Astra 1.4 overheating tried everything (almost)

Hi,
I have a frustrating problem with our car. Symptoms are:

Gauge goes into the red and sometimes goes down again of own accord.
When its in the red, Rad hozes are very hot and very hard with
pressure.

I unsqueeze expansion cap slightly, relieves pressure. Temp goes goes
down IMMEDIATELY.

but there is no cream in the oil. It looks perfectly normal.

I've fitted a new thermostat, a new thermistor (water temp sensor on
engine block), fully flushed and new antifreeze.

Any help appreciated.

DP

 

other wierd thing is - when temp goes down of own accord its often when
its on a run - eg on motorway. It goes up and then down.

 

Other than a dodgey sensor this can happen if air (and I guess exhaust
gasses) gets trapped around the sensor.

Head gaskets have a number of ways of failing so leaking into the oil
isn't always a symptom. However I would have thought that the radiator
cap would have relieved some of the pressure.

 

Have you tried a new cap?

 

I think the symptoms are pointing towards the head gasket, I would examine
the radiator too as the excess pressure can warp it and cause a leak.

Sam

 

Hmm. Hope it's not the head gasket, it had a new one fitted about 15k
miles ago.

Another thing I noticed is that the rad fan doesn't always kick in when
hot from a run but did when I left it idling from cold start. But even
if that is faulty would that affect the temp going up on the motorway?
I bought a new one to replace it but its a beggar to get to so havent
done that yet. I've a feeling it wont make any difference any how.

I bought a new expansion cap today but didn't run it long enough to
test it yet.

 

Thanks for all replies folks.

Took car on a 30 min run this morning, got stuck in traffic etc but
temp seemed to be ok. It hovered around 90 for the whole time. Didn't
stay exactly on 90 but fraction either side. When I got back I lifted
the bonnet and there was no dramatic signs, all looked normal and hoses
were also soft, not under great pressure. Heater nice and toasty and
switched down to medium output. So could a pressure cap cause all those
problems? Looks possibly like it

 

Yes cap is common for seals going on them. usually they go leaky tho and
therefore your water disapears/air locks happen etc. It is a bugger. I only
know from experience after cleaning up things n wrecking the cap in the
process when i done it. Only realised what i done when all my water had
evaporated and the temp hit red. Yes temp will go up very quick Temp slowly
rising andf a hot heater always a good sign. Leave it idling for about 20/30
minutes tho and go out now n then during it n make sure your rad fan is
coming on. Also after the 20/30 minutes check your water level for your
cooling. Sounds like alls well tho anyway. nice one. Bet your glad its ok
now especially at this time of year and bad weather looming fast.

Essexgirl

 

its not cured

after a few more runs temp still going up so i flushed the rad but
still no joy.

latest symptoms are: after flushing the rad i refilled the system and
let it idle. Temp rose slowly and fan cut in accordingly and temp went
down. Took for a drive and while on the run temp went into the red, so
stopped car and within seconds on idle the temp went right down again.
Drove back and temp stayed down. Lifted bonnet as soon as i got home.
The 'nearside' rad pipe was cool and the other hot then after 20 more
seconds of idling the pipe was hot again.

could this be the water pump?

 

do u have another radiator you could temporary fit n try with it. just out
of curiosity. Theorietically you would think no point in doing that. but
thru experience i would do that to rule it out. Doubt its your water pump.
Most of the time when they go they either whine like hell or simply leak
water excessively.

Essexgirl

 

I don't have another radiator. It seemed to flush through clear through
all orifices. There doesn't seem to be anything dramatic happening when
the gauge goes into the red. Not boiling over. I wonder if the gauge is
faulty?

 

Hate to say this, but it looks like you are in self-denial now. Bite the
bullet and pull the head.

Mike

 

I take it you changed/removed the thermostat already?
Water pumps can lose the impellor although I would have thought the
symptoms would be obvious.
The gauge on my car randomly goes up into the red, even when the car is
cold, so my temp sensor is faulty. You coudl try a new one - they're
not expensive.

 

didnt want to mention head gasket quite yet. wont always show creamy water
to indicate head gasket is fooked. Try get a radiator from a scrappy and
throw it on. if it does the same then maybe start thinking about the head
gasket. get it checked out.

essexgirl

 

Sounds as if the fan is not cutting-in when the temp goes up e.g. when in
traffic etc. Mway journey = lots of airflow = cools things down. Maybe the
rad is blocked as well or some such.

 

I have had this problem on a Vauxhall cav 1.7Td. It turned out to be an
earthing strap that had corroded the one that runs from the engine to the
bodywork of the car. I spent a fortune trying to fix mine. Hope this helps.