This could save you $1000

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Check engine light came on in my 2001 LS 430. Investigation found a small exhaust leak in the "Y" pipe behind the engine. Checked dealers for the best price on a "Y" pipe and found the best I could do was $963.00. Decided to see if some repair could be visited on the pipe.
Found that the "heat shield" that encases the pipe after the O2 sensor doesn't have a clamp holding it firm at the forward end and the vibration of the "heat shield" against the exhaust pipe had worn a hole in the pipe. I found both sides of the "Y" pipe worn from the "heat shield".
My solution, after welding the pipe, was to use a couple of gear clamps to hold the forward part of the "heat shield" from vibrating against the exhaust pipe.
Two gear clamps sure beats $1000.00
Don

 

[JBrady]

Wow, that is certainly an unusual failure.

In the USA the Federal manufacturers emission equipment warranty is 8 years or 80k miles. Not sure about Canada. The exhaust prior to the O2 sensor(s) would probably be covered.

If no coverage is available your repair is suggested rather than replacing the Y pipe and center cat.

 

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This could save you $1000.

In an effort to better explain the problem with the heat shield, I took some pictures that you can see here;

http://picasaweb.google.com/donjohnson123/LexusExhaust?authkey=0KHuUdzkHGg

You can clearly see the problem and where the shield rubs on the pipe. This happens on both sides of the Y pipe. At first I was convinced that the car was missing 2 clamps but on checking the diagrams in the service manual, I found that there wasn't supposed to be clamps in that position.
So, it takes about 2 minutes to check under the front edge of the heat shield, and IF there is wear there, my suggestion is to put 2 gear clamps on the shield. As I say, it could save you a bunch.
Don

 

[JBrady]

As I said that is a VERY unusual failure. I would have suggested taking it to the dealer as they may have replaced the part and sent it back to Lexus engineering to resolve.

It looks less like the parts rubbing against each other and more like galvanic corrosion or even possible electrolysis.

http://www.clubmarine.com.au/internet/clubmarine.nsf/docs/MG19-5+Technical
GALVANIC CORROSION

Galvanic corrosion is caused by two dissimilar metals that are in contact and in the presence of an electrolyte.

Diagram 1: Galvanic corrosion is caused by two dissimilar metals that are in contact and in the presence of an electrolyte.

Diagram 1 illustrates an example. This generates an electrical potential, that is, an electrical current. The less noble metal, called the anode, is eaten away. The other metal, the more noble metal, is called the cathode and is protected. Thus the cathode is protected by the anode. In the marine environment, the electrolyte is usually seawater, although rainwater can also act as an electrolyte. Very pure water will not operate as an electrolyte as it cannot conduct electricity. Seawater has approximately 2.5 per cent salt content, which facilitates the conductance of an electric current through the water. Water will generally act as an electrolyte as it contains some form of impurity or pollutants.

 

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I'd be very happy to show this to the dealer but my gut reaction is that they wouldn't be in a hurry to replace the $1000 part. I have talked to Lexus about the issue and no one has gotten back to me yet.
Don

 

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I will bow to the higher authority in determining the cause of the wear, whether it is corrosion, chemical or electrolosis, or vibration.
My only comment is that the heat shield was NOT in contact with the pipe, and that lead me to believe that it was vibration causing the wear.
If it is chemical or electrolosis, my suggested solution of clamping it tight to the pipe, would just make it worse, no?
Is there a way of determining the cause?
Don

 

[JBrady]

Don, the heat sheilds on my 1999 LS400 are held to the pipe with crimped on clamp bands. Your would have been the same or similar. Worm gear clamps (hose clamps) should do the same job as the factory bands. Your repair should leave you in the same situation that allowed the failure to begin with.

I suspect that you get salt from winter road treatment at those points and have faster than usual corrosion. I would drive to a Lexus dealer and have them inspect. It would have been better to do so prior to repair but worth a shot. Competition for business may encourage them to make the repair.

If not, you can have a muffler shop weld a section of STAINLESS pipe OVER the corroded area and then clamp to that.

Here is a picture of my pipes and you can just barely see the factory clamp.

 

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This could save you $1000.

Living in Eastern Canada in the winter, I can guarantee there will be salt up in that area, and lots of it.
On looking closer, I think you're right, there must have been one of those crimped clamps holding the front of the heat shield.
There is some kind of insulating material between the pipe and the heat shield and I'm hoping that will keep the different metals apart, if your idea of electrolysis is correct, or if it's vibration, then the clamp will solve that.
My car has over 80,000 miles so although I won't rule out any help from Lexus, I won't expect it either.
I appreciate all your help in getting me to think of other issues and I hope my experience will help others to avoid a big hit in the bank account.
Don