Hi Everyone

My Astro is overheating. I reckon it must be the thermostat or the water pump?
How do I check if the thermostat and the water pump is working properly?

I'm taking the day off today and I really want to get to the bottom of this problem so I can use my van!
Post back as soon as so I can get this done.


Cheers all

James

 

This steps might helps you.

Cooling System Leak Testing [/align]
[/align][/align]
Leak Testing Procedure (On Vehicle)
Tools Required
J 24460-01 Cooling System and Cap Pressure Tester
Caution:Under pressure, the temperature of the solution in the radiator can be considerably higher, without boiling. Removing the radiator cap while the engine is hot (pressure is high), will cause the solution to boil instantaneously, with explosive force. The solution will spew out over the engine, fenders, and the person removing the cap. Serious bodily injury may result. Flammable antifreeze, such as alcohol, is not recommended for use at any time. Flammable antifreeze could cause a serious fire.
Caution:In order to help avoid being burned, do not remove the radiator cap while the engine and the radiator are hot. Scalding fluid and steam can be blown out under pressure if the cap is removed too soon.
[ol]After the system has cooled, remove the radiator/surge tank pressure cap.



Connect the cooling system tester J 24460-01 to the radiator/surge tank.
Apply normal system operating pressure. Do not exceed 138kPa (20psi).



Watch the gauge needle for an indication of a leak. Examine all cooling system connections and components, including the radiator and the heater core, for leaking coolant.
Tighten the hose connections or repair as required.



Check the radiator/surge tank cap with J 24460-01 in order to ensure the cap maintains the correct pressure.
If the radiator leaks during the pressure test, mark the leak area so the leak can be located once the radiator has been removed from the vehicle. [/ol][/align]

[hr]
[/align]

Cooling System Diagnosis [/align]
Exhaust Leaks
Notice:Exhaust gasses may enter the cooling system through a leaking cylinder head gasket. Exhaust gasses combine with water to form acids. These acids are harmful to the cooling system and the engine.
In order to check for exhaust gases leaking into the cooling system, do the following steps:
[ol]Drain the cooling system to a level just above the top of the cylinder heads.
Disconnect the radiator inlet hose.
Remove the thermostat.
Remove the fan belt.
Start the engine. Accelerate the engine several times.
Note any detectable coolant rise or bubbles in the coolant. These may indicate that exhaust gases are leaking into the cooling system. [/ol]
Coolant Pump
In order to check the operation of the coolant pump, do the following steps:
[ol]Start the engine.
Squeeze the radiator inlet hose until the engine warms. When the engine warms, you should feel a pressure surge.
Check for a plugged vent hole in the coolant pump. [/ol]
Radiator
In order to test for restrictions in the radiator, do the following steps:
[ol]Start the engine. Wait until the engine reaches normal operating temperature.
Turn off the engine.
Feel the radiator. The radiator should be hot along the left side and warm along the right side, with an even temperature rise from right to left. Cold spots on the radiator indicate clogged sections. [/ol]
Overheating or Noise
Restrictions in the cooling system can cause engine overheating or cooling system noise. The following components are affected by these conditions:[align=left]



•
The cylinder head[/align][align=left]



•
The coolant pump[/align][align=left]



•
The engine block[/align][align=left]



•
The coolant outlet[/align][align=left]



•
The intake manifold[/align]The following are symptoms of these conditions:[align=left]



•
The engine may make snapping or cracking noises.[/align][align=left]



•
The heater core may gurgle or surge.[/align][align=left]



•
The radiator hoses may collapse and expand.[/align][align=left]



•
The heater hoses may vibrate and thump.[/align][align=left]



•
The overheat lamp may or may not come on.[/align]
Diagnosis and Inspection
[ol]Isolate the blocked area by probing the engine with a sounding bar (large screwdriver).
Caution:Under pressure, the temperature of the solution in the radiator can be considerably higher, without boiling. Removing the radiator cap while the engine is hot (pressure is high), will cause the solution to boil instantaneously, with explosive force. The solution will spew out over the engine, fenders, and the person removing the cap. Serious bodily injury may result. Flammable antifreeze, such as alcohol, is not recommended for use at any time. Flammable antifreeze could cause a serious fire.
Remove the radiator cap.
Observe the coolant being circulated in the radiator. Feel for cold spots on the front area of the radiator that could indicate blockage. Blocked radiators generally occur on vehicles with high mileage and not on new vehicles.
Check if the thermostat is opening properly.
Check the coolant outlet for any blockage.
Remove the coolant pump from the vehicle.
Remove the back cover of the pump. Inspect all of the internal passages using a flashlight.
Inspect the crossover at the front of the intake manifold. You can only see the entire passage of the crossover with the thermostat removed.
Remove the cylinder heads. Check the engine block using a pen light flashlight. Do not replace a block unless you can see the restricted area.
Inspect the cylinder heads if the problem is not found. Cylinder heads with blocked coolant passages generally have more than one blocked area. Look for signs of overheat discoloration (a dark blue or black area). If no discoloration is found, look in the coolant passages for blockage and probe all of the accessible passages. You cannot reach all of the passages because the cylinder head is intricate. Using a substantial wire, go through or around a partially blocked area. If nothing is found by visual inspection and probing, inspect the passages for a rough, ragged appearance. The roughest internal passages are most likely blocked. Replace a blocked or suspect cylinder head. Inspect the replacement cylinder head before installation. [/ol][/align][/align][/align]



[hr]
[/align][/align]Thermostat Diagnosis [/align]



Table 1:
Engine OverheatBoilingPoor Engine Cooling

Table 2:
Cold EngineSlow Warm-upNot Enough Heat
Tools Required
J 24731 Tempil Sticks

Engine OverheatBoilingPoor Engine Cooling



Step

Action

Value(s)

Yes

No


NOTE: The temperature stick is a pencil-like device that has a wax material containing certain chemicals which melt at a given temperature. Use the temperature sticks to determine a thermostat's operating temperature by rubbing 87°C (188°F) and 97°C (206°F) sticks on the thermostat housing. The marks made by the sticks should melt when coolant temperatures reach 87°C (188°F) and 97°C (206°F), respectively. These temperatures are the normal operating range of the thermostat. If the coolant flows as indicated in the table, the thermostat may be worn.


1

[ol]Remove the radiator cap. Refer to Radiator Filler Cap Assembly .
Rub a 97°C (206°F) J 24731 on the thermostat housing.
Warm up the engine at fast idle.
Check for coolant flow before the mark begins to melt. [/ol]
Is there coolant flow before the mark melts?



Go to Step 2

Go to Step 3


2

The problem is caused from something other than the thermostat.
Does the engine still overheat?



Go to Engine Overheating .

System OK


3

[ol]Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .
Check the system. [/ol]
Does the engine still overheat?





System OK
Tools Required
J 24731 Tempil Sticks

Cold EngineSlow Warm-upNot Enough Heat



Step

Action

Value(s)

Yes

No


NOTE: The temperature stick is a pencil-like device that has a wax material containing certain chemicals which melt at a given temperature. Use the temperature sticks to determine a thermostat's operating temperature by rubbing 87°C (188°F) and 97°C (206°F) sticks on the thermostat housing. The marks made by the sticks should melt when coolant temperatures reach 87°C (188°F) and 97°C (206°F), respectively. These temperatures are the normal operating range of the thermostat. If the coolant flows as indicated on the table, the thermostat may be worn.


1

[ol]Remove the radiator cap. Refer to Radiator Filler Cap Assembly .
Rub a 87°C (188°F) J 24731 on the thermostat housing.
Warm up the engine at fast idle.
Check for coolant flow before the mark begins to melt. [/ol]
Is there coolant flow before the mark melts?



Go to Step 3

Go to Step 2


2

The problem is caused from something other than the thermostat.
Does the engine warm up properly?



System OK




3

[ol]Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .
Check the system. [/ol]
Does the engine still fail to reach normal operating temperature?





System OK
Thermostat Inspection and Testing
Do an operational test of the thermostat using the following procedure:
[ol]Drain the coolant to a level just below the thermostat. Refer to Cooling System Draining and Filling .
Remove the coolant outlet. Refer to Engine Coolant Thermostat Replacement .
Remove the thermostat. Refer to Engine Coolant Thermostat Replacement .



Unless the thermostat is obviously faulty, test the thermostat before replacing the thermostat using the following procedure: [align=left]



4.1.
Place the thermostat (2) and a thermometer (1) in a container with a 50/50 solution of water and ethylene glycol antifreeze.[/align][align=left]




Important:While heating, do not rest the thermostat or the thermometer on the bottom of the container. This causes the thermostat and the thermometer to be at a higher temperature than the solution. [/align][/color]
[align=left]



4.2.
Place the container over a heater (3). [/align][align=left]



4.3.
Agitate the solution in order to maintain a uniform temperature of the solution, the thermostat, and the thermometer.[/align][/ol]
The thermostat valve should start to open at the rated temperature. The thermostat should be fully open after the temperature has increased 15°C (27°F).
A used thermostat can be about 6°C (10°F) above or below these settings without adversely affecting the thermostat and you do not need to replace the thermostat. If the thermostat does not operate at the temperatures specified, replace the thermostat. You cannot adjust the thermostat. Refer to [color=#0000ff]Engine Coolant Thermostat Replacement .[/align]
Good luck!

 

a quick way of testingthe water pump is to hold the upper rad hose and rev the engine. With the thermostst open, the hose will get more pressure(slighty swell). If the stat is stuck closed, try holding the bottom rad hose while revving the engine, you should feel it lose some pressure. There may be a spring in it to prevent the hose from collapsing so it may be a little difficult to check.

To check the thermostat, start the tuck, let it run for a while, if the engine starts to overheat, and the upper rad hose is not hot, then the stat is stuck closed.

Also...the first thing you should be checking is that there is suficient amount of coolant inthe enigne

 

Hi shawnvw

When engine is hot the radiator hose at top of radiator is hot and the one at the bottom of the radiator is cold, which I believe is correct? would that indicate that the thermostat is working correctly? Also, I'm not that mechanically minded so bare with me. The coolant bottle next to the screen wash bottle is nearly full would that mean that the water in the radiator is also full or is that coolant bottle an overflow bottle?

The saga continues!. Went out this morning and had a brain wave, I decided to do something pretty simple, and by the way, for me that's a big achievement. I decided to take off the radiator cap and fill it with water! I thought because the water bottle beside the radiator was full then that would mean that the radiator would also be full? please educate me everyone.

Anyway when I put the water in the radiator cap the water was just pi**ing out the bottom. I had a feel around the bottom radiator hose where it connects with the engine and seemed to be dry, it was hard to see in there but I think the water was coming from above that part, (I know, I'm really mechanically minded and know all my technical parts! if anyone needs any technical advice by sure to mail me and I'll garauntee to make your problem worse!).

Help please, I'm missing my van

I appreciate the help.

James