rad cap blow off

[JOWETTJAVELIN]

Is the rad cap meant to be a tightish fit? Reason I ask is the rad began steaming a couple of times whilst skidding about in the snow (fan removed), and the cap on mine isn't a tight fit, so I had water all over the engine bay. Can I bend the lugs on the cap to make it a tighter fit or was it meant to come on/off easily?
I always thought the overflow tube on the rad filler was meant for excess water/pressure.

Don't want to get the mop out every time she starts boiling.

[mike.perry]

I put it down to lack of maintenance The rad cap should push down against the spring and be a fairly stiff turn to lock in place. It should only be 4psi pressure so will overflow quite easily if you fill the rad to the top.

[JOWETTJAVELIN]

That's it then - I thought it was odd that I didn't feel much, if any, spring resistance. I'll see why it's so slack tomorrow then.
Rad is filled to 1/2" below filler neck.

I blame the lack of maintenance on the previous owner btw! Hehe

[bmcecosse]

There are two lengths of rad cap -sounds like you have a short stem cap - and you need a long stem cap.

[JOWETTJAVELIN]

Must be; the cap looks fairly new and you would expect it to be rusty at that age. There is a plaque on the rad which says 'SERCK SERVICES' and a number, so perhaps this means it was recored at some stage and the wrong cap put on?

[bmcecosse]

Measure the neck and compare with the cap stem...........