Vauxhall Astra loses power when warm

Could be thermostat sticking . Years back I had Vauxhall in that had a similar , strange fault . It was cyl head gasket that had a small leak and was pressurising the coolant system . It was a kind of one off that took some finding . A block test would verify or not . Could also be a partially plugged exhaust / cat

Hi
Thanks for your help when I turn the key but not starting the car it make a weird fast bleeping sound.
No one seems to know what it is and I don’t know how to upload a video of the sound

On some VXs they have a power sounder that can do this when the battery inside is needing replaced .

Thanks for the advice.
I’ve had a coolant pressure test done and all ok.
A code has come back saying the thermostat is sticking and now in garage being fixed.
But the Vauxhall specialist has said he can’t find anything wrong when temperature is up the is power there.
Sometimes it loses power then the is times it’s ok.
Bit of a head scratcher

Pressure test on cooling system is good for checking for external leaks . Looks like it could be an intermittent fault with thermostat .

Hi
Had thermostat housing replaced oil pump and it still loses power when warm.
The garage it went to is a independent Vauxhall specialist he said it’s normal for the 1.6 petrol to lose power.
Is the some truth to this or is he talking BS?
Thanks again for your help I appreciate any help you can offer

You want to get a block test carried out which checks head / head gasket . Never heard of any car that loses power when it gets warm without having a fault , would be interested in knowing the reason / cause of it and why it affects that car .I believe some of those were prone to heavy oil consumption