Exhaust Manifold Removal Questions

Discussion in 'Vortec 4.2L I-6' started by yar02169, Nov 4, 2013.

  1. yar02169

    yar02169 Active Member

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    I'm almost certain that my Bravada has a cracked exhaust manifold. Looking around here I see that's it's a common item that fails. My question is, how many of you that have done this repair have had the bolts snap? If they did snap, how did you go about getting the bolt out in the confined space?
    Would it be recommended to spray the suckers daily for a week, bettering the odds that they come out ok? It's a second vehicle for me, so I can let it sit and allow the spray to do it's thing without evaporating by being heated up while running.
    I'm up for the fun of replacing the manifold, but the fear of broken bolts makes me weary about what to do if that happens.

    Thanks in advance for any and all input
     
  2. The_Roadie

    The_Roadie Administrator

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    I consider myself wicked careful, and I snapped three of mine. And had to pay a professional with a small right angle drill to do the extraction on the farthest aft one. I've heard that doing it just after running the engine can help. The bolts are put together at the factory with high temp thread locker , and replacement OEM bolts come with it pre-applied. So another trick that I've read about is to remove the bolt reverse of the way you thread IN a tap. 1/4 turn in the direction you want to go, then 1/8 turn in the OTHER direction to clear the threads. That way the thread locker is less likely to bind up and increase the torque required, which will break the wimpy bolt.
     
  3. Jtyler77

    Jtyler77 Active Member

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    I was thinking mine was cracked too but when inspecting I noticed that the head had popped off the furthest one back next to the firewall. So I figured there was enough sticking out to get a vise grip on it. Went to remove the bolts with the loosen an tighten method, and a bunch were loose.
    Then I went to grab that SOB in the back with the grips, thought it was coming but it ended breaking off with a inch or so left in the motor. :hissyfit:

    Started looking up different back outs. Matco has an awesome little setup call bust-n-out that would have probably worked If I had the room to play.

    In the end I let a trusted old school mechanic get it to the tune of 600 if I remember. I just didn't want to chance it with no room.

    Oh, I sprayed it with pb for about 5 or 6 days and didn't drive it.

    I will say that if the problem arises again, I'm going right back in there myself just to try. I don't usually pay for car work.

    Good luck!
     
  4. seanpooh

    seanpooh Well-Known Member

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    Removing the manifold bolts weren't difficult at all (to me at least). Trust me, I was praying the whole time. You will have enough room when you remove the intake out the way and tranny dipstick.

    The torque rating is only only suppose to be 18ft/lbs. Also I think the factory put some thread locker, but not too much effort to remove. I already had 3 bolts snapped on the last cylinder so I used the Irwin 5/16-8mm bolt extractor. Made it soo easy to remove.

    If you bolt snaps when removing closer to the cylinder head, then you may have a problem. That's what you will try to avoid. I did soak the bolts every night for about a month an half.

    Another important note, the manifold bolt sizes are 1/2". They fit much more snugly than the mm sockets. Good luck.
     
  5. yar02169

    yar02169 Active Member

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    Thanks for the replies, it does lessen the scare.

    One thing has come to mind. When the manifold is cracked, is it noisy all the time, or just when it's cold? Mine starts with some noise, but once things are warmed up, it can actually be called silent.
    Also, is it possible to patch a crack, or is it in a position where removal is required?
     
  6. seanpooh

    seanpooh Well-Known Member

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    As roadie always says, the exhaust manifold is metal. So if there is indeed a crack, it will be heard the loudest when cold because the metal has retracted. When it warms up, the metal expands and the crack "fills us" and the noise is reduced.

    Same concepts with doors in the house in the summer and winter if you know what I'm talking about.

    I have read before, don't know if it was here or the OS that a member used high temp JB Weld i think... to patch the crack up. It's worth a shot I suppose. I don't know where the crack usually develops, sorry.
     
  7. gmcman

    gmcman Well-Known Member

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    I believe the process is to start the engine and let it run for about a minute. Then tap on the head of the bolt to break the torque in the threads. When heating the cyl head the hole will enlarge very slightly (if at all) and possibly ease the extraction.

    Godspeed my friend. :thumbsup:
     
  8. bfairweath

    bfairweath Member

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    Sorry to bump an old thread, but I just tackled this job largely using the info from this thread. Thought I would share some of my experience.

    I started noticing exhaust noise several years ago. It started getting progressively worse. I could see several bolt heads snapped off on cylinders 5 and 6 with the heat shield on. I purchased a Dorman manifold kit off Amazon to be prepared for a crack. I don't want to tell you how long it sat in the garage (years). I knew this was going to be a tough job.

    I decided last Wednesday was the day to start. I would have the whole Thanksgiving holiday weekend to tackle it (and run back and forth to the parts store). First problem I encountered, the upstream O2 sensor was seized. Couldn't get it out (I have a O2 sensor socket). That was the first casualty. Could have been worse, it had 80,000 miles on it. Lasted longer than the OEM.

    The exhaust noise problem was apparent after getting the heat shield off. No bolt heads on the two bolts for cylinder 6. Top one was also missing on cylinder 5. I actually found a bolt head laying the garage about a year ago. No cracks in the manifold though.

    I used Roadie's technique mentioned above for getting the bolts with heads out. You can feel the torque requirement increasing as you're backing them out. That's your signal to go back the other way for a few turns. I also recommend spraying some PB Blaster between the bolt head and the manifold as soon as there is space. Takes a while, but I got them all out without breaking any. The first bolt on cylinder 1 was loose.

    After getting the manifold out, it was easy to see the problem. There was exhaust soot at the bottom of the port for cylinder 6. Cylinder 5 and Cylinder 1 look like they were still sealed.

    Now on to the three broken bolts. I took Seanpooh's advice above and purchased the Irwin 5/16-8mm bolt extractor. He's right, it works great on the ones that had the heads broken off. They were easier to get out than the ones with heads. Buy it if you're attempting this job! However, there was one hole with no stud sticking out. Could I be so lucky that the bolt backed all the way out and is laying on a highway somewhere? Of course not. It was broken about 1/8" below the surface of the head. Could it be in a location that was easy to drill out? Of course not. It was the one closest to the firewall.

    I was prepared with easy outs and bolt extractors. I even bought a cheap right angle drill to get back there. No luck. I snapped several easy outs. The bolt extractors wouldn't work. Next plan: helicoil. That failed too. The old bolt just would not drill out. I just kept screwing up the aluminum around the hole.

    Here's how I finished it up. Feel free to criticize. I filled the bolt hole in with JB Weld. Then I gooped up the area around cylinder 6 with Permatex Hi Temp gasket maker on both sides of the gasket and put the whole thing back together. I'm hoping the gasket maker along with having one bolt on Cylinder 6 keeps it sealed for a while.

    Haven't started it up yet. The gasket maker needs 24 hours to cure. I'm going to give it all of that - probably more since its about 30 degrees here. I'll let everyone know if it holds (and how long it holds).

    This thing is not coming apart again. I used red threadlocker to put all the bolts in. I figured this can't be any worse than it was before I started (and might be better). If it starts making noise again, I'll live with it as long as I can before getting rid of the truck. It's almost 13 years old. It's done it's duty. Luckily, I don't drive it much. It's my wife's DD!!!:2thumbsup:

    Anyone want an OEM manifold (truck is an '03) with a seized (but functional) O2 sensor in it?
     
    Last edited: Nov 28, 2015
  9. BlazingTrails

    BlazingTrails Banned

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    I hate to be the one to tell you this, but you are doomed to fail. I would have never assembled the manifold with a bolt missing, that's just bad form imo.

    Here is a better thread to go more in depth with the bolt problems.

    http://gmtnation.com/forums/threads/loss-of-engine-power.11346/

    and here is a specific reply of mine on how to properly fix the problem.

    It may work for a while, but I would advise you to go ahead and pull it back off and drill/tap the hole before you even run it. If you have any questions just ask, that is why this site exists.

    :tiphat:
     
  10. bfairweath

    bfairweath Member

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    Too late. I started it up last night. Sounds great (for now). Didn't drive it. Just wanted to get a bit of heat in it to cure the Permatex goop more (again, it's 30 degrees here).

    I agree that it's a hack job and bad form to purposely leave a bolt out but I had to cut my losses with this thing. There was no way I was going to pay for a broken bolt removal. Not on a 13 year old truck for a problem that is aesthetic only (it's always ran great, just noisy). I'll post when the goop blows and starts making noise again. I know it will happen. The next hack will be to try to pack the blown area with JB Weld. After that, Acadia or Traverse. I'm hoping for a couple more years. 1 3/4 of that might be listening to loud exhaust (at least my wife will be).

    As a side bonus, while working under the truck on the manifold, I noticed that the drivers side front differential seal is leaking again. I've tackled that one before with info from this site....
     
  11. Mooseman

    Mooseman Moderator

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    The gasket maker will burn off. Not much is available that can withstand that heat. But, maybe the one bolt on that port will be enough to keep it sealed.
     
  12. BlazingTrails

    BlazingTrails Banned

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    If it was anything beside the bolt at the end I would agree that there may be a chance, but the manifold when heated to full operating temps will expand and naturally pull away from the head. I have seen it many times.

    That is also why a lot of vehicles that have an exhaust leak when cold seems to go away after a few minutes of driving, because the metal expands just enough to seal it off. in this case though, expanding metal is the enemy....
     
  13. Daniel417

    Daniel417 Well-Known Member

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    Best method of extracting a broken bolt is to put a nut over and weld it to the stud.
     
  14. BlazingTrails

    BlazingTrails Banned

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    There is not a "one best method" for removing a broken bolt, every situation calls for something different. As stated above the bolt in question was broken about 1/8" below the surface of the head.
     
  15. MRRSM

    MRRSM Gold Supporter

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    FWTAW...





     
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  16. MRRSM

    MRRSM Gold Supporter

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    When cast iron manifolds are cold...they contract and shrink about 1/64,000,000" per degrees F... not much by most standards... but when added up over the entire length of the mating manifold surfaces, the difference can be more than enough to allow cracks in the webbing to become loose and vibrate. Also, these chilling thermal events can allow the manifold portions adjacent to the broken off bolts to rattle against the broken studs like pebbles in a tin can.

    Conversely... as engine exhaust temperatures rise, they rapidly heat up and expand all the metals in this "sandwich" in the opposite dimension and can substantially close up the gap between the exhaust manifold, the loose laminated metal gasket and the face of the exhaust ports in the engine head... thereby quieting things down for a while.
     
    Last edited: Dec 1, 2015
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  17. Daniel417

    Daniel417 Well-Known Member

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    Your right. There is no best method. Every problem is different. But in my opinion that is my favorite way. Plus you have to have access to the equipment and be competent enough to use it. Or know someonw.
     
  18. MRRSM

    MRRSM Gold Supporter

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    "I'd Just Like to Mention... An Ounce of Prevention..." CRC-FREEZE-OFF

    I encountered a nightmare with my '93 Z-28 Exhaust Manifold on the Triple Stud Flange that involved most of the rusted stud to fasteners mating points just snapping off like they were bread-sticks. Of course it was necessary to pull off both E-Manifolds entirely to extract the broken off studs. For the damaged ones with around 1/2" of the studs remaining, I found this brilliant and extremely helpful Youtube Video produced by "realfixesrealfast" that showed a dramatic procedure involving an OA Torch, some White Paraffin Candles and a stout pair of KemPex Gripping Pliers. Have a look at this:



    The other half involved the MIG Welding Technique with equal success in first welding on the nut and then heating the cast iron while jiggling the newly welded "turnstile" back and forth.

    And here is the "Ounce of Prevention" involving the use of CRC Freeze-Off that, having lived through the Broken Manifold Stud issue... I wanted to try Four Different Chemical Rust-Removers/Penetrating Spray Lubricants and see which of them, if any, actually would work in a timely manner:

    WD-40: Nope... Now don't get me wrong... I LOVE this water-displacing penetrating stuff for jobs like spraying down freshly boiled and scrubbed cast iron parts and engine blocks and for long-term water protecting oil coatings on bare metal/cylinder walls, etc, But sadly... it does not seem to work very well on the Rusted or Busted Studs/Bolts/Nuts problems.

    PBR-Blaster: VERY Volatile and hard to breathe around in confined spaces and DID NOT WORK to loosen the Rusted of Busted fasteners. I only use the PBR on sets of Spark Plugs that I cannot replace on short notice by soaking them in this material from the threads to the innards.

    KROIL: This stuff is GREAT for spraying inside a Zip-Lock bag and dropping in REALLY badly rusted fasteners from an Engine Build involving hard to find or replace fasteners when time is not of the essence. The next time you examine the bolts and nuts in that bag, virtually ALL of the rust will have been dissolved into a brown soup and the fasteners will come out looking almost brand new. So ...Yes.... this stuff will work on the E-Manifold fasteners... but it will require several hours to work well enough to loosen the fasteners good enough not to snap off the studs.

    CRC- Freeze-Off: YES! YES! YES! I finally tried this stuff on the E-Manifold studs/nuts on the GM Atlas 4.2L Engine not only on the Triple-Stud Flange but also on all of the fasteners holding the entire E-manifold to the Aluminum Engine Head (they came out with...ease). The trick was to realize that you want to work the fasteners loose within the first 10 seconds of initially spraying down the bolt head and manifold flange area. What happens is, the FREEZE component has such a rapid rate of evaporation, that the bolt very suddenly shrinks and the remaining Super-Penetrant component in the spray stream works its way VERY quickly along the thread lines. So the techniquethat works is: SPRAY IT LIBERALLY...AND WORK THE WRENCHES OR SOCKETS QUICKLY WITH SMALL, LOW-FORCE, SHORT TURNING INCREMENTS. Once the cooling portion has evaporated... take off the wrench or socket and see if you can turn the fasteners off by hand. I tried this on the Triple Flange of the E-Manifold and was able to twist off two of the three nuts with my bare fingers! Now THAT is PENETRATING OIL!!! Have a look at this:




     
    Last edited: Dec 1, 2015
  19. bfairweath

    bfairweath Member

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    Update on my manifold replacement with leaving the last bolt out and gooping it up with sealer. It had been quiet for over a year (and about 20,000 miles). However, I started hearing exhaust noise last week. Got worse by the day. First reaction was 'Damn, the GMTNation guys were right - it didn't hold.' Took the heat shield off and checked the bolts. Almost all of them were a bit loose - how does that happen with red threadlocker? Tightened them up - no change - noisier than ever. More investigation found the exhaust blowing from the doughnut between the manifold and the cat pipe. Took it apart and replaced with a Felpro. Not an easy job (but easier than replacing the manifold). Had to unbolt the cat pipe from the muffler to create enough space to get the old doughnut out. Don't use a Dorman doughnut. Junk. The Felpro has a higher inner ring that goes up inside the manifold.

    I gooped up the new doughnut with the same stuff I used to seal up the 6th cylinder port. It doesn't burn away. There's still some around the gasket from the repair a year ago. The stuff I used was Permatex Ultra Copper High Temp RTV.
     
  20. Mooseman

    Mooseman Moderator

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    Felpro is good stuff. It should hold up better.
     
  21. MRRSM

    MRRSM Gold Supporter

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    If the need arises to remove the Exhaust Manifold and the old one is damaged and demands a New Replacement... and if the one sold by Dorman is chosen over the GM OEM flavor... Neither the Stock OEM Fasteners...Nor Dorman's own recommended "Gold" Fasteners will be long enough to thread down completely inside of the Exhaust Manifold Mount Holes.

    This is because the Dorman Flanges are about 5 MMs THICKER than the Stock GM OEM Exhaust Manifold. A longer Quality, 10.9 M8 X 1.25 MM X 35MM Fastener is available though... and has the added features of a bare, necked portion under the head face of the bolt head that is also approximately 5 MM in length... and it also features a flared washer like base sloped at the bottom of the Cap Screw Head that will provide a greater surface contact area to hold the flange more securely.

    5 MM may not seem like much in the way of length... but considering how frequent;y these bolts loosen, wear down, rust or just plain snap off in the most inconvenient and hard to find locations along the Aluminum Head... every little bit of additional holding power would be helpful. The attached images bear the proof of the comparison as I miked these flanges myself and the Fasteners are available for purchase at reasonable prices vis the data on the posted Box Ends:
     

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    Last edited: Jan 10, 2017
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  22. MRRSM

    MRRSM Gold Supporter

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    If you think you have an Exhaust Manifold Swap in the works using the Dorman Exhaust Manifold component coming in the near future… these are available for purchase right now on eBay. And since “Having them… and Not Needing them is Better than Needing them and NOT Having Them...” passing the information along might help our GMT Nation Members. These Bolts will be Too Long for any GM OEM Exhaust Manifolds… by 5 MM:

    Flanged Cap Screw Bolt, Steel 10.9 Metric, PT, M8 x 1.25 x 35 mm Length[​IMG]


    … The (50) Piece Box:
    http://www.ebay.com/itm/Flanged-Cap...392203?hash=item1a00ab8c0b:g:ZsIAAOSwAvJXAyLM
     
    Last edited: Jan 14, 2017

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