MK IV Astra - Engine Temperature Questions

HaX · 4 Mar 2009 at 19:18

Hi there,

I have a strange problem, which may not even be a problem, I just need it confirming.

When driving at speed (60/70 MPH), the temperature gauge needle hardly appears to move, even when I've been driving the car for over 20 minutes.

If I leave the car stationary for a while the temp gauge gradually moves up to about mid way(90 c) and after a few more minutes the radiator fan will start.

Similarly in slow moving traffic the temp gauge will creep up a 1/5 of the way across to about 80 c, but as soon as I'm moving quickly again - eg a 60/70 road the temp will go down again..

I thought that initially the problem may have been due to the wrong Coolant being used (blue coolant), so I had the engine flushed and the correct (pink) coolant used. However, this has made no difference.

Is this normal, or is there something wrong with the engine/coolant system?

I have topped up my coolant to just above the mark in the header tank, however I am worried that I may have overfilled it a little. Is this likely to cause problems, or is there an overflow system to cater for these situations?

Cheers

HaX

Chris1712 · 4 Mar 2009 at 19:54

Can't say i have the same problem, mine will get up to whatever halfway is on the dial and stick there pretty much, unless im sat in traffic at the other end of a long run. Don't foget at higher speed, you have more airflow over the rad so more cooling.

Clarkey · 4 Mar 2009 at 19:59

Thermostat probably, I noticed the same thing happens on my mates mk4 astra, Vauxhall quality for you

Lopéz · 4 Mar 2009 at 20:00

Cars have different "normal" operating ranges - what does the handbook say?

The Manta rises slowly to halfway (takes about 4 miles at the most) and stays there regardless of speed.

The Golf rises quickly to halfway, in traffic it creeps over until the thermostat opens and the fan kicks in, drops below halfway, then climbs again, repeat to fade.

loltim · 4 Mar 2009 at 20:04

Chris1712 said:
Can't say i have the same problem, mine will get up to whatever halfway is on the dial and stick there pretty much, unless im sat in traffic at the other end of a long run. Don't foget at higher speed, you have more airflow over the rad so more cooling.

Temperature shouldn't really move once it's upto optimum temp. More airflow over the radiator at high speed shouldn't really matter, the thermostat should close so the engine isn't overcooled (decreasing fuel economy).

I agree with Clarkey. Thermostat is sticking probably.

HaX · 4 Mar 2009 at 20:15

So...

From what you've said I take it there is a thermostat which dictates whether cool water from the radiator is used to cool the engine, or whether the water is recirculated via the header tank?

If this is nackered, how much am I looking at it costing to replace? Is this something somewhere like Tanvic could deal with, or would I be better going else where?

Cheers

HaX

loltim · 4 Mar 2009 at 20:18

That's how I understand it yea, it'll get recirculated if the engine doesn't need the cooler water/coolant. The thermostat opens when it's needed.

Thermostats are really cheap, even for a Honda they're only ~£20. Fitting it normally involves draining a bit of coolant, pulling off radiator hose near block, replace thermostat (2 screws on mine) and top up coolant that's lost.

Phil W · 4 Mar 2009 at 21:10

Vauxhalls are quite well known for the Thermostats playing up, its happened to 3 of my vauxhalls.

I'd advice replacing the thermostat, and then check to make sure the fan comes on, often the fan sender switch goes pop too.