Excessive coolant pressure

Hi all,
My car is a 97 4.6 hse. After loosing coolant for some time I was dreading a failed head gasket or a slipped liner. However, after replacing hoses and clamps and fixing small leaks, the level has been rock steady for a week of daily use. Yesterday I noticed a bit of steam when I parked and found coolant dripping from the small hose connection under the throttle body and onto the hot exhaust. The top radiator hose was rock hard.
I pulled the plugs and they all look like they should, so I still don't think that any water is entering the cylinders. Also, there is no constant bubbling in the reservoir like you would expect If combustion gases were entering the system.
Could this be as simple as a faulty coolant bottle cap? I thought excess steam pressure should bleed out from the cap assembly but this doesn't seem to be happening.
I'd be grateful for any and all tips.

Thanks!
Henrik

get a gas test done on your coolant bottle to see if the gases in there are exhaust gases

+1 to the hydrocarbon test....

Cap failure is a fairly common problem in over pressurising the system, so for the sake of a few sheckles, could be worth a shot.....

The cap should be venting excess pressure have it tested.

I used to get air in the top hose building up as driving around when mine had gone, was rock hard. Let cool, when I took the top cap off air would glug back to it expansion tank if I squeezed it. Then I would have to top up.

I chased it round for ages changing heater matrix overhauling vapourisers.

Hopefully its your filler cap.

Test coolant for Exhaust gas. Head gasket or Block.

Thanks for the input lads. I went by my mechanic yesterday and he said I had poor circulation so suggested I flush the system and check the thermostat before jumping to conclusions. New cap and thermostat is on the way and flush is due next week. Fingers crossed.

Cheers
Henrik