1998 4.6L 106,000 Miles.
Engine overheated in August, water gushing from reservoir cap, tried flushing and refilling, same problem ocurred. Mechanic replaced water pump and thermostat, all seemed fine, then overheated again. Detected gas in the coolant so replaced radiator and head gaskets. New gasket set, bolts, heads skimmed and tested all replaced. (£1800!)

Have done 30-40 miles in truck, temp is good but have noticed a trickle of water from cap again! Any suggestions?

 

Try a new cap. It could be that simple

If the new rad came with a new cap then talk to your mechanic.

 

The system only has a cap on the reservoir, not on the main rad. I did think that the original blowout could have damaged the cap so will try that first.

Cheers
Damo