Anyone with car mechanic know how?

[AnnieOH1]

Would you expect a misplaced filler cap to cause antifreeze to spew out the bottom of the car?

DH asks, is it a filler cap for petrol or antifreeze/coolant?

For the coolant tank

Usually coolant will reach high temperatures sufficient to cause some boiling except for the fact that it is under pressure. If for example the cap was loose it it likely to leak from the coolant reservoir and run down the engine bay. This may be difficult to spoit afterwards as the coolant reservoir will be hot so will only leave behind some residue and wont be sopping wet on the outside. Happened to me once after i didnt tighten the cap enough

DH says 100% yes it would. In modern cars it's a pressurised system and when the heat builds, water is released to the coolant tank and pressure builds which could cause a spillage. With the cap on it keeps the system pressurised which will retain it in the system and will circulate it back in the system when it's cool.

Hope that helps!

Thanks all :)