overheating overcooling

[exminiman]

hi any one help? jeff back on the road and working ok after the heater matrix pips rotted thr u(replaced them with 5/8" rubber hose and 15mm domestic plumbing pipe) The car seemed to be running a tad cool(only a quarter on the the gauge) so i changed the t-stat and flushed thru...Only prob now is after a 30 mile "thrash" at motor way speed, it reads less than a quarter and heater not great. got a new rad cap today, but when i was putting it on all pipes were hot but rad was stone cold( i`m thinking blockage after the flush) tried loads of stuff previous to this i.e. blanking rad off and puuting in more antifreeze than required.... but it dont get hot....water level is constant and there dont seem to be any leaks....and ideas????:banghead: :banghead: :banghead:

[Roperman]

possibly the new thermostat is seated incorrectly, or isnt the right part, or is faulty, as it sounds like its letting coolant past when it shouldnt. or your temp sender might have a loose connection.
the radiator might be cool, but not cold after a run, as if the thermostat is doing its job it wont let any cool water from the rad in so it keeps geting cooler as its sat in there.

[exminiman]

gets worse....just got up to take little`un to school, car has done a wee on the road. Coolant seems to have forced its way passed the bottom hose coming from the water pump(its a perkins) and all the hoses were rock hard. When i took the rad cap off it hissed like hell, obviously still pressurised from 9 o`clock last night..Do i resign my self to the fact that its the head gasket?:banghead: