Ok, I have all the symptoms of temp sensor problem.

 

Car starts from cold as normal. Heater used to come on about the same time as the guage started moving off the cold but now doesn't come on at all. Engine runs rich (smells of petrol and has hestition when warm). Temperature guage stays at normal for a while then shoots up towards max before I kill the engine. Heater is still cold.

Occasionally the heater has kicked for a few minutes and then gone cold so problem is intermittant

 

All what I'd expect if sensor is kaput.

 

Searching through previous posts the black sensor is for the guage, the yellow one is for the ECU. I have taken the connector off the yellow one and cleaned it a bit (it was fairly clean anyway) and its still the same.

 

Do these sensors fail often or is it usually the connectors need cleaning? Could it be anything else?

 

 

 

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...sounds to me like its a blocked or failed shut thermostat. If it works like 'normal' cars, the thermostat stays shut to warm up the top of the engine in as short a time as possible, then opens and allows all of the rest of the water to circulate (inc the cabin heating system). If it's blocked or shut permanently then the water in the top of the engine (loose term) will begin to overheat and the temp guage will let you know. It's the same effect as if your top rad hose was frozen...

 

good luck (you might as well do the timing belt if you're doing the thermostat)

Those symptoms would also hold true if your thermostsat was stuck.

 

You could try a new temp sensor, they're not too expensive as they also fit micras, primeras etc. You might have a blockage in the system somewherte preventing the water circulating properly. Blocked rad?

 

But I'd look at the thermostat first. I think you can test it by placing in water and heating. But i think thermostat is hard to get at. Good luck.

But if it was the thermostat why is the car smelling of petrol and being hestitant like its running rich?

 

Also the climate control interior fan doesn't come on which I'm assuming it would do if it thought the engine was warm (does it use the same sensor on the front of the engine to determine whether to start heating the car or does it have a separate one governed by the thermostat or heater system?)

 

I agree that the thermostat is shut and not circulating the water but I think that it is doing this as it thinks the engine is stil cold (or does it have its own sensor/way of determining temperature)

 

Does anyone know whether the yellow sensor is just an on/off circuit or whether it is a fluctuating voltage? Can I just short out the connector to make the car think its warm all the time? (I was going to drive to London tomorrow, don't think I'll be able to get a new sensor before then)

 

 

 

[This message has been edited by Dylan (edited 14-03-2002).]

Hi Dylan,

 

I've an on-going problem with the Temp Sensor (see mails below entitled "Part Number'). If your ECU's giving a code 13 readout (one long flash, then three short) it's a temp sens. prob.

 

I can offer any pearls I'm afraid, but some of the people who've replied to my mails certainly sound like they know what they're on about. Give them a try... good luck

The water system uses as small an amount of water to get up to normal operating temp as possible, then, when 89 degrees - or whatever it is - is reached, the thermostat opens and allows all the rest of the water to circulate. This includes the bottom of the engine and the rad and the heater. So, if the thermostat is stuck shut, the heater won't work. The stat opens gradually when working, thats why the heater works partially before the temp guage hits normal. I would run the car engine past the normat level mark on the guage, and when the guage starts to rise, check the rad temperature by hand. It should be warm as the stat will have opened and let hot water into it to be cooled. If it's cold, then it's the stat. If it's hot at the inlet and cold at the outlet - there's a blockage somewhere in the rad. You should be able to tell where by feeling for the temperature change. Maybe, if this is the case, reverse flushing may help.

 

good luck

Sound like an air lock in the upper part of the engine and maybe the heater matrix, try running the engine from cold with the rad cap and the air bleed screw out and the heater controls set to 40 (econ button on) and keep topping till only small amounts will go in, replace cap and air bleed, go for 1 mile run return switch off and wait 2 or 3 mins and VERY CAREFULLY remove the cap and a gulp will be heard, now fill up as required and put cap on , bet that sorts it out.

Good luck mate

 

Jeff TT

Or b4 you do that check the rad fluid levels!!!!

 

CheerZ,

 

Andy

Thanks to you chaps I managed to solve the mystery. I always park my car facing down quite a steep hill which means the rad and the expansion tank will be the lowest points on the car. When the water cools and contracts I guess a vaccuum occurs in the highest point of the system (the heater matrix) and this draws in air overnight, so each day my car gradually has more and more air in the heater matrix. As I have just been doing the 10 minute drive to work and back each day this airlock has not shifted.

 

I probably wouldn't have detected it if it hadn't been for Jeff's post (thanks mate, you're a star) as when I checked the fluid level in the rad I could only get a very small amount in (less than 1/4 litre). I drove it around and parked it facing uphill, left it for a couple of hours and as if by magic I could get 2 litres in. I repeated until I could get no more in.

 

With previous cars I've owned the expansion tank has always been much higher than anything else and any shortage of water would have caused steam and/or water gushing out of the overflow.

 

The car withstood London traffic all weekend effortlessly.

 

Thanks again guys

 

 

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