timing chain replacement cost for 2000 ford explorer on 2000 Ford Explorer

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the engine quit running on my 2000 ford explorer. the car has ~ 200,000 miles on it. there was smoke coming from the passengers side of the engine compartment and looks like it was coming from a module below the air filter. The mechanic says the timing chain is broken and due to the location of the the chain the engine would have to be pulled to replace and the repair would not be worth the expense. Does this sound right? Also, how can he tell the chain is broken within removing the covers to see the broken chain?
(1) Answer
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Can you describe what happens when you try to start the engine?
If the timing chain was broken, you should hear abnormal noises from the front of the engine when cranking it over. This should be relatively easy to determine if the timing chain is broken, I would have another mechanic look at this. I would also be very concerned about the "smoking module" under the air cleaner.
it sounds like the engine turns but does not try and start,
you may not hear abnormal noises. this is an overhead cam engine so if the chain breaks the valve springs will pull the valves to the upmost position and there can be no valve to piston contact. therefore the engine would just spin over and the valves wont open or close. It is a high possibility that the chain is broken. This is a common occurence on these engines because of a ford design flaw. 200k is a lot of miles on a factory chain on that motor and your mechanic is correct about the cost. These motors have 2 chains, one of which is on the rear of the engine, meaning you have to pull the motor to replace it. Not to mention if the chain broke there is probably internal engine damage. Your best option is to have a used engine put in it. This is the most common option chosen in the explorers and sport tracs