Coolant leak, 3.7 v6, havering a coolant leak issue, coolant leaks on top of the radiator and trickles down. I've replaced the radiator however still a leak. I cannot locate a leak at the overfill tank but I have put two part epoxy around the seam and still a leak. Does not overheat. And nothing else is on top of the radiator so should I just replace the tank or do you have any recommendations on a direction i could take

fix the leak and flush heater core with a water hose,then bleed coolant system. if not bled proper coolant wont circulate .

You may have

- a coolant leak somewhere, comes out when the engine heats up and pressurises the radiator. Camrys do develop a crack in the plastic radiator top tank, which can be hard to see if on a seam. Another place which leaks is under the intake manifold, which is not visible. There is a test, called a "leak-down" test

- thermostat stuck closed, preventing coolant circulation

- a leak through a head gasket from a combustion chamber to the coolant jacket. This will quickly cause overheating, and sometimes causes white bubbles in the radiator neck, like dry ice. There is a test kit available for gases in the coolant.

Take the radiator cap off and start the vehicle. When it gets hot enough to where the thermostat would open you should be able to see the coolant flowing if the pump is working.
Normally a raditor going bad would be leaking. It could get some rows plugged up if a person dumped stop leak in.

But if that has one of the 3 liter V6 those are grate for having an air pocket that will not burp out on its own. If the coolant was drained or low and got filled it could have an air pocket.

What you would need to do is remove the heater hose at the back of the motor and fill it with coolant there.Should also be parked on level ground or down hill so the back of the motor where you're filling it is at a high point.

Check the bottom side of the water pump for wetness, as well as the lower radiator hose. The water pump if leaking, will run the coolant down the front of the motor,and can appear to be coming from the top of the oil pan. It is nearly impossible for the top of the oil pan to leak coolant.

There are several possible problems causing the temp increase.

1. Low coolant level
2. Leak in radiator hose
3. Leak in radiator
4. Bad waterpump

With low coolant levels by any 1 or a combination of 1-4, the vehicle will run hot at low speeds and at idle. Running the AC or heater pushes the remaining coolant through the system faster, aiding in cooling the engine but all indications are you've definitely have a cooling system issue that should be looked at immediately before doing damage. If the coolant level is good (when car is cold, open radiator cap and check for coolant level), the issue most likely lies in the waterpump.

TO FIX COOLANT LEAK.YOU HAVE TO LOCATE IT.BEST TIME FIND COOLANT LEAK WAIT UNTIL MORNING.ADD COOLANT UNTIL COOLANT LEVEL IN RADIATOR CORRECT. START THE ENGINE LET IDLE UNTIL START GETTING HOT.THEN TURN OFF ENGINE.COOLANT PRESSURE WILL PUSH COOLANT OUT WHERE LEAKS ARE.CHECK TOP RADIATOR HOSE AND BOTTOM RADIATOR HOSE.CHECK AROUND RADIATOR LOOK DOWN BELOW COOLANT FAN AREA BEHIND RADIATOR.LOOK FOR LEAKS AT RADIATOR CORES AND SIDE CONTAINERS.CHECK FOR COOLANT LEAKS AROUND WATER PUMP GASKET OR WEEP HOLE.CHECK FOR COOLANT LEAKS AROUND HEATER HOSES AND HEATER CORE.CHECK ENGINE CRANKCASE FOR COOLANT LEAKS.

ENGINE NOT GOING TO START IF GET TOO HOT FIRST THING I WOULD REPLACE THERMOSTAT AND RADIATOR PRESSURE CAP THEN ADD COOLANT UNTIL COOLANT LEVEL CORRECT THATS WHEN THERMOSTAT OPEN UP AND TOP HOSE HOT.CHECK FOR LEAKING RADIATOR HOSES CHECK TOP RADIATOR HOSE CHECK BOTTOM RADIATOR HOSE.CHECK FOR LEAKS AROUND THE RADIATOR LOOK DOWN BELOW COOLANTS FANS CHECK FOR LEAKS AT RADIATOR CORES OR LEAKS AT THE RADIATOR PLASTIC SIDE CONTAINERS. CHECK FOR LEAKS AT WATER PUMP WEEP HOLE AND CHECK FOR LEAKS AT THE HEATER HOSES AROUND ENGINE BLOCK TO THE HEATER CORE HOSES. THERE IS A REASON CAR OVERHEAT.IF CAR OVERHEAT WHILE DRIVING YOU HAVE FAULTY THERMOSTAT OR LEAKING OUT COOLANT OR BLOWN HEAD GASKET.IF ENGINE OVER HEAT WHILE SITTING DURING A LONG IDLING PERIOD.YOU COULD HAVE FAULTY COOLANT TEMPERATURE SENSOR OR FAULTY COOLING FAN FUSE OR RELAY.HOT WIRE COOLANT TO SEE IF IT RUNS IF NO REPLACE FAN MOTOR. IF YES FAN MOTOR COULD HAVE FAULTY WIRE OR PCM FAILURE. CHECK ENGINE CRANKCASE IF OIL LOOKS LIKE MILK SHAKE ENGINE HEAD GASKET LEAKING.

There could be several problems with it overheating. 1. Low coolant level. Top off with recommended coolant. 2. Have the radiator cap pressure tested. A cap that cannot hold proper pressure can allow fluid to leak. 3. Spent coolant. When coolant breaks down, it cannot keep the engine cool properly. A coolant flush would be recommended. 4. A stuck thermostat. A stuck thermostat can impede the flow of coolant through the system. 5. Coolant leaks. It could be the radiator, water pump, thermostat housing, hoses, or freeze plugs. Have a pressure check done on the system. 6. Blown head gasket. When a vehicle overheats, it puts a strain on the engine and gaskets. Have a compression check done on each cylinder. These are some steps to take toward getting this issue resolved. Good luck.

WHERE COOLANT LEAKS OCCUR
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. 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 bad 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, especially on aluminum radiators with plastic end tanks. On copper/brass radiators, leaks typically occur where the cooling tubes in the core are connected or soldered to the core headers. The core itself is also vulnerable to stone damage. Internal corrosion caused by old coolant that has never been changed can also eat through the metal in the radiator, causing it to leak.

Most cooling systems today are designed to operate at 8 to 14 psi. If the radiator can't hold pressure, your engine will overheat and lose coolant.

Hoses -- 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 -- These are the 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 may develop leaks that are hard to see because of the plug's location 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 cannot 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 floor inside the passenger compartment. 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 50,000 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.

Bad head gasket --Internal coolant leaks are most often due to a bad head gasket. The head gasket may leak coolant into a cylinder, or into the crankcase. Coolant leaks into the crankcase dilute the oil and can damage the bearings in your engine. A head gasket leaking coolant into a cylinder can foul the spark plug, and create a lot of white smoke in the exhaust. Adding sealer to the cooling system may plug the leak if it is not too bad, but eventually the head gasket will have to be replaced.

If you suspect a head gasket leak, have the cooling system pressure tested. If it fails to hold pressure, there is an internal leak. A "block tester" can also be used to diagnose a leaky head gasket. This device draws air from the cooling system into a chamber that contains a special blue colored leak detection liquid. Combustion gases will react with the liquid and cause it to change color from blue to green if the head gasket is leaking.

Head gasket failures are often the result of engine overheating (which may have occurred because of a coolant leak elsewhere in the cooling system, a bad thermostat, or an electric cooling fan not working). When the engine overheats, thermal expansion can crush and damage portions of the head gasket. This damaged areas may then start to leak combustion pressure and/or coolant.

Cracked Head or Block -- Internal coolant leaks can also occur if the cylinder head or engine block has a crack in a cooling jacket. A combustion chamber leak in the cylinder head or block will leak coolant into the cylinder. This dilutes the oil on the cylinder walls and can damage the piston and rings. If the coolant contains silicates (conventional green antifreeze), it can also foul the oxygen sensor and catalytic converter. If enough coolant leaks into the cylinder (as when the engine is sitting overnight), it may even hydro-lock the engine and prevent it from cranking when you try to start it. Internal leaks such as these can be diagnosed by pressure testing the cooling system or using a block checker.

A coolant leak into the crankcase is also bad news because it can damage the bearings. Coolant leaking into the crankcase will make the oil level on the dipstick appear to be higher than normal. The oil may also appear frothy, muddy or discolored because of the coolant contamination.

Leaky ATF oil cooler -- Internal coolant leakage can also occur in the automatic transmission fluid oil cooler inside the radiator. On most vehicles with automatic transmissions, ATF is routed through an oil cooler inside the radiator. If the tubing leaks, coolant can enter the transmission lines, contaminate the fluid and ruin the transmission. Red or brown drops of oil in the coolant would be a symptom of such a leak. Because the oil cooler is inside the radiator, the radiator must be replaced to eliminate the problem. The transmission fluid should also be changed.

continue..

with my experiance on these engines it's usually the upper outlet hoses running from the heads into a t then into the upper radiator hose they are pain to replace but 3 out of 3 of my v6 isuzu's have had the same problem you'll have to pull off the theromstat and the coil pack the hoses are very small and run from the end of the heads one on each into a t then into the radiator hose just under the housing