Ack! Stripped a thread.

Topic: Ack! Stripped a thread. (Read 989 times) previous topic - next topic

Ack! Stripped a thread.

February 12, 2015, 09:28:37 pm

I'm finally getting around to replacing my waterpump and my thermostats. (6v92 has 2 thermostats) Got the pump in and had all 3 bolts finger tighten in. Wrenched in the top bolt till snug then the rear and when I started tightening the lower front bolt it just kept spinning. I backed the bolt out and the threads from the casing were wound around the threads on the bolt.

Boy did this break my spirit. The whole remove and replace has been pain!

Anyway now I'm wondering how I fix it. The threads on the bolt are 1 1/4" the threads pulled out are about 1/2". There looks like there is about 1/2" of threads left in the case. I have no idea if they have been compromised or not. I'm almost tempted to try another install and see if I can use the threads that are left. Thinking I could use my torque wrench to test if it would hold the pressure. Only problem with that is I have no idea how much torque the bolts should be at...

I did a quick search online for Helicoils and found a lot of them but none of the ones I found had anything close to the 1 1/4" depth I need. Most were only 1/2".

Any recommendations appreciated.

see ya
ken

Re: Ack! Stripped a thread.

Reply #1 – February 12, 2015, 09:46:48 pm

Thought I'd add a couple of more photos. First one is where the top bolt goes and 2nd is the casing the waterpump is mounted on. Also thought I'd add that it's aluminum.

see ya
ken

Re: Ack! Stripped a thread.

Reply #2 – February 12, 2015, 09:59:04 pm

Ken use the helicoil you dont need to worry about it not being as long as the threads on the bolt.Get a kit it will have the insert handle and the special tap.The correct drill size is on the tap. I have repaired many stripped threads over the years on my Harley's. You will drill the hole with the correct bit then insert the helicoil. Then you will take a punch and break off the insert tang.Then you can reassemble. It will be fine.

Re: Ack! Stripped a thread.

Reply #3 – February 12, 2015, 09:59:54 pm

Ken, I must be missing something but why do you need 1 1/4" of thread if the bolts only used what is in photo?
Did the bolt fit with the thread amount shown and if so that is all the thread depth you need.
JohnH

Re: Ack! Stripped a thread.

Reply #4 – February 12, 2015, 10:07:15 pm

If you are careful, and good, you can put two helicoils in the hole, one after the other. You will need some really small needle nose pliers to break off the second tab. I personally don't think it is necessary for the installation described, but possible.

Re: Ack! Stripped a thread.

Reply #5 – February 12, 2015, 10:16:27 pm

Bolts always have more thread then you use. One will be enough and will be just as strong as new. If you want it stronger
and have time insert the heicoil with red loctite but leave it for a day before you put the bolt into the helicoil

Re: Ack! Stripped a thread.

Reply #6 – February 12, 2015, 10:25:25 pm

From what I see you have enough threads to use a longer bolt. Just make sure you dont bottom out before it tightens down.
If you really want to do some engineering work check out this link.
Minimum Thread Engagement Equation and Calculator ISO | Engineers Edge

The old rule of thumb was the length of engagement is 1-1/2 times the diameter of the bolt.

Re: Ack! Stripped a thread.

Reply #7 – February 12, 2015, 10:31:41 pm

Ken,

Looks like you have good access and a reasonable amount of metal around the stripped hole.

I have repaired a LOT of 1968- early 1970 VW aluminum cases using threaded inserts (as I recall, we called them "case savers").

These threaded inserts are a LOT stronger than helicoils.

Knife Thread Inserts - Thread Insert - Grainger Industrial Supply

Re: Ack! Stripped a thread.

Reply #8 – February 12, 2015, 11:00:04 pm

Boy I learned a lot in this thread. But, could you not just drill out the old hole, run a tap in for one size larger and use the bigger bolt?

I sure hope you don't screw up again when you help me do the same job on my engine.

Re: Ack! Stripped a thread.

Reply #9 – February 12, 2015, 11:04:59 pm

Thanks everyone! Good solid advise by 6 people in an hour!

I think I'm going to give it another shot tomorrow using the threads that are left in the case. If that doesn't work I'll opt for the Helicoils. Didn't know I could stack them.

@John Haygarth The threaded portion of the case if fully threaded. If I thread the bolt in without the pump in place it doesn't bottom out until almost all of the thread is in the case. Maybe a 1/4" of threaded showing. Since the case is aluminum I assumed that more thread the better! Hope I read your comment right... The thread that is on the bolt is only about half of what is(was) in the case.

@Brett I'll check out the threaded inserts.

see ya
ken

Re: Ack! Stripped a thread.

Reply #10 – February 12, 2015, 11:07:20 pm

Yes, could drill and tap to larger diameter. But, the steel inserts are stronger and retain original bolt diameter (that will still go through the water pump).

We tried larger diameter head studs in those soft aluminum alloy VW blocks, but found the case savers/inserts to be a much better solution.

I really did not do much searching for them just now, but suspect you can find them in virtually every size/length/thread pattern. The ones we used on the VW's were what Caterpillar used on their off road equipment transmission cases.

Re: Ack! Stripped a thread.

Reply #11 – February 12, 2015, 11:12:54 pm

@Kent Speers That might work. I'd have to drill out the pump too for the new bolt to fit and the pump is about 3 inches thick.

see ya
ken

Re: Ack! Stripped a thread.

Reply #12 – February 12, 2015, 11:30:16 pm

We found time serts better than helicoil
++ TIME-SERT Threaded inserts for stripped threads, threaded inserts, thread...

Re: Ack! Stripped a thread.

Reply #13 – February 12, 2015, 11:58:05 pm

Ken,
Your repair is exactly what helicoils were made for - and one will do. The helicoil will hold stronger than the original hole. Many times inserts are installed into all the threaded holes on aluminum parts just avoid having them strip out later. If it were me I might just do the other two holes while I was at it. I think two helicoils in the same hole could cause unnecessary issues - it's not how they were designed to be used.
P.S. Mask-off the hole into the engine - last thing you need is shavings or a helicoil tang inside there.

Re: Ack! Stripped a thread.

Reply #14 – February 13, 2015, 12:18:29 am

These are new to me, but I really like the concept! I have used case savers on VW engines in the past, as well as a number of different approches. Stripped exhaust stud hole threads on these were so common, there was a veritable Eco system formed around solving the problem. I will be filing this method of thread repair away for future use.

Don

Quote from: Barry & Cindy – February 12, 2015, 11:30:16 pm

We found time serts better than helicoil

++ TIME-SERT Threaded inserts for stripped threads, threaded inserts, thread...

Re: Ack! Stripped a thread.

Reply #15 – February 13, 2015, 09:04:51 am

Bendix Besly Tap Company in S. Beloit, IL has a manual that recommends 2.5x the thread diameter bolt engagement length and a minimum of 55% of thread form when tapping in aluminum and the fastener/ bolt should fail before the thread in the hole.

Re: Ack! Stripped a thread.

Reply #16 – February 13, 2015, 09:49:48 am

Ken,
Are the threads that came out an old
Helicoil? Maybe it was repaired before.
I would use the repair method that removes the least amount of material.
Leave something for the next time.
Maybe use some anti seize compound on the bolts.
JD

Re: Ack! Stripped a thread.

Reply #17 – February 13, 2015, 10:03:55 am

Those would not be helicoil threads on bolt as H are steel.
In the big Diesel engines (3000 and up HP ) we used to build in England ( Napier Deltic Diesel engines) we only used helicoils and that was in Aluminum too. Yes must use Loctite, but first I would as mentioned check if you can drill next size or so up as that would work well if enough "meat" on pump body for it. There is not really any pressure in pump enough to cause a failure with thinner wall around new larger bolt after drilling it out.
My 2 cents worth.
JohnH

Re: Ack! Stripped a thread.

Reply #18 – February 13, 2015, 07:03:00 pm

Engineering wise, the standard to have full design strength of the bolted joint is to have 1 diameter of thread.

Re: Ack! Stripped a thread.

Reply #19 – February 13, 2015, 07:32:26 pm

I tried to install the waterpump using what was left to the threads on the lower bolt but just wasn't enough material there to cut it. The bolt tightened but I could feel them striping as I turned the wrench. Decided as much work as I had put into this I wasn't going to do it half assed! So I pulled the pump and installed Helicoils in both the upper and lower bolts. Went pretty easy just drilled them out, tapped em' and then installed the Helicoils with red loctite per Oldguy's advise. Letting them dry overnight before I install the pump. I did some careful measuring and turns out only about 3/4" of the bolt actually goes into the case. I only used one Helicoil on each thread.

The Time-Serts that Barry mentioned looked pretty cool but couldn't find any here in Phoenix and didn't want to wait for a delivery so went for the Helicoil. Napa had them in stock and less than half the price of the Time-Serts.

Thanks again for all the advise. I'll post again tomorrow on how it goes.

see ya
ken

Re: Ack! Stripped a thread.

Reply #20 – February 15, 2015, 11:52:05 am

The Helicoils worked great. Pump went in pretty easy. Have everything hooked up and the coolant back in. (no leaks so far) Just need to finish up reinstalling the exhaust heat wraps and will start it up and see if works! Plan is to move to a new campground on the 23rd. That will be the true test for coolant leaks.

Have friends visiting from Denver so won't get much done in the next couple of days but will report back when I know more.

Thanks again for the help!

see ya
ken

Re: Ack! Stripped a thread.

Reply #21 – February 16, 2015, 08:01:17 pm

If you have to remove the bolts later after using red locktite, remember to use a torch on the head of the bolt for a few seconds to heat it. They come off easily after that.

Pierce

Re: Ack! Stripped a thread.

Reply #22 – February 17, 2015, 12:53:10 am

Just realized you used the loctite on the Helicoils, not the bolt. Really stupid of me.

Have been traveling for a week.

Pierce

Re: Ack! Stripped a thread.

Reply #23 – February 17, 2015, 12:40:30 pm

Ken,
Another excellent post on a DIY repair and you probably saved quite a few bucks. I've also learned a lot and bookmarked this thread for future use as water pump problems and thermostats can malfunction at any time. Never had to use Helicoils but thanks to you and other members' experiences now I know how.

Were you having an overheating problem or a leaking water pump? The Pro-Link will give you coolant temp and mine shows about 5 to 10 degrees hotter than the dash gauge shows.

Thanks,

Jerry

Re: Ack! Stripped a thread.

Reply #24 – February 17, 2015, 02:42:25 pm

Jerry,

That's one of the few aluminum parts on the Detroit. Since they all look the same in silver, I took a magnet out and checked everything in the vicinity of the water pump. Yes, corrosion on the aluminum threads manages to pull some of the aluminum out on a lot of seldom removed fasteners. I have a Detroit maintenance CD that shows how to do it if anyone wants a copy. Think there may also be a site with PDFs of procedures.

Pierce

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