My RX sounds like Lexus, exhaust fixed WU cat DIY
05-12-13, 12:13 AM
#1
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Thread Starter
My RX sounds like Lexus, exhaust fixed WU cat DIY
For a long time, I have had an exhaust leak which I traced to the warm up Catalytic convertor [left, between the radiator and the engine block]. I could see a slight travel of the exhaust pipe ... in and out of the heat shield.
With 10mm socket and a wrench, I undid the heat shield with the cat still mounted. It was pretty difficult to get the shell out. I would not recommend this, but that is hindsight. Once off, I could see the crack in the cat bottom. So I drove it to a muffler shop. On my way, without the shield, the pipe simply moved away and what a racket it produced. Based on his labor charges, I decided to take the RX home and unmount the WU Cat myself.
The things that I considered:
New cat and gaskets $350+
Repair charge first quote was $125
welding by itself $30+ it depends upon the break.
Difficulty level 2/10. Most Diyers would not need these instructions, but hopefully they can pick some nuggets. specially knowing how to extricate the cat and learn from my mistakes (I inserted the cat with the stud side down and there is no room to spin the cat in there)
So here are the steps.
Note: My break was such that there was only one position to weld it back. You may like to mark the two sides of the break for alignment purpose before you open any of the flange bolts.
tools:
Safety glasses. There will be things that drop on your face and eyes.
Sharpie,
Liquid wrench or equiv.
14 mm socket.
10mm socket & wrench [to operate nut and bolt]
wire brush [I used drill mounted brush]
Short and long socket extention.
Torque wrench.
Gaskets , Make sure you get the right part as each joint has a different part number.
1. Soak the nuts with liquid wrench or equiv.
2. Undo the plastic middle shield below the radiator.
3. Use long Extention and undo the two nuts holding the cat to the exhaust manifold. 14mm socket. I used flexible 1/2" adapter to offset the extention and ran it by the gap between the horn and the pipe.
4. Since the bottom had separated, I just loosened the top nuts evenly and then dropped the cat.
5. Undo the two bolts (nuts are welded) of the bottom flange (cat to exhaust pipe). You would need 3" extention to clear the bend.
6. Remove the cat from below. You may have to slightly push the plumping on the radiator.
7. With a wire brush clean the place where the weld will be [you can use a grinder. Make sure you do not remove the alignment marks.] A good welder will do this, but some may not ,,, so do it yourself.
8. Remove the gaskets. Lexus recommends, replacing them.
9. With wire brush, clean the gasket seat. It took me a good 30 mins to scrape and clean the bottom flange gasket seat.
10. Get the cat welded. [I paid a premium and went to a renowned welder, instead of a muffler shop].
Diagnosis: The break was due to thermal stress.
11. Put the heat shield back on. Make sure the bottom side has two metal straps to keep the shield away from the cat.
12. Feed the cat with studs up from below [it gets in fine with the shield on].
13. Install the gaskets.
14. Push against the bottom flange and get the top flange studs through the holes.
15. Finger tight the top nuts.
16. Align bottom flange and finger tight the bolts.
17. Evenly torque the top nuts to 46lb-ft.
18. Evenly torque bottom bolts to 41lb-ft.
19. Examine the complete exhaust system for broken or bad hangers.
20. Test your repair.
21. put on the plastic shield.
Analysis:
Heat shield provides mechanical suspension. You may think the cat is made of steel and it should support its weight, but you will be wrong. The cat can get hot and the weight of the exhaust pipe and bumps will stress the assembly.
Similarly the flex pipe 9the one that leaks most) is supposed to soften the stress. So people who opted to use a solid pipe, may experience a crack in the cat.
So why did mine break? Age or combination with a fact that I ran over a dead dear on the road some time back.
Salim
With 10mm socket and a wrench, I undid the heat shield with the cat still mounted. It was pretty difficult to get the shell out. I would not recommend this, but that is hindsight. Once off, I could see the crack in the cat bottom. So I drove it to a muffler shop. On my way, without the shield, the pipe simply moved away and what a racket it produced. Based on his labor charges, I decided to take the RX home and unmount the WU Cat myself.
The things that I considered:
New cat and gaskets $350+
Repair charge first quote was $125
welding by itself $30+ it depends upon the break.
Difficulty level 2/10. Most Diyers would not need these instructions, but hopefully they can pick some nuggets. specially knowing how to extricate the cat and learn from my mistakes (I inserted the cat with the stud side down and there is no room to spin the cat in there)
So here are the steps.
Note: My break was such that there was only one position to weld it back. You may like to mark the two sides of the break for alignment purpose before you open any of the flange bolts.
tools:
Safety glasses. There will be things that drop on your face and eyes.
Sharpie,
Liquid wrench or equiv.
14 mm socket.
10mm socket & wrench [to operate nut and bolt]
wire brush [I used drill mounted brush]
Short and long socket extention.
Torque wrench.
Gaskets , Make sure you get the right part as each joint has a different part number.
1. Soak the nuts with liquid wrench or equiv.
2. Undo the plastic middle shield below the radiator.
3. Use long Extention and undo the two nuts holding the cat to the exhaust manifold. 14mm socket. I used flexible 1/2" adapter to offset the extention and ran it by the gap between the horn and the pipe.
4. Since the bottom had separated, I just loosened the top nuts evenly and then dropped the cat.
5. Undo the two bolts (nuts are welded) of the bottom flange (cat to exhaust pipe). You would need 3" extention to clear the bend.
6. Remove the cat from below. You may have to slightly push the plumping on the radiator.
7. With a wire brush clean the place where the weld will be [you can use a grinder. Make sure you do not remove the alignment marks.] A good welder will do this, but some may not ,,, so do it yourself.
8. Remove the gaskets. Lexus recommends, replacing them.
9. With wire brush, clean the gasket seat. It took me a good 30 mins to scrape and clean the bottom flange gasket seat.
10. Get the cat welded. [I paid a premium and went to a renowned welder, instead of a muffler shop].
Diagnosis: The break was due to thermal stress.
11. Put the heat shield back on. Make sure the bottom side has two metal straps to keep the shield away from the cat.
12. Feed the cat with studs up from below [it gets in fine with the shield on].
13. Install the gaskets.
14. Push against the bottom flange and get the top flange studs through the holes.
15. Finger tight the top nuts.
16. Align bottom flange and finger tight the bolts.
17. Evenly torque the top nuts to 46lb-ft.
18. Evenly torque bottom bolts to 41lb-ft.
19. Examine the complete exhaust system for broken or bad hangers.
20. Test your repair.
21. put on the plastic shield.
Analysis:
Heat shield provides mechanical suspension. You may think the cat is made of steel and it should support its weight, but you will be wrong. The cat can get hot and the weight of the exhaust pipe and bumps will stress the assembly.
Similarly the flex pipe 9the one that leaks most) is supposed to soften the stress. So people who opted to use a solid pipe, may experience a crack in the cat.
So why did mine break? Age or combination with a fact that I ran over a dead dear on the road some time back.
Salim
Last edited by salimshah; 05-12-13 at 08:53 AM.
06-09-13, 10:07 AM
#4
Moderator
Thread Starter
Flex pipe can be replaced by OEM or walker equiv. The after market can be purchased at muffler shops too.
More info if you search flex pipe.
Lexmex talks about welding over the leak too.
Salim
More info if you search flex pipe.
Lexmex talks about welding over the leak too.
Salim
Last edited by salimshah; 06-09-13 at 10:12 AM.
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