Okay, I bought a 99 L about a month ago. It is in great condition with 33000 miles on it. Well, just like all of you on here, the "itch" has set in. I bought a Magnaflow cat back from LFP and installed it with the help of my brother, who is very mechanically inclined on Saturday night. Now I have what sounds like a VERY BAD exhaust leak. I say very bad, in that in the cab with the windows up running 70 you can't hear the exhaust for the tick!

So today, I had my wife take it to a local trusted exhaust shop to have it looked at, and he told her that it wasn't in the exhaust and that he didn't know what it was and "something about the manifold" as my wife put it. The guy is already gone for the day, so I can't call him.

I have read to many of the horror stories about launching plugs and frankly don't have the money to replace the heads if this happens!!!

The tick sounds like it is coming from the passengers side just in front of the cats. What I thought it was is having to torque the right pipe coming out of the cat so far down to get the Maggy to line up might have cause a leak "up the line." ??????

What now???

Please help!!!

By the way, I have monitored this and the nloc forum for the past month, and I gotta tell you, you guys are great! Such an asset to us "not so mechanically inclined" guys who want to learn more about the beasts we drive!!!

 

do not drive your truck, check all your plugs. Do you have a spark plug puller? If not take the other car or bike and go get one, and pull each plug. My recommndation isnt to stop on the one that you find thats probably barely seated, go through all of them and make sure they are torqued down nicely. Im thinking you know how, but if you need more details on a plug change ill get the unstructions for you.

 

Okay, don't think it's the plugs. Had a local mechanic look at it, and he said the same thing.

The weird and ironic thing to this whole thing is the timing. This didn't happen until exactly right after we put on the catback. Here are a few other interesting tidbits:

When you start the truck up and it is in idle, no matter how high you rev the engine, you CANNOT hear the tick inside or outside of the truck.

We put the truck in gear with the parking break on and mashing the gas up to 2200 RMP's, you CANNOT hear the tick inside or outside of the truck.

THE ONLY time you can hear it is when your are starting the truck from a stand-still and driving down the road.

One other reason I really think it has something to do with the exhaust is that as the truck warms up, the tick is not as noticable??? Is this because the pipes are heating up and expanding, thus closing up a possible leak???

So HELP!!!!!!!!!!!!!! PLEASE!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

These things seem slightly contradictory, please clarify. Btw, even if it has nothing to do with your plugs, you should check them regularily, end or story.

 

Same thing happened to me when I had my first cat back on my L. It took 3 mechanics before they finally found the noise. It ended up being the flange where the manifold and downpipe meet. The guy got a huge 1/2" breaker bar and a 3 foot extension and cranked down the flange bolts with everything he had and the noise finally went away. Apparently when we were wrestling the stock muffler off, that joint shifted and caused a small exhaust leak. I ended up getting headers about 2 months later so it was all for nill anyway. Hope this helps...

 

I had mine do just about the same thing I started hearing a small ticking sound like an old push rod! I drove it for a day like that I even went street racing. Well on the way home I got on it and bang! launched a plug. Passanger side #3 .

Suavy

 

I got the same noise after I installed my LT's and catback, however mine is coming from the right side. I haven't had an exhaust shop check it yet but I'm thinking it may be where the EGR tube connects to the header. Let me know what you find out.

 

Common problem! Read my posts I have had this since I installed my magnaflow... Very interesting...

I could of sworn it was the collector as well (Cats meet up with the exhaust manifold). I took it into the exhaust shop, told him,a nd he felt it and couldn't see or feel a leak at all.

Either way... I bought manifold gaskets because they where almost sure it was that. I dunno now... I wonder if I should try breaking that collector join loose then retighten?

I also checked my plugs yesterday, all seemed very snug. I didn't break any loose. Might have to do that still just for peace of mind.

 

wildneg,

Have you found out what it is yet??? Your problem sounds EXACTLY like what I have!!! I am going to check the collector tonight and if that doesn't help, the next step is gaskets.

Then we'll go from there.

 

my vat back sounded great for about 25k miles ...now it makes a sputter sound when you rev it and it idles back down. I dont suppose that is what you guys have huh?

 

Not mine.. though my mag system, if I sit in park and rev it.. sounds mean..but as it comes down it ... i dunno.. sputtersa bit? WEird.. .but thats fine

I think our problem is constant ... LOUD exhaust leak. Well, not constant, mine i can hear when i'm driving only. Idle, reving, its hard to hear. But driving, espcially along side buildings.. loud...

 

We have the same problem. You CANNOT HEAR it when it is in idle, but you can when driving, especially with the windows up or along side buildings.

It is LOUD and ANNOYING.

If anyone has any other ideas, please let me know!

 

I have the same problem on drivers side (stock exhaust). Been chasing it for two years, been to the dearler 3 times. Dearler told me to take it to a muffler shop. If they find the leak, the service manager said the dearler would pay for them to fix it. I'm sure it's an exhaust leak, when i'm next to a building or curb i can hear it echo.

 

kragle23

I'll be checking the Collector when I get home. I'm going to loosen it and then move it a bit and retighten it. If it sounds nay different, that is where the problem is. Or it just may fix it. Like he suggested, might of just been tugged on while putting on the exhaust and broke loose a little bit?

If that doesn't make any difference at all, I already have two new manifold gaskets i'll be trying .. maybe this weekend. I'll post tonight and let you know about the collectors and so on. Lata!

 

I've read this a couple of times, and based on the fact you cannot duplicate the tick unless the vehicle is moving........

have you checked the wheels?

Earlier you stated you can't hear the tick when you rev the motor, and you can put it in gear and hold the brake to above 2,000rpm's with no tick, however as soon as you begin moving forward you hear it. Just doesn't sound motor related to me.