02 1.8 coolant temperature woes - GazKaz
Firstly, apologies for the length of post. :-(

I have a 2001 1.8 Vauxhall Vectra LS, 85K on the clock, regularly serviced.

Around 8 weeks ago I noticed it was running quite cool and took an age to warm up, so I figured I'd replace the cheapest thing first, the temperature sender. Done this and no difference so I now figured the thermostat was stuck open.

Whilst waiting for stat to arrive, I had the cam-belt, water pump and rollers changed as it was due on the service schedule. Got car back and replaced stat (just stat and not the full stat housing, using QTH600K kit) and everything seemed fine for a couple of weeks, but then noticed car was getting very hot, up over 100 and into the red. The fan would come on eventually to cool it back down to around 95 (normally stays around 90, fan cuts in at around 92 and goes off at around 89). Took out replacement stat because now thought it was stuck closed and ran it for around 4 weeks with no stat. Car ran ok but still noticed it got rather hot sometimes. Installed another new stat again, ran ok for a day or so, but then went back to nearly overheating again. Even when the car was in motion, temp always seemed slightly higher than norm. So then suspected a partially blocked radiator. Replaced radiator for new, tested that everything was ok and that the fan cut in at the right temperature again, car ran ok for a couple of journeys, but went back to spurious temperature readings.

Went out on a 40 mile or so journey the day after replacing radiator, going out was perfect (temp always around 90) left car parked for about an hour, drove home and within 5 mins temp was sitting around 95 even when car was in motion! Got stuck in traffic later on in journey, then within a minute or so the temp went up to 100 then kept on going well into red, and came back down again just as quick! In all this time the car has never overheated to the point whereby it has cut out. As we arrived home the missus pulled on to the drive and temp was at 100. She switched off engine but I told her to re-start it straight away so I could check something, and when she did the temp reading went to 90!? Left car running for 5 mins or so and it behaved perfect, fan came on, cooled down, and fan switched off!

I'm now starting to think something electrical??!!

Again, sorry for length of post, but some help would be very much appreciated indeed!!


Edited by Pugugly on 24/08/2008 at 21:46

02 1.8 coolant temperature woes - Screwloose

I'd borrow/buy myself one of those thermo-lasers and verify that the gauge is reading correctly.
02 1.8 coolant temperature woes - GazKaz
Hi Screwloose

I thought about doing something to verify the actual temp reading, but didn't know how to go about it properly. Certainly haven't heard of a thermo-laser.

I know I've replaced the temp sender but on the stat housing there is a temp sensor. Could it be this that is faulty? Is it worth replacing this?

Thanks again
02 1.8 coolant temperature woes - Screwloose

You must have come across a laser thermometer? The cheap ones are in all the catalogues.

It's that sensor that I was suggesting verifying. You just point the tool at it and get an instant reading of the surface temp.
02 1.8 coolant temperature woes - GazKaz
02 1.8 coolant temperature woes - SpamCan61 {P}
Something like this:-

02 1.8 coolant temperature woes - GazKaz
I'll certainly try to get hold of one. It would be interesting to see if it just relates to be an indication problem from one of the senders.

Has anybody else come across a similar problem in the past?

02 1.8 coolant temperature woes - jc2
Just remember that the actual temperature may bear little relation to the figures shown on the guage-just take them as an indication.
02 1.8 coolant temperature woes - seanti
Hi,I was wondering if you ever got to the root of the problem as i have exactly the same one?regards.
02 1.8 coolant temperature woes - HKTOOR

Hi GazKaz.

I am new on this site and hopefully you guys could help me out.

My car is the same as your and a couple of days one of the main hoses (top one) gave way braking the top inlet of the radiator.

Well the motor mechanic change the radiator and on my way home my car started having the same problem as yours.

I took it out to the workshop and the only thing they could thing about;was a possibility of bubbble trap when they wash up the system.

Lucky for me I have the Opel donggle to analize the problem and I reckon this cars have and ECU assigns specifically to the coolant temperature.

Well;I plugged the laptop and check for faults on the main ECU; none to recall.

When I did the same for the ECU (coolant temperature) I had two errors:

(2) Engine Coolant temperature;Frequency out of range.

(163) Engine coolant temperature; no signal

This indicates to me that there is a problem with the temperature sensor. So I have ask the motor mechanic to chase one for me to try it out.

Well; I would like to know if you fixed your problem and if was the sensor; or anything which could help me out I do more appreciate.


02 1.8 coolant temperature woes - mickeybo

(Old school of thought) remove ect sensor plug and check at ignition on for a 5v feed

if ok replace plug access rear of 5v feed wire with multimeter switch ignition on

at this point multimeter should read approx 3v's ish. If ok start engine and let idle with multimeter attached as engine warms up voltage keeps dropping when engine

running tempature is achieved voltage reading should be approx 1v or slightly less

With engine idling put one hand on top radiator hose and the other hand on bottom

hose both hoses should be same tempature vehicle stationary and idling

Hth Regards Micketbo

02 1.8 coolant temperature woes - GazKaz

Hi mickeybo

Blimey! one of my old posts resurrected from the past!

In short, no. I never fully resolved the problem. I put up with it for around a year. I put in a fan override switch to have a bit more control as to when the fan cut in.

Shortly after that the cam-belt went, which pi**ed me right off considering I had the belt, rollers & water pump replaced about 14 months prior! This happened 2 weeks before I was due to move house and I had the best intentions of fixing it myself, to the point I had stripped the head out ready for re-manufacture, but bad weather, bad light & house move put paid to that not happening! I cut my losses & sold it to a friend of a friend who works at a garage and has I believe fixed it all up.

Now got a Ford Focus, which I must say has impressed me no end. Never thought Id own a Ford, but there you go!

Sorry I haven't been of any real help but hope you get it sorted soon.



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