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Unformatted text preview: After-Run System: Turbo Electric Water Pump, Coolant Hoses The Turbo charger has separate coolant supply hoses as well as oil supply lines. When the engine is running, coolant flows from the engine block, enters the lower end of the turbo, then comes out the top and is routed through a pipe behind the timing belt cover, which then connects to the coolant flange on the cylinder head. The coolant flows through the top radiator hose and back to the radiator for cooling. When the engine is shut off, and the engine coolant temperature at the exit of the cylinder head is above 110C, (230F) a secondary electric water pump turns on, which provides circulating coolant through the top coolant line down into the turbo and then into the engine block to ensure any bubbles from the boiling coolant get purged. The circulating coolant helps keep the turbo center housing temperature down at a reasonable level to prevent coking of the oil in the turbo housing. The electric coolant pump is controlled by the after-run temperature sensor and the after-run control unit. When the Turbo cooling pump is turned on, the low speed radiator fan is also turned on by the after-run control unit. For details on the operation and location of this sensor, go to After-run system section below. Note: When the engine is running, the coolant flow is reversed, coming out the top of the turbo and then over to the top radiator hose connection on the block. This electric coolant pump and connecting hoses are often over looked and can fail at the most inopportune time. See below for details on the turbo cooling pump and after-run temperature sensor. CAUTION:The Turbo secondary electric water pump has plastic fittings which can break off while working under the hood if you bump into the pump fittings and this can spray HOT BOILING COOLANT on you causing severe burns. I have had the "pleasure" of experiencing this and have the burn scars to prove it. WEAR SAFETY GOGGLES and PROTECTIVE CLOTHING while working around a hot engine! The radiator fittings are also plastic and these can break off while working around the engine. You may want to remove the pump and test it in a bucket of water to make sure it is still pumping. The pump uses a magnetically coupled impeller which can seize up, or fall apart as they get older. Use some jumper wires to apply 12V DC to the pump while you stick it down in the bucket of water. The pump has markings near the connector showing the positive + and negative - (ground) connection. There are two metal coolant pipes that are used to connect to the turbo and provide coolant into and out of the turbo. These metal coolant pipes have rubber hoses on each end where they connect to the engine cooling system....
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This document was uploaded on 04/15/2009.
- Spring '08