Engine temperature gauge off the scale

MinuteNoodles · 11 July 2020 at 5:52PM

monaymadlol said:

Header tank? Cracks? What's that?
Do I look for leaks under bonnet or just monitor levels in the tank?

The bit you put the coolant in is called the header tank. It's made of plastic and eventually goes brittle and cracks. It's a DIY fix as it's only a couple of nuts and hose clips to contend with. A garage should probably charge around £50-£60 to change it and top up your coolant.

Monitor the levels in the tank, park overnight with a sheet of cardboard put under the car where the engine bay is so you can see the rough area where it's been leaking from.

AdrianC · 11 July 2020 at 5:54PM

monaymadlol said:

I've added around 2 litres water, bringing it to just over minimum level. Temperature back to normal now. Have already bought ready mixed coolant, but haven't used it yet. Will see how it goes.
Header tank? Cracks? What's that?
Do I look for leaks under bonnet or just monitor levels in the tank?

The header tank is the water tank you put the coolant into. The cooling system is pressurised, so a crack will spray water out. Something is clearly leaking somewhere. The gauge going off the scale was quite possibly due to the sensor not being in water at all.

If you're lucky, it's only a hose or similar cheap and easy component. But if it's got THAT hot, the chances are that there's some internal damage, even if it's just the head gasket.

Top it up to max, and if the level doesn't drop much as you drive, you may be OK. But keep a very close eye on it. Not just the gauge - the level in the tank. It may well drop rapidly to start with as air comes out of the system.

monaymadlol · 12 July 2020 at 10:34AM

Thanks. I drove around 50 miles after yesterday and didn't really see much change in the level I think. From the area I can see, I can't see any wetness or cracks. I had a look on u tube about changing the tank and looks a little fiddly though quite straightforward.

So shall I top up the max with the coolant I bought with the water I already put in there or just water again?

Many thanks

AdrianC · 12 July 2020 at 10:41AM

So how long since you last checked the level...?

If you put two litres in, it would have been very low indeed - so the "antifreeze" is now much more dilute than it was. It's not just freeze-protection, it's also corrosion protection. So, yes, top up with neat - not pre-diluted - coolant.