Coolant warning light - Saxperience

frankie_hr · 17th February 2022, 13:07

Hi everyone,

I've got a 2003 Saxo 1.5 diesel and recently my coolant warning light started to come on. I've checked the coolant level and there wasn't any missing.

What's even more interesting is that the coolant temperature gauge is only at around 1/4, while the coolant warning light comes on, regardless of what the gauge says.

Now I've been driving this car for quite some time and I've never ever seen my coolant warning light come on until now. I know the car and there really isn't any reason why the temperature would rise to a critical level - it's winter time and I haven't been pushing the car, so from my previous experience I'd say the gauge is pretty much showing the correct value, while the warning light is bluffing.

To add to the problem, each time the coolant warning light comes on, it consequently triggers the fan to come on too. This isn't such a problem itself, but the fan tends to stay on for some time after I turn the car off, so I'm afraid after a while it will drain my battery.

I've taken the car to the local mechanic, but he said he couldn't find anything obvious and that I should really look for a car electrician since he suspects there might be a faulty or a short-circuited connection somewhere.

I don't know any good car electricians and I'm kind of vary towards leaving my car at the shop for a week or so while someone is pulling out half of the wiring trying to figure out the problem. Plus, I like to think it could be a simple case of a faulty thermostat or something like that.

My car knowledge is somewhere at the lower-intermediate level and I have the Haynes repair manual for the car.

Check the photo for a better visual: https://ibb.co/RQnhsn5

Any similar experiences, tips or tricks to share?

Cheers!

Manu · 24th February 2022, 10:40

Hi, it's a fairly common, hopefully non issue in your case. If the garage has not spotted any leaks, then you may have air bubbles in your circuit.

http://www.saxperience.com/forum/sho...d.php?t=440302

Try to bleed the circuit, there are many threads on this. Pics are gone but you'll get an idea.

I had the issue on 106, my rad was shot. I had the issue on saxo, bubbles. Try parking facing up and then downhill while bleeding the coolant, this helps moving the bubbles around.

Failing that, if you suspect any electrical gremlins, unplug the temp sensor and run some contact cleaner on the plugs (engine off)

MartinObviously · 25th February 2022, 13:37

Sounds to me like the sensor is faulty.

It's a 2 part sensor, the overheat trigger and the thermistor are part of the same sensor on the head. It's a blue sensor next to a green one on the thermostat/fuel filter housing at the front next to the vacuum pump.

These 1.5d models have an ECU with an OBD port, with Peugeot scanner (or good aftermarket like snap on etc) you should be able to read the actual coolant temperature from the sensor.

Bleeding these is only required at the heater matrix "tyre valve" style bleed nipple. Just fill the header tank until there are no bubbles with the engine off and cold. It's a totally different setup to petrol models.

Does the light come on random? Or straight away? only when the gauge reaches 1/4?

frankie_hr · 25th February 2022, 13:52

Thank you for your thoughts and useful information fellas!

For whatever reason, the coolant warning light hasn't came up for the past couple of weeks, but if it does, at least I know where to start. Maybe the mechanic did something after all, but hasn't told me about it.

Anyway, I'll keep my eyes open in the future.

Cheers!