Do I chanage water pump when changing timing belt on 2002 lexus GS300?
Most Japanese designed engines have an internally mounted water pump, usually driven by the cambelt.
When we talk in terms of cam design, there are two types of engines: a) Interference and b) non-interference.
An interference egine means - if the cambelt were to break whilst engine is running, there will be major internal engine damage.
A non-interference engine means - if the cambelt were to break whilst engine is running, there will NOT be any serious internal damage to the engine.
Note: the GS300 engine (3.0L 6-cyl) is considered a Non-Interference engine.
So, one of the most critical compenents which MUST be changed, is the cambelt itself. Most manufacturers recommend changing this belt every 90,000 - 100,000km's (80,000 miles). If you have a non-interference engine, this period is not as critical, but should still be changed soon, to avoid the inconvenience of a breakdown whilst travelling.
The 2nd critical compenent is the Water Pump. The worst possible outcome of a failed waterpump, is your engine will suddenly drain of all coolant, resulting in serious overheating, causing serious internal damage to your engine.
Although there is no specified time to change the waterpump, a waterpump endures wear and tear like any component and lifespan can reduce rapidly beyond 100,000km's (80,000 mles). As the waterpump is situated next to the cambelt, it is a general rule to change out both cambelt and waterpump at the same time.
The majority of the cost to replace the cambelt, is in labor (ie opening the engine etc). If you choose to replace only one of these components, you will need to be prepared to pay for same procedure again in future, to replace the 2nd component.
Therefore, it can be more economical in the long term, to have both components changed together.
Hope this helps...
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