tensioner?

Hi,
My Corolla 2002 makes some squeaky noise sometimes, especially when it's at rest for sometime and I start my car. I went to the dealer and said that they had to replace the hydraulic tensioner because it was leaking pretty badly, and they think the sound must be from that. They estimated like $360 nearly. I was wondering what the hydraulic tensioner actually is? and it's purpose in the car? I would apprecite if anyone could give me any information and also if the price they quoted is the usual....
thanks!

I have a similar problem and was wondering if you replaced the tensioner yourself? :confused:

The serpentine belt on your engine requires that something keeps it in streched positon, so that it does what it is supposed to do , like rotating the various equipment like the alternator, a/c compressor , powersteering pump, and the various parts of the engine. The hydraulic tensioner is supposed to do the streching part. If it does not do its job , then the belt starts to slip and this is the most likely sound that you are hearing. Hope it explains .

I know its been quite some time since you posted this, but if you are reading it, then I would like to know what was done about the problem.

The serpentine belt on your engine requires that something keeps it in streched positon, so that it does what it is supposed to do , like rotating the various equipment like the alternator, a/c compressor , powersteering pump, and the various parts of the engine. The hydraulic tensioner is supposed to do the streching part. If it does not do its job , then the belt starts to slip and this is the most likely sound that you are hearing. Hope it explains .

I know its been quite some time since you posted this, but if you are reading it, then I would like to know what was done about the problem.