Destroyed Aluminum Threads (and how did I?)

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Just a shot it the dark here. Something caused the pulley bolt to snap. Could it have been one of the accessories the belt drive seized and caused the bolt to break? If that happened the added stress on the mounting bolt could have caused the damage to the threads in the timing cover. I would check all the belt driven accessories before putting it back together.

Reading your description of the work you did, I can't believe it was something you did to cause the damage.
 

JHZR2

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Possibly started it cockeyed? If its really only the first few threads run an 18mm spark plug chaser down it they are that size. If you do get it in do not torque it to 100nm go about 80 nm, it is not an issue.
I bought a thread chaser and it will come tomorrow. I also bought the time sert kit just in case. I went with the time sert because I’ve used them before and because it comes with a tap alignment tool that will help me get it straight. And I like that I am definite that the time sert can’t go too deep, since the timing chain is in there. I couldn’t find a legit helicoil kit that was cheaper.

Question becomes what length of insert should I do?

A80B3D6A-631B-4ED8-B615-C318918CE125.jpeg


Do I try to cut threads and put an insert all the way in, or can a more shallow one, like 10mm be used instead? The thought process with that is if I can drill shallow, tap shallow, do an insert shallow, and then somehow get the threads from the aluminum to mate up (maybe an impossible ask), then chip collection and avoidance of FOD from getting in the engine would be easier.
 

JHZR2

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Just a shot it the dark here. Something caused the pulley bolt to snap. Could it have been one of the accessories the belt drive seized and caused the bolt to break? If that happened the added stress on the mounting bolt could have caused the damage to the threads in the timing cover. I would check all the belt driven accessories before putting it back together.

Reading your description of the work you did, I can't believe it was something you did to cause the damage.
I was thinking the same but I’ve run all the pulleys by hand and they’re all smooth and good. AC doesn’t have charge so can’t run. Declutched it’s smooth.

I could have overtightened it. I heard a “clank” which was the bolt head hitting on the fan blades. Believe it or not the auxiliaries still worked reasonably - I had power steering, alternator light only flickered, fan turned… just with the pulley captive there in the loop of the belt between the water pump and crank.

Wouldn’t make a habit of it, but I was only a few blocks away.
 

D60

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When dealing with aluminum threaded parts, you don't have to do anything wrong. A little corrosion or the prescribed loctite may be enough to distort the threads.
I'd try a retap first, especially if you can start the tool from the back side of the casting.
This. Once aluminum starts to gall it's all over.....it just seems to start a cascade effect and one mildly bad thread then trashes or distorts all threads after that.
 

D60

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OP I understand pics and perspective can be deceiving but it looks to me like you've got gobs of room as it is. Yes, you'll need a RA drill but everything else should be straightforward with the space available....again, assuming you might need to shorten the drill shank

That said, if it's not a ton of work to pull the radiator, it's never a bad idea just due to the risk of damage if nothing else.
 

JHZR2

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OP I understand pics and perspective can be deceiving but it looks to me like you've got gobs of room as it is. Yes, you'll need a RA drill but everything else should be straightforward with the space available....again, assuming you might need to shorten the drill shank

That said, if it's not a ton of work to pull the radiator, it's never a bad idea just due to the risk of damage if nothing else.

Thanks! Yes I plan to pull the radiator. My luck would be that the neck cracks when I pull the hoses, but we’ll think happy thoughts :)

I have a RA drill, but the challenge will be keeping everything straight and square. I got the kit with the tap guide to help. I’ll probably plug the back of the hole somehow, and hope for the best… if I can do a shallower insert I’ll do that to minimized the chance of FOD.
 

Astro14

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The drain plug kit has a shorter drill. And the drill can be turned with a socket. Might not need to pull the radiator at all. With the controlled speed of a hand turned drill, I would stick with the grease in the flutes.

Sorry about the price.

You’ll want an insert that’s the length of the faster, which is 22mm. But if you’re forced to choose between the 18 and 27mm, I would check the depth in your cover, and I might go shorter - so you don’t hit the chain behind the insert.

 
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JHZR2

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The drain plug kit has a shorter drill. And the drill can be turned with a socket. Might not need to pull the radiator at all. With the controlled speed of a hand turned drill, I would stick with the grease in the flutes.

Sorry about the price.

You’ll want an insert that’s the length of the faster, which is 22mm. But if you’re forced to choose between the 18 and 27mm, I would check the depth in your cover, and I might go shorter - so you don’t hit the chain behind the insert.

I bought the 1815C and a couple 18mm inserts. I was thinking about the csm with the shorter bit, but I had used one like that for an oil drain plug repair and remember thinking that how slow it went and how that affected control and it’s ability to snag. I don’t know. Probably overthinking everything at this point.

Hope I have enough space. Removing the radiator will help me meet another objective to transition this engine to John Deere Cool Gard II as well.
 
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JHZR2

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Meh- brake clean it and torque the bolt with JB. Just know the next to get a replacement cover.
lol that is an option, isn’t it? Maybe the best one in the end! If I just torqued it and put JB in there, I’d suspect that we would run a major risk of shreds of metal, and epoxy, down in the engine.
 

JHZR2

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32B467DA-F6F9-4950-890F-F0F63F4F4353.jpeg


Just checked - this is the RA drill I have.

Just realized that supposedly the time sert kit needs a 1/2” drill. Tool time???

SMH
 
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View attachment 120798

Just checked - this is the RA drill I have.

Just realized that supposedly the time sert kit needs a 1/2” drill. Tool time???

SMH

I ran into the same issue with an transmission pan. Even short bits were a little too long in my case (frame rail in the way).

One option is a right angle attachment from Harbor Freight. Not idea as it becomes a balancing act.

Good luck. If it helps - you can always sell the kit on ebay, short one insert - and recover some of the cost.
 
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Uhmn,up here,under my shade tree, ground zero in the Rust Belt, fasteners doan need no steenking thread locker. Just saying. Factory thread lockers need to be heated to break the chemical bond. A steel shoulder bolt passing through aluminum is bound to be ALO2 bonded into place. I would buy or make a thread chaser and try to finesse the threads by peening the hole to scrunch down the top threads just a bit. I can fashion a crude but effective thread chaser out of the same pitched bolt with a bench grinder and a Dremel. Then I would use a brand new bolt and dispense with the torque values and get the bolt snug. Granted, they weren't Mercedes' but old BMWs had their ways too
 
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I bought the 1815C and a couple 18mm inserts. I was thinking about the csm with the shorter bit, but I had used one like that for an oil drain plug repair and remember thinking that how slow it went and how that affected control and it’s ability to snag. I don’t know. Probably overthinking everything at this point.

Hope I have enough space. Removing the radiator will help me meet another objective to transition this engine to John Deere Cool Gard II as well.
The 18 mm long insert should be fine. How deep are the old threads?
 
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Maybe I got this wrong but I'm going with what I see in the pictures of the threads. The threads , except for the first two look ok. The threads must have been holding tight for the bolt to have sheared or the bolt may have backed out to the last threads then sheared, not likely. I don't see any way you could have over tightened that bolt to weaken the bolt or the threads. Is it possible that this bolt was faulty, had a flaw. How much of the broken bolt remained in the hole and can you post a picture of the sheared bolt? If the remaining piece of bolt was in the hole below the damaged top threads it would have to be fastener failure.
 

JHZR2

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Maybe I got this wrong but I'm going with what I see in the pictures of the threads. The threads , except for the first two look ok. The threads must have been holding tight for the bolt to have sheared or the bolt may have backed out to the last threads then sheared, not likely. I don't see any way you could have over tightened that bolt to weaken the bolt or the threads. Is it possible that this bolt was faulty, had a flaw. How much of the broken bolt remained in the hole and can you post a picture of the sheared bolt? If the remaining piece of bolt was in the hole below the damaged top threads it would have to be fastener failure.
We may be talking two things here.

The bolt that ruined the threads in the engine timing cover. This one looks brand new.

04311CE2-C383-4868-AF28-B100B017B2D0.jpeg


Then also the much smaller bolt that holds a pulley to the tensioner, which sheared off somehow.

3A4603B7-260B-40D6-8307-C8AD7F0CB139.jpeg
043A3E7B-8344-4E32-ADBD-C3746C61B349.jpeg
 
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Those threads dont look that bad to me....I'd chase the threads and bolt in a new one. I'd also be very suspect of the torque wrench .....you sure its accurate??
 
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We may be talking two things here.

The bolt that ruined the threads in the engine timing cover. This one looks brand new.

View attachment 120837

Then also the much smaller bolt that holds a pulley to the tensioner, which sheared off somehow.

View attachment 120838 View attachment 120839
Ok, sorry my mistake. It seems I was confused about which bolt had sheared. I think you may still be able to chase those damaged threads. Good luck with what ever method of repair you choose.
 
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We may be talking two things here.

The bolt that ruined the threads in the engine timing cover. This one looks brand new.

View attachment 120837

Then also the much smaller bolt that holds a pulley to the tensioner, which sheared off somehow.

View attachment 120838 View attachment 120839

This all makes me wonder if you got a very real looking counterfeit part. Pulley bolt breaks, threads on block damaged ( slightly undersize bolt/threads) ?

Have to wonder.
 
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