Coolant system Service required

[Kev the Ace]

A few weeks after having its annual service at a Volvo dealer 'Coolant system Service required' appeared on the dash (see attachment). I noticed the cooling fan was running continually and the hoses only got luke warm, cabin heating cold, engine running rough when accelerating 1st/2nd and when in slow moving traffic. Took it to the dealer. On the way to the dealer the message disappeared and the cabin heating started working again. Dealer said the temperature sensor had gone and charged £210.84 to fix. About 500 miles later it happened again: same message, cabin heating stopped working, hoses luke warm. It was over a weekend when we did about 500 miles. After another 100 it all started working again then after another 100 all stopped. Dealer says this time it is the thermostat costing £350! But its the same symptoms as last time. Has the dealer misdiagnosed? Anyone had this problem?

[cheshired5]

The first problem you had did sound like a temp sensor failing but seeing as that's now been replaced, your current problem could well be the signs of a thermostat sticking open.
They can give similar symptoms because the constant fan from the bad temp sensor is cooling water that doesn't need it, hence the not as hot hoses and a stuck open thermostat doesn't allow water to constantly circulate around the hot engine, so the water ends up being able to flow to the bottom half of the cooling system and be prematurely cooled by the radiator.
If your cooling fan is no longer on constantly, then the temp sensor diagnosis was likely right.
It just sounds like you've been really unlucky to have both fail.
To test your thermostat, start your engine from cold and keep feeling your radiator top hose. If it starts to get warm after 2-3 mins, your thermostat is stuck open.
At this time of year, your top hose should stay cold for easily over 5 minutes.

[Kev the Ace]

Originally Posted by cheshired5

If your cooling fan is no longer on constantly, then the temp sensor diagnosis was likely right.

Cooling fan is still on constantly. Everything is exactly the same as last time. I can't check the hose temperature because car is in dealers.

[cheshired5]

It's very simple to test a coolant temp sensor and wiring to confirm a fault so if the dealership is just using a fault code to determine the problem, they're not very good.
Your problem could be either the stat or the sensor or both or neither. There may be a problem with the sensor wiring or the fan wiring.
If a garage doesn't fix a fault yet charges you, you need to be asking them exactly what they've done and why they've done it.
What is your car, engine, year and mileage?

[volvo for ever]

2 things this can be ether faulty level cooolant sensor or theres a sensor behind plastic big pip in front of engine ,,i had similar issue it was chaffed wire cured this

[AimarP]

i had the same symbol in my dash. And it was thermostat.. it cost 260eur. And the cooling fans worked all time.

[Divegimp]

Originally Posted by cheshired5

It's very simple to test a coolant temp sensor and wiring to confirm a fault so if the dealership is just using a fault code to determine the problem, they're not very good.
Your problem could be either the stat or the sensor or both or neither. There may be a problem with the sensor wiring or the fan wiring.
If a garage doesn't fix a fault yet charges you, you need to be asking them exactly what they've done and why they've done it.
What is your car, engine, year and mileage?

Hi. I have exactly these symptoms on my 2010 D5. I'm going to change the Sensor first,then the Stat. But where are they located? I can't find either? Cheers.

[Divegimp]

Originally Posted by volvo for ever

2 things this can be ether faulty level cooolant sensor or theres a sensor behind plastic big pip in front of engine ,,i had similar issue it was chaffed wire cured this

Hi. I have exactly these symptoms on my 2010 D5. I'm going to change the Sensor first,then the Stat. But where are they located? I can't find either? Cheers.

[cheshired5]

Originally Posted by Divegimp

Hi. I have exactly these symptoms on my 2010 D5. I'm going to change the Sensor first,then the Stat. But where are they located? I can't find either? Cheers.

I would be testing them before even looking for them.
No point changing a perfectly functioning part.

[Tatsfield]

I was always taught that after a suitable number of years, between 3 and 5, depending on who was administering the lecture, you should routinely change the CTS and the stat as, even if they are working, they may be deteriorating slowly and the ECU will be getting dud data and having to work with the stat sabotaging the cooling system. On another make of car I failed to change the CTS and little by little the engine began to misbehave at particular running temperatures. When the CTS was renewed the engine not only behaved itself but I suddenly found a lot more power available that I hadn't noticed that I had been slowly losing. All that bothered me from the OP was that changing the two cost him £560! Are these Volvo parts made of solid gold and fitted by the crowned heads of Europe?