I have a 2002 Astra 1.6 with the 8 valve engine. It has done 53,000 miles and the temperature gauge does not move above the first two markers until you reach traffic where it climbs up to 80 degrees, the fan does kick in when it indicates 90 degrees. From the manual it states the thermostat shouldn't open until 92, the fan around 100.
I suspect the thermostat is slightly open or else open fully and needs replacing - however I understand these engines are prone to cool running and creating 'mayo' under the oil filler cap. It does warm up eventually and maintain it's heat, I thought if the stat was open all the time it would never warm up.
The heater does produce warm air after about 3 miles and seems fine even though the gauge isn't near 80. It could be a dodgy temp sender unit or the coolant ecu unit.
To change the stat on these you are advised to remove cambelt, camshaft sprocket and timing belt covers to get to the stat housing, I'm tempted to try it in situ - has anyone done this?
Thanks for any suggestions.
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I'll happily stand corrected but isn't the thermostat there to keep the water from circulating through to the radiator until normal operating temp is reached? So if after a cold start the top hose stays cool for quite a while and then suddenly gets very much warmer then thats the 'stat opening. Older cars had a radiator cap you could remove and watch for the water to start moving. I wouldn't use a car temp guage as a device of any great accuracy.
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Yep, it's running cold. These normally run at just under the 90, with the fan starting at 90 or just over. Probably a faulty thermostat.
JS
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I've had four Vauxhalls now and the temperature gauge has been incorrect (reading low) in all 4, maybe I have been unlucky. Changing Thermostat and sender did not help.
Before doing anything else check the temperature using a known good electronic or other surface themometer on the thermostat cover and allow for a temp drop across the cover of around 5deg.
Otherwise you have to box clever and assume the gauge is only an indication of the temperature and mentally adjust the reading for the 'Stable' temp = 90deg C and fan start temp of 100+deg C.
WBD
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Unless it's running in the blue when warm & no heat your gauge sounds perfectly normal for a Vauxhall gauge . The marks on the gauge & the real coolant temperature are a bit approximate! My Cavalier gauge from new would crawl to just under the 90 degrees then stat would open & it would run from a little over the blue to about halfway between the blue & 90 degrees on the move. When stationary in traffic it would soon go to 90 degrees & fan would cut in & out until on the move again.
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Vauxhall do seem to have changed the way the displayed engine temperature moves with time over the years. My Omegas - 1994 and 1995 - would rise fairly quickly to 92/93 and stay there unless the engine was working really hard, when it would move up to 95 and the electric fan would go into full speed mode. Ambient temperature or heater control made no discernable difference to the readings. Looking at the circuit diagrams the dash display is just driven from a thermistor, no fancy electronics playing with the readings.
However SWMBO's 2001 1800 Zafira operates very differently, in summer the displayed temperature rises quickly to the bottom mark - 80C IIRC - sticking the engine under a moderate load, or queuing, will get it to the middle, where the fan kicks in. During winter months the gauge hardly moves off the end stop at all, the engine has to be worked pretty hard to get it above the 80C mark, even harder with the heater on full. In general the displayed temperature changes much more under typical driving conditions than the Omegas.
It looks like the thermostat is stuck open, but I've checked the top hose and this doesn't appear to be the case, indeed this seems typical for Vauxhalls of this age.
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Thanks for your replies and suggestions. I am coming round to thinking that many Vauxhall engines run a bit cool and the gauges are very approximate. Possibly the engine design on this 8 valve model is inefficient and not good at warming up quickly. Considering the trouble in changing the stat on my car I may just monitor it, change the temp sender which is a quick job and see if that makes the reading improve. Checking the actual temperature with a probe sounds a good idea, I will look for a suitable diy digital thermometer.
Just a bit annoying as every previous car I have owned has run steady in middle of gauge and warmed up quickly in comparison.
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Lucky you my 56 astra does not have a temp gauge just a light might come on to tell me it's about to boil if the bulb still works then!!!
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As mentioned above, measure the temperature with something better than the dashboard mounted gimmick! It really is a travesty to call them instruments.
Most likely, everything will be OK when measured properly - has the gauge always read in this position since you have had the car?
If the engine really were running cool, I would expect that the fuel consumption would also be too high.
This engine design is definitely tried and tested, in various guises, it has been around since about 1980!
Number_Cruncher
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I agree Number Cruncher, the instruments are very crude when you find out how they work and are susceptible to fluctuations etc. Probably is inaccurate by 10 degrees. I am going to get one of those hand held thermometers with a probe you can get from electrical wholesalers, about £20, make some measurements around the thermostat and top of radiator to identify the stat is staying closed during warm up then opening.
Heater gives out good hot air after 3 miles in the morning, even with the gauge needle not registering anything at all. In the past I have experienced a Fiesta with no stat and it was very lukewarm so probably no issue at all and a characteristic of the model.
Fuel consumption isn't that bad either. If it ain't broken I don't want to start meddling about.
These engines are basic but reliable if looked after. It starts first time and runs smoothly so I'm willing to forgive it any odd characteristics, having heard of other more frustrating problems ECU, EGR valve, etc then I consider myself fortunate!
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The same temperature sensor is used for the gauge and the ECU - it might be a faulty sensor but more likely a sticking thermostat.
GM 8v 1.6 engines do seem to run cool, probably because the air intake and cooling system is designed to cope with much higher output engines. They also suffer from "mayonaisse" in the oil breathers.
It may benefit from partial blanking of the lower radiator grill.
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Update - at the weekend decided to grasp the nettle and stripped it all down, renewed the thermostat with brand new 92 degree one, replaced timing belt, tensioner and water pump as per best practice with it all accessible, took about four hours and put it all back. Result - no difference, still tends to take about ten miles to fully warm up especially in the now cold weather. Decent heat out of the vents though after about four miles so I think thermostat is trying it's best. If in traffic it does creep up to halfway (approx 90 degrees) then fan kicks in. I suspect the design is chronically over cooled, as suggested by previous posters.
Approx 85bhp using cooling system capable for the 1.8 engine isn't the best. Deciding to experiment with blanking off part of radiatior to stop wind chilled rad water going round block when thermostat opens, give it a fighting chance. Hopefully will stop the mayo from forming in rocker cover.
Couple of theries, perhaps using 5/30 oil would make engine more efficient and warm up better? Also may try the Bosch Super 4 plugs recommended to get more efficiency.
At least cambelt and major items replaced and now good for another 4 years or so. It's a reliable old lump just a bit annoying.
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