Help - Overheating/Losing Coolant

[vit4]

Not what I need, considering the MOT is on Monday Car is a 1991 Vauxhall Astra 1.4


This has only presented itself today; car is getting up to temperature quicker than normal. Noticed on the way to work it was running hotter than normal. Checked after work and the car has lost a bit of coolant, but no obvious signs of a leak and not that much. On the way home again it was running hotter than normal on temp gauge but still 'ok', but as soon as I pulled off the dual carriageway and into the town the temperature gauge went right up, had to turn the heaters on full blast to stop it overheating.

Does anybody have any ideas what could be causing this? Need to perform any checks possible myself and hopefully fix it by tomorrow, my other car's off the road so a bit stuffed! Also there's been no build up to it

[turbopug]

Is your thermostat working ok, check if the radiators warm.

Is the fan coming on when it's spposed to?

Failing that, I'd be looking at a head gasket/cracked head. If it is the gasket and the engine has been overheated, you may need the head skimmed.

[Amused2death]

Could try back flushing the cooling system, and maybe take the thermostat out to help it run cooler. As for the cause..maybe a hose which is leaking when warm? HG failure doesn't always show up in the usual mayo under the oil cap way.

[turbopug]

Amused2death said:

Could try back flushing the cooling system, and maybe take the thermostat out to help it run cooler. As for the cause..maybe a hose which is leaking when warm? HG failure doesn't always show up in the usual mayo under the oil cap way.

Taking the thermostat out is OK as a quick fix but it's no good in the winter when you're sitting in the car freezing your bks off for 20 minutes waiting for the heater to warm up.

[bazking69]

Presuming you have checked both the oil and coolant for contamination, and checked under the car for puddles or drips, my first port of call would be the stat.

[SuperHangOn]

The old putting the themrmostat in boiling water to see if it works/opens works a treat. Also thoroughly flush the system.

Coolant loss could be through the overflow pipe when it overheated.

Fingers crossed the HG isn't cooked

[maniac0796]

Amused2death said:

Could try back flushing the cooling system, and maybe take the thermostat out to help it run cooler. As for the cause..maybe a hose which is leaking when warm? HG failure doesn't always show up in the usual mayo under the oil cap way.

That's because mayo under the oil cap is where engine oil congeals with the coolant which has got in there somehow (HGF or water cooled oil cooler leaking) or condensation in the engine from short journeys. Bearing in mind that oil runs at a much higher pressure than water, it's more common to find oil in water.

Wait for it to cool down, and then fire it up, and see if it pressurizes the system really quickly, hoses getting hard, lots of hissing when taking the cap off the expansion tank, even after running for a couple of minutes etc.

Sounds like HGF to me, if the thermostat was stuck closed, then it would overheat constantly, not just when in traffic.

[vit4]

bks with bells on I had a gut feeling it could be HGF but wasn't sure so didn't want to mention it in case it swung replies. I think I'm right in saying it's not uncommon on these engines too.

I'll fiddle with the stat and carry out the checks mentioned. Tonight it seemed a bit better than earlier, but I was constantly moving. Out of interest, what 'causes' HGF?

[WhoseGeneration]

Consider the waterpump as another possibility.

[maniac0796]

vit4 said:

bks with bells on I had a gut feeling it could be HGF but wasn't sure so didn't want to mention it in case it swung replies. I think I'm right in saying it's not uncommon on these engines too.

I'll fiddle with the stat and carry out the checks mentioned. Tonight it seemed a bit better than earlier, but I was constantly moving. Out of interest, what 'causes' HGF?

Overheating, age, bad cylinder head/gasket design, lack of mechanical sympathy.

You get 4 different types:
Cylinder to cylinder, this will give a fat misfire on both cylinders.
Water to cylinder, this gives smoke out the exhaust the symptoms you're having. Overheating, pressurized coolant system and all sorts.
Oil to cylinder, well, oil gets in the cylinder. Not that common though.
Oil to water, in theory, oil should only go into water, but water does manage to get into the oil aswell sometimes. 'Mayo' in the coolant bottle and on the lids of the coolant bottle and oil filler cap.

You can also get it where they don't leak across each other, but simply leak out of the gasket. Peugeot TU engines are infamous for having an oil leak on the front left side of the block due to bad HG design, and some cars might leak water out.