How to change a heater core

if it consumes fluid only two ways a leak or burning it ---look for leaks -dried /damaged hoses- reservoir -radiator cap-water pump-heater core -- have a pressure test done of system ----burning coolant would mean problem with --possible head gasket--intake gasket -damaged head

Clean or have a radiator shop clean or replace your radiator core.

Check the heater core by checking the hotness or coldness of the 2 tubes at the firewall that lead to the heater core.

If both tubes are hot, the heater core is fine. If both tubes are cold, then the heater core is plugged up and will have to be flushed out or replaced.

The thermostat, if stuck open, will delay the heating up of the heater core. It's not hard to replace the thermostat.

Thermostat Removal & Installation 4.2L Engine To Remove:

1. Before servicing the vehicle refer to the precautions at the beginning of this section.
2. Remove or disconnect the following:
   • Some of the coolant
   • The upper radiator hose
     
     
   • The bolts (A).
   • The water outlet connection (B)
   • The water thermostat and paper gasket assembly (C)

To Install:
NOTE: The water thermostat is indexed and must be installed correctly.

1. Install or connect the following:
   • The water thermostat
   • The thermostat
   • The water outlet adapter
   • The bolts
     1. Torque to: 80 inch-lbs (9 Nm)
   • The upper radiator hose
   • The coolant

4.6L/5.4L Engines To Remove:

1. Before servicing the vehicle refer to the precautions at the beginning of this section.
2. Remove or disconnect the following:
   • Some of the coolant
   • The upper radiator hose
     
     
   • The bolts (A)
   • The water outlet connection (B)
   • The water thermostat
   • The O-ring (discard)

To Install:

1. Install or connect the following:
   • A new O-ring to position the water thermostat in the upper intake manifold
   • The water outlet connection onto the upper intake manifold
   • The bolts
     1. Torque to: 18 ft-lbs (25 Nm)
   • The upper radiator hose
   • The coolant

the 4.3 engine has a problem with leaking intake manifold gaskets. check for leakage behind the water pump. did you change the thermostat? This controls the engine temp. check for rusty radiator cap and replace if worn

you don't say what year caddy. but older models (especially the 4.1L) did have a problem with intake manifolg blockages and gasket leaks. if that sounds like it could be your problem try replacing the intake manifold gasket, and clean out the inside of the manifold while it's off either manually, or by having it put in an acid vat at a rebuild shop or napa center

maybe 3 things....leaking intake manifold gasket(very common on this car because pontiac used plastic manifold gaskets) may also be air in the system....bleed screw is located on the top hose and is painted blue. it may have some air cavitation. you may have a leaky or bad seal on overflow cap. check your oil dip stick...if there is a milk shake type foam look to it then the gaskets are ready to fail. get a compression test done and it will confirm everything the easy way. harbor freight sells a radiator pressure test kit and it works like a champ and its cheap....good luck

any external leaks?coolant stains? would check the intake for signs of leakage also the heater hose quick connect.also check the sides of the block for leakage from the core plugs.

1 Inspect Cooling System Mix Coolant level low or flow is restricted. 2 Inspect Belt Incorrectly routed, adjusted, tensioned, missing, or worn water pump belt(s). 3 Inspect Oil Pan Gasket - Performance Ruptured, cracked or leaking radiator hose. 4 Inspect Radiator Cap Worn or damaged radiator cap 5 Inspect Thermostat Thermostat stuck closed 6 Inspect Fan Blade Broken, missing, or defective fan blade(s). 8 Inspect Water Pump Damaged, worn or leaking water pump. 9 Inspect Intake Manifold Plenum - Perform Leaking water pump gasket. 10 Inspect Cooling Fan Control Faulty cooling fan control or circuit. 11 Inspect Cooling Fan Switch - Radiator Faulty radiator cooling fan switch or circuit. 12 Inspect Engine Temperature Sensor Faulty engine temperature sensor or circuit. 13 Inspect Temperature Switch Damaged or faulty temperature switch or temperature switch circuit. 14 Inspect Fan Clutch Worn, loose or faulty fan clutch. 15 Inspect Ported Vacuum Switch Damaged, leaking, or faulty ported vacuum switch. 16 Inspect Radiator Obstructed radiator core or radiator cooling fins. 17 Inspect Head Gasket - Performance Head gasket leaking coolant into cylinders

Coolant leaks can occur anywhere in the cooling system. Nine out of ten times, coolant leaks are easy to find because the coolant can be seen dripping, spraying, seeping or bubbling from the leaky component. So open the hood and visually inspect the engine and cooling system for any sign of liquid leaking from the engine, radiator or hoses. The color of the coolant may be green, orange or yellow depending on the type of antifreeze in the system. The most common places where coolant may be leaking are:Water pump. A bead shaft seal will allow coolant to dribble out of the vent hole just under the water pump pulley shaft. If the water pump is a two-piece unit with a backing plate, the gasket between the housing and back cover may be leaking. The gasket or o-ring that seals the pump to the engine front cover on cover-mounted water pumps can also leak coolant. Look for stains, discoloration or liquid coolant on the outside of the water pump or engine.Radiator. Radiators can develop leaks around upper or loser hose connections as a result of vibration. The seams where the core is mated to the end tanks is another place where leaks frequently develop, as is the area where the cooling tubes in the core are connected or soldered to the core headers. The core itself is also vulnerable to stone damage. But a major factor in many radiator leaks is internal corrosion that eats away from the inside out. That's why regular coolant flushes and replacing the antifreeze is so important.
oses. Cracks, pinholes or splits in a radiator hose or heater hose will leak coolant. A hose leak will usually send a stream of hot coolant spraying out of the hose. A corroded hose connection or a loose or damaged hose clamp may also allow coolant to leak from the end of a hose. Sometimes the leak may only occur once the hose gets hot and the pinhole or crack opens up. Freeze plugs (casting plugs or expansion plugs in the sides of the engine block and/or cylinder head). The flat steel plugs corroded from the inside out, and eventually eat through allowing coolant to leak from the engine. The plugs may be hard to see because they are behind the exhaust manifold, engine mount or other engine accessories. On V6 and V8 blocks, the plugs are most easily inspected from underneath the vehicle.
Heater Core. The heater core is located inside the heating ventilation and air conditioning (HVAC) unit under the dash. It is out of sight so you can�t see a leak directly. But if the heater core is leaking (or a hose connection to the heater core is leaking), coolant will be seeping out of the bottom of the HVAC unit and dripping on the carpet. Look for stains or wet spots on the bottom of the plastic HVAC case, or on the passenger side floor.
Intake Manifold gasket. The gasket that seals the intake manifold to the cylinder heads may leak and allow coolant to enter the intake port, crankcase or dribble down the outside of the engine. Some engines such as General Motors 3.1L and 3.4L V6 engines as well as 4.3L, 5.0L and 5.7L V8s are notorious for leaky intake manifold gaskets. The intake manifold gaskets on these engines are plastic and often fail at 30,000 to 80,000 miles. Other troublesome applications include the intake manifold gaskets on Buick 3800 V6 and Ford 4.0L V6 engines.
INTERNAL COOLANT LEAKS
There are the worst kind of coolant leaks for two reasons. One is that they are impossible to see because they are hidden inside the engine. The other is that internal coolant leaks can be very expensive to repair.


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