I overtorqued!!!!! - PeachParts Mercedes-Benz Forum

nestorb98 · #1 01-24-2015, 03:53 PM

Mea culpa!

I over torqued and broke a camshaft bearing bracket bolt after succesfully replacing eight valve stem seals in my 190e 2.3.

I knew I shouldn't have gone that far but all the other bolts clicked at the proper torque setting...this one didn't and I just turned it one-more-time and "snap"...and everything else was going soooooogood!

My thoughts are:

#1. Take the head off and take to machine shop.

#2. Three bolts could hold the bracket down...75% how bad could that be?

#3. Find a device that can extract the broken bolt out of the head and get a new bolt.

#4. Wait for one of you guys to show me an alternate way.

#5. Buy a bottle of Famous Grouse and start drinkin' again.

Thanks in advance for your kind words.

pwogaman · #2 01-24-2015, 04:24 PM

#3 https://www.youtube.com/watch?v=lYdYc6hdIao

https://www.youtube.com/watch?v=A7ftJTUbp4o

mpolli · #3 01-24-2015, 04:26 PM

Where on the bolt did it break? If you remove the bracket will there be a piece of the bolt sticking up? Then you could just use pliers. Otherwise #3 is what I would probably try. Do you know why the bolt broke? Bad torque wrench? Maybe it was already fractured by someone else?

slk230red · #4 01-24-2015, 05:48 PM

Quote:

Originally Posted by mpolli

Where on the bolt did it break?

If you remove the bracket will there be a piece of the bolt sticking up? Then you could just use pliers. That was my thought.

Otherwise #3 is what I would probably try. I agree.

Do you know why the bolt broke?

Bad torque wrench? Yes, and if so, you might want to re-torque all of the bolts.

Maybe it was already fractured by someone else?

I agree with mpolli, you should be able to get the remaining stud out.

Good luck

Skippy · #5 01-24-2015, 06:38 PM

#3. Drill out, use extractor. You may have to re-tap the hole to the next bigger size or use a helicoil. Annoying and time consuming, but not really difficult.

nestorb98 · #6 01-24-2015, 07:40 PM

Thank you for your answers...it did not occur to me that it would be that easy. The bolt broke three threads in and so when I removed the cam bracket, there was the very top of the bolt bottom. I was able to remove it with vise grips.
Now off to the bolt store on monday, all is well!

This is a great forum!

pwogaman · #7 01-24-2015, 07:45 PM

Great!

lsmalley · #8 01-25-2015, 12:23 AM

Blessing in disguise. The bolt was probably already weak poor cracked which is good you broke it when you did. Had it broken when everything was back together you wouldn't have noticed it until that broken bolt caused a second bolt to weaken and then break also which would've surely caused some serious damage

Hirnbeiss · #9 01-25-2015, 09:35 AM

consider tapping the threads first.

Stretch · #10 01-25-2015, 01:50 PM

Quote:

Originally Posted by nestorb98

Mea culpa!

I over torqued and broke a camshaft bearing bracket bolt after succesfully replacing eight valve stem seals in my 190e 2.3.

...

= M102 engine =>

FSM chapter is here =>

http://www.startekinfo.com/StarTek/outside/11832/Resources/201Create/PDF/30005.pdf

Quote:

Originally Posted by nestorb98

...The bolt broke three threads in and so when I removed the cam bracket, there was the very top of the bolt bottom. I was able to remove it with vise grips.
...

The specification for fitting the rocker arm / camshaft caps is only 20Nm (see link for FSM above)

The bolts are about M8 if I remember correctly - I don't see how on earth you managed to snap a steel bolt in an aluminium alloy head - congratulations (!) - I'd have expected the aluminium alloy head to die first.

What torque setting were you using?

20Nm == 14.75 ft lbs

oldtrucker · #11 01-25-2015, 04:03 PM

I think, the scale of measure is most likely ft/lbs and it is easy to forget this, athough some wrenches do have a Nm scale on the other side.

nestorb98 · #12 01-26-2015, 12:41 AM

Here's the thing...the Haynes Mercedes Benz 190 book states that the torque setting for camshaft bearing bracket bolts is 15 foot/pounds.

During the installation all the bolts made the torque wrench click at 15 ft/lbs except the one that broke. When I heard the snap, I almost threw in the towel because I thought that the bottom of the bolt was going to be deep in the threaded area. Fortunately and after reading the posts here I realized that on removing the bracket i would be closer to where it snapped and I was...enough that the vise grips just clamped on the bottom of the bolt and took it right out!

So my new concern is...if I put a new bolt in there, have the threads been compromised in any way?

So Stretch...I don't know what to tell you.

Stretch · #13 01-26-2015, 06:30 AM

Quote:

Originally Posted by nestorb98

Here's the thing...the Haynes Mercedes Benz 190 book states that the torque setting for camshaft bearing bracket bolts is 15 foot/pounds.

During the installation all the bolts made the torque wrench click at 15 ft/lbs except the one that broke. When I heard the snap, I almost threw in the towel because I thought that the bottom of the bolt was going to be deep in the threaded area. Fortunately and after reading the posts here I realized that on removing the bracket i would be closer to where it snapped and I was...enough that the vise grips just clamped on the bottom of the bolt and took it right out!

So my new concern is...if I put a new bolt in there, have the threads been compromised in any way?

So Stretch...I don't know what to tell you.

It is possible that the threads have been compromised.

Get a new bolt (I'd personally prefer one from the dealer not from the local hardware shop) and try fitting the bolt on its own - remove the bolt and look for any evidence of swarf or metal muck on the threads.

If there's no evidence of thread damage then you should be good.

Test your torque wrench =>

Try something like this How to Calibrate a Torque Wrench (with Pictures) - wikiHow