# Exhaust Gasket



## zakgord (Jun 11, 2007)

Im probably going to replace my exhaust manifold gasket this weekend. Noticed smoke leaking around that area. Also some around the muffler, but wont worry about that now. 

Should be a simple task, correct? Any tips?

Would this improve my idling and possibly my code showing misfire on multiple cylinders?


----------



## Asleep (Jan 19, 2003)

no it shouldnt affect the codes youre getting. 
very straight forward to replace them. you might have to loosen the alternator and move it forward, you may even have to disconnect the egr pipe. otherwise, its pretty easy... unless the heat shielding is in the way...


----------



## zakgord (Jun 11, 2007)

Reading through my haynes about the O2 sensor on the manifold...it senses Oxygen in the exhaust fumes and with ECU adjusts fuel mixture to achieve optimal ratio. My leak would allow for extra air/oxygen in the exhaust, causing sensor to misread exhaust fumes, resulting in poor ratio.

But I think this would only cause poor fuel mileage, not misfire; but my mileage has been pretty darn good through this all, hmm....just thinking out loud.


----------



## Altima SSS (Oct 10, 2007)

zakgord said:


> Reading through my haynes about the O2 sensor on the manifold...it senses Oxygen in the exhaust fumes and with ECU adjusts fuel mixture to achieve optimal ratio. My leak would allow for extra air/oxygen in the exhaust, causing sensor to misread exhaust fumes, resulting in poor ratio.
> 
> But I think this would only cause poor fuel mileage, not misfire; but my mileage has been pretty darn good through this all, hmm....just thinking out loud.


I don't think any fresh outside air (oxygen) would get into the exhaust leak on the manifold as there is always some positive pressure in the exhaust manifold ... that is why you see the smoke leaking out because it's being pushed out from the slight pressure.

What kind of mileage do you usually get?


----------



## zakgord (Jun 11, 2007)

I was getting anywhere from 27-29 mpg a few weeks ago. I've been pushing the engine a bit more lately, down to about 24-25 mpg.

Well, went to replace the gasket and found out the manifold has a nasty crack. About a 3 inch crack on the Y crotch where the 2 and 3 cylinder exhaust pipe join....that would explain the leaking smoke. Didnt bother to replace the gasket, no need right now. Gonna look for a used/new manifold at a salvage yard or on ebay. 

That heat shield is a pain to remove. Had to remove the alternator, coolant hose, bracket on the radiator....even then it still wouldnt come out all the way. Seemed to be caught on the flange on the exhaust connection. Looking forward to fooling with that later.

I see what you mean about backpressure coming out of the exhaust, not allowing air to seap in. I was just hoping this exhaust problem might be connected to my CEL codes somehow and might solve them. O well...


----------



## Mr.Nissan (Nov 23, 2007)

I recommend you spray those bolts with alot of PB Blaster or WD40


----------



## zakgord (Jun 11, 2007)

Also, I completed another compression test. It seems the seafoam may have helped clean these cylinders. My results came back nearly all 175 psi, +/- 5 psi. There was the sign of some oil on a few of the plugs when I pulled them out, but not much. Maybe the sign of slightly worn piston rings, or carbon residue that failed to flush out after seafoam cleaning.

I hope she's enjoying all this attention, sheesh.....women.


----------



## zakgord (Jun 11, 2007)

Ok, after further research and thinking, I would like to install a header instead of replacing the stock manifold. Im looking at this OBX 4-2-1:

eBay Motors: OBX 4-2-1 Racing Header 93-97 98-01 Nissan Altima 2.4L (item 170170946602 end time Nov-25-07 13:02:18 PST)

I've read through about it, get what you pay for, have to shave the block yadda, yadda, yadda...im cool with all that. Hard to pass up at under $200.

Only thing is, i read where it says includes the gaskets, but then in the picture it only shows the main gasket where the header attaches to the head. 

Do you think these type kits would also include the other 2 gaskets, or would i have to buy them myself? And any special tips handling or lining this up if i get it?


----------

