Thread repair on intake manifold coolant port

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ericg75

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While cleaning up my intake manifold today I noticed the threads for the coolant port near the distributor are basically non-existant. Then I remembered that fitting leaking 25 years ago (truck has been sitting for the last 20 years) and paying a shadetree mechanic to fix it with JB weld. I'd prefer a little more permanent solution this go-round. Does anyone have experience with this port leaking and using a helicoil? I'm assuming this is an NPT fitting and NPT helicoils exist.
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Schurkey

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The first thing I'd try is to put a regular, plain ol' 1/2 NPT tap into that hole, run it in enough to clean the existing threads, and then go 1/4, 1/2, maybe 1 turn additional.

Screw in the stock fitting using Locktite 592 thread sealer.

Done.

NPT fittings almost never screw down "all the way" to the end of the male threads. You clean the existing threads, deepen them just a bit with the tap...and screw the male fitting in a little farther than usual using a high-quality, highly-effective sealer. I've done this many times on damaged NPT threads. Sometimes, you end up with the male threads going too deep into a shallow hole--grind off the last 1/8 inch or so, of the male threads.

IF (big IF) you've got such a damaged hole that the male threads go in all the way...sure, you might need to do something more drastic.
 

ericg75

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Update on the intake. So if you look at the original pictures you'll see a flat ring about 5 threads down in the hole which made no sense to me. The tap just rode on top of it and wouldn't engage. Turns out that was some kind of pipe dope that hardened and created a seat. It also filled most of the upper threads. I bent about 3 picks trying to get that stuff out and finally had to resort to a dremel to remove enough to start the tap which I eventually got to grab. Problem is, I think I sent her a little too hard. i was really focused on getting the pipe dope out and when I was satisfied I threaded the old fitting back in. You can see the result. I have my doubts it will seal. I know @Schurkey recommended loctite. Would teflon tape work on this fitting to maybe tighten things up or am I setting myself up for failure?
 

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PlayingWithTBI

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Are you trying to reuse the original quick connect fitting, or are you getting a replacement one? Dorman actually makes a good replacement which is real steel instead of aluminum/pop metal, or whatever GM originally used. The only thing is, they mislabeled the package, it does fit 87+ manifolds. :biggrin:

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I use PTFE pipe dope instead of teflon tape. If the fitting doesn't seat well in the tapered pipe threads then, maybe thread locker or something else.
 

Schurkey

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1. I bought a Dorman quick-coupler over 20 years ago. It's still in BEAUTIFUL condition. One of the few Dorman products that's actually better than OEM, not just cheaper than OEM. Very recommended.

2. I just hate thread tape. Sometimes that's "what you have to use", but I'm not convinced that this is one of those times.

3. Be aware that I recommended "Loctite" 592 THREAD SEALER. It's got PTFE, it works GREAT--enormously better than the cheaper "brush-top tub" of PTFE sealer. It might be helpful to use a primer/activator since the 592 thread sealer is anaerobic when used with "active" metals, and aluminum isn't "active".
www.amazon.com/gp/product/B0002KKTSG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

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All that said...yeah, you probably tapped too deeply. You've run out of threads on the coupler. MAYBE the Dorman product has a longer/bigger-diameter threaded section. Or maybe you have to put the coupler in with epoxy like the previous guy did.
 

alignman88

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Years ago I cracked the intake on my 99 Tahoe while trying to replace that leaky fitting. It was seized, broke off then cracked when I tried to EZ out it. What I did was take it to a local machine shop, with the replacement fitting, and they welded it up and re-tapped it. Worked without leaking until it was sold. Cheap fix and turned out to be the best answer for me.
 
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