How to test for a blocked catalytic convertor (MX83)

[amichie]

I have an MX83 7MGE that keeps blowing out exhaust flange gaskets. I now suspect my catalytic convertor may be blocked. I'm planning on taking it out on Tuesday morning and having a visual inspection.

Question is can you see anything by taking it out?? I have read on the net that there should be an internal honeycomb structure. Question is can you see it or is it concealed behind internal baffles.

Thanks in advance.

[kingmick]

yes you can see if there blocked, i havnt had one you could tell straight away but there is alway exeptions to the rule.

[bansheebuzz]

It keeps going through manifold flange gaskets? Do you replace them with genuine toyota seals and new genuine flange nuts? If not then i suggest you do so. A blocked cat will just snuff the motor, it should not blow out the gaskets

[slide86]

if your cat is blocked you will notice a few different things.

- the engine will become very sluggish and wont rev much.
- you will hear a rattle from the cat, that will be the honeycomb rattling round.

if you take the cat out and look through it you shouldnt really be able to see through it. if heaps of crap falls out and its rattly, then its no good.

you may also have a warped flange, causing it not to seal properly. this would cause the gasket to blow out. its common on VL's and late model falcons and stuff like that.

[amichie]

I used ACL flange gaskets. Last set I put in with a coat of maniseal. So far so good.

So if my cat is blocked can I just blast it out or is it a throw away job??

I'm tempted to jam a crow bar through it and make a nice big free flowing hole. But that would be a bit naughty.

[kingmick]

yes you can punch it threw, but its a big fine if you caught on the street, and is not good for you in confined spaces as it converts the gasses, it cant without the core!
i change all mine over to copper gaskets on everything i do with regards to exhaust.

[EldarO]

blocked cats suck teh wang, have a gander under the car and see if the bolts look like they'll come off, most of the time, they'll be rusted on, and it looks like god himself wouldnt be able to move them.

looks can be deceiving, so give it a go, if you get the cat out, it will be very, very easy to tell if its block, just use your peepers.

although bare minimum, just take the cat-rear section off, and have a look, if it all looks healthy, then it probably isnt blocked, and you may just have crunched a pipe, somehow, although i cant see any possibility of that ever happening!

Eldar.O.

[Jorrs]

took mine out other nite, just one looks and can pretty much tell its blokced, bout 60% was hardended oil, tried get a torch and shine through couldnt c any beams,
that day we did an emissions test on car and were gettin barely any carbon readings, which pretty much pointed to the cat, was gonna gut it.. but didnt get around to it and i will just fork out for a new highflow cat,
so yeh try get an emssions test if u want, bout 30 bucks or if its easy to take of just do that, mine is very hard to get two and involved about 12 bolts.

[LeeRoy]

You may be able to see if it's stuffed by climbing under the car and banging on it from underneath and it should rattle.

- LeeRoy

[EVOSTi]

a cat wont necesarily rattle if its stuffed, it could be melted and not broken. and sometimes its not enough to just take off one end of pipe and look through, its best to take it right off and put a light under it and look through the top, should be clear.
if its sweet, put it back on. if its rooted you can either gut it which will ensure you dont have issues, also give you SLIGHTLY more power however is illegal. last time i heard it was a $10K fine, but ive never heard anyone getting caught. its pretty common, and how did you know the cat was gutted when you bought it?


but back to the topic of flange gaskets blowing, if your cat is blocked enough to blow gaskets it most likely would be severly down on power. possibly your flange is warped, this was the cause of mine blowing out often, i took the manifold off and put a straight edge on it and it was warped. got it machined and it was sweet.

[amichie]

Thanks for all the tips.

I pulled the little tin plate cover off today and found that there is now a leak on the downstream end of the cat converter where it bolts onto the next section of pipe.

All the bolts on the cat are megatight and I think I will take to them with an angle grinder tomorrow to get the cat out. Then just use new nuts and bolts to put it back together.

No rattles when you bang it by the way.

I'll try the torch trick when I get it out.

[amichie]

I also read on the net that coolant entering the exhaust can cause the cat to get blocked.

My 7mge has just had its third head gasket fitted and prior to this it was using coolant.

BTW It's no longer overheating or using coolant, so I think the head gasket atleast is now fixed.

Any thoughts??

[sxyrollachic]

Any thoughts??

Sell Adam your cressie..









LOl just kidding ...

[Adam_Cressi]

yeah .. sell it to me

["Z" UTE]

Well guys CATS aint CATS. I picked up a newly complied car (RAWS) from Sydney. On the way back to Canberra, after about 100k's, the power level drops, and I have to give it heaps more throttle to cruise at 110K's.

The compliance company had used some cheap arse catalyctic converter. The honeycomb was fitted to the front and rear quarters of the can.The half in the middle being empty. Resulting in the back section of the honeycombe, being able to rotate tthrough 90 degrees, effectively blocking the freaking cat. The backpressure would have been huge!

cheers Chuck.