Would my fuel economy be affected if the exhaust was leaking? The exhaust was noisy, so I had a look and the cat was leaking, and coz I'm a cheapass, I used muffler putty as a kind of liquid gasket. The original gaskets were still there, so I coated them and put it back together. That's not leaking anymore. BUT STILL NOISY! So I have a bit of a look along the pipe, don't see or feel any holes, so up to the engine I go. I pulled the manifold of the block and once again, the trusty muffler putty and repair the gaskets and put it back on (coz I'm still being a cheapass). STILL NOISY! So I undid the flange between the manifold and the exhaust pipe and low and behold the gasket there is mising about 3/4 of an inch due to it being blown out! So I used some aluminium plate and....you guessed it, MUFFLER PUTTY! and repaired the gasket (coz I am the ultimate cheapass!). I applied more putty to the gasket faces and put it all back together! Voila! No more noise! So now I can hear the engine when I am driving around instead of a loud exhaust! It's so sweet. But now I'm stuck trying to track down a vibration noise that I can hear now due to the relative silence. So back to my original question, will the fact that the exhaust was leaking like that affect my fuel economy, or more to the point, will I see any improvement now that it is fixed?

I doubt it'd be noticeable. (was it leaking before the O2 Sensor? then it's possible) Depends how you drive it.

I sometimes drive like a leadfoot, mostly I try to eek as much out of a tank as I can. The leak was after the O2 sensor, at the exhaust manifold flange.

how many km's do you get to a tank? If it's a NA good fuel economy is generally 450-550km/tank (depending on driving conditions). I generally get about the 370km mark with a fair chunk of fuel left in the tank (~12-15L's)

I get roughly 350-400ish out of a tank. The engine has 270000 on it, so I'm not complaining really. It also needs a good service and tune by someone who knows what they are doing. I can do bits, but A good computer tune would be better. I'd also like to get all the fluids drained, flushed and refilled. But In the next 12 months I want to put a new engine in, so I'm not going to go overboard.

my car makes a weird sound as well when i put my foot down and its under 2500rpm, but once i get to 2500rpm it stops, my dad said it might be a flange gasket? now ive read this i think that it is, so how much for a new 1 and is it hard to do ur self?

Quote: Originally Posted by Uter my car makes a weird sound as well when i put my foot down and its under 2500rpm, but once i get to 2500rpm it stops, my dad said it might be a flange gasket? now ive read this i think that it is, so how much for a new 1 and is it hard to do ur self? Nah, it's as easy as! I dunno how expensive it is for the gaskets, but its really easy. Two of the nuts on the flange are easy and accessable, but the third is a bit of a bugger. I had to use 3 medium extension bars and 2 universals on the socket drive to get to it. Other than that, its real easy. I've now really noticed this annoying vibration noise when I accelerate, doens't matter if I put the boot in or drive off slowly. I dunno if it would be a dry/worn bearing or the muffler somewhere, but it sounds like crap. Any ideas? Generally once I get up to speed, its gone, but about the middle of each gear its really noticeable.