I went to Home Depot and bought some bolts, washers and nuts. I THINK they are 3/8 by an 1 1/2 inches. It was awhile ago so I could be totally off. I would take yours and compare them.


As far as the metal gasket goes, it is a pretty common part.


Amazon says it's this one

 

The exhaust shop that did mine said that the Y-pipe came with gaskets but that he knows that those gaskets are no good (either they don't fit right or they fail quickly, I forget what he said), so he specially-ordered the OEM gaskets.

We know for sure that OEM gaskets are known to fail after 10-13 years of winters on salted roads. I don't know if aftermarket gaskets fail even faster. OEM exhaust manifold gasket part # is 17173-50021. They should be about $20 each.

 

Well if you wanna know about the exhaust being replaced on the LS430 just ask me. :-(. I had everything from one of the exhaust manifolds replaced($90,ebay), both cats($300,RockAuto), y-pipe($150,Rockauto), and both mufflers(CL member). Manifold had a crack, Y-pipe had the usual rust issue, both mufflers had holes on the top side(used OEM replacements are starting to do the same). Now i mistakenly replaced both of my cats due to a faulty diagnosis. The price wasn't bad for both, i did the labor myself and still have the old ones. The gaskets that came with the y-pipe do not seal all that tight and is now starting to leak at that area. The exhaust has been my Achilles heel for the is car. Otherwise she's been great. This weekend will be full of patch work. I will seal up holes in the mufflers and replace the CAT-ypipe gaskets with either new oem's, aftermarkets heavy duty, or combination of gasket and permatex gasket maker stuff. and see how it works. Stayed tuned! The LS-exhaust chronicles continue.....

 

Hi Tom. For this job I'm going to try DiY. Just want to make sure I have all the parts before I start. I looked at a diagram on myLparts but didn't see the gaskets or bolts. I'll check out the link you sent. Thanks!

 

Yes the exhaust seems to be a weak spot on this car. I was shocked when they told me everything needs to be replaced and it was going to be 2500. Good luck on the repair hope it works out!

 

Thanks for the shop recommendations. I'll check those out!

 

So it's only been 4 months, since I posted this and since then I had to take out my Amazon Gaskets and replace them with the OEM ones. It turns out the aftermarket gaskets took out most of the sound but let exhaust pass by them under hard acceleration. This messed up the exhaust metering by the car's computer and made it think my cats were below efficiency.

Since I replaced the gaskets, I have not had the P0420 error.