We’ve all been there. You just sold that high-dollar, low mile overhead cam V8 engine from a popular truck series. Truck was just dropped off last week, inventoried, and you got the engine sold right away. Things are great. But, the shop guy walks in and says, “sorry man, you are going to have to call your customer and see if they want this engine – a few of the exhaust manifold bolts are broken off.” Talk about a sinking feeling. Last thing a salesperson ever wants to do is call the customer about a defect we were not counting on. That’s when you know getting down to the nuts and bolts is important.
There is hope though. If your shop is equipped with the right tools and the right person, you may be able to extract the offending bolt and be right back on track. I am in a very fortunate position, and my time is split between being a salesperson and a shop man. Kind of depends on the day and what is required. I have spent several years as an auto tech, which has gained me experience in the field of car problems, but has also given me a lot of insight into what our shop type customers need from us and what drives their biggest complaints.
When it comes to broken bolt removal, the most important tool is patience. We will almost never get those pesky rusted bolt remains out if we are in a rush, and all we will do is make things worse.
We want to keep it simple. If there is enough of the bolt sticking out, we want to clamp a vice grip type pliers to it and see if it wiggles. If it does, gently turn it back and forth until it comes loose enough to thread it out. Too easy, right? I find this happens, mostly on GM engines with aluminum heads. I believe that heat and expansion is popping the bolt heads off rather than rust, or they are overtightened on installation and the bolt is weakened so they are not necessarily that stuck in the hole, they are just broken off. If it is too stuck to wiggle loose, I like to heat the bolt until it is glowing, rapidly cool it with a spray bottle of water, and then try to wiggle it loose. We are operating on the theory that the expansion from being so heated makes the outer metal a little larger around the bolt, and the rapid cooling quickly shrinks the bolt until it is loose in the threads. I feel that if we can cool the bolt but not the surrounding metal, this is a good thing.
What about if the bolt is broken off flush or even below the surface? This does add a challenge, but we have become highly successful at removing those. You could try to drill it and use a bolt extractor. My success rate with that method has been pretty poor with the smaller bolts used on most exhaust manifolds. What has worked the best is a welder.
Now, I’m pretty well spoiled. I have access to a TIG welder, which offers amazing precision. If the broken bolt is flush or below the surface metal, I start by using the welder to build up the bolt until it sticks out a little. I then weld a flat washer to the built-up “bolt.” After this cools, I weld a nut to the washer. Most of the time, the cooling only takes 15-20 seconds because the heat is rapidly absorbed by the mass of the cylinder head. I then gently try the new “bolt head” with a wrench to see if it will come out. I feel that the action of welding to the bolt is the best way to get heat into the bolt to help loosen it. You can use a MIG welder for this, but you won’t have the same control. Oxy-Acetylene welding is good too if you are old enough to have been trained in that. Funny thing, if I am working on an LS Chevy engine, the bolts are usually just about finger tight after I get the nut welded on. If we are talking about a Ford Triton type engine, I usually have to try the same bolt several times before I have success.
If we are working on an engine with aluminum heads, we want to be careful not to melt too much of the aluminum while we weld. The precision of the TIG welder really helps in this. If we do melt a little, that’s usually ok, and a nice feature is that the steel of the bolt won’t bond to the aluminum. If you have cast iron heads, we need to be extra careful not to weld the bolt to the head. The reason for that should be fairly obvious.
One more aspect that really helps the process is vibration. We were taught to use a short box end wrench to turn that welded up bolt head because we want to be careful not to snap it off again. That is true – we should be careful. Over the years, I have become more confident in the process and have begun to rely on an impact wrench. Now of course, you don’t want to haul out your big boy impact that you use to change loader tires. This calls for finesse. I have a ¼ drive pneumatic impact wrench I use to gently “rattle” the bolts out with. This works pretty good as long as we are…patient.
Keep the gun at a low setting. We are not trying to force the bolt out at this point, but coax it out. The vibration from the impact wrench seems to work wonders. Sometimes, even if it doesn’t move right away, keep the gun on it. The prolonged vibration is a good thing. There is also a handy tool that goes into an impact hammer and holds a socket. The idea is to vibrate the bolt with the impact hammer while turning the bolt with a box wen wrench. I have found this to be pretty effective as well.
Finally, we will finish where we started – with patience. My old mentor, Pete, who started teaching me this stuff drilled it into my head when I was 16 that you couldn’t go slow enough when wiggling out a stuck bolt. Back and forth, back and forth. Gently work it until it is out. Force it, and you have another broken bolt. Also, if you go to pull out a manifold bolt (or any other bolt) and the first one twists off under the impact wrench, it would be really foolish to assume the next bolt down the line will be any different. We must now slow down and treat every successive bolt like it is ready to snap. Heat and patience will work them out. It takes longer, but sure is faster than welding on washers and nuts.
Just about every LS engine we pull has at least one manifold bolt broken off in it, and I expect yours do as well. Customers hate getting an engine like that. Take the time to pull them out before the customer gets it and they will be very grateful.
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