Exhaust leak that keeps coming back to haunt me!!!

[roel03]

I still am KA and still am using the stock header/downpipe on my S14 and where the header meets the cat I keep getting an exhaust leak. Ive tried using new gaskets but it wont let me tighten the bolts enough to keep any air from seeping out. And if I overtighten the nut takes the whole bolt that come with the stock Nissan bolts. (Only on one of them, the other wont budge so I can get that side pretty tight).
Any ideas on how to get this fixed permanatly while still keeping the setup I have. I like my car really quiet thats why this bugs me and why I wont upgrade to a testpipe.

[MrChow]

What I did was I got an aftermarket CAT to replace it that cat. I also just got a new reflex gasket. Look it up there great.

Also are you lowered and have you scrapped the bottom of your car? That one of the reason why you'll get leak is from the movement of the downpipe to the cat.

[smurfgcr]

why dont you just sandwich more gaskets on to it? or run a shorter bolt through it to catch the threads before it maxes out.

[roel03]

Im going to look up that cat and try these ideas today.

Yes I am also lowered and only scrape my exhaust about 2 times a month.

[finesses240]

If it is a 2 bolt flange you don't want to over tighten it. If you do then the flange kinda "bows" in the middle causing a leak. I had the same problem on my s13. Also make sure that both flanges are clean of old gasket or debris

[roel03]

Ok I lifted the car today and found out its not the connection between downpipe/cat causing the leak its actually the connection from the cat/exhaust causing it. I tried repositioning the gasket and I went to an autoparts store to try to buy a new 3" gasket but they dont stock them so I tried to also use gasket sealant but no use. Should I just order a new 3" gasket? Or will that not solve the problem either.

[g6civcx]

This is simple.

Smooth out both mating surfaces. Anything that shouldn't be there should be cleaned off.

If they're not mating then grind/cut/chop whatever you have to to make the two sides meet up.

I would drill out whatever bolts you have in there and run nice thick bolts with locking plates.

They make hi-temp silicone gasket makers you can use for exhaust. Run that over the flange. Have a beer. Mate them up. Tighten the bolts.


Done. Have another beer.

[Bigsyke]

whats the respectable torque spec for a 3" exhaust? I torqued mine @ 36lbs. I noticed if you stack up gaskets, you WILL warp the flange;

Then you need a grinder to re seat the flange.

I was sick of exhaust leaks, so I did this;

Pulled apart exhaust, after I got the fake cat off with some hammering, I grinded/deburred all the edges and wirewheeled the crap out of all surfaces. Make sure you clean off all flange surfaces else any grease will make a quick excape for exhaust pressure. I got out some permatex grey (same as hondabond) evenly applied some to both sides of all gaskets. I then put a thin layer on all flanges (haze). I let dry for about 20 minutes. You want to let it get past a tacky phase. Carefully bolt everything together evenly. I would torque (all) the bolts in this order

5
20
36

This way the gasket and sealant all gets evenly crushed and prevents open air pockets from the flange reseating itself durring the tightening process.

make sure you let it dry for an hour or so before starting up; hell id even wait a few hours before torquing the final 36lb step, this way starting up the car the exhaust wont spit the non dried super thin layer of gasket out.

Using any liquid gasket on an exhaust gasket is a bad idea UNLESS you take the proper time to seal and torque it.

[krisdeezy]

add another gasket !

[g6civcx]

Using any liquid gasket on an exhaust gasket is a bad idea UNLESS you take the proper time to seal and torque it.

Good info.

Nissan uses liquid gasket on most stuff.

[roel03]

I have a gasket sealant that was specified mainly for exhaust gaskets. So I'm going to order a 3" and when that comes in I'll have another go at it. I dont have any power tools though so those torque specs have no use to me. Any hand specs? lol

[roel03]

I just ordered a Vibrant flexible gasket to replace my garbage one.

[Bigsyke]

on a 3", I doubt the permatex grey will burn off. Its crushed between the gaskets.

Honestly torque specs are VERY important. One bolt being torqued more than the other will warp the flange, and cause improper seating.

[TheBigDirty]

I had the same problem on my old s13, except it was my fault for overtightening one side, like finesses240 said. Make sure the two surfaces are clean, and you tighten both sides evenly.
(http://zilvia.net/f/members/finesses240.html)