[Mk2] [NA] Replacing the Engine Coolant Temperature Sensor

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Perkinstien
Posts: 10
Joined: Sun Aug 06, 2017 5:03 pm
Location: Hampshire, UK

[Mk2] [NA] Replacing the Engine Coolant Temperature Sensor

Post by Perkinstien »

Hi All,

My 1999 Rev 5 NA has been suffering from terrible fuel economy recently (18-21MPG), from looking at other posts on here I think I have identified that the cause of the problem may be the engine coolant temperature sensor.

I have bought a new ECTS from my local parts store put have noticed that it doesn't have a connector on the end, its just simply a probe with a large thread on the engine side and a small thread on the connector side. Please excuse the stupid question, but should I have to re-use the connector from the previous sensor, or should this be supplied on my new part?

I understand that there are two sensors (engine & gauge), I believe this one is often referred to as the green one (although it looked grey when I stuck my head in earlier) located in front of the distributor.

Second stupid question; If I were to replace this sensor wouldn't coolant come pouring out? If so would this not introduce a pocket of air in the system? I haven't had to work on the cooling system yet and I wouldn't know where to start if I had to bleed it.

Cheers,

Jake.
SonicSW20
Posts: 3681
Joined: Mon Nov 29, 2010 7:54 pm

Re: [Mk2] [NA] Replacing the Engine Coolant Temperature Sensor

Post by SonicSW20 »

You've got the wrong sensor. Any replacement sensor is plug and play. If you need one ASAP Euro Car Parts do stock the correct sensor.

The colours refer to the OEM sensor, aftermarket ones may be any colour which will confuse things.

Yes, a small amount of coolant will come out, and yes, this will introduce a small amount of air into the system which you will need to get out.
pbmr2
Posts: 929
Joined: Fri Jun 18, 2010 12:49 pm

Re: [Mk2] [NA] Replacing the Engine Coolant Temperature Sensor

Post by pbmr2 »

what he said ^

there are 2 sensors, one with the multi-pin which is for the ecu temp. the other with the single pin is he gauge sensor.

Leave the rad cap on while swapping over the sensor, it slows the poring out of coolant. You will have to top up and bleed the system after (quickly) changing the sensor.

Have you put a multimeter on the current sensor to prove or not if it's faulty?
Perkinstien
Posts: 10
Joined: Sun Aug 06, 2017 5:03 pm
Location: Hampshire, UK

Re: [Mk2] [NA] Replacing the Engine Coolant Temperature Sensor

Post by Perkinstien »

Thanks for the prompt responses guys.

I'll look into getting another sensor with the correct connector on.

I haven't tested the sensor actually. I was under the impression you'd have to take it out to test properly. I do however share the symptoms that others have experienced, the car always used to get 30-32MPG. All ignition components (expect igniter) were replaced on the last service.
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