Exhaust / Header Question - Broken Bolts - Need some insight

[Next Phase]

Just had my M&M headers installed, high flow cats and Random Tech exhaust. (Big improvement in sound and performance, not to mention cooler cabin temps)

Went for a long drive and had the opportunity to really open the car up. Drove for about 1.5 hours in 90 degree plus heat. At the end of the day, I washed the car and as I was pulling it back into the garage, noticed that the passenger side sounded louder than the driver side. Figured it was just a clamp or some bolts coming loose. Wasn't an exhaust leak from the header from the sounds.

Long story short, took off the side sill and found 4 broken bolts on the Y-pipe collector coming off the header. Bought some new bolts and got it buttoned back up. My question is has anyone experienced anything like this before? Batch of bad bolts? Possibly a bad motor mount causing too much flex in the motor?

Now that I think back when I was driving, I can remember hearing something pop/bang when I was getting on it on the top of the RPM band a couple of times. Thought it was something in the trunk or my fire extinguisher, but it was probabl the sound of the bolts breaking.

Thanks for any insight.

 

[Next Phase]

Car just turned 11k miles if that matters...

 

[ViperTony]

Bolts were probably over-torqued during installation.

 

[99 R/T 10]

Use some grade 8 bolts, but I think you may be right about the engine mounts, very possible the engine was moving enough to pop the heads of the bolts off. Have you replaced the engine mounts yet?

 

[KNG SNKE]

Grade 8 bolts for mine, no issues thus far. 5k miles on it at least.

 

[ViperTony]

I've seen the header flange bolts loosen with bad mounts and have even seen/heard of cats breaking (at the hanger/weld) with bad motor mounts. But I'm finding it difficult to believe that the 4 bolts in the Y-collector would all break from bad engine mounts. By chance, is your turnout utilizing the stock factor hangar bar/mount? If so, I can see the possibility of this scenario with bad engine mounts as there would be no flex and the weak point possibly being the Y-collector. Even still....the Y-collector is a stout area and I would expect the header manifold to warp or manifold bolts to loosen first. There are a few DIY's on checking/replacing the engine mounts in a GenII. I replaced mine about 3 years ago as my shifter was bouncing all over the place when accelerating. Found out my mounts were toast but I never experience exhaust issues probably because there was enough flex in the exhaust system and I wasn't utilizing the hangar on the turnout. With Woodhouse mounts...the car felt like new and NO more shifter bouncing.

 

[Next Phase]

Use some grade 8 bolts, but I think you may be right about the engine mounts, very possible the engine was moving enough to pop the heads of the bolts off. Have you replaced the engine mounts yet?

I haven't replaced the mounts yet... will probably do that this winter if not sooner. I'm not sure that they are bad as I don't see any movement in my shifter. The original owner didn't even spin the tires or drove it hard before before I bought it.

I still need to install my plugs wires and fuel filter... and the rear diff fluid. Everything else has been done.

Two of the bolts were still on the the car and they broke at the threads, not at the head.

Grade 8 bolts for mine, no issues thus far. 5k miles on it at least.

I got my replacement bolts from Lowes Home Improvement... where did you get the grade 8 bolts?

 

[Ratical2]

I am sure that you could find them at Lowe's or Ace Hardware. I have bought them at Orchard Supply Hardware, Home Depot and Fastenal.

A few years back, I remember a story of poor quality chinese bolts being sold as high grades and they made their way into commercial aviation. Airplanes were grounded until the bolts were replaced with the real deal.

 

[Jack B]

You can tell if the bolts had a flaw. Look for what looks like an air pocket contained within the bolt. I do not know why, but, my Balengers have 7/16" bolts, that seems too large for holding sheet metal together. It would seem that the any torque on the system would distort the tubing before the bolts would reach their max tensile strenght.

 

[FrgMstr]

Grade 8 bolts for mine, no issues thus far. 5k miles on it at least.

The yellow viper does not generate enough horsepower to make your comments worthwhile in this thread. I suggest you go play with cars you can keep up with.

 

[Next Phase]

Just took the car out for a drive tonight and it seems to be holding up pretty good with the new bolts. Didn't beat the hell out of it as I don't feel like tearing off the side sills again this coming weekend, but did run through the gears quite a bit. Love leaving the car in a lower gear or down shifting to hear the exhaust.

I'm really enjoying the louder exhaust, but the random tech exhaust does have a good bit of resonance in the cabin at certain RPM.

 

[mbccenter]

Wow I have never had that problem. I did just get a new batch of bolts but I do purchase them at the same supplier every time. You should not be even close to the limit of the bolts even with a bad motor mount. If there is anything I can do to help let me know. Please look at the bolts to see if there is a defect. Glad you like the sound

 

[Next Phase]

Wow I have never had that problem. I did just get a new batch of bolts but I do purchase them at the same supplier every time. You should not be even close to the limit of the bolts even with a bad motor mount. If there is anything I can do to help let me know. Please look at the bolts to see if there is a defect. Glad you like the sound

I'll post some pics... we had 5 bolts total that broke. (I still have two of the heads.)