Stripped Bung
 

So I installed a new gasket between the UP and ex. man. today. It went fairly well (the exhaust leak is fixed) except when I was reinstalling my EGT probe, I think I tightened it too much. Everything was good and tight but I guess I gave it just a touch too much torque, because it started to spin more easily when I gave it that last 1/4 turn. :unamused: So I just stopped and left it.

I figured that it would leak on my test drive but it didn't. I got into full boost a few times and it sounds perfect.

I'm tempted to just leave it but I feel like that could bite me later. What should I do? I think I've heard that the best thing to do would be to tap the hole to the next size and put a hilacoil or something like that in it to restore it. Is that right?

This is the DIY I followed like 4 years ago when I originally did the install except I did the passenger side for some reason: http://www.scoobymods.com/forums/mod...=egt+probe+tap He suggests that you can check for a leak with soap and water. I suppose I could try that, but I'd think I would hear it under boost if it leaked.

The tap I used is labeled as "1/8 27 Pipe". The gauge (and probe, I'm assuming) are Omori. The gauge hasn't even worked right for a while but I had just emailed JspecTuning on Friday afternoon asking how much a replacement probe would cost, as I believe that may be what's causing the gauge to read incorrectly.

I'm tempted just to tap it to the next largest size and put a short bolt into it since the gauge is most useful after a tune or maybe at the track, things I have no plans to pursue any time soon. Thoughts?

is pipe thread what most exhausts bungs use? doesn't seem right to me (although I'm wrong most of the time).

I seem to remember that it was recommended for my application and it seemed perfect before today.

Maybe I should use this opportunity to get PP&C'd OEM headers.

Pull it out, get it fixed by having a peice of metal cut to match and welded in. and put your probe on the otherside this time? or you could place it back in the same spot it is now, though it would be harder to cut though. you could even just get a small bead of metal welded in around it and retap . :?:

You could try cleaning up the threads inside the bung with the tap and then the threads on the sensor with a diamond file or die. If you're sure its not leaking just leave it alone.
Did you do the standard leak test?
-stuff the tailpipe with bananas or a potato (bananas might work better with your yellow car).
-start your car
-spray soapy water on your "bung" and see if it bubbles/leaks gas

:lol: I like the way you think Van.

It'd be great if I could simply add a layer of teflon tape but obviously I'd need something much more heat resistant. Any other solution requires that I remove the header to avoid getting metal shavings into the turbo.

Well, a short bolt that's a touch wider than the probe or welding it shut are options too I imagine.

Personally, I wouldn't do anything until you can hear a leak or your EGT readings get wacky.

My EGT gauge displays nonsense and has for a while. Part of the reason for that was a faulty vampire connector that I replaced but I think the last time I had the probe out, I damaged it because although the needle doesn't jump around to the beat of the music I play like it used to, it still reads way low and intermittently reads zero. That's why I emailed to get a quote on a replacement for the probe on Friday. I could really live without the gauge, I think.

Check that the gauge is getting a good ground and a filtered +12. More aftermarket gauge problems are due to incorrect wiring than anything else. They, just like ECU sensors, have to share a good reference ground and regulated power.

It uses ground and hot from the OEM clock wiring, just like my Omori electronic boost gauge which has always worked perfectly. I guess the EGT may just be more sensitive. But I really don't value the EGT gauge nearly as much any more. It'd be cool to fix it, but there's too much uncertainty regarding the real issue and it's just not worth it to me anymore.

I've got it all taken apart again. Soapy water revealed that it was leaking. I have confirmed that the threads I cut into the ex. man. are what stripped. I really wish I had a slightly oversized bolt I could just plug it with and be done.

Do you have a full-on bung welded in there or just a tapped header? If you don't already have a bung welded on the header, you can just drill out the hole a little and get a bung welded over the top of it.

If you do already have a bung on it, you could have it grinded off and a new one welded on. I wouldn't try to heal-a-coil an EGT probe... lots of those heal-a-coil solutions use the equivalent of JB-weld. A full-on repair insert might work, but even that's going to add yet another layer of metal that has to heat cycle over and over w/o loosening up.

...

It's just tapped. Can you just weld in a bung? Jeremy of Crucial Racing posted that you have to heat up cast iron to 500*F before you can weld on it. I didn't think that helacoil required any JB Weld type stuff. I actually considered JB Weld, but at least the "Quick" version I have says it's only good to 300*F. No good.

In the interest of saving me from typing two updates, here's the latest update I just typed on WRXFanatics:

http://www.wrxfanatics.com/index.php?showtopic=60022

When I had a shop weld a bung to my old headers, they just welded it on... I'm pretty sure there was no oven involved.

Also, if the EGT probe uses the bung as a ground, there's a chance your readings are crappy because of the loose threading.

If you really want this taken care of once and for all, get a bung welded on, and get a stainless plug for it so you can run w/o the EGT probe if you need to.

Yah, it seems like if you had to heat the pipe to 500, you could just do so with a blow torch. It's on the wrong side so if it can be welded, I just want it welded shut.

You don't have to preheat cast iron, but it's definitely helpful. And if you preheat a part, you want to do it uniformly.. not just focus a blowtorch flame on the spot you're gonna weld.

http://www.lincolnelectric.com/knowl...ronpreheat.asp

Would you recommend that I tap it for a bolt and use a bolt to plug it instead?

I'd rather not make a specific repair recommendation like that, since I don't own one of these cars and I've never even seen the part in question.

Well, if it helps, it's a heavy cast iron OEM exhaust manifold and the probe regularly saw temps upwards of 1500*F. The hole that needs filling is tapped into a casting button (small raised bump on the surface) and it's nowhere near any existing creases or welds.

In cast, I'd try a NPT plug of the right size. they are often slightly tapered and might bite. if not, tap one size larger and plug rather than welding.

Yeah, I think threading in a plug is probably the better idea.

I held one of the correct size (if the threads weren't stripped) in my hand at True Value yesterday but figured it'd be useless.

I called R&E and they said they'd be able to fix me up with a tap and a bolt for $20-30. I think I'd rather buy a tap on the cheap and then go there to grab the bolt to plug it.

Any recommendations for a single tap? I'm thinking Sears since I could grab a pair of shorts while I'm at the mall anyway, and that's where I got the first tap years ago.

Shit, for $12.99 maybe I should just grab this set: http://www.harborfreight.com/cpi/cta...emnumber=39384

Oh, and Jspectuning says Omori went out of business and they were taken over by Omori USA and they no longer support the "old style" gauges. The new probes may work if spliced in but no guarantee. He said he'd sell one to me at cost if I wanted to try it ($50 shipped) but this just enforces my desire to say fuck the gauge.

I have that or a similar HF kit in both English and metric. You are welcome to borrow it. And NPT plugs can be had at lowes, Home Depot.

Wow, the only thing cheaper than buying that set would be borrowing it. :lol:



Can I stop by after work? :oops:

Sure

Taps and Dies are one of those things where the cheap stuff isn't as good as the good stuff. I'd spend the $30 if I were in your spot Cody.

Hmm. Dean, do you feel confident that the taps in that set are good enough to get the job done.? I don't think either of us want me to ruin one of your taps. I'll be stuck and feel like I need to buy you a replacement which will cost more than the entire set. :(

Hmmm, but I don't want to be caught agreeing with Kevin. :P

The Harbour Freight NPT tap worked fine for my EGT install in OEM headers, FWIW.

And that's a finer thread than the thead of the tap I'll end up using so it should really be fine. I even have cutting oil.

Let's put this plan on hold for now, please. My co-worker thinks he has a tap set at home. He's going to check and bring it in tomorrow if he can find it.

90+% sure the correct tap size is 1/8"-NPT (or 1/8"-BSPT - "metric" version with same thread pitch but different thread angle).

90+% sure I have a machine-shop quality tap if you need one.

90+% sure that nobody can be 100% sure of anything (at least not without walking down to the garage and digging to find out). :D

Ha!

Thanks but I already have the tap that's the correct size for the probe, but the hole is stripped completely. All I need is a tap for an appropriately larger size hole and a very short bolt that matches the tap, a washer maybe (?), and the right drill bit, which I may have.

I'm going to take the original tap to R&E tomorrow at lunch tomorrow. The guy I spoke to said he could use it to determine the best diameter of bolt and sell it and the tap to me. Hopefully I'll have the tap from my co-worker by then as well as the right drill bit at home already.

Alright, I think R&E set me up right with a short grade 8 bolt (1" long I think), a grade 8 washer (to hopefully help seal the bolt head to the header, and a nut to re-true the theads after I shorten the bolt to about 1/2". I would have preferred to stick with pipe thread, but he didn't have pipe thread plugs in an apropriately larger size in grade 8.

I have the correct size tap thanks to my coworker (and it's Craftsman so I don't have to worry if I damage it). The drill bit I have is a 1/64th of an inch too narrow, but I think that's fine.

Anyone see any issue with any of this before I go at it?

Thanks to the 3 of you that offered me taps. :)

Sounds like a good plan. I would measure the depth of the hole before cutting down the bolt though- no sense leaving it longer or shorter than the material you're filling.

Good point. I'll error on the side of too long but try to get it flush. I honestly doubt that half an inch of bolt sticking out would cause more resistance than the probe that's currently sticking more than halfway through the pipe (though much thinner than the bolt) but I definitely want to cut the bolt shorter just to keep efficiency as high as possible.

I would have just gotten it welded. I've had both a hole welded shut and a bung welded on the stock cast headers, and never had an issue, nor did the welder complain about doing the job. Had it done years ago at the muffler shop next door to Indy Auto (I think that's McVay's?).

It probably would have cost you less than the price of that nut and bolt to get the hole closed, and it would have been less work just to take the header off and bring it to the shop than all the non-sense w/ cutting bolts, tapping holes, trying to get a washer to seal, etc.

Well, the bolt, washer and nut came to a whopping $3.22.

I'm certainly open to suggestions. I just called Alex's friend Ansel since he's an acomplished welder and he said he'd just do exactly what I'm doing, though Alex and I think he was probably just trying to avoid me asking him to weld it for free (:P), which wouldn't have happened.

I'd honestly rather get it welded so I don't have to worry about the bolt coming loose or me re-stripping the new larger hole. I'll call McVay's if I can find them.

My big concern is that w/o NPT threading, you're never going to get that bolt tight enough in the hand-tapped threaded cast iron to have a washer seal from exhaust leaks. Even if you do get it tight initially, the expansion difference between cast iron and grade 8 stainless will eventually loosen that bolt.

There's a real reason EGT probes use pipe-thread. I'd pay the $15 or whatever it costs to get the hole welded... actually, I'd pay the $25 or whatever to get a real bung welded on there and then just put the correct plug in the hole if I wasn't running the EGT sensor and leave myself the option of putting an EGT in there painlessly in the future.

Just spoke to Rusty at C&C and he said he doesn't know anyone who can weld cast iron but he said they tap and plug manifolds with bolts all day long. I think it'll be fine. It's not like the car's going to explode if the bolt backs out or starts leaking. I can check it without pulling the heat shield off too since there's a hole in the heat shield for the probe wire.

It's on the wrong manifold so I want to plug it permantently for sure. Maybe I should have gone with the next size NPT and a plug but the plug was an unspecified metal and the only metal I know gets used with exhaust manifold heat is grade 8.

Hrm... I never thought cast iron was that bad to weld that "nobody" in Reno can do it.

Also, I doubt that Rusty's plugging headers that see 1750 deg F temps and pressures like our turbo headers see. On a N/A motor, a tiny leak in the headers would probably go unnoticed... on our cars they become "rape whistles" as you so eloquently put it. :lol:

But hell, give it a shot. Worst case scenario is you've just got a slightly bigger hole to patch up later.

Is this the muffler shop you went to, Scott?

http://maps.google.com/maps?hl=en&ie...A&iwd=1&dtab=2

Rusty didn't say nobody in Reno could do it, just that he didn't know of anyone who could. But I really want to call the shop that you had your headers welded at.

:lol: Yep.

But who are you gonna believe, me, or some SRT-4 owner w/ a blown up car posting on google maps? WTF is a "blown respirator" anyway? Is that grandma's oxygen tank?

Anyway, I got my headers welded there back in 2002 or so. In fact, I believe Dean still has those headers on his car, unless he didn't swap the headers over to his STi when he sold his WRX.

Ha! I didn't know the link was going to pull up the review. I'll give 'em a call.

Spoke to a real nice guy at McVay's and he actually suggested that what I plan to do is the best solution. I said wow, thanks, but if it does back out or leak or whatever, can you guys weld cast iron and he said they might be able to wire weld it on the vehicle, but he said, "after a couple heat cycles, that grade 8 bolt is going to practically weld into the hole with the swelling and contraction of the metal."

:huh:

So now I have Rusty, Ansel, and some nice muffler shop guy telling me I'm doing the right thing. Guess it's worth a try.

Oh, Dean and Kevin too. :P

:P

Oh you want on the list too? I'll see what I can do. :P