I have a 1.4i Astra CD on an M plate and I have a fault with the temperature gauge on the instrument panel. The gauge rises into the red fast when driving. I have been to vauxhall about this and they can't find anything wrong mechanically - the engine does not overheat and the thermostat is working correctly, I have had fitted a new temperature gauge sensor and still the same problem. Vauxhall think the problem is electrical. Can anybody help with a suggestion of what the problem might be and how to fix it??
Thank you
subject line updated
Edited by Pugugly on 11/01/2009 at 20:49
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Ok, If its electrical, It could be the Voltage regulator to the instrument panel (usually makes the fuel guage over read as well)
OR bad engine / body earth (the engine could be earthing thro the fuel guage so remove, clean and refit the engine earth straps)
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Thank you for that advice, I know the fuel gauge is working fine so would the voltage regulator be difficult to replace?
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Unlikely to be the voltage regulator then. Old style instruments (fuel and temp) are supplied with a regulated known voltage. The sensors (temp and fuel level)then variably earth the instrument to get a reading. The instruments themsleves work by heating up a coil of wire round a bi-metalic strip, which bends and works the needle. As the fuel guage is OK, the the regulator should be ok.
Go for the engine earth straps.
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Forgot to mention, bad earth was the cause of an over reading Temp guage on my 405 years ago.
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how do you rectify bad earth and where do i find it in the engine??
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thick wires or wire braided straps that connect the engine to the bodywork. Take them off and clean the connectors and the part of bodywork and engine they connect to.
You can check if this is the cause by using one wire of a set of jump leads. Connect one end to a nice clean engine part, and one end to a bit of the body that has no paint.
If you have a good earth, if the sensor has been replaced, and it still reads hot then its either a knackered guauge or the engine is really over temp!
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It sounds as though either the regulator is away ( is the fuel gauge reading high ) or there is a short to groung on the wire from the gauge to the block temp sensor. Regards Peter
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Hi Peter,
The fuel gauge reads fine I have no problems with it at all i know when the tank is full and when its empty. It appears to be a mystery as to why the temperature gauge rises quickly into the the red, when the fan cuts in it does drop out of the red and hovers just below it.
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Hi Astra-Man;
I'm getting a tad confused here as to whether the engine is overheating or the sensor is knackered : your original post said that >> the engine does not overheat and the thermostat is working correctly .
But yor last post says the fan kicks in; and the needle then drops out of the red. Does this mean that the fan is coming on regularly? If so that suggests that the engine is running somewhat hotter than I would expect; based on all the VXs I've owned.
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I'm getting confused now!
Basically what's happening is the temperature gauge is rising quickly when i drive the car be it from cold or driven throughout the day. within 5-10 mins of driving the needle hits red, the fan cuts in and drops just outside the red zone. vauxhall have looked at it and have replaced the sensor but the problem still remains. Vauxhall have told me that the engine is not over heating that they are not sure what the problem could be.
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I'll have to put me thinking head on... assuming the Astra is the same as a mk3 cavalier (agreed not 100% sure) then the fan operation is controlled by the thermal switch in the radiator. This is in no way connected with the temperature gauge on the dash; which is just a variable resistance connected near the water pump.
So if the fan is coming on within a few minutes of cold start with normal driving, and the system is the same as a cavalier, then I think you do have a cooling problem, not a gauge problem.
As already posted by others; if your voltage regulator had gone; then the fuel gauge for one would be all over the place. As stated above the temperature gauge on the dash is a probably a simple circuit with very little to go wrong.
However if it is a real cooling problem I would hope a VX dealer should be able to spot a jammed thermostat, for example, but I suppose you never know ;-)
What year / model /engine is the vehicle? I'll try and see if there's anything on the TIS CD if I get chance this evening.
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Any help you can give would be very much appreciated.
The fan cuts in when the gauge gets near the red not when cold. i had a new radiator fitted earlier in the year and the thermal swith on the fan was replaced as was the temperature gauge sensor in the engine was changed yesterday. VX clearly said the the thermostat and water pump are working properly. As you know it's a Vauxhall, Astra 1.4i CD 8v on an M plate 1994, I'm not sure if it's the same as a mk3 Cavalier.
To summarise the temperature gauge needle rises quickly to the red zone when driving(even from a cold start)within 5 mins of driving it's passed the 100C mark the fan cuts in as the needle moves into the red zone then drops just below the red zone but when i drive at high speeds(70-80mph) it stays in the red and the fan is running constantly.
The temperature gauge needle rises to fast for my liking making me worry the engines about to overheat and blow up so we need to find the casue of this mystery.
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Adding to SpamCan61's comments. The gauge should never go to the red as usually Vauxhall gauges go to about 90 degrees or about three quarters of the gauge when stuck in traffic for some time and then the fan cuts in for a few seconds to a minute or two until the temp drops a little and the fan switches off. If you are still stationary the fan cycles on & off. It should never come on when you are moving at a reasonable speed. The wasted petrol of a constantly running fan will be horrendous over time. Unless you are losing coolant and have "brown mayonnaise" on the inside of the oil filler cap which would suggest a blown head gasket, I think you either have a jammed shut thermostat or an air lock in the cooling system or a possibly a complete blockage of some part the cooling system. Any decent garage should be able to diagnose the exact problem.
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Spam again;
I'll read your original posting properly next time before posting ;-)..
If the coolant is reaching 100C within minutes of cold start ( fan probably cuts in around 95 ish) then that sounds very much like you have a cooling problem; not a gauge problem. Most of the likely cuplrits have been changed / checked already - I'd have put money on a thermostat jammed shut.
So looking at this from another angle; a few more queries :-
1) did the problem start suddenly; or has it slowly got worse?
2) Was it OK immediately after the radiator change?
3) Was it OK before global warming kicked in this summer?
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Just thought of another line of attack : is the coolant level OK? do you have to top it up much?
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Coolant level OK never had to top it up.
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Funny, I kept questioning the thermostat with vauxhall they kept saying it's not the thermostat.
The porblem started with my old radiator having a tiny leak at the bottom and becoming partially blocked so had it replaced so it slowly got worse.
It wasn't OK immediatly after the radiator was changed
It wasn't OK before the global warming kicked in
How we doing??
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Possibly an air lock because they didn't bleed the cooling system properly when they changed the radiator. If your temp gauge goes straight to red from a cold start and doesn't go to say something over half way after the first two or three miles and then drop back a fair bit as the thermostat opens to allow the coolant to circulate, then it could still be a jammed thermostat. Either way the coolant will need partially draining (and then bleeding when topped up again) to change the thermostat which is a very cheap part. Provided the thermostat cover bolts undo without snapping the procedure is fairly straight forward.
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thanks for your response to this, i need all the help i can get.
the temperature gauge doesn't go from cold to red instanly it moves up gradually over the space of 5 or so minutes. could it be the thermostate stuck closed or partially opening, not allowing enough coolant through??
thanks
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What mileage has the car done? (couldn't find it previously mentioned)
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The airflow from the heater gives clues, is that very hot when you have high reading, and does the temp drop when heater on. If does then the radiator is inefficent. A problem I had years ago and a £5 scrap one solved the problem.
John
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I have a 1991 J registered 1.4i Astra Merit.
My experience we have had the car since it was 10 months old is that the temp gauge is lazy not t'other way round. I confirmed this recently by independant measurement with a laser thermometer.
I have never known a thermostat to fail in the closed position, they always seem to fail either fully or partially open. But I suppose there is always a first time.
Whatever - the cooling water in the vicinity of your temp gauge sensor AND the radiator fan switch agree with each other its f'n hot.
I would concentrate diagnosis on why your cooling system is ineffective. There is not a lot it can be:
a. water pump not pumping.
b. collapsed hose (s).
c. fouled coolant passages in head/block (unlikely)
d. fouled radiator.
d. massive airlock (unlikely)
Knowing the engine as I do, I would do the easy things first items b and d!!
Good Luck and let us know how you get on.
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Spam again;
Had a look on the TIS disk last night; couldn't see anything special about the 1.4 Astra; the cooling system is unsurprisingly similar to my Cavalier. Having thought about it a bit more myself; then if the thermostat was jammed shut ( local AA man says it does happen) then I doubt if enough hot coolant would get into the radiator fast enough to get the fan going within 5 mins. of start up.
The only other possibility I could think of was a blockage in the block / water pump area, I think NormanB has covered that area pretty well.
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Hi NormanB
I know that it can't be B or D because i've had vauxhall fit a brand new radiator and renew the coolant in the system
Vauxhall told me that there is nothing wrong with the water pump
it has just been serviced and MOT'd by vauxhall and they reported no major problems.
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hi dynamic dave
it has done about 42000 miles
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Hi Spam,
Any more ideas on wht to do about this?
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more spam;
I must say I'm running out of ideas now. However, just one more thing which might just help.
1) Has the vehicle ever run 'properly' in terms of temperature i.e. needle sits between 1/4 and 1/2 way up the dial unless sitting in traffic for a very long time?
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Yes it used to work fine, I think the problem started ealier this year January time before I had the radiator replaced. I thought it was the thermostat then. took it VX to have it checked they told me i needed a new radiator not thermostat, had it renewed and the same problem ever since.
do you think it could be the thermostat?
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I REPEAT yesterdays comment, try the heater temperature with your hand, if very hot then it is a true indication of a jammed stat or inefficient radiator and the temp should drop proving the point. The heater is another form of radiator, on old cars a valuble aid to cooling in jams, with the driver suffering.
John
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This thread seems to be going around in circles and repeated ideas suggested.
If it\'s a new rad, then chances are it\'s not blocked.
You\'ve had a new sensor fitted, but IIRC there is more than one sensor. There is one for the rad fan, there is one for the temp gauge, and I believe there is also one for the ECU as well.
Time to remove the thermostat and drive the car without it and see if the problem is still there or not.
From memory the thermostat on this engine is located behind the cambelt. It can be changed without the need to remove the cambelt, allbeit a little fiddly. Haynes manual should show you how.
Remove the stat, then come back and let us know the outcome.
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Sorry but since when was the vauxhall dealer the expert!;-) - well at anything other than taking your money!!
I am not an expert but can tell you I do not think it is possible to replace the thermostat without removing crankshaft pulley front timing covers, cam belt and rear timing cover.
If you want to check that the thermostat is jammed shut I would just wait until engine is well cold, remove hose from thermostat housing stub and then start the engine - should be pretty obvious.
As I said, I am no expert but - I believe your temp gauge and fan sensor are telling you the truth and you need to eliminate the reasons why your cooling system ain't hacking it.
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Come on then Astra-Man !!
Wots happening with your Astra then - problem sorted?
Curious.
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Fascinating. Got exactly the same problem on my N reg Astra 1.4, had it since I bought it 6 months ago. Diagnostics have told me it is the exhaust blocked (incorrect) or head gasket (also incorrect). Spent hundreds of quid and no nearer it being fixed.
Is your acceleration sluggish? Mine was lousy at acceleration, and was unbelievably bad getting up hills (not good when you live in a very hilly area). The spark plugs were all changed and it seemed to improve it for a while, but then it went back to normal i.e. nearly needing to push it up a hill.
The temp gauge rises in standing traffic, gets to about 98 degs, fan kicks in at 95, and takes a bit to get it under control. In standing traffic, I can only stop it from getting to 100 and into the red by blowing all the hot air off the engine into the car (not good in summer). Even then after a certain amount of time, it just won't help, and I have to pull over until the car cools. The temp increases on acceleration, and particularly when trying to pull up hills.
Coolant is fine, oil is fine, head gasket is fine, plugs are fine, thermostat is fine. Will take it back to garage and suggest a few of the options you guys have offered, see if they can get to the bottom of it before the damn thing blows!
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i have the same problem, when im driving the tempeture gauge rises to red very quickly, the hose is instact and working the engine overheats badly! i have an idea it could be the thermostat? but where is it and how do i come across replacing it?
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Hi Bennett, and welcome to the site.
What size engine, and what model Astra do you have? The thermostat can be in different places depending on the engine - eg, behind the cambelt area, or at the side of the engine just before the top hose returns to the radiator.
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As we all should know wax stats are a pretty simple and very basic tool for regulating coolant temperature. As they work quite hard they are often overlooked .They should be replaced at regular intervals box standard 92 deg opening temperature being fully open above boling point. These do have a habit of sometimes opening early as the spring weakens or opening late or only partially opening which sounds as though yours might be .If it was jammed fully shut your radator coolant would be cold and the thermal fan would not kick in. Because they are tricky to get at they are often left until they fail completely by mant diy ers. Big mistake . I would add if changing it get a genuine vauxhall quality part although posibly more expensive they will be calibrated more acurately this I cannot stress enough this is very imporatant . From memory you may need to remove powered steering/ alternator belt first . And air filter rectangular box on multipoint injection. You will definately need to remove timing belt cover on box standard 8 valve ohc engine and line up camshaft pully timing mark using a suitable bar lock its position and remove bolt .You will then be able to remove pulley with timing belt still on it to gain access to the thermostat housing . Unless you are a competent diy mechanic I would leave to the proffesional.
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