S40: Overheating at speed

[NerdyKitt]

Good afternoon,

Last night I noticed something wrong with my 1.8 S40 (GDI engine).

When doing 30-40mph, the temperature gauge was smack bang in the middle, as it has always been.

When doing 60-70mph, I was touching the red at the top of the gauge.

Car is parked up now and I could really do with finding/fixing the problem this weekend so as not to do any permanent damage.

I've checked the top hose on the rad and coolant is flowing through fine.

When I turn the heaters on full, it gets as hot as it normally does (very hot if you are sat in it too long with the 23oC that we had yesterday!)

All the pipework seems fine and the coolant level in the reservoir is up to the max level.

There is a small whine coming from around the aux belts (belts recently replaced) but not sure I would call it anything worrying.

Can anyone suggest anything else I need to check to solve this problem?


Thanks in advance.

Stu

[elainesvolvo]

Thermostats? Are all the areas of the radiator warm? No cold spots. Has the water pump been replaced?

[NerdyKitt]

Back of radiator (where fans are) is hot as much as I can tell (front is cold)

Water pump has not been replaced but am leaning more towards that as a possible issue.

[Clan]

Originally Posted by NerdyKitt

Good afternoon,

Last night I noticed something wrong with my 1.8 S40 (GDI engine).

When doing 30-40mph, the temperature gauge was smack bang in the middle, as it has always been.

When doing 60-70mph, I was touching the red at the top of the gauge.

Car is parked up now and I could really do with finding/fixing the problem this weekend so as not to do any permanent damage.

I've checked the top hose on the rad and coolant is flowing through fine.

When I turn the heaters on full, it gets as hot as it normally does (very hot if you are sat in it too long with the 23oC that we had yesterday!)

All the pipework seems fine and the coolant level in the reservoir is up to the max level.

There is a small whine coming from around the aux belts (belts recently replaced) but not sure I would call it anything worrying.

Can anyone suggest anything else I need to check to solve this problem?


Thanks in advance.

Stu

when it is showing very hot and you stop are teh radiator fans running? And if so are they blowing very hot air out over the engine?
If lukewarm , your symptom is classic of a blocked radiator .

[NerdyKitt]

Thanks for all your responses.

Spent the afternoon under the bonnet as the sun finally came out and think it's the thermostat.

Ordered a new one as it's a cheap part to replace and will see how I get on.

[elainesvolvo]

Excellent!

[chomerly]

It's still worth checking to see if the radiator fans are still working when the car is running.
And if you want to check the thermostat then try putting into a saucepan of boiling hot water to see if it opens up.
It should do so in a smooth action but if its sticking then it obviously needs replacing.

Also, i should add that it would be worth running water through a hose pipe through the whole system.
Especially the heater matrix and radiator sections as this is where most of the crud from the cooling system of an engine likes to gather.
Run the water through both lines of the heater matrix until it runs clear and do the same for the radiator.
Once you've done that then put in a good quality coolant mixture that has excellent anti-corrosion properties.
This should keep your coolant system nice and healthy without having to resort to doing the same thing again for at least a few years.

[NerdyKitt]

Cheers chomerly.

Did the boiling water test and it was sticking badly which is what drew me to conclusion that it would be thermostat.

Fans seem to be working fine as well.

Took the car for a run without thermostat fitted which I assume would slow down the car getting up to temp but it didn't. Once I hit 70 on the A14, up goes the temp gauge again.

New thermostat ordered anyway as they are cheap.

Think I will have to flush the system fully out next. The bit that confuses me is that when sat on my drive with the car idling, it sits at the half way mark on the gauge and does not move. Tried this for a good 20 mins yesterday. If there was a blockage in the system, surely the temp would rise if sat with the engine running to simulate being sat in traffic?

[pierremcalpine]

Based on what I read in this forum recently: the tstat performs 2 roles:
1) It pops open at a certain temp and allows cool coolant to flow through hot engine
2) It limits the flow rate of the coolant to make sure it has time to cool as it makes its way through the rad.

Not sure about the second bit but if true it would also account for your baby heating up at high speed even without the tstat installed.

[NerdyKitt]

Thanks Pierre,

New thermostat arrived and fitted yesterday along with a coolant drop, flush and new coolant in.

Took for a test drive and still the problem is there but when I got back I decided to have a feel around again.

Half of the radiator is cold (right side as you look at the front of the car) where the left side is hotter than I can touch.

Starting to lean towards the radiator now as the issue.

This whole process of elimination has been doing my nut in but we will get there in the end.