4.6 lit cadillac overheats although I replaced the thermostat

Are the cooling fans coming on ? Go under the hood in the engine compartment , with the vehicle running have some one turn on the A/C , do you see and or hear the cooling fans come on ? Could be the coolant temperature gauge is bad ! How many miles on the vehicle ? Ever have water pump replaced ?

1

Check for a loss of system pressure.
Is there a loss of system pressure?
--
Go to Step 2 yes
Go to Step 3 no

2

Inspect and repair any faulty hose connections.
Does the engine still overheat?
--
Go to Step 3 yes
System OK

3

Check for low coolant protection (-37?°C/-34?°F).
Is there low coolant protection (-37?°C/-34?°F)?
--
Go to Step 4 yes
Go to Step 5 no

4

Test solution. Replace the coolant if necessary.
Does the engine still overheat?
--
Go to Step 5 yes
System OK

5

Check the water pump belt for low tension.
Is the water pump belt tension too low?
--
Go to Step 6 yes
Go to Step 7 no

6

Replace the water pump belt tensioner.
Does the engine still overheat?
--
Go to Step 7 yes
System OK

7

Check for an inoperative thermostat bypass.
Is the thermostat bypass inoperative?
--
Go to Step 8 yes
Go to Step 9 no

8

Replace the bypass.
Does the engine still overheat?
--
Go to Step 9 yes
System OK

9

Check the water pump.
Is the water pump inoperative?
--
Go to Step 10 yes
Go to Step 11 no

10

Replace the water pump.
Does the engine still overheat?
--
Go to Step 11 yes
System OK

11

Check the radiator fins for obstruction.
Are the radiator fins obstructed?
--
Go to Step 12 yes
Go to Step 13 no

12

Inspect and clean the radiator fans.
Does the engine still overheat?
--
Go to Step 13 yes
System OK

13

Check the cooling system passage for obstruction.
Is the cooling system passage blocked?
--
Go to Step 14 yes
Go to Step 15 no

14

Inspect and flush the system. Reroute or replace the hose if necessary.
Does the engine still overheat?
--
Go to Step 15 yes
System OK

15

Check the water pump belt for damage.
Is the water pump belt damaged?
--
Go to Step 16 yes
Go to Step 17 no

16

Replace the water pump belt.
Does the engine still overheat?
--
Go to step 17 yes
System OK

17

Check the cooling fans.
Are the cooling fans inoperative?
--
Go to Step 18 yes
Go to Step 19 no

18

1. Inspect the electrical connector. Replace if necessary.
2. Does the engine still overheat?

--
Go to Step 19 yes
System OK

19

Check the throttle body circuit flow.
Is the throttle body circuit flow restricted?
--
Go to Step 20
Go to Step 21

20

1. Inspect the orifice and associated hose. Replace if necessary.
2. Does the engine still overheat?

--
Go to Step 21
System OK

21

Check for a stuck thermostat.
Is the thermostat stuck in the closed position?
--
Go to Step 22
--

22

Replace the thermostat.
Does the engine still overheat?
--
--
System OK

With the thermostat out you should see a lot of circulation. If not investigate water pump. Is the fan electric fan working? Bypass the relay and run the fan whenever the engine is running. If it doesn't overheat with the fan running then investigate fan control. make sure the coolant is topped off and use a thermometer in the radiator to verify temperature.

replace your fan radiator sensor; your fan should come on without the ac anytime the engine heat becomed excessive

occasional sticking of the thermostat may be the culprit if it has not been replaced or may be seizing up

Probably not water pump. Engine is notourious for vapour lock.
Cooling system must be blead of air before thermostat will work. Cool bottom rad hose is a dead give away. If you are still watching this forum reply , and I will walk you through the only way I know how to make it work properly. It's actually easy if you do it my way. I have worked on lots of cars , and this engine was the hardest to bleed out. Did one Yesterday , and works perfect.

On a water cooled engine... the impeller on the water pump is no longer working correctly. It has probably come loose from the input shaft and is no longer pumping water. You can prove this on a warm engine by filling the radiator to the top and then accelerating / decelerating the engine... if you don't get a change in the water level the water pump is shot.

Kelly

Overheating can be numerous things: Fans not working, water pump, thermostat, overflow cap, and the list keeps going. When the engine is running and heats ups, feel the heat of the top hose, if the hose isn't hot, the thermostat is most likely stuck open and needs replaced. If it is hot we know you have circulation. The cap on the expansion tank may be defective, if it can't hold the pressure of the water, it will release at the overflow cap if the cap is bad. Also check the coolant level.

Check the radiator, hoses, and water pump for leaks. If you don't see any coolant loss, the problem is most likely a faulty thermostat. Hope this helped and best wishes.

well without the vehicle in front of me I can mention a few things for you to check
1) possible water pump impeller is rotted away or cracked,
2)check for correct belt routing cause if its wrong the water pump will spin backwards??it happens
3)are you seeing and hearing it overheat ?or are you looking at the guage?may be a faulty sender
4)check electric fan for operation
5)Ive even seen people put the mechanical fan on backwards after they replaced things.
6)grab the fan blades(with enging OFF)that are attached to water pump and see if there is any excessive slop?
hope something helps have a good day DB

take a look at the hoses on the radiator sometimes they will collapse and stop the flow of water under high rpms