Aygo Manicat

[Ben565]

Looks like I'm in for a new manicat on my 2012 Aygo (128,000 miles) 

I can smell exhaust fumes inside the car and under the bonnet. And its not really running right.

I've heard the 3rd party manicats are rubbish and make the car perform like crap. Anyone got any experiences of this ?

[Mooly]

That looks extremely crusty and rusty around the manifold. The securing nuts look rusted to the point of having split. Is there some hidden history here as I've never seen anything that badly corroded on an engine.

[DerekHa]

Hi there Ben,

Last year I fitted a 3rd party Cat (or manicat as you call it) to my partners 2006 C1 which only had around 46k on the clock.

(I can't believe the state your manifold is in, unsurprising you have fumes inside the car looking at the rot down there, even the bolts heads are badly corroded!)

It was my fault the cat failed as I misfuelled and didn't realise I had until it was too late and the MIL came on and even when cleared returned! I wasn't too popular for a bit but she's a forgiving woman fortunately. I tried everything I could think of to clean the original cat out but nothing worked.

I ended up with a 3rd party Cat which I found on eBay which I think cost around £100, off the top of my head. I couldn't justify spending on a genuine new Toyota one, even the used ones on eBay are astronomical price.

Anyway I choose to do the job myself which went ok, though the replacement wan't a 100% perfect fit, but it did the job the MIL went off and stayed off. Haven't noticed any difference in performance at all. The C1 is very low milage for it's year and my partner only does about 30 miles a week so can't say how long the new one on the C1 will last.

BM Cats Approved Petrol Catalytic Converter - BM91263H

£86.93

Have just looked back and the above is the one I purchased back in May last year, It cost around the £100 mark all in counting the cost of treatments I tried. Its done around 2 - 3k since being fitted and is still fine.

[DerekHa]

Just been looking back at my actual order and I purchased that BM Cat through Arnold Clarke Autoparts, they have an outlet on eBay. Went for that one as Arnold Clarke have been around for many years so though they would be the safest bet.

[flash22]

that's how the manifolds go, hot/cold cycles and driving rain - the welds are non-existent it must sound like a tank

BM cats arnt bad, but there is a LOT of Chinese and eastern euro junk on the market

 

that's going to be a fun job you will need all new nuts, studs and a few miracles

[Ben565]

Thanks for the info

No particular history to this car. I've had it from 3yrs old / 20,000 miles. Usually do a 50 mile round trip to work each day up the motorway. Its now on 128,000 miles. 

Doesn't sound especially loud, but it is leaking. 

 

Yeah those bolts aren't coming out easily. 

 

Already had a new clutch, subframe  and suspension arms so far this year. 

[fossyant]

We had to replace the lot, cat and exhaust. Used a local company and overall cost was about £700. Cat £250, exhaust £200, 2 x sensors £200ish from memory.

Weld went on cat to manifold, and exhaust was crusty. Bank on needing the two sensors as they won't come out

[flash22]

a good hard tap with a cold chisel should remove them nuts, hopefully it hasn't eaten into the head, the cat may even come off the manifold and give better access

[Big_D]

It may be worth using some penetrating oil. Put some on a day or two before you want to do the repair. I used to use a 50/50 mix of ATF and acetone. This may help get the nuts and bolts off easier.

[DerekHa]

If your DIYing this Ben then Big_D's advice is good but would also give it a go with whatever penetrant you use but keep applying it over a number of days before you start.

Also looking at the crusty state of those bolts/nuts, when you're trying to remove them you'll likely find the correct sized socket no longer fits. Try dropping down a size and hammer the socket on if need be to get enough purchase but be careful not to break it.

Let us all know how you get on Ben.

[Ben565]

I'm not planning on diy'ing it. Fortunately getting the bolts off will be someone else's headache (and probably my expense) I'll give them a squirt of something anyway. 

I know a reputable local independent who can do the work for me. Just wondered if it was worth asking them to fit oem parts.. or accept 3rd party replacements. 

[Derek.w]

Lets hope a right angled hammer(impact) gun works.

[flash22]

How deep are your pockets OE cats are, sit down in a corner and cry money

A garage will get the cutting torch out and lop the bolts off, let the garage supply the parts as then is their job to warrantee the parts and cover the labour

o2 sensors specify Denso items if they need replacing

[APS]

If you can smell exhaust gasses, chances are the weld at the top of the cat has cracked. This is a fatigue issue that happens when the support bracket on the side of the cat has failed. That support is crucial for off loading stress on the top neck of the cat. So, make sure your mechanic installs and tightens the bracket on the side of the cat. 

This is really important to prolong the life of the manifold/cat.

 

Edit/update:

Looking at your photo. This is the bracket and nut that I am referring to:

From what I can tell, it looks like it is attached. But you never know, these have a tendency to rust and can snap off. It might not be obvious until removed and inspected. 

Bracket on the new cat (circled) and weld that may crack (arrowed):

 

[flash22]

10 minutes ago, APS said:

If you can smell exhaust gasses, chances are the weld at the top of the cat has cracked. This is a fatigue issue that happens when the support bracket on the side of the cat has failed. That support is crucial for off loading stress on the top neck of the cat. So, make sure your mechanic installs and tightens the bracket on the side of the cat. 

This is really important to prolong the life of the manifold/cat.

the rot has eaten the welds and dined out on the flange, at this point its rust holding hands

[APS]

On 8/15/2023 at 5:27 AM, Ben565 said:

I've heard the 3rd party manicats are rubbish and make the car perform like crap. Anyone got any experiences of this ?

Yes, don't bother with cheap aftermarket stuff. Get OEM or a good second hand OEM. 

For a 2012 Aygo that is a crusty manicatsu-rust-curry. Do you live near (or in) the sea?

Anyway, I'm sure it'll run ten times better when you get a non-leaking one with a good O2 sensor on there. Note, the sensor may not be faulty as exhaust leaks can throw the air/fuel ratio right off.

[Ben565]

Been into the garage today, confirmed what we all thought,  the manicat is leaking, £425 fitted for a new one.

Obviously not oem part, but as other have said the cost of those is eye watering. For a 2012 Aygo with 128k on the clock it isn't really worth the expense of the oem part.

Its running pretty rough at the moment.

 

I live in the Midlands, about as far away from the sea as you can get 😄

I do a lot of motorway miles in it, maybe gets more spray and road salt entering through the grille than town based Aygos. 

[Big_D]

£425 sounds like a fair price, especially with all the rusted nuts/bolts etc.

[Ben565]

Well I got this done last week. It doesn't have a heat shield over the manifold now, not sure how important that is.

I can confirm though the cheap 3rd party CAT does strangle the engine. I mean it was never a fast car, but it's so slow now on the motorway. It just won't go anymore. 

[Mooly]

Sorry to hear of your ongoing troubles... perhaps the original diagnosis of the fault is not correct and there is actually more amiss than just the cat.

57 minutes ago, Ben565 said:

It doesn't have a heat shield over the manifold now, not sure how important that is.

Its there for a reason, the cat radiates extreme amounts of heat and that could cause issues with plastic parts nearby such as radiator housing etc. If the original heat shield won't actually fit the 3rd party cat then I'm afraid the cat is not really a suitable replacement.

If you've paid for fault diagnosis and repair then you should take it back as not satisfactory. 

[Ben565]

I'm not quite sure what you mean. The original diagnosis of what fault exactly ? I never said there was a fault with the car originally.  It's pretty clear the manifold was corroded, leaking, and needed replacing. There was nothing amiss with it to start with. Just the obviously corroded and leaking manifold. The CAT's part of the manifold, it was replaced because the manifold was corroded and leaking. There's nothing more to it than that. And now it's been replaced it's got no power, because aftermarket CATS are clearly crap. 

I'm with you on the radiated heat from the CAT and manifold, they do chuck out a lot of heat and Toyota wouldn't have fitted a heat shield for the fun of it. I would imagine it was also corroded and/or damaged beyond repair, but a replacement should have been fitted. 

 

I haven't paid for any fault diagnoses, it's patently obvious the manicat was corroded, leaking,  and needed replacing. It's going back for a service next week so I will ask them about the heat shield. 

 

You get what you pay for I guess. Take it to a main dealer and it would have been repaired to OEM spec with OEM parts... at a price that would make you cry. Take it to a 3rd party independent, you pay less but end up with inferior parts and bit's missing. 

[Mooly]

It was just with you saying in post #1 that:

On 8/15/2023 at 5:27 AM, Ben565 said:

And its not really running right.

 I would have thought that if the replacement cat is not obstructing the gas flow then it should perform correctly performance wise whether or not the cat is doing a good job of cleaning things up. It just sounds like there might be something else amiss...

[Ben565]

Oh I see, well no it wouldn't be running right if the manifold was leaking. The air/fuel mix would be off and it'll run rough.

 It was running fine prior to the manifold leaking (and subsequently running a bit rough). It still pulled fine on the motorway, and now the 3rd party manicat has been fitted,  it doesn't.

So its clearly the 3rd party manicat thats caused this. It obviously more restrictive and doesn't flow as well as the OEM one. 

[Mooly]

Fair enough. So if it is the cat then it must be really restricting things but ultimately its no good as a repair if the car isn't right.

If your independent ordered, supplied and fitted the part then you should have some comeback but if you supplied the part for him to fit then its a different story I'm afraid.

Good luck and I do hope you get a solution. Keep us informed 🙂

 

[flash22]

Disconnect the Battery for 15-20 mins and let everything reset, the plugs may be fouled also

A massive exhaust leak like that, will throw the fuel trims well out and possibly have damage the O2 sensors as well