How do you get all the air bubbles out of the cooling system?

Asked by shadetree Jan 24, 2007 at 10:26 AM about the 1983 Volkswagen Vanagon

Question type: Maintenance & Repair

engine runs hot at idle and cool air from heater... fast idle and engine cools down and hot air from heater. trying to get the air out of the cooling system after flushing system.

1 Answer

As you have no doubt encountered, shadetree, specific information for your Vanagon isn't easy to come by. Here are some general tips for bleeding a cooling system from popular mechanics. This should get you pretty far down the road and give you some specific questions to ask if you need to call your local VW dealer. Good luck! : "Let it bleed Now comes the hard part–filling the system. If the system holds 12 quarts, you want to install 6 quarts of undiluted antifreeze, or exactly half of the cooling system's capacity. The cooling system has lots of nooks and crannies that trap air, making it difficult to fill the system with coolant. The fill cap and neck are supposed to be at the high point of the system to help air bleed out, but often they aren't. And even if they are, you need all the natural help you can get. So jack up the front of the car, which gets the coolant fill neck as high as possible. Check for air bleeds on the engine. Sometimes you'll see an obvious air bleed, such as a boltlike item threaded into a hose. If there's an air bleed, open it. If there are several, open them all. If you have access to a factory service manual or PM CD-ROM for your car, check it for a coolant fill procedure. Pour in the required amount of antifreeze slowly until you see coolant oozing out of the open air bleeds. Then close the bleeds and top off the system with the remaining antifreeze and then plain water. If the system has a heater coolant valve, close it by moving the temperature control lever or knob to cold. With the engine running at fast idle and warmed up, have a helper move the lever or knob to hot while you listen at the coolant valve. If after the first rush of coolant you hear a continuous gurgling noise, there's still air in the coolant, and you should be prepared to watch the coolant level in the reservoir over the next few weeks."

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