Im looking to buy a 2002 Saturn 4 door sl cylinder had problems with the timing chain breakinat how many miles should be changed?

There's no scheduled mileage interval for replacing a timing chain on a 2002 Saturn SL. Unlike timing belts which are rubber and wear out predictably, timing chains are designed to last the lifetime of the engine. However, they *can* fail prematurely due to several factors, including:

* Wear and tear: Over time, the chain stretches and the sprockets wear down.

* Lack of maintenance: Insufficient lubrication can accelerate wear.

* External damage: A major impact to the engine could damage the chain.

The fact that you've had problems with timing chain breakage on your specific 2002 Saturn SL suggests a problem beyond typical wear and tear. This could be due to a manufacturing defect, a previous repair that wasn't done correctly, or other underlying issues. Replacing the chain isn't a preventative measure in this case.

Instead of focusing on mileage, you should:

1. Find the root cause of the previous failure: A mechanic needs to diagnose why the timing chain broke. Was it a faulty chain, worn sprockets, a faulty tensioner, or something else? Addressing the underlying problem is crucial to prevent future failures.

2. Thorough inspection: If you buy a 2002 Saturn SL, have a mechanic inspect the timing chain and related components *before* you purchase the vehicle. This is especially important given the previous failure.

Simply replacing the chain without fixing the underlying cause will likely lead to the same problem again. A good mechanic can assess the condition of the entire timing chain system and advise you on the best course of action. Don't just change the chain based on mileage; address the reason for the failure.