Snapped skid plate bolts and rusted threads - need a long term solution to replace the skid plate

I was just doing my first oil change after getting this truck (changed all the fluids as soon as I bought it at a trusted independent shop - didn't have a place I could work on it at the time to do it myself). Front two skid plate bolts snap. It's missing one of the rear ones, and on the final bolt holding it to the truck, the nut on the inside of the frame snapped off inside the frame. That was a real delight to fix, let me tell you. I was able to finally cut the bolt off which was a real bear because the access to that bolt is recessed. Finally was able to wiggle a rotary tool in there with a cutting wheel I had to trim down first and got it cut and freed the skid plate. Completed the oil change (used the OEM 2UZ filter since it's bigger but still fits - I recommend) and greased the driveshaft.

Now I'm left without a way to reattach my skid plate.


Here's what I'm looking at in the front. I tried to drill one out, but I think I need a better drill bit. I started with a pilot hole and tried an extractor set, but that didn't even bite into the old screw. I gave up. And honestly, even if I get a hole drilled through it, I don't think it'll matter because it's so rusted to the threads, it's never coming out.

I bought new OEM bolts, and the missing bolt hole won't accept a new bolt. I think the threads are rusted.

What do you guys think about drilling it out (need better bits) and putting in a rivet nut? I would need to buy the rivet nut tool and some rivet nuts, but I've heard this is a solution? Anything easier? I'm a little nervous about having to drill monster holes in the frame. I think I need a 7/16" hole to pop in the M8-1.25 rivet nuts. That's the OEM bolt size and thread.

So to summarize = front two are snapped off flush and appear mega rusted. Back two - one is empty but threads rusted so can't use it, and the second one doesn't have a nut inside the frame to accept a new bolt. I don't think my PO removed the skid plate in 20 years.

It sounds like this is a somewhat common issue. I searched and didn't find anything immediately, but hopefully you guys have a good solution.

2004 Tundra V6 manual transmission AC

 

I had this same thing happen on my truck, trying the same things as you (two different extractor sets) and nothing worked. Just ran it with no skid plate for months. Finally came across a cheap but excellent used tap and die set and used that to drill out the broken bolts and retap the threads. Now I change oil without removing the skid plate.

Good luck to you!

 

I roll with no skid plate 90% of the time and only install it if I’m going somewhere I need it, it’s not a problem for it to be off. Not ideal morning the rust belt, but … I’d fix this problem first.

If you have no access to the back side of the bolt to grab the shank or spray penetrant on it, get a better drill set and progressively drill to larger sizes until there’s nearly no shank left.

After drilling it to the point you’ve only got 1-2 millimeter of outer shank wall remaining, the heat from all that drilling will typically help break the bond (you can quench with penetrant between drilling as an accelerant), maybe try to extract. If it doesn’t pop out with very little force using extractor, drill one size larger, and repeat until there is no shank left. Make sure to spend the time to hit your initial pilot hole near-center, so you can do what @JasonC. suggested, running a tap thru it. If you need the OEM bolt part number let me know. I had some missing, and had to order new ones.

 

going through something similar myself. I believe someone had used the wrong bolt and just rammed their impact wrench. so easy to not realize the bolt is the wrong size or your cross threading when you're using those damn things


I also looked into a rivet nut, however could not find any with the fine thread. I believe they are M8x1.0.
Edit to correct: M8x1.25
Thanks @assassin10000

and my hole is stripped out so large a tap and die kit would not work unless I want a different size bolt for that hole so I'm getting a local welder to help me out so all the bolts will be the same


And yeah, it's a PITA on those rear bolts being recessed




I tried going without my skid plate for a while. Didn't really cause any problems, but it did seem like at times at cruising speed on the Interstate I could feel the wind or wind resistance more.


I'm going to get the welder to reinforce those front little hanger thingy-Bob's on the front of the skid plate They're not very strong to begin with and mine have been bent over the years and are very weak. That way you can leave the front of the skid plate hanging when you need access for an oil change. Much easier than having to completely take it off.

PS if the broken bolts are rusted soak those things with PB blaster. Even the holes for the ones you've already gotten out. I also put some anti seize on mine when I put it back in. They seem to be more rust prone than other bolts on the truck

 

Welcome to the club. If you're lucky, not only will you have a bolt broken off in there, but the end of the extractor bit will break off and be stuck inside the bolt, making it all even harder.

First time I changed the oil on my Tundra, I noticed there was already one broken off front bolt head, and I broke another. So I'm running one in the front, two in the back. Really annoying. Had the same problem with my Tacoma. I have no luck with extractor sets. Always break off the extractor in the bolt. I know other people get them to work, so it's probably my technique. Still, to date I have no luck with them.

 

The real trick to extraction is to remove as much of the shank as possible, so you're only backing out the threads of the fastener with <1mm of shank holding those threads in. Even if you initially drill off-center with your pilot, and end up taking 20% of the threads on one side of your hole, keep going, the bolt will still hold even if you knock out half the threads. As a matter of fact, breaching one side of the fastener is a tactic some folks use. Just like splitting a nut, anything you can do to either break the circle of the fastener OR stretch/wallow it out so percussion/twisting will introduce play, it's in your best interest.

That ultimately is the trick though: Start with a pilot hole, then step up through one or two larger bits until most of the shank is gone. Then and only then should you use an extractor, especially if/when you're using reverse-fluted extractors. When choosing one of those things, the shank should always make up at least 60-70% of the thing you're extracting, i.e. you want to remove at least 60-70% of the shank that's there before making an attempt.

 

Great info. I struggle so much with getting a drill bit into the stuck bolt, I usually do as little as possible. Once there's any kind of hole to get the extractor into, I call it good and try to extract. Must be my problem.

 

Suck it up and get a couple good drill bits rated for hardened steel drilling. Usually called cobalt or something like that I think.
Once old broken bolt piece is drilled out, I would not use a rivnut there. Just retap it. If new bolt seizes in a rivnut you end up spinning the whole thing while trying to loosen bolt which is a real pita.

 

Fyi it's: M8x1.25

 

How do I retap it? Is this another kit to buy? I'm planning on dropping the skid plate now for every oil change. Hopefully the bolts won't seize up in 6 months especially with adding oil to the bolts.

This is correct. And @shifty` I found an old post of yours with the part number and bought a few at my dealer. Appreciated.

I'm thinking I might just take it to my local guy and let him drill this out and fix it. He said he'd do it for a half an hour of labor.

 

Ideally, a thread chaser in the correct size. Won't work as aggressively as a tap from a tap & die set. There's a 15pc kit on scAmazon that will technically work for around $25 from a bullshit company named "CMTOOL", look for Metric Thread Chaser Set 15PCS

Alternately, a Tap and Die set. Something invaluable to add to the toolset and it doesn't take up a ton of space. Allows you to clean up threads on bolts, create threads in drilled holes, and you can technically chase (you need to be careful) threads to clean them up. For around $45 you can have a pretty substantial set at Harbor Freight. Look for their Pittsburgh SAE and Metric Tap and Die Set 60 Piece

Either way you go, you're talking about equal $$ buying both/either the kits above and suitable drill bits and doing yourself.

One saves time and reduces frustration but robs you of experience while putting food on local guy's table.
The other robs you of time, adds tools to your collection, increases your hands-on experience, and boost confidence.

I understand anyone who wants to save that fight for another time, believe me. I'm sure your local dude will appreciate the work.

 

So just to make sure I've got the workflow now:

For the front bolts (both snapped):

1. Drill out bolts with progressively larger bits using a cobalt or titanium-tipped bit.
2. Once I've got a hole drilled through the bolt all the way through leaving 1-2 mm of old bolt around it, how do I get the rest of that bolt out? Can I pick at it with an awl or something? Should it fall out at that point? Or do I run the
   CMTOOL 15PCS Metric Thread Chaser Set, M6 M8 M10 M12 Thread Repair Tool Kit, Rethreading Tool Kit with Case, Includes 7 Taps, 7 Dies, 1 Thread File
   metric thread chaser set through it? sorry I've never had to drill out a bolt before. Lucky me.
3. Then just replace with new M8-1.25 bolt.

Back bolts (one missing and threads rusted, the other with no nut on the other side remaining so nothing to screw into).

1. For the rusted one, run the thread chaser through?
2. For the missing nut, run the tap and die set through? This would create threads on the short piece of frame where that bolt went through. I'm not sure these are great options because the way it came from the factory was Toyota welded a little crappy nut on the inside of the frame with 4 tiny spot welds. It breaks off easy. Let me assure you. So I'm running the risk of having to chop another bolt in the future if I leave it.

Leaning towards just letting him do it at this point. Might buy all these tools and still not be able to attach it. He also has a first gen Tundra so he's familiar with this issue. He does riv nuts.

 

Future word of advice for someone who’s been taking off and putting back on the skid plate for every oil change for almost 23 years.

Coat the screws in used oil before putting them back on and you’ll never have another issue removing them. They only need to be hand tight.

 

Yep that will be the plan for sure.

 

For drilling ... maybe kill two birds with one stone - you don't need to buy this at HD specifically, but most people have a Big Orange store in their town, and this will give you the gradual bits and left-hand extractors. That's a kit, you drill the fastener through, then hammer in the extractor and carefully back the bolt out. Where most people fuck up with this is, you want to remove the AS MUCH material as you can get out of the bolt, taking it right up to the edge of the thread holes if you can. I'd pilot with the smallest drill bit, then drill with the 3rd then 5th, or 4th then 6th drill bits. Then use the correct extractor for the final bit size you chose to back out the carcass. Ideally you'd want to use a tap/die T-handle to hold the extractor to turn it. And of course, I'd quench with penetrant from above before, if possible, before/between drilling.

If you're careful, you won't need to chase anything. Just thread in the bolt. But chaser is advised if stuff is rusted heavily. And on O2 sensors. I guess you could try tapping the frame on the other one? I have heard of that happening with the nut rusting off, but haven't seen it yet.

Everyone should have a can of Permatex anti-sieze in their arsenal, all auto parts stores have it.

​

 

I bought my truck used in 2005. PO must have used impact on my skid plate bolts. I replaced the OEM bolts with new ones multiple times and after one use the threads were destroyed. Finally got an M8x1.25 thread chaser and fixed the female threads and all is good since.

 

They only need to be hand tight if you drive mostly paved roads. Which most people do. Most people don't have a problem, but I found with my Tacoma if I didn't crank them down, not just tighten with a wrench but really get them tight, they'd loosen and sometimes even fall out after a lot of washboard. I only ever lost one, but I had a couple get really loose on me a few times. Like I said not many people seem to have this problem but I definitely had it with my Tacoma. I've since gotten older and don't drive 50+ mph on dirt roads anymore...

Otherwise I completely agree.

 

GD lubies haha

 

Since new, I've only ever just snugged them up past hand tight and they have never loosened up between oil changes, but me, and the Tundra reside in SoCal and don't face the salt and other winter muck lots of others do. Anti seize on the threads for sure.

 

If guy is only gonna charge half hour labor and you trust his work, I'd let him do it. You could easily spend same amount on drill bits and taps plus your time. Sounds like you understand what to do though if you want to try it.
Tricky one might be where welded nut is totally missing because the remaining hole might be bigger than tap. Only having 3 out of 4 bolts in skidplate isn't end of the world either though.

 

In this case, I believe it's 4 out of 5 bolts. 3 along the front, two along the rear corners? But I think it's one of the rear corners that'd be lacking a fastener which wouldn't be ideal...

 

Yep I can't get either rear bolts in for now. I didn't even realize there were 3 up front. I only had two. I bet that bolt is missing and the threads are fully rusted as well.

 

After you get done fixing everything and get new hardware apply a good coat silicone to all threads on assembly and they will come off like new years later, anti-sieze will dry up/wash out after so long.