Can I clean a catalytic convertor?

[spstan]

Full story; 1975 Chrysler New Yorker, 440 engine with Holley spread bore. When stopped at traffic lights the engine will idle very smooth in Drive (so there's a load on). Idles almost like it were fuel injected and you can't tell the engine is running. But then sometimes the idle will degenerate to rough and the engine will bog down upon acceleration from the light. Replaced the gas filter and PVC valve and cleaned the EGR. These measures helped but not completely. Now I'm thinking the catalytic convertor is starting to clog.

Is there a way to clean a catalytic convertor (cause Advanced Auto wants $500 for a new one). I know you can take it off and ram a rod through it and I've been trying to bang on it with a rubber mallet to knock the crud loose but it there another way to clean it that works? Also is it possible to buy a used catalytic convertor that is still serviceable? Thanks for any help. Paul

 

[CBODY67]

IF you could see the small passages in the ceramic in the converter, you might wonder how anything gets through it. Why GM went to the beads instead . . . until they overheat and stick together.

A ceramic-gut converter is NOT variable. Once they might "clog", it will NOT change. So that is NOT the issue with your drivability problem!

When a converter clogs up, it restricts flow through it and the engine will not run much above idle, period. NO good or bad times, just all bad and slow speeds result from restricted flow. PERIOD.

The test of a clogged converter is to just unhook it from the pipe, at the front. IF the engine suddenly responds to throttle, then a new converter is needed.

There are MANY places to buy cat converters than your local auto supply. Or perhaps I got spoiled working for a dealership? MANY brands, too. MagnaFlow is just one. A few years back, Holley had a sale on them, universal, for about $75.00 USD each for 2.5" pipe diameter universal converters. I bought a couple for future use, in 2.25" and 2.50". Just cut your old one off, add piping if needed, and clamp it all back together. Walker and others have some "factory direct fit" converters, too. MORE options than just the local auto supply! Even Rock Auto!

As to "cleaning it out" (removing the ceramic), that can take more effort than suspected, but once you start, you have to complete the process. Reason? Any debris left will be blown back into the muffler, where it will ALSO restrict flow. So leave the muffler unhooked until you have done this and all is clear.

As to "chemical cleaners", Edelbrock came out with their "Cat-A-Clear" fuel additive years ago. Summit Racing carries it, as do other places. It is designed to clean the rare earth metals attached to the ceramic base, if it is coated with deposits from engine oil and such, over time.

You can use an IR heat gun to check the temp of the converter. After checking it, it should be hotter than the pipes in front of it (as in the exhaust system pipe to the exh manifolds). THEN you realize WHY the verious heat shields that Chrysler used on the converter bottom and on the floorpan!

Perhaps you need a new ignition control box, or similar?

Just some thoughts and observations,
CBODY67

 

[volksworld]

a clogged cat is like hammering a potato in your tailpipe...they usually idle but once you increase the rpm to the point that the exhaust flow exceeds the restriction in the pipe the car just bogs down and wont go any faster...usually accompanied by a distinctive sound as exhaust tries to force itself out of any available leak...it won't bog, get past the bog, and continue to accelerate...if the guts of the converter have broken up, pieces can jam up the outlet on an intermittant basis so the problem can come and go but if you hit the converter you can hear the pieces rattling around...I think there's some kind of emissions law where junkyards aren't allowed to sell used converters

 

[Lefty71]

"Clogged" in my experience is a buildup at the entire surface of the inlet end. There is no way that i know of the remove the impurities from that surface. I would imaging anything hot enough to burn them off would also break down the ceramic core and add to the problem.

 

[halifaxhops]

Your kind of screwed replace it with a new one not used. Then sell the other one to lets say scrap yard $50-75

 

[CBODY67]

In the case of replacement cat converters, MOST have a guaranteed "30K Mile" spec. Although some can go higher. That is their perceived/projected "useful life". Whereas the OEMs had to go higher than either of those. More catalytic substances, more money = longer lasting. So read the fine print.

As to regulations, some states classify the cat converter as an "emissions device" as others classify it as "an exhaust system component". AND there can be model year specs as to when and if those distinctions might change! So check your local vehicle emissions laws for these things.

Enjoy!
CBODY67

 

[Big_John]

Take it off and replace it with a straight piece of pipe if you want to get rid of it. It's not worth replacing. NYS annual inspection doesn't check for them on older cars, so no issue there.

But, I don't think that's your problem because those aren't the symptoms of a bad convertor.

 

[Lefty71]

MOST have a guaranteed "30K Mile" spec. Although some can go higher. That i

Surely a part of that equasion is because they figure (in many cases), whatever is wrong with your whole motor that ruined the original, will indeed ruin this one as well. No way they can tell what you are really doing with/to their new product.

 

[413]

No to all of your questions. STOP hitting it with a hammer!

Can't buy a used one anywhere, illegal.

Will the car rev to 4000 RPM? If so the converter is not plugged.

 

[1970FuryConv]

Full story; 1975 Chrysler New Yorker, 440 engine with Holley spread bore. When stopped at traffic lights the engine will idle very smooth in Drive (so there's a load on). Idles almost like it were fuel injected and you can't tell the engine is running. But then sometimes the idle will degenerate to rough and the engine will bog down upon acceleration from the light. Replaced the gas filter and PVC valve and cleaned the EGR. These measures helped but not completely. Now I'm thinking the catalytic convertor is starting to clog.

Is there a way to clean a catalytic convertor (cause Advanced Auto wants $500 for a new one). I know you can take it off and ram a rod through it and I've been trying to bang on it with a rubber mallet to knock the crud loose but it there another way to clean it that works? Also is it possible to buy a used catalytic convertor that is still serviceable? Thanks for any help. Paul

Hi Paul
Exhaust System Test for Restriction: put a vacuum gauge on intake manifold vacuum at idle and then increase engine speed to 2000 rpm using the throttle linkage and hold it at that speed. Watch the needle on the vacuum gauge. If it starts to drop toward zero, you may have an exhaust system blockage. Generally vacuum should be 17 – 21 HG at idle. If your vacuum is well below that, you may also have an exhaust system blockage. 17 – 21 HG is an OEM figure. The 360 engine in my 1972 Fury was worn, but had a rock steady idle vacuum of 15.5 HG with no exhaust system problems. If yours is well below that, might be time to see how it runs without catalytic converter or mufflers. Ben

 

[Toolmanmike]

Full story; 1975 Chrysler New Yorker, 440 engine with Holley spread bore. When stopped at traffic lights the engine will idle very smooth in Drive (so there's a load on). Idles almost like it were fuel injected and you can't tell the engine is running. But then sometimes the idle will degenerate to rough and the engine will bog down upon acceleration from the light. Replaced the gas filter and PVC valve and cleaned the EGR. These measures helped but not completely. Now I'm thinking the catalytic convertor is starting to clog.

Is there a way to clean a catalytic convertor (cause Advanced Auto wants $500 for a new one). I know you can take it off and ram a rod through it and I've been trying to bang on it with a rubber mallet to knock the crud loose but it there another way to clean it that works? Also is it possible to buy a used catalytic convertor that is still serviceable? Thanks for any help. Paul

You can't "clean it". You can knock the insides out of it. You will have other issues though. The system is made to operate with that converter in place and working properly. I can guarantee SES light issues related to an O2 sensor code. Lots of good information above on testing if there is an issue. If it's bad, bite the bullet and replace it. They even sell them on E Bay. Catalytic Converter for 1975 Chrysler Chrysler 5.9L V8 GAS OHV | eBay

 

[spstan]

that link you gave me is for a 5.9L Chrysler engine. Do you have a link for a 7.2 L engine.

Separately, been watching You Tube and there's several videos on the use of laquer thinner added to the gas tank to clean a catalytic converter. Has anyone on this board tried laquer thinner? Paul

 

[Toolmanmike]

that link you gave me is for a 5.9L Chrysler engine. Do you have a link for a 7.2 L engine.

Separately, been watching You Tube and there's several videos on the use of laquer thinner added to the gas tank to clean a catalytic converter. Has anyone on this board tried laquer thinner? Paul

You'll have to look it up yourself. I'm sure some one makes one for your application.

 

[CBODY67]

In many cases, it appears that "lacquer thinner" is related to the carb cleaners of old. As in Berryman's B12, which removed the "gas stains" from the exterior of carburetor bodies in the 1970s and cleaned the venturis when it was splashed on them. I'd prefer to use an "approved" fuel system additive, personally. Besides, they used to cost similarly, so no real cost savings to use that paint thinner product, to me.

YMMV
CBODY67

 

[65CopCar]

If you need one, something like this might work........

CHRYSLER AP Exhaust 604006 AP Exhaust Universal Catalytic Converters | Summit Racing

Free Shipping - AP Exhaust Universal Catalytic Converters with qualifying orders of $109. Shop Catalytic Converters at Summit Racing.

www.summitracing.com