What's the average repair cost of an exhaust leak at the headers?

until you actually verify that it is leaking at the header start the car up when its cold up on a lift and you can feel the air hit your palm, giving you an idea where the leak is. watch it though the headers heat up quick. The good news is it does not damage the engine. The question is what kind of headers and how old are they? they tend to warp from excess heat. And a poor quality header with a too thin flange needs to be replaced. As for price, its relative to how many header bolts break off, and some do break off. Rust, heat , time all add up, and one bolt may already be broken, and could be the cause of the leak. A muffler shop does this for a living, and thats the best place to go for an estimate.