Hi all, I have a 51 reg skoda octavia 1.9 TDI, recently when staring the engine the red water light flashes maybe 10 seconds after you start the car, so I replaced the water coolant temperature sensor from eBay and it fixed the problem for maybe 1 month! Now the light is back on and the only way to stop it flashing is to unscrew the cap on top of the water tank (which releases a big hiss and gargle) and that keeps the light off untill the next day. So could it be the cheap sensor from eBay at fault or is it somthing serious someone said it could be the head gasket if there is pressure in the water tank? Any help would be greatly appreciated!

It's late in the season for this one, but when you take off the expansion bottle cap, you'll can see 2 metal prongs pointing down into the water. Scrape those a few times with a large screwdriver and that should stop your overheating warning.

Flashing red is the coolant level? Well it is on the vrs lol

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It's dual purpose.

And best case it'll fix the OP's problem for nowt: Worst case it won't do any damage as long as other problems are investigated fast.

Thanks will try this later and also the coolant level is not low should have said that before, will post later to say how I got on!

If coolant level is not low but you have pressure in the bottle high enough to expel coolant from the bottle, it is beginning of a head gasket leak. Later it'll start expelling coolant, resulting in low level and the need for increasingly bigger top-ups, until finally the coolant colour changes and you can see dirt in it.

Has the car been recently serviced (TB/WP ?). If cooling system is not refilled fully (top hose disconnected) after a service, it is very easy to overheat the head gasket on the 1.9TDI.

It's not had a service in maybe 3/4 years, but the coolant level is fine the whole time doesn't require topping up. But as I say when I first start it the light comes on so I stop the car and undo the cap and it lets of a big hiss and releases pressure? Is there any way I can check other symptoms of head gasket going?

I do no think so, as at this stage the gasket only leaks a little exhaust when engine is under load, and it's a diesel so what leaks is mostly air. Standard cylinder pressure check is equally unlikely to show it, as the head lifts (and gasket leaks) at 100bar+

Eventually the gasket will go enough for coolant to be expelled, until then (or until gasket job) all you can do is undo the cap.

I had my Mk1 Octy do that (dealership overheated the gasket by not refilling the head properly on TB/WP job), your description so far is spot on when it comes to early stages of that gasket leak.

Edited 7 February, 201313 yr by dieselV6

Thanks for info, so do you think the head etc is not warped as this happens when the head gasket goes?!? I will look into getting a gasket ASAP then

Also how much is a garage Likely to charge for head gasket job? Is it somthing you could do yourself? And does the timing belt need to be changed at the same time im sure I read somewhere?

I bet the prongs need a scrape(as ken said) or a new bottle is needed.

When you say temp sensor replaced do you mean the one in the water system ?

It was a sensor like the one in this post

http://www.briskoda.net/forums/topic/61178-fabia-coolant-temp-sensor-how-to/

What's your temp gauge reading?

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Just rises to half way as normal mostly, sometimes sits just low of half way that maybe due to air in system due to changing sensor?!?

Edited 7 February, 201313 yr by mal180

Are the fans coming on?

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Well the low coolan t warning is controlled by the prongs in the bottle, the sensor you changed controls the fueling and gauge reading, if the gauge is boucing around it's either the temp sensor above or the thermostat playing up, seeing as you said it does it sometimes my money would be on the sensor even more so you saying that it's off Ebay. The thermostat would stick open and your temp gauge would sit just below 90 all the time.

Give the prongs a scrape and see how that goes.

Thanks David I will do that tonight and see how it is in the morning, and raf the fans don't come on or not enough to make me notice anyway

Thanks David I will do that tonight and see how it is in the morning, and raf the fans don't come on or not enough to make me notice anyway

Cheapest first and all that !!

If the scraping fails I will try a new sensor, is there anywhere online to get a decent one?

You say that sensor controls the fueling and guage reading does it affect the fuel guage as well?

No, it controls what your temp guage reports, and what info the ecu gets regarding engine temp, which in turns controls the fueling for cold start warm running etc.

Is your fule gauge playing ?? you could have instrument panel issues.

No it's fine now, see this thread at the bottom http://www.briskoda.net/forums/topic/239093-faulty-speedo-fuel-gauge-solved/page__gopid__3053848

I will let you know how I get on with the scraping tomorrow morning,

Edited 7 February, 201313 yr by mal180

Thanks for info, so do you think the head etc is not warped as this happens when the head gasket goes?!? I will look into getting a gasket ASAP then

Also how much is a garage Likely to charge for head gasket job? Is it somthing you could do yourself? And does the timing belt need to be changed at the same time im sure I read somewhere?

It's a big job, you can only do it yourself if you are capable of doing a timing belt, but you'd need locking and other tools. Cost last time I did was 1.5x belt job, but timing belt was part of it.

Re why gasket went, hard to say, most are due to overheating at some point in life.

Also would someone be able to send me a link or site I could get the sensor of a genuine skoda part to make sure it's not an aftermarket one I get again?!

mal, is there really not a VAG dealer (any of Audi, Seat, Skoda or Vw will do) in the Orkneys?

If not, I'd try Eurospares or GSF since their parts are usually OEM in the actual OEM box rather than in a $marque one.