temperature rises above 250 degrees at which time the temp warning lamp goes on
and/or there is poor heat from the HVAC system.
Time to complete:
This problem is caused by air
bubbles that are trapped in the HVAC system that interfere with the water
pump’s ability to circulate the coolant throughout the engine. An obvious
indicator is that the coolant level rises above the fill line which is
normally the seam of the overflow tank.
A simple fix is to bleed the HVAC
system to eliminate the air bubble. There
are many methods to accomplish this but the simplest is shown below.
Although this may solve the
problem, in many cases, the air bubbles are re-introduced into the system in
a short period of time. To correct,
this, GM has released an air check Valve intended to eliminate the air
Pontiac has released a TSB for this condition and the fix is
A clear indicator that there is air in the system can be seen by observing
that the coolant level in the overflow tank is above the “Full level” (the
seam on the tank)
Obtain GM air check Valve P/N 20876185
The price for this piece varies between
$7-28 Plus shipping depending on where you purchase it. An internet search will reveal several
You will need to order two of these
Set the heat knob in the car
to full heat.
Disconnect the small hose on the
top of the overflow tank and insert hose into a small clear bottle. Make
sure the bottle is clean and dry.
With a cold cooling system, lower the coolant level enough so that when
removing the coolant return hoses from the cylinder head and radiator
return ports coolant will NOT leak on to the ground or on surrounding
Pump a shot of air into the tube
on the top of the overflow tank. You will hear a gurgling noise through the
top of the engine and at some point the coolant will start to spurt into
the clear bottle.
Remove the coolant overflow hose
from the engine, save the clamp; you will need it to reattach the hose.
Using a non-silicon based tire lubricant, lightly coat the check valve
(P/N 20876185) and insert it in to the engine return hose (1) 15 mm (0.5
in) in the hose with the tapered end pointing toward the nipple that is
on the engine.
Press the hose on to the nipple and seat the hose to the base of
the fitting. This will push the valve in to the hose. You will see a bulge in the hose in the
middle of the bend.
The valve should not be pushed in the hose to the point that it is
in the horizontal position. A check valve in the horizontal position will
not function properly.
Install the hose clamp on the hose and reinstall the hose
Now we will repeat the procedure on the coolant return hose from
the radiator. As before, remove the clamp from the hose and set it aside so
it can be re-installed later.
Remove the hose form the Radiator.
Note: pull the hose in a straight motion. Excessive side pressure
result in a broken radiator nipple.
Using a non-silicon based tire lubricant, lightly coat the check
valve and insert it in to the radiator hose return line 15 mm
(0.5 in) in the hose with the tapered end pointing toward the
radiator nipple. Press the hose on to the nipple and seat the hose to the base of
the fitting. This will push the check valve further in to the hose resulting
in a slight bulge in the hose.
the hose clamp on the hose and reinstall the hose on the radiator return
coolant to the "Full Cold" line of the bottle and replace the
from the system by injecting air into the overflow tank as shown above.
Again, you will hear a gurgling noise through the top of the engine and at
some point the coolant will start to spurt into the clear bottle.
cap again and add more fluid the "Full Cold" line of the bottle
and repeat this procedure unitl there is no more
air in the system. When you are
done, the fluid level should be even with the seam on the overflow tank.
Replace the hose on
the top of the coolant reservoir. Inspect the cooling
system for leaks. Rinse away any excess coolant from the engine and the
Verify the procedure was
successful by taking the car for a ride while keeping an eye on the
temperature in the DIC . The engine temperature can go as high as
220 degrees and then the fan will turn on.
The temperature should go back down to between 190-205degrees as you