2002 Oldsmobile Silhouette

Our 02 silhouette kept overheating and would smell of antifreeze. In idle it would keep a constant temperature at times and other times it would not. The temp would bounce to almost hot, then back down to normal then hot again.(Very spuratic)
we took it to the local town mechanic who sent the heads in to get checked and we were told that they were bad, but they had a set on the shelf that would work. ($364) after the heads and intake and head gaskets and $1400 the temp still rises in park when the van is idling, there is a strong anti freeze coming from the motor compartment. But when going down the road, the temp is fine.
any help will be GREATLY APPRECIATED! Thx