I had my cats replaced under warranty a couple of weeks ago.

This morning I went under to car to check to see if the transmission wasn't leaking fluid anywhere because I smelled something and found that the dealer may have used manifold studs to connect the cats to the manifold.

I have never replaced the cats myself so I don't know if this is how you are supposed to do it or did they use the studs instead of using regular bolts.

to my it looks like the nuts are missing, but I don't know .. never replaced these myself.

Thank for info from someone that has done this before.

 

It looks like it's missing the nuts to me as well

 

Yeah, do over!

 

hehhhhheIIf-`

 

Sorry for the previous meaningless post, my crappy wireless Insignia Keyboard is now in the trash.

If that hole in the cat flange was drilled and tapped (threaded), then it would be an acceptable method. Really hard to tell from your pictures, but to me they look tapped.

 

I changed my oem cats out for berks a few months ago and I remember nuts being on the studs and bolts. I would say they left them off. I think it's worth at least calling or going back to have them verify/correct.
As far as the odor goes new cats will take a few days to a couple weeks till it burns off.

 

Even if they're tapped I don't see evidence of a thread locker on it? The bolt will loosen up with out it due to all the vibration

 

We use a mixture of manifold studs with backing nuts and bolts, backing nuts with bolts, and nuts with bolts at the Toyota plant I work at. But to me it looks like you're missing a backing nut.

If they're going to use a manifold stud the backing nut should be welded on to the back of the manifold/cat.

I would take it back to the dealer and tell them you want all three bolts to be consistent. Install backing nuts and either use manifold studs with nuts or shoot a bolt through the backing nut. Regardless there needs to be a backing nut otherwise you will have a exhaust leak down the road.

 

the installation looks to be correct. you do not need another nut on the other side of the stud because it is threaded onto the exhaust manifold flange. in addition it is better to have a stud and nut configuration on the exhaust sys especially on the exhaust manifold, downpipe, or onto catalytic converter, the reasoning is bolts can break off at the head due to corrosion or vibration and stress from high heat.

 

I just installed my test pipes this summer so I would consider my knowledge about this fresh. The brown rusted bolt/nut on the left is the stud that is built into the stock header, that one seems to be fine. The lower and upper new looking bolts are definitely missing the nut, perhaps the dealer thought the hole was threaded but on my test pipes they definitely weren't.

 

Looks right to me. Both bolts in the photos looks the same. They just installed the other one backwards?

 

it is not backwards. one stud is threaded onto the flange on the catalytic convertor end. the other stud is threaded onto the flange of the exhaust manifold end.