TimYang

I have a 2000 Lexus ES300 with 215k miles on it. Apparently I need a new catalytic convertor and the first quote is $951. It also needs a new main seal and the first quote is $881. I've been living with the slow oil leak for a while but the catalytic convertor problem makes it run very rough if you try to go 40 mph or more. Everything else on the engine is work well and the body is in good shape with the biggest issues being wear on the drivers seat. I am looking for thoughts and advice. My son drives it to school and back but right now it is setting in the driveway. He will be going away to college in 7 months and I would like to get him something newer like a used Tacoma. Right now does not seem to be the time to try to buy a car but I'm having to swallow hard to spend this much on an older car. Do these quotes seem reasonable? Is the catalytic convertor a job that is do-able if one has access to a lift?

LeX2K

Which one are you looking to replace? There are 3, two on each exhaust manifold and one under the car. The exhaust manifold ones can be replaced with basic tools the one under the car either requires the entire pipe with catalyst replaced (expensive) or a replacement welded to the existing pipe.

I'm always skeptical when a shop says the catalytic needs to be replaced, they do go bad but most often the problem is elsewhere. Rockauto shows the various parts
https://www.rockauto.com/en/catalog/...converter,5808

Arsenii

Hello,

Are there any Check Engine Lights?

Those cars are pretty good at picking up issues with the catalysts, showing a Catalyst Efficiency Code, if you don't have one, I would look elsewhere. The only issue in terms of car running that clogged catalyst could present is the engine not revving correctly, it won't cause the car to not accelerate beyond certain point, so there may be something else to consider. You can rent an OBD2 scan tool at any major car parts store for free, use it to check for codes and Engine Live Data.

If it is indeed a catalyst, depending on your state laws, you may be able to get away with something like a flame suppressor in place of a catalyst or something aftermarket that you can weld in, though be aware that those don't usually last long.

As for Rear Main Seal, while the part is cheaper than that, there is no easy way to get it out, since it does require the engine and transmission to be pulled apart to gain access. With that, as long as it is a pretty mild leak, it may not be worth investigating, especially if you are not planning on keeping the car for long. There is also that stop-leak oil additive stuff that you can get, but I never tried it, so I don't have a whole lot to say, maybe someone else can chime in..

Hope this helps and best of luck!

TimYang

Here is some more info, I have a scanner as well as having it scanned at Advance Auto. I had a P0300, P0302, and P0304 as well as a P0171 code. I had more but I cleaned the MAF sensor and later replaced it and they went away and these came back. The shop I took it to is one I have gone to for years and it is located very near the GE plant where I work and they know I work there and they know a big chunk of their business comes from employees there. They changed the three ignition coils on the front bank even though I had changed them less than two years ago. I am not sure what to think about this, it seems unnecessary but in the end they did not charge me for labor. Can a failing catalytic convertor cause the ignition coils to go bad?

They also said they don't do exhaust work and they recommended a few places. Other than that I saw a picture of what looks like honeycomb material in the exhaust pipe. I think the material basically is causing a restriction in the exhaust pipe.

Looking at Rock Auto and other places it seems like the front bank Catalytic convertor and manifold is $200-300 dollars and it bolts on so if I can loosen the nuts as well as get access to the underside then changing it should not be too bad. I have not tried any additives for the seal leak, I have just been adding oil and I am OK with that plan for now.

LeX2K

Where in the exhaust pipe?

TimYang

It appears that they just unbolted the flange in front of the third cat. I plan to get it up on ramps tomorrow and look myself. My exe has a friend who gives her car advice. She used to double check with me untiI I told her that I think he has good sense and is steering her straight, after all he has a tow truck company and a garage. (I throw these details in because to me its funny.) His advice is to disconnect the catalytic convertor and if the car has full power then there is a blockage. I am not sure that he is fully aware of the three catalytic convertor configuration but the idea makes sense to me.

LeX2K

If one of the converters is clogged you need to make sure the root cause is not there anymore like prolonged misfire, running lean or too rich that kind of thing.

TimYang

I agree. One of my questions was does the failing cat cause the misfires or do the misfires cause the cat to fail.

LeX2K

Misfires (or other issues) cause the cat to get cooked. If the catalytic is clogged the car will idle smooth but have no power unless it is severely clogged then the engine will idle low or die.

TimYang

Today I will separate the exhaust pipe from the section closest to the engine and see what I can see. I'll also see what codes I get. I have yet to get a P0420 or P0430 which seems odd if there is a catalytic convertor issue. I think if it is the front catalytic convertor that I can change it myself. I will also try to run it with the main cat and muffler disconnected and if there is not change then I feel confident that those components are not the issue. I don't know anyway to try to determine if it is cat for Bank 1 or 2 that is causing the issue. Am I missing anything?

TimYang

I wanted to wind down this story since i have now replaced all three catalytic convertors. The two bolt on cats coming off bank 1 and 2 are fairly easy to replace if you have a set of car ramps and are willing to crawl under the car. The main cat that is further back can be done by disconnecting the exhaust pipe at the muffler and it would already be disconnected at the front end. This one is welded in but if you are willing to try welding it can be done as well. The pre-cat on bank 2 was completely gone, all the honeycomb had crumbled and gone downstream. Most of it was lodged in the pre-cat coming off bank 1. The main cat was probably ok but it was the least expensive of all three so I went ahead and replaced it.

After all of this, I have driven the car maybe 40 miles and it runs like a new car. There are no CELs and it accelerates without hesitation. Just before I did all this work it would top out at 40 mph but now it hits 75-80 with ease. I have not pushed it harder but clearly the car is running like it is supposed to.

A few weeks ago a mechanic had replaced two ignition coils but I now think there was nothing wrong with them and he was guessing at the problem. I had replaced all coils about two years ago and there was no oil or other obvious issues with them.

One question left in my mind is if an oil leak at the main seal was caused at least in part because of the failing cat and the engine running at a higher pressure to overcome the back pressure due to blockage in the exhaust.