05 Corolla Exhaust Leak

[The Critic]

2005 Corolla.

LT Fuel trim, at idle, is between 12-14%. Injectors were cleaned and flow tested. Intake was smoked, no leaks. I smoked the exhaust and found a leak at the exhaust manifold to catalytic converter flange. Replaced the worn donut gasket with a dealer gasket and also installed new spring bolts. Leak remains.

Engine mounts are not torn, no visible damage to the flange, sealing surfaces or pipes.

Any ideas?

 

[atikovi]

Just because it's new doesn't mean it's good or the right part number. Maybe try Fel Pro.

 

[The Critic]

Just because it's new doesn't mean it's good or the right part number. Maybe try Fel Pro.

Already did. The Fel-Pro gasket fit worse.

 

[eljefino]

Since you're replacing this gasket multiple times what's the crush like on the old one?

You could do butchery like I do and slather the seating surfaces in orange/ copper high-temp RTV.

When you get the flanges together, give it all a wiggle a few times while you torque the spring bolts down, to make sure everything centers.

 

[mehullica]

Those exhaust manifolds like to crack before the flange under the heat shield

 

[Astro14]

There may be no visible damage to the pipes/manifold, but I bet the either the manifold flange is bent, or the converter flange is bent, enough that you can draw the bolts tight without compressing the gasket. Take a good look at those flanges - might need to replace the flanges (if you can) or flatten the "ears" with a file to create more space and allow the gasket to be compressed.

 

[JeffKeryk]

As @Astro14 posted, perhaps it is the mating surfaces.

 

[AKhan87]

Hey Critic, I never dealt with a 2005 Corolla

But I worked on 98-02 corollas
00-05 Celicas
Quite a few Pontiac Vibes from all year.

I always used a Fel-pro exhaust donut and re-threaded the bolts and threads in the exhaust manifold, and applied anti-seize before installing and they always worked, I have used Dorman (bolts and springs) to success as well, never seen a leak like yours but I always took the steps I have outlined because rusted out threads weren't worth dealing with.

 

[The Critic]

Since you're replacing this gasket multiple times what's the crush like on the old one?

The original one? It was in pretty rough shape.

The Fel-Pro one fit rather poorly. You could push it onto the male-end of the flange quite easily and the two sides bolted up with little resistance.

So I tried a Genuine Toyota gasket. That one required some effort to compress.

Those exhaust manifolds like to crack before the flange under the heat shield

That is what I heard as well, but the smoke test only showed smoke from the area between the two flanges. Should I try a different test method?

Someone suggested that my leak at the flange could be due to excessive backpressure from a clogged cat?

There may be no visible damage to the pipes/manifold, but I bet the either the manifold flange is bent, or the converter flange is bent, enough that you can draw the bolts tight without compressing the gasket. Take a good look at those flanges - might need to replace the flanges (if you can) or flatten the "ears" with a file to create more space and allow the gasket to be compressed.

Good tips - thanks. Unfortunately, I do not see how either flange can be "repaired." If an issue is found, I think I am looking at a new cat and/or a new manifold....unless an exhaust shop can weld in a flex section.

Hey Critic, I never dealt with a 2005 Corolla

But I worked on 98-02 corollas
00-05 Celicas
Quite a few Pontiac Vibes from all year.

I always used a Fel-pro exhaust donut and re-threaded the bolts and threads in the exhaust manifold, and applied anti-seize before installing and they always worked, I have used Dorman (bolts and springs) to success as well, never seen a leak like yours but I always took the steps I have outlined because rusted out threads weren't worth dealing with.

Thanks, it is the exact same set-up. The bolts and threads are in good shape. Unfortunately the fel-pro gasket did not work for me -- it fit very poorly. However, even though the Toyota gasket fits better, the connection still leaks.

 

[The Critic]

I found the issue:

My theory:

Old (failed) donut gasket "wore into" the catalytic converter flange and left pits. The pits feel like a cheese grater.

New gasket, obviously, can't seal against that. That is why the exhaust leak got worse after replacing the gasket.

Now, what is the best way to repair this?

 

[clinebarger]

Sure it's not left over graphite from a aftermarket gasket?

 

[Trav]

If that is really damage to the metal you will need to replace the flange with something like this, this is only an example not necessarily for this car.
Its a simple weld on deal. A good exhaust shop should be able to fit something for you if you dont want to mess with it, do not replace the cat for this.
I have not seen damage like that from a donut gasket.

FX1758 2" Semi Direct Fit Exhaust Converter Pipe Flange Repair Kit w/ Gasket

Regardless of the vehicles this item is advertised to fit, you must check your pipe size as this item only fits applications with 2" pipe. Applications: Saab 9-2X 2.5L '05-'06 Subaru Baja 2.5L '03-'06 Subaru Forester 2.5L '98-'05 Subaru Impreza 2.2L '95-'01 Subaru Impreza 2.5L '98-'05...

www.bearriverconverters.store

 

[The Critic]

Sure it's not left over graphite from a aftermarket gasket?

Tried scraping with a screwdriver and none of it budged. I am going to remove the catalytic converter today and try with more aggressive methods.

 

[The Critic]

Sure it's not left over graphite from a aftermarket gasket?

Not sure how this damage occurred, but it definitely isn’t removable. I tried grinding with a wire wheel and it doesn’t change.

 

[The Critic]

If that is really damage to the metal you will need to replace the flange with something like this, this is only an example not necessarily for this car.
Its a simple weld on deal. A good exhaust shop should be able to fit something for you if you dont want to mess with it, do not replace the cat for this.
I have not seen damage like that from a donut gasket.

FX1758 2" Semi Direct Fit Exhaust Converter Pipe Flange Repair Kit w/ Gasket

Regardless of the vehicles this item is advertised to fit, you must check your pipe size as this item only fits applications with 2" pipe. Applications: Saab 9-2X 2.5L '05-'06 Subaru Baja 2.5L '03-'06 Subaru Forester 2.5L '98-'05 Subaru Impreza 2.2L '95-'01 Subaru Impreza 2.5L '98-'05...

www.bearriverconverters.store

Thanks. Looks like a flange can be welded.

I think this is what I need:

Megan Racing Large JDM Exhaust Donut Flange for Import at PRO Import Tuners

Product page for Megan Racing Large JDM Exhaust Donut Flange fitment for the Import.

www.proimporttuners.com

 

[Trav]

Yes, that will probably have to be tig welded. No big deal get the flange, make sure it fits and give it to a welder.

 

[TeamZero]

If cant easily get and weld a new flange on, use a disc on a die grinder and clean it up a bit. Then maybe add some washers over the bolts to add tension to the springs. It should soon wear in and seal. I have done that before with great success

 

[The Critic]

Went to the muffler shop earlier. The owner and the tech both looked at the flange and wanted to try cleaning it up with a die grinder, so I allowed them to proceed. We also looked thru their pile of used flanges and found a matching one in good shape.

Their "cleaning" resulted some of the damage but it did widen out the flange a bit. He asked me to reinstall the assembly and smear a bit of Permatex Ultra Copper onto the donut gasket for extra sealing. I can't say I am a fan of this fix, but I complied. I will allow the RTV to cure overnight and recheck in the morning. If the repair fails, he asked me to bring the car down for them to weld on the new flange.

 

[t1snwrbrdr12]

Just a thought (no familiarity with this vehicle or it’s common problem) but if the cat was clogged, could it have heated up enough to cause that donut gasket to melt into the flange causing that damage? Have you run/driven the car enough or know it’s history enough that you know this cat is worth repairing and reusing?

 

[Trav]

Went to the muffler shop earlier. The owner and the tech both looked at the flange and wanted to try cleaning it up with a die grinder, so I allowed them to proceed. We also looked thru their pile of used flanges and found a matching one in good shape.

Their "cleaning" resulted some of the damage but it did widen out the flange a bit. He asked me to reinstall the assembly and smear a bit of Permatex Ultra Copper onto the donut gasket for extra sealing. I can't say I am a fan of this fix, but I complied. I will allow the RTV to cure overnight and recheck in the morning. If the repair fails, he asked me to bring the car down for them to weld on the new flange.

The reason for these types of joints that use these donuts and spring devices is they allow for a slight amount of movement at the joint.
The RTV even if it initally quiet will hinder any movement and fail in a very short time.