Catalytic Convertors: 80K mile warranty

[Ron in SC]

The Catalytic converter warranty is only 80K miles or 8 years whichever comes first, at least on my 1999.

If your vehicle is getting near that number of miles you might want to inspect your convertors, even if you can not hear an exhaust leak. If they have a hairline crack in the weld bead you may not be able to hear them leaking because as the metal expands the crack decreases in size.

My driver's side converter cracked on the top so it was not visible from below. However, there will most probably be some exhaust gas stains on the heat shield immediately above the convertor. See photos below.


This is what the shield looked like after I cleaned it.



This photo shows the shield before I cleaned it off. The stain is most visible on the top near the location of the crack in the convertor. If any part of your heat shield is discolored you may have an exhaust leak. You might also what to compare the color of the shield on the other side of the vehicle and see what it looks like as far as color.



This photo shows the hairline crack in the weld bead. It has been cleaned in preparation of TIG welding which I going to have done on Monday.


I can't figure out why it cracked, other than excessive heat, as there is very little air circulation above the convertor because of its proximity to the heat shield. But then on the other hand the passenger side has not cracked, at least not yet.

I really don't want to get in to manufacturing, design or quality issues since I don't think that's really helpful. I just want others to have MB pay for their convertor should they fail within the warranty period.

I huge thanks to Gilly who walked me through the process of removing all the stuff that needed to come off to remove the convertor which in case anyone is wondering is not just a small round chamber, but a lenght of pipe with three chambers that runs from the exhaust manifold to the muffler, about four and one-half feet.

[azinn]

A big thanks for the heads up Ron. You've earned it. The Mercedes Experience, Unlike Any Other

[Gilly]

Ron
A theory I have is the cracking may be caused by a hot converter being splashed with water, either natural, ie a rain downpour or puddle, or by going through a car wash with the under-body flush.

Gilly

[Ron in SC]

Here's a photo of the cat installed back on the vehicle after it was TIG welded this morning.


The entire circumference of the top weld bead was re-welded in case it wanted to crack more. Prior to welding the center of the bead where the crack appeared was cut about 1mm in depth to allow better penatration of the new weld and to remove contaminates. Hopefully it will not crack again.

The fellow who did the welding really did not know why it cracked. He said it was a lower quality weld being a MIG weld. He said the TIG weld will have better penatration and should not crack as easily. He also said it looked like it was done on a machine and that it looked like a good weld.

He said maybe it cracked due to vibration, but he really did not know for sure.

[Gilly]

Ron
Did you mention my theory to him?

Gilly

[Ron in SC]

Did you mention my theory to him?

Gilly,

I did ask him about your theories and he said that they were possible. He added that it might be vibration too. He really doesn't do much in the way fixing convertors. The exhaust systems he's made were for race cars and hot rod's and they don't have convertors or in lots of cases mufflers at all. He basically does custom welding not automotive related at all expect for the race cars and hot rods.

He did say that most all vehicle are subject to vibration and water and they don't have cracked convertors; of course we are aware of this fact.

He went on to explain that with these convertors being welded by machine that you can get less than ideal results because if anything goes wrong as far as the welding process or the preparation (like some kind of contamination) prior to welding there may be no human to intervene.

Bottom line he really could not tell from my convertor why it failed.
I sure hope this don't happen to that many people because if they replace the convertor, out of warranty, and the other stuff attached to it and don't do it themselves it will be quite costly.

[Ron in SC]

I spoke with a friend of mine who use to work at the MB dealer in Charleston, SC and he told me the crack was probably caused by improper preparation during the welding process. He said there was probably some sort of contamination. I showed him the photo of the hairline crack and he said the weld bead looked fine and that the weld did not hold because the parts were not free of contamination. He said that crack was probably there for a very long time and that it was bound to fail but that I should not feel bad for not knowing about it because most people don't routinely check for exhaust leaks and residue on the heat shields.

[itb76]

Originally Posted by Ron in SC

...most people don't routinely check for exhaust leaks and residue on the heat shields.

When it gets bad enough the car really sounds like a beater! My neighbors are giving my wife a hard time about this. My RH converter looks like this. Looks like I have a project for next weekend...

[Ron in SC]

Lenny,
Check link below for my adventure fixing my driver's side Cat.

If you problem cat is the passenger side it will be a piece of cake, you'll not have to remove and reinstall the torsion bar.

(R&R catalytic converter)

[itb76]

Originally Posted by Ron in SC

If you problem cat is the passenger side it will be a piece of cake, you'll not have to remove and reinstall the torsion bar.

I beg to differ! I'm trying to wrestle the cat out of there, and the crack grew way beyond hairline! Still nowhere near coming out; I'm afraid I'll attack the torsion bar now...

[Ron in SC]

I beg to differ!

Lenny,

I'm sorry to hear that. I recall it looked like it could come out without removing the torsion bar, of course looks can be deceiving, and I thought someone else said the torsion bar did not have to come out for the passenger side CAT.

In any case should you have any questions feel free to sent me a PM and I'll do my best to offer whatever assistance I can.

Ron

[itb76]

Originally Posted by The Blind Man

I see!

Actually Ron, you were correct. The torsion bar need not come out to remove the passenger's side cat. However I had to remove the adjusting screw so the rear of the bar could be swung out of the way. At least I didn't have to hassle with the air hammer bit at the front.

All that jostling aound getting the cat out opened the gap considerably. Had to use a pipe clamp to close the gap to tack it together--this may be the first time in my years of wrenching that I had to get the woodworking tools out! Will post photos tomorrow.

[itb76]

Photos attached:

(1) Initial crack extended 3/4 way around cat.

(2) Clamped up for tack welding.

(3) All welded up. Not as pretty as Ron's, this was done with an el cheapo stick welder and stainless electrodes. Excuse the photo taken after dark.

[Ron in SC]

The crack on your converter is in the same place as mine; where the parts are welded together. It just seems that when they were made the machine or whoever or whatever did the welding did not get very good pentration at the weld site. Don't know whether its from contamination, or it being a MIG weld or what.

Mine was welded about 15 months ago and so far so good.

[YuCrew]

itb76: Is the repair you made to your cat still holding up? Thanks.