Exhaust manifold bolt broken.

I just discovered that the rear driver's side bolt is broken on the exhaust manifold. Sounds like crap when the engine's cold, sounds better after it's warmed up.

So, can it be drilled out? Can it be done in the car? I'm assuming that these are cast heads?

Thanks

This is a common occurrence. They are iron heads, but the space is limited if you do not want to remove it from the car. Some have welded a nut to the top of the remaining bolt, and turned it out. When replacing the bolts, use grade 8s. It might be more accessible if you remove the wheelhouse, and steering shaft.

I too have an exhaust leak. Could it be caused by a loose bolt that just needs tightened up? Instead of tightening it would it be better to replace it with a grade 8? If there is a leak would it be better to replace the manifold gasket and use new bolts? Is this a job that an amateur can tackle without specialty tools?

Also the fsm says to apply 1/4" of GM P/N 12345493 to the bolts. Is there an auto parts store alternative?

Thank you.

Eureka, I just checked and the left rear manifold bolt is loose but intact. I tightened it up. Should I instead take it off and replace it with a new grade 8? Should I put goop on it?

I only checked the front and rear bolts on the left as they are easy to get to.

Thanks

Grade 8's!

Wagoninabox wrote:

Grade 8's!

Thanks. I bought a grade 8 ($1.60), slapped on some anti seize, and put it in.

You should replace all of the bolts with Grade 8. Anti seize is a really good idea.

Grade 8's break too.... and they suck a little more to drill out if you need to do that again.
1/4" to 1/2" spacers on all the manifold bolts are a good idea if, and when bolts break again.

Put headers on it.  They don't use the outermost bolts.

dissimilar metals expanding at different rates is the problem,.

I tighten the bolts till they are just snug,.with a split washer under the head of the bolt,.

the manifold expanding breaks the bolt,.

People like to tighten things down as hard as they can, use grade 8 bolts,.and as was mentioned the grade 8 bolts can break too,.

I agree with Nick. GM put spacers on the outermost bolts to help absorb some of that expansion. I used grade 5 and lots of flat washers on ALL my exhaust manifold bolts and never broke a one after that. Then again, I also replaced them every couple of years when I lived in the rust belt.

I used high-temp Loctite (Loctite Blue I think?) to keep them in place.

Mike also brings up a good point - extracting a grade 8 sucks more than a grade 5.

200OZ wrote:

Grade 8's break too.... and they suck a little more to drill out if you need to do that again.

I highly recommend these [You must be registered and logged in to see this link.] for anyone trying to drill out an exhaust stud or other hardened bolt.

M42 is a type of HSS containing 8% cobalt. They will stay sharp and take a hell of a lot more speed and pressure than regular HSS or even M35 (5% cobalt) and will drill out a hardened bolt were regular HSS or M2 will just smoke and dull. The next best thing to carbide, but nowhere near as brittle as carbide. They are a left-hand spiral, so sometimes you get lucky and they will dig in and wind out the bolt while drilling the pilot.

That particular set is sized to match the most common sizes of bolt extractors, so if the drill bit doesn't wind the bolt out, you are all set for an extractor.

Downsides: you have to have a reversible drill motor, obviously. A keyless chuck can be a problem in a tight space -- if you bump the chuck against something while drilling, it may loosen off while running in reverse. Also, while far tougher than carbide, M42 is more brittle than other High Speed Steels. So when hand-drilling, make sure you don't flex the bit by letting the drill motor wander and use just enough steady pressure to bite in -- ie: let the drill do the work, don't try to push it through the bolt!

Buickwagon, you are my hero. My dream vacation would be to totally dismantle a junk Roadmaster under your supervision and learn all about it!

I saw a YouTube video where instead of using a gasket they used high temp copper silicone. Is this recommended?

rjathon wrote:

My dream vacation would be to totally dismantle a junk Roadmaster under your supervision and learn all about it!

Uhhh, Sorry, I'm busy that week.

I'm personally not a big fan of high temp silicone as a manifold gasket. A lot of GMs didn't have an exhaust manifold gasket at all, relying on flat surfaces to mate up and stay straight. I'm not a big fan of that idea either. I prefer the standard metalized gaskets because they can't burn away, they provide some measure of allowance for warpage and they're not too hard to replace if necessary. But that's just my 2¢.

I've been lucky when I've had broken manifold bolts, most have come out by hand. I've drilled a few though, and drilling manifold bolts is a pain in the backside. There is maybe just one or two bolts that are not obstructed by some bracket, shaft, or what not. Compact right angle drills are the only way to go. There is little advantage, if any switching to grade 8s.

Stick with the grade 5 bolts, there's absolutely no reason to make a crappy job crappier.

... And I agree with buickwagon on gaskets. Don't use high temp. silicone in place of gaskets.

How do you remove the heat shields?

If I go back to grade 5 bolts should I use the old ones or new ones?

Thanks

I've have a broken bolt in the same location. I think mine is broken flush with the cylinder head. Mine has just a faint tick when cold that goes away...for now. I've been following this thread hoping to learn of a magic trick where it fixes itself. Looks like the trick is a lot of patience and little luck.

If the problem is heat expansion stressing the bolts, I wonder why it seems like a worse problem with reverse cooling engines and later LS engines. I don't recall this being a common problem with old SBC engines. GM buying Chinese bolts?

Heat shields? The shields on the manifolds are part of the manifold. The heat shields that cover the spark plug boots just slip off.

Use new bolts.

Heh heh. I lost a bolt down there and now it makes a noticeable sound. It broke off with most of it coming out of the hole. I'm wondering what I should do next. Drill it out? Leave it as-is (northern rustmachine here)? Put a new one in with the piece still in there?

OCCruiseship wrote:

Heh heh. I lost a bolt down there and now it makes a noticeable sound. It broke off with most of it coming out of the hole. I'm wondering what I should do next. Drill it out? Leave it as-is (northern rustmachine here)? Put a new one in with the piece still in there?

If I'm picturing this correctly, the end of the bolt broke off inside the head casting, but the hole through the manifold casting is clear. Do you still have the old bolt? If you measure the remaining portion, is it longer than the thickness of the manifold casting? If you don't have the remains of the bolt, you can stick something in the hole and estimate how far inside the head the remaining portion is. I would suspect the bolt broke off flush or nearly flush with the surface of the head. It is also possible that the bolt elongated slightly at the shear point if it twisted apart.

If you think the bolt broke off well inside the head, then you might get away with a new bolt of appropriate length, but you need to engage 6 threads for maximum strength. The fewer threads that are engaged, the more likely it is that you will just strip out those threads that do engage when you tighten the bolt. If some is sticking out of the thread, you could unbolt the manifold, shift it away from the head (leaving the exhaust pipe connected) heat the remaining bit to a dull red with a torch and grab it with vise grips to twist it out. Of course, you risk breaking (or rounding off) another bolt in the process.

"To drill or not to drill, that is the question..." Actually, better questions might be "How bad is the noise?" and "Are you getting exhaust fumes inside the car?"

Assuming it's broken off flush with the head and depending on how much clearance you have at that specific hole (may have to go through the wheel well or something, you could use the manifold hole as a guide. Pick a drill bit the same size as the manifold hole (3/8", IIRC) to clean up the end of the broken bolt. Preferably, use a split-point drill. Take note of the drill motor position so you have a reference for "straight". Drill in 1/8" or so -- just enough to clean up the break with a nice dimple, not enough to start drilling out the threads of the head. Then switch to a 3/16" or 1/4" drill bit (a nice left hand cobalt bit would be good here!) and try an extractor.

Be very cautious how much force you apply to the extractor, and don't apply any bending force at all! Extractors have to be hard enough to bite in to the bolt and hard means brittle. If you apply too much force then you just end up with a broken extractor in the hole. Treat them like a thread tap. If the bolt doesn't move with a reasonable torque, you could try removing the extractor then starting the engine and getting it up to operating temperature. Once hot, shoot a good penetrating oil (eg: PB Blaster, Kroil, Liquid Wrench) into the hole and try the extractor again.

If it still won't budge, then the only option is to drill out the body of the bolt and pick out the remaining threads. A 19/64" left-hand drill might just clean it out for you or 5/16" bit should remove most of the bolt (if the hole is straight and centered), leaving only a spiral of thread to remove with a dental pick. However, picking out the threads will be a lot easier if you remove the manifold first and that may mean a whole lot of fun with other bolts, including the ones holding the exhaust pipe on.

If it's in a bad spot where you have insufficient clearance, then the only way to get the bolt out is to remove the head and work on it on a bench.

mig welder works best,.

None of my bolts are broken. I replaced four of six and re torqued everything (passenger side). The check engine light went off and the mpg shot up. Sadly the light came on again. I re torqued them again and it went off again, only to return.

Now I'm thinking a new gasket is in order at a minimum and maybe the exhaust manifold might be warped a little. i looked at the bolts that connect it to the cat and they don't look bad so I ordered a new manifold kit off rock auto for $56 delivered. I'm going to try to tackle this one myself.

For this job where exactly would you place the Jack stands? Any other helpful hints would be appreciated.

Thanks,