exhaust manifold - found half a bolt on the driveway

Lv1G6He3V2 · November 30, 2012

'99 Sierra 1500 GMT-800 V8 5.3L, mostly stock except for a CAI

It's the driver side, furthest back toward the cab, hard to reach because of the steering wheel stuff. Fun times ahead... What's the best way to get this fixed? I assume the rest of the bolt has to be drilled out and then all the bolts (and gaskets) should be replaced. Where to go for this service: exhaust shop or dealer?

This might be a good time to get aftermarket headers... and if possible use bolts that don't disintegrate over time? Suggestions?

Also I have another problem and wonder if it is related. I had installed a CAI, and shortly after that the truck started throwing lean codes (0171 and 0174; always both banks). I wonder if the codes are related to the exhaust manifold problem, whether running lean caused the aging parts to fail or maybe the failing parts caused the codes.

Re: the lean codes, the truck ran/idled smooth with the CAI. We had cleaned the MAF, checked all the seals between MAF and throttle body. Fuel line pressure had been tested earlier in year due to fuel pump replacement. Also throttle body was cleaned last fall and still appears fine (no deposits). I saw no obvious vacuum leak but I've been told that's a probable cause. Oddly, the truck had thrown no codes with the factory airbox/filter/duct - not sure why a gasket or other tube would fail at same time as CAI installation...

SILVERADOSC540 · November 30, 2012

The exhaust manifold bolt is a common and known issue for our trucks. I had the same with my '02 2500HD.One story I got was dissimilar metals, iron manifold and aluminum heads, heat and expand at different rates, causing the bolts to stress and break over time. Supposed fix is a slighlty softer bolt is now used that can "stretch" slightly when one metal expands faster than the other. The other story that I heard was that it is simply torque twist on the motor and the exhaust hangers aren't long enough. Don't know which is true if either, but it always seems to be the driver's side rear bolt. In my case they had to remove the head and drill and tap it. Made me nervous but never an issue afterwards. Mine would seal up pretty well ater warming up, but if your's isn't then the O2 sensors may not be getting all of the exhaust, creating a faulty reading and prompting codes. When you installed your CAI, did you disconnect the battery? I've heard that is a must in order for the system to "relearn" the new intake and changes to the MAFS reading. Don't really know if that's true either...good luck.

Lv1G6He3V2 · November 30, 2012

Yeah, I disconnected the battery for at least 30 minutes during install and let it idle 15 minutes after install. Looks like I'll get the exhaust manifold fixed first, then go from there.

Re: the bolt, thanks for confirming it's a known issue. The break in the bolt's shaft is uneven but curved - like it could have been twisted apart - so maybe it was "torque twist" in my case.

aflesch · November 30, 2012

A leaking exhaust manifold will not throw a lean code on both banks. It will just throw it for the bank where the leak is. I would say you have a vacuum leak somewhere. Get out the starting fluid and start spraying it all around the intake and see when the engine revs up. Or do it the right way and have it smoke tested.

Lv1G6He3V2 · November 30, 2012

A GM dealer can handle both types of repairs, right?

I'll have to look for one. Last time I looked the one in my area was a small Buick/GM combo dealership ... not very confidence-inspiring.

kstruckcountry · November 30, 2012

Go with a private shop, JMO

Bad Bowtie2 · November 30, 2012

I wouldn't worry about a single broken exhaust manifold bolt..... Unless it starts leaking.

Try cleaning your mass airflow sensor with CRC electronics cleaner too. Have the top two O2 sensors ever been replaced?? Might try new AC Delco replacement's- I'd consider them a maintence item after approx.75K anyways....

bluArrow · December 1, 2012

I would wait on the manifold bolt issue unless it was leaking. This is a VERY common problem on Ford's Triton motors. My last SuperDuty (F350 w/ 6.8L V10) was missing 8 out of 20 exhaust manifold bolts when I got rid of it. Ford went to a copper plated stainless bolt that was supposed to have been "the fix".

yukon25008.1 · December 1, 2012

Dealer will get pricy.. Find a good guy with expierience in the issue and good tools/bits.. Others will snap but its not bad with the right tools.

I just went through this with my 8.1, 3 bolts came out after 1/2 can of PB blaster.. the othe 5 snapped off and got drill&tapped,

I would definitly go with a set of good headers,If you have the money i would go long tube! thats when you see real results 'like 20-35 HP' depending on the application

stainless works is the set im getting they are the best when it comes to long tubes. the shortys look cool and make sound better but no real power! Now is the time to do it, do it right the first time ya know....

yukon25008.1 · December 1, 2012

The stock manifolds arent cheap either, And if you try to reuse the stock manifolds you have you should get them planed or resurfaced..They mightnot looked warped but after all that work, and you have a leak it sucks..

Lv1G6He3V2 · December 1, 2012

Thanks for all the feedback!

Still not fully convinced I should drive it much. There has been a ticking sound at speeds 45+ mph and a rare vibration/loss of power around 40-45 mph, but I thought those were due to the loose wiper cowl (the big plastic thing, which rattles if I tap it with my finger) and maybe driveshaft/u-joints that needed work. From searches those symptoms could be from an exhaust leak? However, I see no smoke and smell no fumes under the hood or in the cab.

I've been looking at headers. Good to hear there are real performance gains. I am getting a BBP tune - someday I will get usable datalogs to them when the truck runs out of problems; seems every weekend something new pops up - so the CAI and headers will reach their maximum potential. Is the 20-35 HP figure for your 8.1L or did you scale down for my 5.3L? From what I hear, it's a percentage gain, so I'm thinking 15-20 HP for long tubes w/ the tune.

That aside, just searching online I see it may cost $200-400 labor to replace some broken bolts. And this has been a recurring problem in the industry for ... how many decades?

There were some posts, made by people who swap/rebuild engines in vans and trucks, and they were talking about using grade 8/9 stainless flanged bolts as a permanent fix. If possible, I'd rather spend $30-40 on good header bolts once than have this problem recur every 5-10 years. A lot of kits come with header bolts - just have to verify the quality.

yukon25008.1 · December 1, 2012

The total number with the stainless works long tubes, and a good custom tune will be near 40 for sure!!

Lv1G6He3V2 · December 1, 2012

Try cleaning your mass airflow sensor with CRC electronics cleaner too. Have the top two O2 sensors ever been replaced?? Might try new AC Delco replacement's- I'd consider them a maintence item after approx.75K anyways....

I don't think the sensors are the problem. When the CAI was installed I set up a read-only gauge; the MAF and fuel consumption numbers appear to scale reliably with throttle (i.e. no spikes). Not sure I got the units right but idle settles to 4 g/s (air) and 0.3 gph (fuel) after a few minutes. Next step is the smoke testing as aflesch suggested.

I'll keep it in mind but the MAF sensor will not be easily reinstalled. The aftermarket air box is very sturdy and solid, but the tube diameter seems to be off by like 1mm; it will go into the MAF housing's rubber seal about 1/4 inch, but getting it to the full 1/2 inch depth takes work (and cursing). The airbox tube probably just needs heat to make plastic expand but c'mon, couldn't they test the design before selling the product?

Lv1G6He3V2 · December 1, 2012

OK, with more data there seems to be 2 or 3 problems here.

0171 & 0174 - came on randomly during trip or at idle, but no longer happens as the duct was loose - only started after CAI
0171 & 0174 - comes on following heavy acceleration, but does not happen with conservative driving - cannot verify if this happened before the CAI as I only drove conservatively
0171 - comes on now under normal driving - only started after exhaust bolt

It's annoying that they all throw similar codes but whatever. Need exhaust manifold fixed and still need smoke testing. I think I found a local shop that does both custom exhaust and CEL repairs; will call on Monday. Also will ask about O2 sensor replacement as someone mentioned it for preventative maintenance at 75k.

Looking at headers, the Stainless Works stuff for my model/year is about $1300 for milled longtubes (or $1800 for thermal-coated longtubes), and $800 for a catback exhaust (not needed but an option). WOW! That's expensive. If I go cheaper what should I look for? The only thing I care about for finish is that it doesn't rust as bad as the factory stuff.

Lv1G6He3V2 · December 5, 2012

I understand this a little better now. The $1300 is for a bolt-on system w/ longtubes + Y pipe w/ cats.

SW also sells their long tubes separately for $800. Texas Speed has an apparently equivalent product for $370. For the price difference I could almost get the cam kit, too...

Anyone have experience with Texas Speed?