Car Trouble (Renault Scenic)

Just checking FC as nFrost says he knows next to nothing about what goes on under the bonnet.

Thanks regarding the avatar, it was taken over Douglas Bay two years ago but it won't be around long as I'm still trying to settle on something.

 

Had same problem with my Peugoet 405 the fan would come on when it shouldn't, and it was the fuses for the cooling fans, the ones that are under the bonnet not inside the car (think they were 30amp fuses)

 

Not had 10 minutes to myself this weekend, will try in the week.

My old man was saying that it might be spinning up because the coolant is low so car thinks it's hot but the temp gauge says it isn't so why is it spinning up so much?

Where do i find the fuses under the bonnet, quick fix?

 

A common misunderstand going on here, and I think the car manufacturers have a bit to answer for with this.

There are at least 2 temperature sensors on most cars. One is usually located in the radiator, and reports coolant temperature, the other(s) is usually mounted somewhere in the engine block itself. The dashboard reading usually reports the former, while every decision the car makes based on temperature is usually based on the latter. That effectively means the temperature gauge on your dash is almost pointless, presenting no useful information about what's going on, except in the rare event that the coolant gets too hot, which is not necessarily the same as the engine getting too hot. Unless of course your radiator has burst, poured all your coolant all over the floor, so now the gauge on the dash is reporting that the coolant is actually remarkably cool, while the engine is frying itself, because the coolant that has now left the vehicle is no longer passing over the temperature sensor in the radiator.

Fear not though, I don't think your radiator has burst and spewed the coolant all over the road (I've seen it happen a couple of times, there is no possibility of failing to notice, unless you're blind, in which case you probably ought not to be driving). I'm just saying, don't rely on the temperature gauge to tell you anything useful.

 

Scrap it and buy a new 'un. Or buy a bicycle.

 

That's not helpful Aln!

 

UPDATE: just poked my head under the bonnet today for a nosey and the fan doesn't spin at all. Am I to assume it should spin all the time?

This is bad isn't it?

 

No.

When the engine is cold, the coolant flow is blocked off by the thermostat, so it can't cool down at the radiator. So the radiator stays cold for a while.

As the engine heats, the coolant trapped in there will warm up, heated by the engine.

At some point, it will reach some set temperature, usually between 87 and 92 degrees C. This is normal operating temperature. The thermostat will open, and coolant is allowed to circulate through the radiator at the front.

As you drive along, there will be airflow around the radiator (because you're moving along). This will take heat from the radiator (and therefore the coolant inside it) thus keeping cooling the coolant, which in turn will cool the engine block, holding it at around 90 degrees C.

Now here's the twist. Sometimes you will get stuck in slow moving, stop/start traffic. The car isn't moving enough to create a lot of airflow around the radiator, so the radiator doesn't serve its purpose of cooling the coolant and therefore cooling the engine. The coolant starts to exceed normal operating temperature. Something has to be done.

Queue electric radiator fan. A sensor monitoring the coolant temperature decides it isn't cooling enough, so the fan is activated to assist cooling.

When you're sat in stop/start traffic, you can watch it happening on your temperature gauge. It will creep up to higher than normal, causing your heart rate to increase proportionally as you start to worry that the engine is going to overheat. Then just before it goes into the red, it will suddenly start dropping again and will drop below normal operating temperature. Then it will creep up again, and keep doing this warming/cooling cycle until you get moving again when natural airflow will relieve the fan of duty.

In the olden days the fan was always on, driven by the engine (hence the archaic but still commonly used term, fan belt). Manufacturers, keen to reduce emissions to remain competitive, realised that they were using engine power unnecessarily to drive the fan, so they started putting electric ones in instead, because they are lighter weight and don't need to use any energy at all in normal conditions, only coming into use in the comparatively rare circumstances that you're stuck in a traffic jam.

 

Hello, sorry, I hadn't seen your replies as my notifications have been a bit irratic.

The car runs fine at the mo but since the fan started spinning up all the time it hasn't span at all. But I haven't really done a long drive in a while, maybe 5 miles at the most. I've now filled the coolant right up and the situation is still the same.

The temp on the readout is the same as it has been previously, but this is the rad temp isn't it? Not the engine temp?

No water loss as far as I can see.

 

Car's been running fine for a while, no fan trouble so thanks for your help.

Just out of interest sometimes in the morning when it has been quite a cool night compared to previous nights/days when it has been roasting why does the car struggle to start? It sort of judders a bit and I get no response from the throttle. If I start the car again and really give it some it's just fine. It's like it's refusing to wake up!

 

That's Renault for you. They have adaptive ECUs, and a fuel saving measure is that they remember the conditions they were last running at. The idea being that if it doesn't have to retune every time, you don't get the usual few minutes of inefficient burn when you first start up. Trouble is it is a flawed design, because of course the weather can change very significantly between switching it off at the end of one day's use, and switching it on again the next day. So, your ECU will have remembered that its red hot, that the oxygen content per litre of air is low etc, and of course that's not the case the next morning when its cool, so it has to retune itself.

 

Thanks clueless, that's my mind at rest then. Stupid car.