After all of that dealer repair hassle I went through last month I thought everything was fixed on my Disco and then I started hearing the obvious sound of an exhaust leak on the passenger side where the exhaust pipe flange attaches to the manifold, mostly when the engine is first started and cold; as the parts heat up and expand I hear it less but it is still there. I got underneath my rig and put a socket wrench on the nuts at the flange where the Y pipe connects to the manifold and found that the outer side stud nut just spins without tightening and I could tell that the stud is what is spinning, not just the nut. It appears from the bottom to be a new stud and nut but from the top side when you look at the manifold you can see the rusted old stud which leads me to believe that the stud broke off during the dealer repair attempt and some of it is still in the threaded part of the manifold flange. I'm thinking that the new stud stripped the manifold threads because it may not go in very far.

I took my rig back to the dealer since they were supposed to have fixed all this. The technician confirmed what I suspected and said the threads in the manifold lower flange on the outside stud were stripped so the stud was just turning and thus not tightening up. The service manager said the only option was for me to replace the entire manifold with a new one ($$$$) and that this was not a warranty repair. So I thanked them and left.

Here are what I think my options are:

1. Carefully drill out the remainder of the stud in the manifold, clean up the threads of any remaining metal particles with the correct tap and see if the stud can't get a good grip on the remaining threads and reassemble.

2. Drill out the bolt and enlarge the hole and re-tap it with the next size up in diameter stud. Install stud and reassemble using the appropriate nut. There appears to be plenty of metal to do this option.

3, Drill the hole out as in #2 and just insert a grade 8 bolt instead of a stud and slap a washer and nut on the other side and tighten it up.

Any thoughts or suggestions?

 

If it were me I would take it to an old timer mechanic/machinist that I go to when I am in beyond my skill level. He would charge me $40 to drill and re-tap it and send me on my way.

 

i would either take it a small shop machinist or JB weld it

 

my choice for quick fix is your option #3. You could drill it out--install a heli-coil--reinstall a stud & nut , but thats more work & $ for the same result. Yup, drill straight through and install a good bolt...done

 

#3
Also, depending on which one it is, you can get little c-clamp manifold-to-header pipe bodges that you just clamp on. Like I said, it's a bodge, but they will last a long time. I've seen them still in place after 10 years.

 

Are dealership mechanics not trained to improvise? I guess not because the dealership makes more money if they sell parts and unnecessary labor!!!

I just looked at the flange in question and found that the stud was gone and only about 1/3 of the threads in the manifold side were stripped out. I had a few extra new manifold studs and nuts laying around so I got to thinking that normally the shorter threaded section is what you screw into the hole and the longer section is what the nut attaches to. So I did a little measuring and sure enough, if I reversed the stud the longer section would screw into the remaining threads in the manifold and then the nut could be put on to cinch it tight.

I used a 8mm x 1.25 tap to clean up the rusty threads and applied a little machine oil. I put the nut on and tightened it up against the non threaded section. I got under the truck with a socket and long extenstion and tightened the sucker up! NO MORE EXHAUST LEAK!

And the service manager would have loved to sell me a new manifold and instillation!

 

CONGRATS ! feels good to win one now and then doesn't it !!


(oh, by the way, that'll be $1200.00 please)

 

Do you know right off hand what size these nuts are?

 

The flange stud is an 8 x 1.25 mm size thread. Hope that helps!

 

thanks so much. I think we can find it from here. THanks again.