Hi to all on the forum. This is my first post.

I own a 51 reg Octavia Elegance 1.9TDi. I've had the car for a few months and have been very impressed with it. It's my first Skoda. However, after several thousand miles of trouble-free driving, recently I've had a problem with (small) loss of engine coolant.

This only becomes apparent around 100 to 200 miles into a journey -- the low coolant level warning indicator lights up and three bells sound. When I check the expansion reservoir the coolant is low, with the water level below the sensor. I've been topping up the reservoir to the maximum line. I can then drive for 50 to 100 miles before needing to top up again. However, the problem is intermittent -- sometimes I can drive for several hundred miles with no fall in water level in the expansion tank.

The car has been in to the dealer, who pressure tested the coolant system and could find no sign of a leak.

Could it be a faulty cap to the expansion reservoir? Or a fault with the reservoir itself. Has anyone had a similar experience?

Cheers

Simon

Hi

I've had exactly this kind of problem.

My dealer has replaced the header tank cap and they put in some gunk that was supposed to stop small leaks.

They performed a pressure test on the coolant system and could find no leaks.

Then recently on a trip to Spain the car boiled while climbing a long hill.

First the warning bell went off then I noticed the temperature climbing off into the red zone.

I had a pressure test done in Spain again - no leaks.

On the way back to Holland the car boiled again twice, also on long hills.

Once back home, I filled the expansion tank to the brim, ran the car until the temp was normal and I could see a continuous stream of bubbles appearing in the water.

I suspect the leak is quite small as there is very little coolant loss in everyday driving (seemed worse this last winter, but improved with the warmer weather).

This leads me to believe that I have a blown head gasket - see my earlier post about skimming heads.

Simon, are you showing any signs of the water temperature rising? If so, then I think Paulo may be right. Otherwise I'm left suspecting a pinhole leak somewhere. Did the dealer do a plain pressure test, or a leak-down test?

Paulo, I've had a blown head gasket in another car, and had similar symptoms to you describe, eventually accompanied by it throwing a litre of oil over a garage forecourt!

Thanks to KenONeill and Paulo_NL for helpful replies.

KenONeill: there is no sign of the water temperature rising -- the gauge stays at 90 degrees. I'm not sure if the dealer did a plain pressure test or a leak-down test. I'll ask them. I'm not sure of the difference between the two types of test. The dealer did say that they had ruled out a gasket leak, but I'm not sure how.

Paulo_NL: I'll try your test of filling the expansion tank to the brim and checking for bubbles.

A leak-down test takes longer (but isn't much more work). Instead of blowing the system up and looking for a visible rate of loss, you blow it up, and check back every hour or so across a day. Basically it finds smaller leaks, or ones where something is flapping and blocking the leak site sometimes.