Peculiar head gasket behaviour

[MrMoonyMan]

Evening there ph-ers,

My trusty dog car/tip run/old reliable Astra was diagnosed with head gasket failure about 6/7 months and probably 5000 miles ago.

Before that it started to make a gurgling / sloshing noise from the middle of the dash board, presumably the heater matrix.

With the use of some dye that shows if exhaust gas has gotten into the coolant a hgf was diagnosed. Along with a failing heater matrix.

Now, we've had this car about 8 years, it's been faultless, performed every single task thrown at it from flat out trips up north, to off roading and brick concrete carrying.

Fast forward to now and seems as if the ever faithful Astra is still not ready to give up.

I've been using it to get to work and back on a 30 mile round trip daily. There seems to be no let up, no use of water or oil (mayo is present though) and the only difference in day to day running is that it never seems to get up to temperature where as it always used to run a little hot.

So, here is my question to you - What's going on? Why is it running cool? How does it still work?

Here it is hanging round with some inferior cars;



tldr; Car diagnosed with hgf, still works, runs cool, why?

[Superhoop]

Thermostat stuck wide open would make it run cool

[MrMoonyMan]

True, but I'm not convinced that's it.

I popped a brand new one in there about 2 years ago and flushed the coolant to see if I could get it to stop running hot.

If you leave it idling now or get stuck in traffic it will get up to temp.

[Superhoop]

It'll do that if the car is stationary as there is little/no airflow through the radiator cooling down the coolant. Once you get on your way again, airflow increases, the coolant cools down.

If the thermostat was closed, air flow through the rad would have no effect on engine temperature - pop a thermostat in it.

[MrMoonyMan]

Okay, will do.

But on the other point - why on earth hasn't the whole thing given up in a big cloud of steam yet?

[9mm]

Had the same thing with a Mk 4. It will eventually start using lots of water but it could go on 'as is' for another year or two yet. You could spend £300 getting it fixed or run the car until it drops. We did the latter.