff around. If you can smell coolant you have a leak!

[Graham-W]

Just to complicate things, I had overheating problems just over a year ago. Finally came down to water pump impeller spinning on the shaft. I had already backflushed the radiator and then replaced it before discovering the fault was the water pump. I'm not saying that the radiator can be ruled out, as it was a cheap one off the 'net, but I would have expected it to last more than a year. I will, however, continue to do the sniff test. I'll also replace the pressure cap again. I guess I could have got a faulty one and they are cheap and easy to replace.
Thanks a lot guys for your input. Much appreciated.

[bikerscum69]

if its had an overheat its worth checkin all the plastic fittings on the coolant system including the expansion tank its quite common for these modern plastics to go brittle with too much heat or age
most of the time it starts as a fine mist of steam and is very very hard to locate the problem
town drivin causes more vibration and stress on the leak than a long run because of stop starts in traffic etc
so sometimes you notice it uses more water on short runs
had the same prob as you but on a volvo t5
6 months later i found the prob but only because it had got bad enough to see the leak (tiny crack in bottom of header tank) if it was the head gasket half a litre of water every couple of days in a diesel engine would show itself by creaming the oil or the pressure would push water out of the rad cap or overflow pipe
if it were entering the pistons it would misfire on startup after standing overnight so i doubt your head has gone
but its also worth noting oil coolers are prone for leaking water into the oil
which can also make you think the head is leaking