broke head off NEW wheel cylinder bolt

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rich006

rich006

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Installing brand new Dorman wheel cylinders on 10" rear drum brakes. FSM says 220 in-lbs torque, but the bolt head broke off before I got to that. I felt like I was overtorqueing it, but was going for the specification since I don't have a feel for how tight it really needs to be to function well. What am I doing wrong?
 
Wow, I'm not sure how much 220in'lbs is but obviously it's too much. I could be doing it wrong for a long time, but I just use tight!
 
220/12=18 ft lbs and is a heavy spec for 5/16 bolts into non-aluminum. I usually torque those a lot less, using my calibrated right hand.heehee

If the bolt jammed up in the threads before the head got tight, I would return the part as defective, as it will be a bear getting that broken part outta there. Might it have been a thread mismatch?
 
Only 18 lbs-ft. Doesn't seem all that drastic. I don't know the actual. Bad wrench? Cheap bolt?:dontknow:
 
using the cheap POS bolts that came with the kit - and following the directions - IF you can get the broken piece out without destroying the threads- go to your local hardware store and get some good bolts - minimum grade 5 - 8 is better - overkill is just enough here.
 
any chance you use foot pounds instead of inch pounds ?

if you did, you got of lucky

a buddy of mine did that once, only he snapped a spark plug in half, and we had to pull the head off :banghead:
 
Dorman wheel cylinders are a lot better than they used to be but like most Chinese auto parts ,the bolts are crap. In our shop ,we may use those brand cylinders but always put on grade 8 U.S. bolts . Seen this very thing happen too many times. Sometimes they give you the wrong length bolts and it bottoms out in the threads and the cylinder will never be tight against the backing plate. On another note here-when you go to bolt the wheel cylinder up,put a thin bead of RTV or permatex #1 or 2 around the hole in the backing plate where the cylinder goes through.That way when you bleed the brakes out,brake fluid won't run down and get inside the drum and consquentially on the brake shoes.
 
I usually go about half a grunt on those. You may have went a full grunt. Lol. I just go by feel. I had one strip out before and since it was a USA made one I drilled and helicoiled it to save it. I hate Chinese brake parts.
 
I did manage to get the broken piece out. The threads were fine; I guess it was just a cheapo bolt. Also, at one point I had the cylinder misaligned on the backing plate. That might have put excessive sideways force on the bolt head before I got the cylinder lined up correctly. I'll try again with better bolts. And I like the tip to use sealant between cylinder and backing plate.
 
A generic grade 5 (3 point) 5/16 course bolt is 17 ft lbs 17 X 12 gives you inch pounds so 204. I'm sure these charts vary a bit

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cool - bet that got your attention! LOL I always check the hardware quality with anything I buy - this is where "they" usually cut corners - especially if it says Made in China (or some such other crap) - have I spent and likely wasted $$ buying better hardware - -piece of mind is priceless.
rich006 said:
I did manage to get the broken piece out. The threads were fine; I guess it was just a cheapo bolt. Also, at one point I had the cylinder misaligned on the backing plate. That might have put excessive sideways force on the bolt head before I got the cylinder lined up correctly. I'll try again with better bolts. And I like the tip to use sealant between cylinder and backing plate.
Click to expand...
 
I should mention the head hex was 7/16 on this bolt. And the wrench I was using only has inch-pound markings.
 
In that case it's probably a 1/4" bolt not 5/16. That calls for only 8 ft lb or 96 inch lbs
 
LOL I've been reading from first post down and thinking all the while... Those are 1/4-20 bolts. Heck back in the mid to late 80s there were some GM products with no bolts there. only a pizzy lil steel clip held the rear wheel cylinder in place. If one should let the linings wear far enough, that wheel cylinder could rotate about 30 degree and spew it chunks in the drum. My point... 2 bolts only finger tight is better than some.
 
67Dart273 said:
In that case it's probably a 1/4" bolt not 5/16. That calls for only 8 ft lb or 96 inch lbs
Click to expand...

Bingo. It's 1/4 x 20. The bolt that didn't break is bent too, presumably from when I had the cylinder misaligned. Fortunately I found some bolts that size on an old wheel cyl I had lying around.
 
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