What's the difference between the 0.9 and 1.1 radiator cap?

I a having a overheating problem especially when using the 1.1 radiator cap

Small hole right under radiator cap on neck of radiator, beside overflow hole.

Hi! This is my first question.

I've owned a 97 Honda Accord for two months and I'm not being lucky.

To celebrate the car purchase I drove from LA to San Francisco and back without any major issue.

One month later, I decided it was time to get the oil change since I didn't really know when the last change had been performed.

I got my oil changed and a courtesy check. They suggested some repairs I declined (like draining the cooling system) just because I didn't plan to use the car extensively.

After 15 miles driving (two days after the oil change) the car engine is suddenly overheated. The temperature gauge rises and I pull the car off the freeway. I open the hood and I see the radiator cap is half open and coolant liquid is poured everywhere.

I got towing assistance and at the repair shop they tell me that the engine is severely damaged. The bill ascends to $1500 and the car is still under repair (only one cylinder had water inside)

I want to know if there's any possibility for the radiator cap to open itself (maybe due to excesive pressure) and if I can have arguments to blame the mechanic responsable for the oil change and the courtesy check (they say they don't touch the cap for any reason during the courtesy check)

Thanks for the quick response! I went to the place I got the oil change and talked to the manager. He adopted a very defensive position, saying that his guys don't touch the cap to perform a visual inspection. He said that the cap could come out under very high pressure and if the cap had been open when I left the repair shop I should have noticed smoke before two blocks (this is fun because the parking lot where I leave the car is two blocks from the repair shop)

I'm from Spain and talked to my mechanic there and he told me that was almost impossible.

My hypothesis is that the cap was not correctly locked and opened progressively. The mechanic who inspected the car after the overheating said that the cap was in good condition

So if the service technician did not remove your radiator cap to inspect the coolant ( witch is a sealed system) meaning there's no sight glass to look at the coolant. So if said person did a
visual inspection on the reserve tank an that was enough for him to recommend a service is unbelievable. That's definitely not the way you should do an inspection of the cooling system. I would recommend you getting a second option on anything they've told you a start researching a new place to do business. This isn't consider professional advice simply my opinion on the problem you have on hand. Good luck. God Bless.