Exhaust manifold leak

I have a 2009, 4.0 tacoma, I have an exhaust manifold leak on my driver side, which is causing terrible mpg for me. I would normally just have the manifold replaced, but it's rusted on there badly, so it has the potential to be an extremely expensive repair I don't have the money for. So I did some research on some high temp sealants and picked one up that's good for 2400 continuously. Now the only thing is, I cant see any kind of crack on the manifold! So I'm looking for suggestions what's the best way to find an exhaust manifold leak?

 

How do you know it is an exhaust manifold leak if you can't find it?

Why do you think the manifold is cracked?

I would suggest that the leak isn't the manifold at all but the doughnut seal between the manifold and the exhaust pipe.

 

If it's an actual crack on the manifold sealant isn't going to do you any good. Just weld it. The 2001-2005 Honda civics were plagued with cracking exhaust manifolds. I would just weld them shut. Solved the problem. Haven't seen a cracked manifold in a yota yet.

 

Subbed. Mine is making a tinny noise on acceleration and was thinking of replacing my gaskets

 

I'm almost 100%, the ticking sound is exactly like a leak, keeps with rpm, and no check engine but I get terrible mpg because it's throwing off the O2 sensor with the extra air flowing in making it think it's running lean, so it constantly adds more fuel. And thanks I'll look into that too!

 

And idk if I'll be able to do the gaskets because the bolts are rusted on, and if they break, it's gonna be a very expensive repair which I don't have the money for. =/

 

Did you ever fix this ?

I have a similar condition I would like to figure out exactly what the problem is and then fix

 

Any updates on this old thread

 

Here you go.

 

The OP hasn't been here since Oct 26, 2017!!

Another person that asks other people for advice, but then can't find it in themselves to update those that helped him out, with the outcome.

 

The best way to find an exhaust leak is to lay under the vehicle while someone else starts it when the vehicle is cold. Follow the noise and use your hand to feel for the leak.

 

Another way that’s always interested me is the use of a shop vac taped to the tailpipe. Not to suck air out, but blow air back in, then go around with soapy water ina. Spray bottle around where you think it might be leaking, set we to blow and watch for bubbles..

 

And yes, a leak at the manifold between head and manifold will suck air in and cause AFR sensors to read lean, which causes your fuel trim calcs to increase (which in turn increases the amount of fuel your engine dumps into the intake) and causes chaos among what’s supposed to be an awesome closed loop fuel tuning system - ultimately resulting in a truck that runs rich and has issues running consistently.