My peugeot 308, 2008 is using water (filled many times)

[Kyros]

It has been pressure tested but no one knows where the water is going, no visible leaks but as I say its been pressure tested and temp gauge goes to boiling then back to normal then boiling again with STOP sign coming on + decompression system faulty. Been serviced and new thermostat fitted, both me and garage perplexed.

[Kyros]

It has been pressure tested but no one knows where the water is going, no visible leaks but as I say its been pressure tested and temp gauge goes to boiling then back to normal then boiling again with STOP sign coming on + decompression system faulty. Been serviced and new thermostat fitted, both me and garage perplexed.

[sherman]

A hole in radiator or pipe thats only opening up under high temps. Wont show under pressure test if its done on a cold engine or ypu have properly tightened the top cap of the radiator?

[stevemcs]

Can you see water staining ? there is a pipe that runs around the front of the engine that fails and another that runs around the back - assuming its a 1.6 petrol.

If not possibly head gasket.

[Every day a journey]

It's French. Try using cheap wine instead

[jamesson]

Not the same car, but I once had an untraceable coolant loss. My mechanic, whom I trust, said it was likely the head gasket had gone and the coolant was being burned in the cylinders. He also said I could end up spending the value of the car (which was pretty low to be fair) chasing it and still not cure it.

Unless you're massively attached to your 308, I'd be inclined to do a WBAC type sale and buy something else as it's 13 years old and not worth much.

Just my opinion though.

[neutral 3]

Sounds very much like head gasket

[Ivan stewart]

You could try a bottle of k seal in it ??

[CraigyMc]

Kyros said:

It has been pressure tested but no one knows where the water is going, no visible leaks but as I say its been pressure tested and temp gauge goes to boiling then back to normal then boiling again with STOP sign coming on + decompression system faulty. Been serviced and new thermostat fitted, both me and garage perplexed.

That sounds like head gasket failure. Is there any steam/vapour/sweet smell coming out of the exhaust?

Is there any "mayo" under the oil filler cap on top of the engine?

[paintman]

Possibly a tiny leak to atmosphere which only manifests when hot under pressure so no running/dripping coolant visible as it boils off instantly or hgf/cracked cylinder head again only opening up when hot and under pressure and disappears out of the exhaust.

Get your garage to use a UV dye in the coolant as this will help to show it.
E.G: https://www.ringautomotive.com/en/product/rld2

[mickyh7]

As above , K-Seal is very underestimated.
It really is very good on cars not worth spending too much on.

[GreenV8S]

Do a block / sniff test on the cooling system to see whether there's a leak into one of the cylinders.

If that comes up clean then do a hot leak test on the cooling system. That will show you there is a leak but not where it is. If you can also see the leak cold then you have a much better chance of finding and fixing it. But if you prove there's a slight cooling system leak that only shows up when hot, it wouldn't be unreasonable IMO to think about using a sealant on an old engine.

[anonymous-user]

UV dye would be best bet, check at night.