Hole in exhaust damage an engine over time?

It depends where the O2 sensor(s) are. If the hole is downstream from them all, the car will not know the difference and the only problem is the noise. If it is ahead of them or between them, you will probably start getting an engine light because the oxygen level in the exhaust is being altered by the hole.

Greetings.

Will a hole in the Y-pipe of a vehicle cause any damage if left for a while? Like 6 months?

Right - its between the sensors. I have an engine light. But still, can this damage the engine or cats?

Fresh air from a nearby exaust leak will cause the front sensor(s) to read artificially lean, which the ECM will see and enrich fuel mixture to compensate. The ECM will not know that anything is wrong until it sets a "System too lean" code (P0171, P0174) from hitting its limitations of fuel trim. The extent of this really depends on where the hole is as much as the engine/exaust design, as negative exaust pulsations from companion cylinders are what help draw fresh air into an exaust hole.

So... with the "right" hole present, you will be wasting excess gasoline, washing out your piston rings, and polluting CO unnecessarily. The wear to your engine will probably be minimal, but can include the following: gas getting into the crankcase, cylinder wear, excess carbon deposits on combustion chamber/piston tops/exaust, improper back pressure for EGR operation, and deteriorated catalyst. Of those, the cat would be the most likely to fail from extended driving at maximum system enrichment.

Other things to ponder: exaust leaks fail every state safety inspection I have seen or heard of, and excessive exaust noise can be fined on the spot by the police.

Toyota MDT in MO

Well, the engine mixture is going to be way off, which probably isn't good for either.

--scott

Engine light comes and goes now, mostly its off. I fixed a leak, and it came back after a few days, presumably the fix was no good. Trying to weigh up fixing the deck, the septic system, playing with the 4- and 1-year olds, and doing the exhaust!

Well thanks all, I will get to it anon.

Dean (96 Lexus LS400 / 177K)

If you are tight for cash, you might be able to put a patch on it (if the hole is accessible..not right in the Y) which would last until you could see your way clear to fix it properly.

Auto parts stores have the patch material.

You can get some fibreglass-epoxy patch material from the auto parts store that mostly works. You HAVE to get the area very clean before you apply it, and it's not as solid as a proper welding job, but it will keep you running for a while.

--scott

I put the fiberglass/epoxy patch on it (though it was not especially clean), and on top of that some gray exhaust putty. Maybe its opened up on the other side, I need to check.

Where is the leak? No room for a tin can and pair of hose clamps?