dealer or private mechanic

[Gimme3steps]

Originally Posted by MrRational

This isn't my first time at the rodeo.

I expect a timing belt to last about 60,000 miles
I expect a water pump to last about 180,000 miles

That's obvious from all the BS

[Professor Griff]

Originally Posted by Nativechief

You bring up a good question. Few people do not know to check to see if the car they are buying has the "interference" engine as they are called. In the design of these engines you need to know that the water pump is enternal and driven by the same belt. Water pumps seldom last the life of a car and its better to replace a belt when replacing a water pump that is driving it and less possible internal damage from a broken water pump coming apart and jamming up the metal chain and sprockets. You should always replace the water pump when replacing the belt to avoid paying the same labor price again when the pump does go out.

Seems that more automakers nowadays are putting timing chains on their interference engines. Honda K-series motors, for example, are all interefence and all timing chain driven. The older J-series engines are non-interference and belt driven. If the belt breaks or slips, the car will just shut off. As for the water pump, the external is much easier to replace.

I've seen some nasty jobs on certain cars to get the belt off, like removing the oil pan to get the cover removed, but then to remove the oil pan you have to remove stuff like the axle and exhaust components. Not fun.

[Professor Griff]

Originally Posted by rbohm

timing belts are usually made from a synthetic rubber compound which does wear over time. also they use a cloth reinforcement that also stretches and wears over time. add in the heat cycling that happens, and the fact that the belt runs on metal gears and plastic belt tensioners, and it is easy to see why timing belts wear out.

as for steel timing chains, they stretch over time, and again because of heat cycling, they lose their temper and break. even the top quality double roller chains used in high performance and race applications break. nothing is forever.

I've owned several high mileage 4 cylinder Nissans, all chain driven. My brother is driving the old Altima, 240,xxx miles on it and last time I pulled the valve cover, the chain looked fine. I agree they can stretch and break but I haven't had this happen yet. Most I had was a noisy chain due to a weak tensioner.