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Over torquing and breaking bolts
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Author:  vertical_downpoint [ Fri Aug 04, 2017 8:01 am ]
Post subject:  Over torquing and breaking bolts

In the process of installing a new water pump, timing belt, etc. I've managed to break off two of the 10mm water pump bolts in the block, as well as one of the four crankshaft pulley bolts. My torque wrench works, and I'm at or below what the service manual indicates.

With the crankshaft pulley bolt the service manual calls for 12 ft lbs (144 in lbs). I broke the head of the bolt clean off at 120 in lbs. Am I going crazy? Or are the bolts in a 25 year old economy car just not reliable? I've bought a pack of high strength bolts from Autozone but they're a little long. I have the washers to match, is it safe to replace the four crankshaft pulley bolts with slightly longer and stronger bolts with washers?

Anyone have any experience with this?

Author:  blueturbofly [ Fri Aug 04, 2017 6:16 pm ]
Post subject:  Re: Over torquing and breaking bolts

I use 10.9 strength ''socket cap'' (allen head) bolts. washer should work fine, double check them after a few miles. use blue loc-tite on them as well.

8.8 grade bolts should work fine as well. stainless bolts are a hair stronger than stock bolts.


double check that torque wrench!!!!!

Author:  suzukitom [ Fri Aug 04, 2017 11:24 pm ]
Post subject:  Re: Over torquing and breaking bolts

Quote:
With the crankshaft pulley bolt the service manual calls for 12 ft lbs (144 in lbs). I broke the head of the bolt clean off at 120 in lbs. Am I going crazy? Or are the bolts in a 25 year old economy car just not reliable? I've bought a pack of high strength bolts from Autozone but they're a little long. I have the washers to match, is it safe to replace the four crankshaft pulley bolts with slightly longer and stronger bolts with washers?

Anyone have any experience with this?


A bit longer might be okay. Thread hole is all the way through the crank gear.

Washers might interfere with center bolt flange. Factory bolts have tiny washers already.

I agree that torque wrench accuracy might be off. They stay accurate for only a few years unless you bought a top grade wrench. Most people don't store them with about 10% of max torque set to preload the wrench a bit. Low torque accuracy is a challenge. I practice sometimes with some bolts and mark them with a pen index to develop a by feel tightening sense using a standard wrench.

Author:  suzukitom [ Fri Aug 04, 2017 11:24 pm ]
Post subject:  Re: Over torquing and breaking bolts

Deleted duplicate post

Author:  vertical_downpoint [ Sun Aug 06, 2017 5:54 pm ]
Post subject:  Re: Over torquing and breaking bolts

It was definitely the torque wrench. I was using an Autozone $30 torque wrench, and trying to torque at very very low inch lbs.

I returned that POS and rented their loaner tool torque wrench is an OEM brand and works really well. I used it to tighten the crankshaft timing gear bolt and it worked perfectly.

For the crank pulley and water pump pulley I just torqued them very tightly using a regular ratchet. Everything is running fine.

Moral of the story is don't use a cheap torque wrench, especially when dealing with inch lbs.

Author:  CMA [ Sun Aug 06, 2017 11:44 pm ]
Post subject:  Re: Over torquing and breaking bolts

hey what about start to trust your arm? :lol:


it almost never failed me :mrgreen:

Author:  91 ragtop [ Thu Sep 07, 2017 6:41 pm ]
Post subject:  Re: Over torquing and breaking bolts

I bought one of those POS Autozone torque wrenches too. All it's good for is using as a long handled ratchet.


Ken...........

Author:  91 ragtop [ Thu Sep 07, 2017 6:45 pm ]
Post subject:  Re: Over torquing and breaking bolts

I bought one of those POS Autozone torque wrenches too. All it's good for is using as a long handled ratchet. Oh, buy the way, my engine manual shows those bolts at 96 inch pounds so you over torqued them by 50 %.


Ken...........

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