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Discussion Starter #1
Hey - thanks for reading this if you've made it. I've owned my is300 forever and have recently taking an interest in working on it myself. I am not a mechanic - but I've had experience replacing things here and there and I'm pretty good at following directions and have the resources to acquire tools I need.

Recently I started taking things apart to replace my exhaust and do some other minor maintenance things, and in this particular example when I was removing the Air Intake Inlet the bolt that was securing it pretty much just snapped right off. This also happened with one of the nut head things holding down the engine cover. I anticipate it probably won't be the last time I run into this.

I've scoured google, the is300 Repair Manual and Shop Manual, the owner's guide and pretty much everything I can find - but I can't get a single beat on what bolts are used where, part numbers or anything. So what do people do? How do you know find a particular replacement part or bolt when you don't even know what the bolt is?

I'd imagine this is probably a really dumb question to any experience mechanic...
 

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They are all metric threads, so are going to be m6, m8, m10, m12... the threads may be a fine or a coarse pitch thread depending on where its used and into what material. If you are any good with a set of calipers you could measure the bolt od and the thread peak to peak or trough to trough and you will have the thread, otherwise you will need to order one from a dealer or get one from a wreckers yard.
 

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When I’m working on stuff and lose a bolt or come across a rusted bolt/nut that I want to replace, here’s what I do. I take the rusty one (or if it’s one I’ve lost - I take one from the same assembly so I know the diameter x thread are exact) to Lowe’s or HD to the hardware aisle. They have these displays where you can thread your offending bolt or nut on to and figure out what the numbers are, then find a replacement. Sometimes I will take them to Fastenal and those guys are the fastener experts. If they don’t have it, they can find it.
 

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Hey - thanks for reading this if you've made it. I've owned my is300 forever and have recently taking an interest in working on it myself. I am not a mechanic - but I've had experience replacing things here and there and I'm pretty good at following directions and have the resources to acquire tools I need.

Recently I started taking things apart to replace my exhaust and do some other minor maintenance things, and in this particular example when I was removing the Air Intake Inlet the bolt that was securing it pretty much just snapped right off. This also happened with one of the nut head things holding down the engine cover. I anticipate it probably won't be the last time I run into this.

I've scoured google, the is300 Repair Manual and Shop Manual, the owner's guide and pretty much everything I can find - but I can't get a single beat on what bolts are used where, part numbers or anything. So what do people do? How do you know find a particular replacement part or bolt when you don't even know what the bolt is?

I'd imagine this is probably a really dumb question to any experience mechanic...
Like Pnutt said, pretty much every bolt is metric, ranging from M6-M12 for the majority of bolts. If there are any bolts larger than M12 missing, you may have bigger problems haha.

Your best course of action is to get a single M6, M8, M10, and M12 bolt in both Fine and Course threading pitches (even though I think it's all just fine thread) and that way you have a nice reference set you can use to determine which size you need for any given screw hole. And if you're missing bolts completely, and you don't have that reference set I mentioned to get, look around for some bolts that may be a part of the same mounting group that may fit the screw hole.

And similar to what Kris said, you can take either a broken bolt and match it up with a direct replacement at either a home improvement store or autoparts store; since both have dedicated hardware sections. I personally like ACE Hardware if there's one nearby since they have a good selection.
 

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Your best course of action is to get a single M6, M8, M10, and M12 bolt in both Fine and Course threading pitches (even though I think it's all just fine thread) and that way you have a nice reference set you can use to determine which size you need for any given screw hole. And if you're missing bolts completely, and you don't have that reference set I mentioned to get, look around for some bolts that may be a part of the same mounting group that may fit the screw hole.
Problem is with that method there are a few different versions of metric fine, and not all the ones used on vehicles are the most "common" metric fine. Ive found you are better off either measuring if you have a caliper handy, or else talk to the dealer or do as Kris mentioned and take it in to a fastener company. The only problem i foresee with the fastener companies is that even in a metric country like NZ and Aussie they dont always stock all the different fine varieties of fasteners, so in the US where your predominantly inch based finding some of the fine metric fasteners might prove more difficult. Also bolts and screws from the fastener companies may look different in appearance to the OEM ones, so might depend on how pureist you want to be. ;)
 

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Problem is with that method there are a few different versions of metric fine, and not all the ones used on vehicles are the most "common" metric fine.
See, that's what I thought. However with metric, based off what i've experienced, I thought they were all just a single thread pitch, at least for the IS. Which is partly why I thought the metric bolt system was easier than imperial. Sure you lose some granularity vs imperial, but it sure is a whole lot easier to say a single number for a single bolt.

Ive found you are better off either measuring if you have a caliper handy, or else talk to the dealer or do as Kris mentioned and take it in to a fastener company.
I would personally measure last, since if you have a sample bolt that fits you just match it up to another and as long as they are truly parallel, then it matches the thread pitch.

And if you don't have a bolt for a screw hole, then measuring can be a daunting task. Hence why having a labled sample set lying around is nice.

The only problem i foresee with the fastener companies is that even in a metric country like NZ and Aussie they dont always stock all the different fine varieties of fasteners, so in the US where your predominantly inch based finding some of the fine metric fasteners might prove more difficult. Also bolts and screws from the fastener companies may look different in appearance to the OEM ones, so might depend on how pureist you want to be. ;)
Here in the US, I've never had a problem finding any metric fasteners, despite it being predominantly imperial. I've found myself in the isles looking for the right stuff for hours since there is so much.

There is ONE time I've had a problem with threads, and it was recently for trying to find a thread pitch adapter for a shift knob. And those sorts of things are nearly impossible to find even on the internet, it would have cost me over $100 to get a custom piece made since shit was so wack. I just 3D printed the adapter and self tap and died the plastic till it stopped moving, a lot more fun and cheaper haha!
 

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Discussion Starter #7
Thanks for the responses so far, I appreciate it. This is all good to know. Wonder what type of luck people have at junkyards with these cars at this point, I know they aren't ancient but being 15 years old now they probably aren't as common.

I've actually seen some beaters listed pretty cheap recently as parts cars, might start looking at those a little differently now!
 
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