Weird heating problem

[drcdude]

Hi everyone. I need to discuss a heating (not really overheating problem) problem with my 2001 Corsa Classic sedan. It's the 1.4i (65kW) CD model with a/c and p/s.
It all started about 2 months ago, I don't really drive the car often, maybe three times a week and that too, relatively short journeys of 10 to 20km. Once a month I do a long journey of atleast 150km. So anyway about 2 months ago I noticed the heat gauge going to the half mark. This was on a 10km journey. I found it a bit strange but nevertheless it was a hot day and I didn't think much of it. Fast forward to a longer journey and it happened again, only this time the car was packed with 4 people on a hot day and the heat gauge was spiking to the 3/4 mark. I never really took note of the heat gauge before as it used to stay at the quarter mark and never go higher whether I had a load of 4 people on a hot day or not. So my question Is, where do I start? It's clearly not normal but as time is going, it is heating up to that 3/4 mark faster. As I said, it's never went to the red and when it goes over half, the big fan does kick in, sometimes it drops it a little, but usually it just keeps it at that mark.
Another thing to note is that if I start the car from cold and idle it at 2k rpm, it never goes over the quarter mark and acts completely normal, did that too when the mechanic took a look at it. He suggests drilling 3 holes into the thermostat to see if that helps and if it does then we will replace the thermostat. Radiator seems fine, there are no leaks or anything. Coolant level stays the same too. I don't want him to drill my thermostat as it's an original part and it's gonna be replaced by a generic part so my concern is what if that doesn't help? Then I will be sitting with a k@k thermostat.

Any advice will be appreciated guys. I'm thinking of flushing out the coolant and putting new coolant myself this weekend to see if that helps. Since as far as I know, the coolant hasn't been replaced for atleast 2 years or even longer. But I highly doubt it will help since this problem started randomly in 1 day. When the a/c is on, on a hot day, it does make it go to that 3/4 mark even faster and with a load in the car up some hills the gauge sometimes goes a little above the 3/4 Mark, with the fan on trying it's best, but it doesn't really drop the heat gauge from there. Giving it more gas up hills also makes the heat gauge go higher. Something it's never done before.

[Corsa Addict]

Mileage?
Could be thermostat & water pump that needs replacing? Have you ever replaced either?
Strange though cos' your coolant level not dropping..
Fyi, aftermarket waterpump & thermostat for the C is good to go

90 degrees (halfway) is normal heat for the C. Opel's get up to engine operating temp quickly
3/4 is high though

[drcdude]

Mileage is 161k kms. No I have not replaced anything besides the gearbox and battery since we got the car in 2016 March.

Its actually a Corsa B sedan, will try and get some pics of the heat gauge later when I get home. I have pics of it saved at its usual normal temp as well as when its heating a bit higher at that 3/4 mark. It always seemed to take a good few minutes to get to operating temp since we got it. I wouldn't say it was ever quick to get to operating temp.

Do these Corsa B's have coolant temp sensors?

[DJ7]

Mileage?
Could be thermostat & water pump that needs replacing? Have you ever replaced either?
Strange though cos' your coolant level not dropping..
Fyi, aftermarket waterpump & thermostat for the C is good to go

90 degrees (halfway) is normal heat for the C. Opel's get up to engine operating temp quickly
3/4 is high though

Think this is a B, not a C CA. The year model and stuff definitely seems like a Corsa B sedan.

They usually go up to about 1/4 mark. Only thing I can think of is possible process of elimination. Maybe replace the coolant like you want to but test another thermostat if you know of someone who has one or can replace it. But an aftermarket thermostat for a B would also not give any hassles.

[drcdude]

Mileage?
Could be thermostat & water pump that needs replacing? Have you ever replaced either?
Strange though cos' your coolant level not dropping..
Fyi, aftermarket waterpump & thermostat for the C is good to go

90 degrees (halfway) is normal heat for the C. Opel's get up to engine operating temp quickly
3/4 is high though

Think this is a B, not a C CA. The year model and stuff definitely seems like a Corsa B sedan.

They usually go up to about 1/4 mark. Only thing I can think of is possible process of elimination. Maybe replace the coolant like you want to but test another thermostat if you know of someone who has one or can replace it. But an aftermarket thermostat for a B would also not give any hassles.

Yes its best for me to start off small with the cheaper stuff and make my way up until the problem is fixed. It used to always stay at the 1/4 mark for almost 2 years, and it just started behaving weirdly all of a sudden which makes me doubt that changing the coolant will help. Maybe a radiator blockage?

[Corsa Addict]

Best of luck with the fault finding process dude. Let us know how it goes

Think this is a B, not a C CA. The year model and stuff definitely seems like a Corsa B sedan.

Aah ok cool
My bad

[DJ7]

Mileage?
Could be thermostat & water pump that needs replacing? Have you ever replaced either?
Strange though cos' your coolant level not dropping..
Fyi, aftermarket waterpump & thermostat for the C is good to go

90 degrees (halfway) is normal heat for the C. Opel's get up to engine operating temp quickly
3/4 is high though

Think this is a B, not a C CA. The year model and stuff definitely seems like a Corsa B sedan.

They usually go up to about 1/4 mark. Only thing I can think of is possible process of elimination. Maybe replace the coolant like you want to but test another thermostat if you know of someone who has one or can replace it. But an aftermarket thermostat for a B would also not give any hassles.

Yes its best for me to start off small with the cheaper stuff and make my way up until the problem is fixed. It used to always stay at the 1/4 mark for almost 2 years, and it just started behaving weirdly all of a sudden which makes me doubt that changing the coolant will help. Maybe a radiator blockage?

I was thinking about that, but if so, then a flush could help. But I was also thinking that, that might have had a more severe. But who knows hey. Hope you come right.

[DJ7]

Best of luck with the fault finding process dude. Let us know how it goes

Think this is a B, not a C CA. The year model and stuff definitely seems like a Corsa B sedan.

Aah ok cool
My bad

No, worries.

[GmanWP]

Does the fan come on, could be fan switch problem

[DJ7]

Does the fan come on, could be fan switch problem

He stated in the original post that the fan does go on.

[drcdude]

Guys I'm taking it either tomorrow or Thursday morning to my local mechanic. We will try drilling some holes in the thermostat since you guys said there's no prob with aftermarket thermostats so if it solves or helps then a thermostat replacement is definitely in the works.

Haven't got around to flushing the coolant this weekend though.

[drcdude]

So just an update... I left it like that (biggest mistake ever) and eventually it got worse. Learnt the hard way when I was relocating to Pretoria (6 hour drive) back in July.

Not even halfway through my trip, heat gauge went into red after some hills and I had to pull over and be towed back.

Turns out it was the thermostat after all. R400 with part and labour and all was right ever since.