Losiracer2

I found out that my Y-pipe behind the heatshields is completely rotted and rusted out, confirmed at a muffler shop this afternoon, the pass side has a leak behind just after the flange on the pipe itself. They wanted $60 to fix that section, but I already am thinking the other side and the Y section where they both merge are going to be in just as bad of shape.

I found this Y-pipe on Ebay for a decent price made by MAC autoparts that has the heatshields and the provisions for the exhaust dampers. There were two of them on there the MAC autoparts one, and another made by DEC which looked pretty basic with no heatshields and damper provisions and the bends looked a bit crinkled?

MAC Autoparts $182.65
https://www.ebay.com/itm/Front-Y-pip...frcectupt=true

DEC $201.71
https://www.ebay.com/itm/Exhaust-Y-P...frcectupt=true

Which one would you recommend? or should I remove the heatshields on my OEM one and replace the pipe?

Amskeptic

I do not believe that that the pretty picture with the shields is what you are actually going to get. So many of these parts purveyors just scarf pretty pictures for their online catalogs ...
Call/email/online query, and make sure.
Colin
Colin

bradland

Some interesting info, post #8 and #9, in this thread- https://www.clublexus.com/forums/ls-...st-piping.html

YODAONE

Also have a 1999 LS400....

Very few exhaust systems last 20+ years.

I think ours are stainless steel.

The aftermarket are Aluminum and ?

What is Country of origin?

The original heat shield can be reused. Will require a skilled muffler technician and special.stainless tension straps to work this.

In addition to serving as heat shields, they also help retain and maintain exhaust temperature, thus exhaust velocity.

It is a mass produced Y-'pipe that has room for improvement, so perhaps you can find a stainless steel pipe fabrication shop to retain shields and pick up a few HP.

Losiracer2

Here's what my Y-pipe looks like beside my 299k mile 97' AZ, rust free y pipe that I was planning on swapping due to selling the car, but then realized only afterward, they don't interchange because of a different flange.

I'm planning on removing the heatshields to see the condition of the pipe underneath on my 99'. The resonator looks like its in good shape, as is the pipe after it.

99' on left, 97' on right

Losiracer2

So here's what I'm working with...would you recommend fixing this OEM Y pipe with new pipes? an exhaust shop estimated it would be about $130 (65 each side) or would you just buy a new one off eBay, which is an aftermarket part for $182 shipped?

YODAONE

Stainless steel.for fabricated exhaust or aftermarket system?

Will (or can). fabricator reuse exhaust shields?

Material thickness vs OEM?

Does fabricated or aftermarket system use correct flange with undercut for gasket to nestle?

Can fabricator form stainless pipe below the flanges instead of sharp cut welded (60 degree?) transition?

Losiracer2

So...I went to MRT Custom Exhaust in Plymouth, MI and he wanted to make a new Y pipe section out of 304 SS somewhere around $800, but having something like that would exceed the cost of a new OEM Lexus Y-pipe and I'm not looking to make power so I kindly declined. I spoke with the owner who was very friendly, who after researching about him, used to work with Ford and the 01' Mustang Bullitt program, interesting. Also the smallest diameter he works with is 2.5" mandrel bends, so that would be MUCH bigger than the initial pipe cross section but should gain a good amount of power. He also looked at the flanges and said he can't reproduce something like that, it would be a flat flange and regular gasket which is subpar I think. Didn't ask about the material wall thickness, but I did ask about keeping the rubber dampers. He would make a nice smooth pipe transition from the flange, but it might hang a bit lower and not have the OEM ground clearance.

https://www.shopmrt.com/MRT-Exhaust-Pieces-s/2116.htm

As much as the OEM heatshields deteriorated the pipe, I want to reuse them. Right now I tried this Mufflerweld made by JB Weld and slathered it on the sections of the pipe with holes after cleaning them up slightly with a 4.5" angle grinder to get a clean surface for it to stick to. We'll see if it works. It looks horrible, partly because I didn't have a putty tool to make it smooth, so I just used my glove to smooth it out and made sure to apply liberal amounts of it to the cracked sections.

I also went to Harbor Freight and picked up some 304 stainless cable ties for $5.50 which should be able to replace the factory clamps that were originally holding the shields on.

spuds

Enjoying watching your repair,keep it coming

jaaa

Be sure to use 'lots" of "Permatex ultra copper high temp rtv" on both sides of the gasket when you put it back together. That is ultimately what sealed my flanges, after trying other products.

YODAONE

Are you selling your LS400 soon?

A more durable solution is to weld a metal patch or collar vs "JB Weld"

Consider replacing the flanges ...must be correct material.and undercut for gasket.

Also, why not remove all.oxidation before reinstallation?

Losiracer2

I'll be keeping this one for a few years, as it only has 149k and the paint/body/interior are immaculate, just unfortunate the underside isn't.

I decided to leave some oxidation due to the coating that the pipe I believe originally had. I think Lexus added some anti corrosion powdered coating to the pipe for rust prevention as it feels slightly rough, but I could be wrong. I just ground away the sections that I was applying this muffler cement to so it would have a clean surface to adhere and followed up spraying with brake clean to get all contaminants off.

I figure this would buy me enough time to source a clean, good condition OEM pipe from the west coast or the south from someone parting an LS out. In the meantime, I was curious to see if this putty would hold up to the exhaust pressure and heating/cooling cycles. I think the heat shields play a role now of preventing rocks and pebbles from chipping away at this repair. I was also considering adding some exhaust heat wrap, stuff made by DEI comes to mind, to help contain this repair better and to act as a replacement for the insulation that's worn away over the decades.

Its a nice 60 degree day today, so I'll try reinstalling the Y-pipe this afternoon once I get home from work. The muffler cement should be fully cured by then (24 hrs time has elapsed).

KKOG

Here is my solution.

My car also had rotted out flanges to the cats. Too much rot to be able to seal well against the cats even with new gaskets.
Had to change these flanges and chose 2,5" v-band clamps.

It is only the middle and rear section of the oem exhaust that is made from stainless.

I also cleaned the exhaust and painted the exhaust tips black again as stock.

spuds

thats some nice work Kdog

Losiracer2

I got everything put back together this afternoon. I was glad that I didn't overdo it with the muffler cement, as the original heat shields still fit snugly over the pipe. I couldn't find anyone that had this specific type of insulation, so I just reused what I had and carefully placed it back where it was.

The stainless clamps work decently. I reused the Y-pipe OEM clamp though in the rear since it was a little tricky to get the harbor freight stainless clamp to stay in that part and I didn't trust that it would stay put over time.

I also bought some new nuts and bolts for the cat to Y-pipe connection since my old parts were an odd ball 13mm size that I wanted to get rid of. But the Dorman hardware is a 15mm size, though the nuts have teeth on the back so I didn't have to put a wrench on the other side when impacting them on.

All said and done, my car is sooo much quieter! The engine is a lot more responsive too and has more low-end torque when gently taking off from a stop. I don't have to hit the gas pedal as much when starting now so this should also improve my fuel economy. I can actually hear the engine revving a bit better too, as well as hearing the VVTi engage also in the 5k RPM range. I don't expect this repair to last forever, but I'm certainly happy with the results!