replaced mixer elbow. However have 2 0ut of 4 stripped treads

[friscoron]

Hi all,

I replaced my Mixer elbow & exhaust extender in my Yanmar 3JH2E. However 2 out of 4 exhaust female treads are stripped in exhaust manifold.

My Question? What is the fix besides re- tapping with a bigger tread tap. Is there another fix besides re-tapping? I am assuming the exhaust manifold is aluminum.

Attached is photos of elbow and exhaust extender attached to exhaust manifold.

Lower right and upper left female threads are stripped inside exhaust manifold.

Any idears on this fix will most appreciative?
Thanks,
Ron

[kmacdonald]

Heli-Coil. https://www.stanleyengineeredfasteni...ands/heli-coil

Google heli-coil for videos on how to make the repair. They work great.

[Uncle Bob]

Originally Posted by friscoron

Hi all,

I replaced my Mixer elbow & exhaust extender in my Yanmar 3JH2E. However 2 out of 4 exhaust female treads are stripped in exhaust manifold.

My Question? What is the fix besides re- tapping with a bigger tread tap. Is there another fix besides re-tapping? I am assuming the exhaust manifold is aluminum.

Attached is photos of elbow and exhaust extender attached to exhaust manifold.

Lower right and upper left female threads are stripped inside exhaust manifold.

Any idears on this fix will most appreciative?
Thanks,
Ron

+1 on the helicoil and a nickel based anti-seize compound suitable for aluminium.

[sailah]

What they said, done right it's stronger than the original threads.

[Sailmonkey]

Again, Helicoil. Threads end up stronger than the aluminum

[Dymaxion]

See if you can rent/borrow a helicoil kit, the little inserts are cheap enough but the whole kit is pricey if only repairing a couple of holes. Take care following the original hole squarely, a tilted stud will block the manifold from slipping back on.

[Frankly]

What makes you think the exhaust manifold is made from aluminum, cast iron would be my guess. If you have really stripped out the studs where they thread into the end of the casting, might just drill, tap and oversize the studs per your original thinking . Drill out the extension holes if more clearance is needed. Helicoil is a great fix but oversize studs might be an easier fix.

[01kiwijohn]

2 Suggestions: 1) Yes, heli-coil is the only way to make a solid repair (apart from welding and re-tapping).
2) If you don't have a good, experienced, hand for feeling the approximate torque, then get a torque wrench and don't over tighten the bolts!! The manifold is cast iron but I have seen a number of people strip those threads.

[darrelweb]

That part of the exhaust system (part bolted to the exhaust manifold) plus the exhaust gas/water mixing chamber are cast iron. NO ALUMINUM HERE.

If the studs are stripped, then they need to be removed off the exhaust manifold, and new ones inserted. This can be difficult. You can not drill them out and keep the integrity of the casting. Very difficult to center on a hardened bolt and drill it out without damage to the manifold.

These studs can be removed with patience. Remove the manifolt extender. Soak or oil up studs with some sort of penetrating oil. Go to an automotive store and see if you can rent a stud removal tool that works off a long 3/8 or 1/2 inch drive.

If you can not find a stud removal tool, grind or file two flat spots on each side of the stud and use a new (sharp jaws) large vise grip pliers, put on very tight.

The very worst thing you may have to do is remove the exhaust manifold and have a machine shop replace the studs.

Never used heli coils. The studs/nuts will be a metric fine thread.

The old studs should come out. You can also put some heat (small propane torch) in the area around the stud on the manifold to help expand the casting.

My two cents worth. I have a Yanmar engine too and have had to replace studs also. Im also a mechanic.
Darrel

[friscoron]

Thanks all,

I check into Heli-coil repair at website provided by Kmacdonald.

https://www.stanleyengineeredfasteni...ands/heli-coil

Just for everybody's understanding.

1) Studs are not seized or stripped (they come out exhaust manifold). Female threads in exhaust manifold are stripped.

2) I am not guilty of over tightening bolts. I learned that lesson 42 years ago when I was a teen. snug em, don't over hug em! Prior boat owner is guilty.
I'm Innocent! LOL

[a64pilot]

I would helicoil, and blue loctite the helicoil itself in, and anti seize between the stud and the helicoil, you want the helicoil to stay and the stud to come out next time.
There are arguably better inserts than a helicoil, but a helicoil ought to be just fine here.

[Lepke]

There are other similar brands, helicoil is just one of them. Helicoil is like a coiled spring and can be damaged easier than the ones that are slightly bigger around, and the threads come as one solid piece.

[friscoron]

I'm assuming Loctite or other epoxy type fix is out of the question. Because the maximum heat of the epoxy fix is 300 degrees F. And the exhaust manifold and extender is probably hotter that 300 degrees F. Just asking LOL

[kmacdonald]

Originally Posted by friscoron

I'm assuming Loctite or other epoxy type fix is out of the question. Because the maximum heat of the epoxy fix is 300 degrees F. And the exhaust manifold and extender is probably hotter that 300 degrees F. Just asking LOL

Sounds like you don't want to tackle the job yourself. Take the exhaust manifold off and take it to a mechanic or machine shop and have it fixed. Might end up cheaper than the heli-coil and tools to do it yourself.
While you have it off, soak in in Rydlyme. http://www.apexengineeringproducts.c...RoCFg4QAvD_BwE

[friscoron]

I bought the Heli-coil kit. size. M-8, 1.25. It was $43 out the door at O'Reilly auto parts. Looks like a piece of cake. Thanks all.