Cooling system I have a problem with overheating.I have put in a new radiator,hoses.The head and head gasket have also been changed,the engine runs hot after 20 mins or so.I can also hear coolant or some other liquid flowing while sitting in the drivers seat.Thermostat checks out,water pumps fine.

make sure you have the right cam timing. if its retarded it will overheat. did you use the proper cylinder head torque values and sequence? did you check if the cylinder head and or engine block is warped. start the car and it the upper radiator hose is getting stiff you are getting combustion pressure in the cooling system.

Steve, there's many causes of overheating. You say you have a new water pump and thermostat, so it's obviously not those at fault.

Just a question ... you say your car is not cooling, but is it actually overheating? A faulty temperature sender unit (it screws into the engine block, usually..) can give an incorrect reading on your gauge.

If it is overheating - steam/you can feel the excess heat - is your radiator fan kicking in? Is your car overheating as soon as you drive it? Or overheating when stuck in traffic .. and the fan isn't kicking in..?

Other things that cause overheating which spring to mind include a blocked radiator and/or a collapsed radiator hose.

Hot coolant enters your radiator via the TOP hose and cools as it goes down the radiator, then back into the engine via the bottom hose. Check both top and bottom hose after the engine has warmed - sometimes a hose can become 'flat' and blocked.

Another thing that causes overheating is a burnt head gasket/cylinder head problem.

Switch the engine on and look at your coolant bottle - a continuous 'bubbling' indicates that exhaust gases are finding their way (via a burnt head gasket) into the cooling system.

Any oil in the coolant bottle also indicates cylinder head problems. Also check the oil dipstick. If coolant (because of a defective head gasket/head) has found its way into the oil system the oil on your dipstick may appear a creamy/greyish sludge.

try a pressure test on the radiator while it engine is running.. If your head gasket is broken the compression of the engine goes into the cooling system. If the pressure rapidy increases it would indicate a head gasket problem.

SOUND LIKE COOLANT FANS HAS A FAULTY THERMO SWITCH LOCATED AT THE BOTTOM OF THE RADIATOR ON LEFT HAND SIDE.CHECK THE FUSES 8 IN THE ENGINE COMPARTMENT AND CHECK FUSE 16 IN THE PASSENGER COMPARTMENT FUSE BOX.WHEN ENGINE OVERHEATING IF BOTH COOLING FANS WORKING.OVERHEATING PROBLEM COULD BE BLOWN HEAD GASKET.CHECK ENGINE OIL LOOKS LIKE MILK HEAD GASKET LEAKING.SEE WHEN YOU DRIVING LOW AND HIGH SPEEDS THE COOLING FANS SUPPOSE TO BE RUNNING.IF THEY NOT RUNNING THAT IS YOUR OVER HEATING PROBLEM.

It could be due to age. Split hoses aren't uncommon.
However, it could be due to either a radiator blockage or a cylinder head problem - which is allowing exhaust gases to find their way into the cooling system via a leaking head gasket. When this happens the cooling system becomes pressurised by the exhaust gases.

To check if your radiator is blocked, run the engine until it is hot. The coolant goes into the radiator via the top hose and into the engine through the bottom hose.

Carefully feel the top and bottom hose. If the bottom hose feels much cooler than the top hose, then that indicates a radiator blockage. If the bottom hose feels 'flat' and 'squashed' that is another indicator - though it also can point to head gasket problems.

To check if there are head gasket problems, first check the oil on the dipstick. If it is a 'creamy sludge' then that indicates coolant has found its way into the lubricating system via a leaking head gasket.

Also remove the cap from the raditor expansion tank (where you fill it with coolant/water). Is there any sign of oil/sludge in the expansion tank? Another sign of head gasket problems.

With a COLD engine, remove the cap from the radiator expansion tank and then fire the engine up. Watch the coolant as the engine ticks over ... at first bubbles will appear as air in the coolant escapes. The bubbles should stop after a few moments as the engine warms. If the bubbles continue -or there is 'violent bubbling' that's teling you there is a head gasket problem.

I presume that your car hasn't been overheating or 'running rough' at times, as you haven't mentioned that. Overheating and 'running rough' can also be symptoms of head gasket problems.

All being well .. no radiator blockage or apparent head gasket problems, it is more than likely that the hose burst due to age/mileage.

There is a blockage in the engine coolant path causing insufficient cooling. When the coolant flows, it removes the heat produced from engine combustion to radiator to cool. If there is no flow then the coolant becomes stagnant, therefore the heat is built up without being dissipated to nowhere hence the engine gets overheated. If this is not fixed then the heat will cause the head-gasket blown due the the metal expansion.
Repair at this stage becomes very expensive.
1- Take off the thermostat.
2- Put back the hose connection.
2- Run the engine and feel the upper hose to see if cooling flowing through it.
4- IF Yes. Run engine like this for few days, if no over heat , buy a new thermostat and put it back. Your problem is resolved.
5 IF No. You have a bad radiator. It clogs up so you don't feel the cooling flowing. Buy a new radiator, don't ever use a rebuilt one.
Good luck.

CHANGE THERMOSTAT AND RADIATOR PRESSURE CAP.CHECK COOLANT LEVEL.MAKE SURE YOU HAVE 50/50 ANTIFREEZE AND WATER.MAKE SURE COOLING FANS COMING ON WHEN ENGINE REACHES 190 DEGREES.TO SEE IF COOLANT FANS RUNNING TURN ON CAR AIR CONDITIONER TO SEE IF FANS RUN IF NOT CHECK COOLING FANS FUSES.IF FUSES GOOD I AM LOOKING AT A FAULTY COOLANT TEMPERATURE SENSOR.IF ALL IS GOOD.NO LEAKS AT RADIATOR HOSES + HEATERS HOSES. NO LEAKS AT WATER PUMP WEEP HOLE OR GASKET.NO LEAKS AT RADIATOR.LAST RESORT CHECK ENGINE OIL. IF LOOKS LIKE MILK SHAKE YOU HAVE LEAKING HEAD GASKET.THAT WILL CAUSE ENGINE OVERHEATING.

The most common overheating problem with the Northstar engine is a blocked purge line(small hose).The purge line is designed to purge air out of the cooling system.
There is a small diameter hose coming from near the top of the coolant tank (not the cap) ,this is the purge line.
With the engine idling,pull the purge line from the tank,if there is no coolant flow from this small hose,it is blocked and this will cause overheating.
If the hose is clear, check for blockage at the nipple on the tank.Or trace the hose back until you find the blockage.
The hose goes in to the engine to a crossover and comes out the other side close to the thermostat housing,the blockage may be there.

check your fan clutch. chances are its worn out not allowing for sufficient air to be pulled through the core of the radiator.

If you have white smoke from the tailpipe, coolant in the engine oil, engine oil in the cooling system, that indicates a head gasket failure. However, the most definitive way to test is to have a hydrocarbon test done on the cooling system (checks for exhaust gasses that obviously don't belong in there).
If the system comes up clean, you still can have either a leaking intake gasket, partially obstructed radiator (many times flush will go around obstructions not through them), a malfunctioning electric fan or fan relay, or even an obstruction in front of the a/c condenser or between the condenser and radiator (leaves, plastic bags etc) Don't forget though even if the cause is other than a gasket, if repeatedly or severely overheated the head gaskets can also fail. That is why complete testing is very important.
good luck