View Full Version : Burping the Cooling System

09-12-2002, 08:52 PM
Anybody know how to "burp" the cooling system? I recently overheated because my coolant level was low. I refilled the system properly (I think) but the vmm sensor says its still low. A mechanic told me there is probably air in the system and you need to burp the air out and put more coolant/water mix in. I see where the burp bolt is, but how can you tell if you got the air out?:confused:
BTW, do you think the mechanic was right?

09-12-2002, 10:41 PM
If I'm not mistaken, the low coolant light sending unit is in the overflow. When you top off your rad, be sure to top off the overflow tank as well.

As for "burping" the cooling system, I think when you fill up the rad, your supposed to undo a screw/valve by the thermostat that says "DO NOT OPEN HOT". Or you could do it the conventional way:


1) remove rad cap
2) start car
3) fill radiator to bottom of fill neck
4) wait for thermostat to open and top up as needed
5) run for about 20 minutes with a constant eye on the rad filler neck
6) when no more air appears, shut car off and replace rad cap.

This way can get very messy because when the thermostat is closed, coolant will most definitely overflow our of the rad with the cap off.

Enjoy and I hope this helps.

09-13-2002, 07:00 AM
Just as the plastic cap on the banjo bolt says. "Remove before radiator refill, Install before engine start"

The rad cap is not the highest point in the cooling system on these cars. That's why they put the air bleeder bolt on the motor. Remove that bolt, fill it up through the rad cap, then snug that bolt down before you start the motor. It will burp any other air out into the overflow bottle itself. You may have to top off the overflow bottle a bit later. This is also where the VMM sensor is.
Pull it out and clean the two electrodes carefully if they are gunky. Mine rotted off, and was no longer working. Ford wanted 100 bucks for a new one, but I was able to find a working used one.
Plug the elec in and leave it dry and out of the bottle. Within 30 sec of starting the car "Low" should light beside radiator.
Then shut the car off and put the sensor in the bottle, making sure the end is immersed in coolant. Re-start the car. If "Low" doesn't come on next time you start the car then your sensor is good.