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Robert, Peugeot Technician
Category: Peugeot
Satisfied Customers: 4716
Experience:  Fully qualified 19+yrs exp/self employed technician in the UK
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Hi got a peugeot 1.4 8v 307 on a 51 plate. Flushed out the

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Hi got a peugeot 1.4 8v 307 on a 51 plate. Flushed out the water system and changed the thermostat and engine temp sensor, had an erratic temp gauge b4 but now even worse. The sensor i fitted was blue as i was told to get one the same colour as the plug. The one i took out was green. Have i put in the wrong one and why is my gauge going erratic.


Hopefully i can help...

What your VIN number ? ( vehicle identification number )

Which one did you replace? i recall these having two sensors...

Customer: replied 3 years ago.

where will i find the vin number on the car. I took my log book home to Wales last week,( i work in London,) and didnt bring it back.


For RHD - It's normally on the bottom corner of the passenger side corner windscreen

start off with VF then 15 digits it should 17 digits in total
Customer: replied 3 years ago.


Hi..there thanks for that..

Ok..As i say these cars actually have 2 temp sensors which from going by your VIN says so too looking at the engine diagram - one for the temp guage and the other one for the ECU for cold/hot start - You dont mention which one you've replaced but im sort of guessing its the one on the thermostat housing which is normally green or blue - there is also another on the cylinder head /just up from the thermotat housing at the side with a blue plug thats also a temp sensor.try disconnecting it and see if the guage falls - if it does then thats no doubt the one to replace , the problem being is these system tend to swap colours al over the range .even brown ones are found on them - normally with that id say get the green sensor - it had a green one - why fit a blue to fit colour for colour..and check the blue sensor as i highlighted above - but normally with erratic guages/rising and falling etc then its normally a sensor fault with them..but carefully check the wiring too/pins on those plugs...I do hope this helps

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Customer: replied 3 years ago.

There is No sensor on the side of the thermostat housing. There is only one sensor. It has a sky blue plug and it plugs into the sensor which is the one i re placed. The sensor i took out was green but i replaced it with a blue one as i was told it matches the plug. The sensor plug is located on the rhs ( as you look into the engine bay) above the bleed valve which is above the thermostat. Please advise again.


Yes i know what these look like,and yes this engine does have two temp sensors according to yuor VIN number and i always knew working on these before - There is only one sensor on the thermostat housing or ontop - its a green sensor - the other sensor is not on the themostat housing as i highlighted above - its screwed into the cylinder head in the same area ' just short of the housing towards the side corner of the head or under the housing just up from the bellhousing as the thermostat housing is bolted to the cylinder head..thats the sensor you need to look for..

Customer: replied 3 years ago.

I do see a sensor quite low down, i.ll have to check it in the light. I still need to know why i was told i needed a blue sensor. like i said, the original one was green. Is this the reason my temperature guage is very erratic when i.m driving. The needle doesn,t fuctuate much when the car is idling.

Customer: replied 3 years ago.

I,ve just looked again and the only sensor i can see is located quite low down at the bottom of the engine. It also looks totally different to the s3nsor above the stat.


The colour doesnt make any differance to how the gauge reads..for that one anyway,as long as the pin set up is the same and the sensor nib is the same length..on the thermo housing.. like i say these cars or engine tu3jp varies alot. some sensors are green/blue/brown and even light grey - Are you sure you've actually bled the system properly..if thats an air lock causing that then - that too can cause a guage to fluctuate aswell as anything like sealing additives that been put in prior before at some stage - normally to bleed these you have to have the heater set wide open on hot setting..fill slowly,via expansion tank with bleeder open until a steady stream of coolant comes out then close the bleeder,and run the engine until most of the airs out..but like i say normally with a guage fault is down to the sensor on these...Yes its a different plug on that sensor to the one on the thermo housing


Customer: replied 3 years ago.

We did put in holts wondarweld as i may have another head gasket leak. The sensor i changed was identical to the old one except for the colour. We drained the water system, flushed it out, refilled with anti freeze then run the engine as you said, the water came out of the bleeder steadily. We then put in the wanderweld. Would that cause problems with the new sensor we fitted. Plus, is it easy to change the other sensor.?


Ok..Im not sure why you should have another headgasket problem - unless - 1. the job wasnt done right the first time/miss diagnoses - 2. the coolant system is blocked causing a flow issue - 3. the water pumps not circulating the coolant around properly - 4 the heads at fault of course there other things that could cause a failed headgasket - Either way you shouldnt have to use any type of sealer at all - in the system after a previous headgasket replacement if that's whats been done... the problem with sealer is they have habit of blocking the heater matrix and they are only deemed as a temp repair anyway or for emergancy - if as you say you think you have an engine internal leak then that has to be dealt with and the temp doing what it is doing is possibly a factor of that and not sensor initially - a proper garage should test the system pressure/compression test across all four cylinders and compare/combustion leak test - As far as the other sensor goes you need to remove that air box - and you get better access to the sensor.either a ring spanner "will be ackward" or what use a long deep reach socket the same size as the nut onthe sensor over the top of the sensor and undo it with a ratchet and it will come out....