Timing Belt Tensioner stripped

TKB4 · **Posted:** Mon Jun 05, 2017 2:09 am

Well I got weeks kit on and timing belt changed this weekend and after some headache getting retimed correctly all was good. I went to re tension the timing belt after confirming correct timing and rotating crank many times and:

THE TENSIONER POPPED OUT !!!!

Imagine my surprise to find that PO had stripped the tensioner and had put helicoil in . The helicoil popped out and kinda hung down from the coil.

Now, I had extra tensioning bolt on hand. Good thing since the end threads on original bolt kinda flattened where they screwed into the helicoil.

Question: Is there a better way to fix this other than another helicoil?

A mechanic friend tells me he thinks it may not have been installed well and he would redo it using copious locktite and let it set overnight to cure before use. I also noted the hole isn't all that deep and initial portion is through rear timing cover . Hopefully rest is at least in iron.

If there is room I suppose an insert could be threaded in to receive the bolt. Part of the problem is the bolt cannot be replaced with larger diameter bolt because it goes through tensioner and acts as its pivot .

Would replacement of the bolt with same size stud be better ( in helicoil or whatever) I tend to think that since tensioner had to be removed to be replaced and you need to loosen the tensioner to retweak tension after few rotations of engine that a stud may be better. I believe the helicaoil may not do well when bolt has to be removed. I had this jeep for 4,000 miles so it lasted at least that long with the helicoil.

Anyone know if there is enough clearance to drill hole deeper?

Has anyone else had to deal with this?

Thanks

papaindigo · **Posted:** Mon Jun 05, 2017 7:03 am

That helicoil is OEM. Just replace and move on although IIRC someone on the forum posted something like a stud setup which you may or may not be able to locate.

flash7210 · **Posted:** Mon Jun 05, 2017 7:56 am

When my helicoil stripped out, I installed a new coil and used a stud.
I went to home depot, found a bolt of good length and correct thread, and cut the head off.
Then I threaded it into the inner timing cover and got it as tight as possible, put the tensioner on with nut, and torqued it to spec.
This way the stud will stay tight in the cover and never have to be pulled out.

TKB4 · **Posted:** Tue Jun 06, 2017 11:19 am

I can't believe that in the thousands of pages of posts I have read that I never new the tensioner had a helicoil from the factory. What a engineering mistake!!

Thanks for replies and info at least now I am not too worried about replacement working.

I think I will go with the stud, Just seems to make more sense.

papaindigo · **Posted:** Tue Jun 06, 2017 11:29 am

The cover that the tensioner bolt goes into is aluminum and I suspect the amount of torque used to tighten that bolt would be marginal with aluminum threads. Helicoil in aluminum will work with more toque.

apardo001 · **Posted:** Tue Jun 06, 2017 11:46 am

Go with the Stud, simple long term solution.

My tensioner fell off while on the road, 2 weeks after replacing the timing belt, lucky to avoid valve damage :mrgreen:

papaindigo · **Posted:** Tue Jun 06, 2017 12:02 pm

I'll defer to others that may know more but the stud sounds like a good idea although I'd be inclined to use red Locktite when seating it which should keep it in place permanently as "red" requires significant heat to be applied before it lets go.

TKB4 · **Posted:** Thu Jun 08, 2017 7:28 pm

By the engineering mistake I meant a mistake not having a design with the bolt threaded into cast iron, I did find threaded insert that would probably work but likely have to drill larger hole than the 21/64 needed for the helicoil which of course had already been drilled and threaded by the factory :furious:

I just made sure no helioil left in hole with the help of trusty modern gadget called a cell phone camera :lol:

and cleaned up the thread with tool for helioil meant to thread it put the red loctite on helicoil and threaded it in with the special tool let it cure about 30 minutes after threading stud in to make sure everything grabbing good and clean. Then put the red loctite on the stud put it in appropriate depth making sure the outer timing cover would fit on. and let that sit overnight.

I used a 8mm x 1.25 threaded stud (the same as original tensioner bolt ) that I am pretty sure was 65mm long or about 5mm longer than head on the original bolt and it just touches the outer timing cover at the depth i inserted it . Maybe that will keep it from just falling out!

It worked, at least so far. Stud, nuts and lock washer total about $9 here at local supply place immediately available. I bought 2 nuts to use to screw it in tight against each other with lock washer in between. Could probably use the stud or a new tensioner bolt to clean up the thread and that would be the total cost plus helicoi but you wouldn't need the helicoil kit.

Now I wonder why if the factory was going to put helicoil in why they didn't use a stud also. ? maybe because they didn't want to be liable after 100k miles if it came out?

Either way glad its done and working.

thermorex · **Posted:** Fri Jun 09, 2017 11:09 pm

Timesert. Best there is for things like this.

WWDiesel · **Posted:** Sat Jun 10, 2017 6:56 am

Good for you! Your description sounds just like what I would have done. Helicoils when installed properly are much stronger than the metal they are threaded into...
Your fix should be good to go from now on... :wink:

TKB4 · **Posted:** Sat Jun 10, 2017 11:23 am

I think I am going to prophylactically install a stud each time i do a timing belt till each li done. Fixing to do TB ARP Studs and Possibly Head Gasket Rockers Valves if necessary. Might do rockers anyway.

Might need to do search or start new thread but does anyone know if any of the new style rockers that ID parts sells that are supposed to oil better have failed as designed to with a Timing belt failure yet? Just wondering if they in reality fail as designed to prevent valve ,piston damage etc. Doubt anyone that would know enough to install them or had a failure would have enough miles etc since then and probably a new TB at same time to have any experience with it. :!:

Dennis MacGyver · **Posted:** Fri Jul 12, 2019 4:17 am

To add to a possible solution, I located these, seems like a good fit because this type of "helicoil" would have more aluminum surface to grab onto since it is a larger external diameter and still maintaining the 8x1.25 mm standard bolt requirement. Notice it can be bought on Amazon.

http://www.timesert.com/html/bigsert.html

https://www.amazon.com/dp/B003QAZUIS/re ... EWWITZXTMB

TKB4 · **Posted:** Sat Jul 13, 2019 1:26 am

That looks good to me, just more expensive. Similar to the Timesert Thermorex recommended but maybe larger diameter. Maybe the extra cost is worth the extra "insurance". Either way should solve your problem. Thats the beauty of this site everyone doesn't have to learn from scratch but that doesn't mean you can't put a little twist on it. :BANANA:

Timing Belt Tensioner stripped

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