Precat removal - How I did it...

[GSB]

For those of you that dont know, when designing the MR2 Toyota went down the path of making it a Ultra Low Emissions Vehicle (ULEV). Doing this meant adding a whole load of extra emmisons control equipment to the engine, chief among these being 2 additional catalytic convertors installed in the exhaust manifold. The theory behind it being that when starting from cold, these cats heat up and get working a lot faster therby reducing the emmisions that bit sooner.

The problem with these cats, is that in order to endure the very high temperatures in the manifold, they have to made of a ceramic material. This ceramic might be good with high temperatures, but is incredibly brittle and doesnt like vibration. The particles that do break free are also very-very hard, so if they manage to get into the cylinders they aren't going to be to friendly to the insides of yor engine...

I've been regularly inspecting my own precats for a while now, and they've always been in good condition, However after a recent check revealed that they were starting to deteriorate, I decided it was time they came out beofe they took my engine with them. The first signs of deterioration were noted at around 30,000 miles, 2000 miles after my previous inspection. 200 miles later, the situation had deteriorated even further. These cats go bad very-very quickly...

Heres how I removed the cats...

Note: Clearly, neither I nor MR2-ROC can condone you ripping lumps of emmisions control equipment out of your car. Its safe to say the the warranty on my manifold at least and probably my main cat as well have now been well and truly voided, so the same will go for you. Basically, if you decide to go down this route as I have, you're on your own... On the plus side, if its not in there, it cant break.

Toolkit required

Trolley Jack
Axle Stands
10mm spanner
10mm socket on 6" extesnion
12mm spanner
12mm socket and various extensions
14mm socket
Hammer
Vice
Long flat bladed screwdriver
High pressure water or air supply
Large vocabulary of swear words

In order to remove the precats, you first have to remove the exhaust manifold from the car, Care should be taken to apply penetrating oil to the various nuts and bolts some time before undoing them

1/ Jack up the rear of the car and place on axle stands.
2/ Remove the splash guard from under the rear bumper
3/ Remove 3 bolts from the forward splash guard to let it hang down.
4/ Remove the 3 14mm nuts that secure the main cat pipe to the manifold

In the engine bay;

5/ Using a 22mm O2 sensor socket, remove the 2 O2 sensors from the manifold.
6/ Remove the 4 bolts securing the manifold upper heat shield
7/ Remove the 2 bolts that secure the lower part of the manifold to the engine block. These are 'behind' the manifold and not readily visible. ! of them is 12mm, the other 14mm.
8/ Remove the 5 nuts securing the manifold to the cylinder head.

The manifold can now be lifted out of the top of the engine bay.

Decatting the precats...

Actually getting the precats out is pretty simple, here's what mine looked like from above and below before I started, you can see some of the degradation thats taken place in the first photo:



And here are the surgeons tools:


Removal is simply a case of attacking the precat matrix with hammer and screwdriver until its broken up into lumps small enough to be able to get them out through the lower exhaust port. The ceramic material gives up very easily, it only takes 1 or 2 taps on the screwdriver to do this...


After digging around for a while you will also expose the glass fibre that surrounds and supports the cat matrix, this has to come out too.



Once out you'll have a big pile of very useless, but rather expensive catalytic material left over. I beleive some places do recycle this stuff to reclaim the precious metal content, so if your now feeling guilty about your effect on the environment, this could be a way to ease your concience


Once its all out, you'll be left with an empty manifiold like this;


You now need to clean it, as there is still an awful lot of potentially damaging dust and particles left inside. I would recommend high pressure water like a jet wash or an airline for this, as an chemical residue from solvent cleaners may have a damaging effect on the O2 sensors.

Once clean and dry, re-building is simple the reverse of the process used to take the manifold out in the first place.


Happily, I've not noticed any increase in noise level from removing these. Performance certainly isnt any worse, and in fact the car may have benefitted in the form of slightly increased torque, but I cant say for sure... What is certain though, is that the pre-cats are going to have a hard time damaging my engine from the workshop bin, and I'm a lot happier now that these ticking time bombs are not a problem...MOT tests wont be a problem, as I still have the main cat in place, which is more than capable of doing the work. I dont have a ULEV car anymore, but I do have one that with a bit of luck will last a bit longer.

[Hanslow]

Good report

One to be ported to the articles section?

[Slacey]

One to be ported to the articles section?

Definately! Good work Grant, it will come in handy

[Liz]

Great article Grant, can we organise a gut the cats party! I really want mine out now that my Mr T warranty is up.

[GSB]

Great article Grant, can we organise a gut the cats party! I really want mine out now that my Mr T warranty is up.

A good point, no warranty, no need for time bomb lumps of china in your exhaust.

I will add this to anyone who's going to gut the pre-cats...

Use plenty of penetrating fluid.

The removal, gutting, cleaning and re-assembly process only took me an hour and a half. Its pretty simple and all the bolts are in places you can get at them without to much difficulty. However, it took me a further two and a half hours to extract a broken stud from my manifold. No amount of heat, applied torque, or liberal quantities of swear words would make it budge, so I had to drill it out and re-tap it with a slighty larger thread size. Not a nice job to do...

[RaGE]

Is it not possible to get the Pre Cats out without gutting them, Toyota managed to get them in there!

... This is a stupid question if there was a way thats how you would done it. So what have Toyota done to stop us getting them out?

[GSB]

They're welded in...

The precat sits inside a cylinder, thats then welded to the primary tubes and O2 socket at the top, and the down pipe flange at the bottom. Once they're in, they're in for good, unless you break them down into smaller pieces.

[lilylaville]

Jeez....This is something I don't want to even contemplate doing. I think Liz's idea of a party is a good one, I'll provide the jelly and ice-cream

[bradders]

Excellant thankyou......

Mark

[heathstimpson]

Excellent write up. Do you think your car will show any improvement with the better exhaust flow now:?: Shame you couldn't have dome a pre and post dynos to prove the possible torque and power changes

[Tomr2]

dont think ill be attempting this one myself! think id rather leave it to someone who knows what they're doing

[Peter Laborne]

Excellent write up. Do you think your car will show any improvement with the better exhaust flow now:?: Shame you couldn't have dome a pre and post dynos to prove the possible torque and power changes

It would be good if someone planning on gutting their (pre)cat could do before and after dyno runs and also emissions tests.

If it still remains within the ULEV figures after gutting then maybe we could ask Toyota if they would consider a voluntary recall so that people can have their (pre)cats gutted and save their engines.

[markiii]

if it still fell within ulev figure without them, I somehoe doubt they would have been fitted.

besides the economies fo scale are the only reasons they are in for the european market, and based on that I doubt it would be economic to recall them all.

[Tem]

You most likely won't pass the EU standard emission test without the precats. You will pass the sniffer emission test though.

The first test is done by starting a cold (=20C) car and driving at predetermined speeds for some time. The speeds vary between 0-60mph or so and "simulate" a drive to work...first you have speeds like you would around typical residental area, then some highway speeds and finally "heavy traffic in a city". All that comes out of the pipe is measured, from start to stop.

Precats start doing their job the moment you start the engine. Without them you will pollute so much before tha main cat warms up, that you shouldn't have any chances of passing that test.

(also, I don't think UK/EU Toyota could care less about ULEV, as that's only used in US)

[John Woodward]

I am really not sure about all this to be honest. I have read all these threadsa about decatting and it still seems a very dangerous thing to me. Yeah, I know there is a risk of them breaking up and getting sucked into the engine (and I am VERY worried by that. I don't fancy paying for a new engine or whathaveyou now that the motor is out of warranty) and causing untold damage, but they are there for a reason. Not only that, surely if you request the dealer to check them on a regular basis (I understand that they can break up over night almost), then hopefully there should be SOME preventative measure in place.

I originally started reading this thread cos I too was worried about the damage broken pre-cats can do and wondered if I should do something about it by decatting myself. Now I have read through and seen the amount of change and the possible legalities and emmissions changes and so on...........I just don't know. If anything, this thread has made me even MORE paranoid that my engine is going to go POP! The way things are worded and sound, it seems like this happening is more "inevitable" than "possible" and I am really quite worried now. I don't want to rev then engine too much cos I think I am going to wreck something, yet I don't want to mollycoddle it either cos its a 2 and should be driven..........

I don't know. Someone PLEASE put my mind at rest and tell me this is either an inevitable occurance and if I leave the cats in place that my engine is GOING to go pop, or someone tell me that I don't have THAT much to worry about and its rare. I jsut don't know anymore...........

Sorry for being a wet blanket, but I am very much a believer in that a manufacturer designs things to the best of their ability (with some notable exceptions, granted) and Toyota DO have a good reputation for reliability, so I like to leave things as standard as they are cos that is how they were built, for a reason. But, this is really really giving me the collywobbbles and I just don't know what to do..........

[markiii]

simple answer,

whatever the reason for them being fitted they don't have to pass that test anymore. Only the MOT.

you can pass the mot without them.

they are hazardous to your engines health.

there are no legal implication to you in rfemoving them.

personally I'd get shot.

[GSB]

I am really not sure about all this to be honest...

Fair enough, niether am I...

To put things in perspective...

Precat failure is unlikely to happen, but theres no such thing as a 100%reliable component so it will affect some cars. Unlike most cat failures, (which will eventually effect ALL cars, regardless of make or model) It just so happens that due to the design and location of these particular cats, failure seems to lead on to catastrophic engine failure. (its not proven, its just an educated guess based on owner experience so Toyota wont even acknowledge the problem yet.)

The MR2 engine is used across the Toyota range. The rest of the toyota range using this engine doesn't have precats. Now niether does mine. Emmsions testing is not an issue, as the main cat is more than man enough to cope with the MOT.

My advice would be to check your precats regularly, and at the first sign of degradation, whip 'em out, or warranty them. The check takes 5 minutes so its not a big deal..

[John Woodward]

markiii wrote:

simple answer,

whatever the reason for them being fitted they don't have to pass that test anymore. Only the MOT.

you can pass the mot without them.

they are hazardous to your engines health.

there are no legal implication to you in rfemoving them.

personally I'd get shot.

Is this definate? I am not questioning your knoweldge Mark, so please don't take this the wrong way. Its just that when MrT test these cars, they hammer the buggers under all conditions. Ok, there are some things that get past these tests and show themselves at later dates when the car is out in the public and then we get the recalls and so on........But it does make me think that when they were doing their tests, surely these problems would have shown themselve up to MrT? I agree that there is evidence for them breaking down and causing damage, but if it was such a problem, surely MrT would have called them back? And if not (which I CAN see them doing), then what have we got to stand on against MrT if they do go t*ts up?

I am still not sure and I am not sure I want to take them out just straight away. I think I am going to take GSB's advice on this and just get them checked VERY regularly and if there is any sign of degradation, then I shall ask for them to be changed ot removed.

Further more, even though there is a VERY good write up on how to do this job, I am garageless, toolless and mechanically (in the practical sense) a bit of a nonce with this kind of thing. I FULLY understand the engineering and mechanics of MANY things (I am fascinated by it), but practially, this is a big job for me. I wouldn't want to tackle it on my own.

I take what you are saying and appreciate it, but I think, for now at least, I am going to take my chances........I may lve to regret that and you are going to say "told you so", but I still am not sure........

Thanks for the help though Mark and GSB!

[Peter Laborne]

But it does make me think that when they were doing their tests, surely these problems would have shown themselve up to MrT?

Remember the way that engine failures have shown themselves up on the forum. You could be very lucky and never suffer an engine failure, however you could have one after a few hundred miles.

Mr T could have been one of the lucky ones. Also they had no forum to compare with hundreds of other owners. So at the end of the day they would have believed that there was nothing wrong.

You never know....if they had tested it for another 100 miles maybe we wouldn't be having this discussion about pre-cats.

[GSB]

Excellent write up. Do you think your car will show any improvement with the better exhaust flow now:?: Shame you couldn't have dome a pre and post dynos to prove the possible torque and power changes

It would be good if someone planning on gutting their (pre)cat could do before and after dyno runs and also emissions tests.

The jury is still out on weather any performance increase has occured, Ive only done about 60 miles since the cats came out, but on the whole I think yes. There seems to be a little bit more life in the car...
I deliberatley limited the work I carried out to the precats, and made sure nothing else changed, i.e. I left the battery connected so the ECU would not reset, and held off cleaning my MAF for another day. That way I would have a better idea of just what effect the change has had.

As for dyno testing, having identified a potentially catastophic problem in the precats, the last thing I was going to do was strap the car to a dyno!

[markiii]

John,.

I take your points, however my thoughts;

Toyota may do in depth testing but I doubt they are hitting 20-30000 miles in testing which is typically when problems seem to start. Granted there are a few exceptions to this such as MrMikes.

next, Toyota are aware of an oil issue as the material comprising the rings that seal the pistons has supposedly been changed for the 03.

while this doesn't count as definative proof it indicates they know there is an issue in this regard. Also the roadster is supposed to use more oil than many cars according to the handbook. While oil getting past the pistons is no biggy on it's own, I doubt they have the data to determine the effect after 30000 miles. besides putting my cynical hat on anything that lasts long enough to get past the warranty period, is often classed as good enough by the manufacturers.

This isn't by the way just a toyota problem. If you google for it, there are a couple of nissans in the last few years with similar issues, and what looks liek the same cause and effect (oil and pre-cats), fortunately Nissan did issue a recall.

Again any testing done by Toyota will liekly be with the car maintained in accordance with their instructions, oil type for example. an awful lot of dealers seem to liek magnatec, which again if you google is hated by many perfromance drivers because of the bad effects it's chemical makeup can have on the engine. As for what is the definative oil recomended by Toyota, I don't know, but there is enough variation just going on past polls on forum that we use, that pretty much guarantees most of us won't be using the same oil used under testing.

In addition most sports cars are driven hard. do toyota thrape the nuts of tehir test cars? I don't know. Certainly I'd expect more engine failures for us than your average corolla or Yaris, even without the cat issues. In the states when the first failures occured Toyota tried to blame it on people driving their cars too hard. Odd since the advertising encouraged them to do just this. Advertising which has subsequently been witthdrawn, you can take your own conclusions from that.

Now add in what extras people may have on their cars taht could exacerbate the problem, Blitz air filters for example allow far to much s**t into the cylinders, this could score the walls and increase the oil getting past the rings. Will Toyota have tested these? I doubt it.

Finally, I can't give details as this was in confidence, so take it for what it's worth, but I did have a conversation with someone I would consider an expert on Toyota engines and ours in particluar where it was stated that toyota are known for using not substandard but shall we say some of the less desirable catalytic converters that are around, and that better ones could have been sourced. I beleive that statement, you may not.


At the end of the day while we know of a fair few failures in the grand scheme of overall sales it is probably few, and hence it is cheaper for each case to be assesed on it's merits that it would be for them to issue a recall.


However at the end of the day only you presented with what evidence/speculation there is can decide upon whether your convinced by it or not. Personally I don't see a downside to removing them out of warranty, the potential downside of leaving them if they fail is a new engine. but again Only you can make the asessment.


If your decision is to keep them then fine. I would advise howver that in addition to getting toyota to check when serviced (MAKE sure they document it on the service record) I would be checking them every few thousand miles. As Grant said, when they go they don't hang about.

[Tem]

Finally, I can't give details as this was in confidence, so take it for what it's worth, but I did have a conversation with someone I would consider an expert on Toyota engines and ours in particluar where it was stated that toyota are known for using not substandard but shall we say some of the less desirable catalytic converters that are around, and that better ones could have been sourced. I beleive that statement, you may not.

That's easy to believe and I'd be surprised if it wasn't so. Better ones cost more and Toyota is making cars to make money. When normal ppl go buy a car, they couldn't care less if their cats are good or not, they just stare at the pricetag.

[John Woodward]

Mark, that is excellent stuff. Thank you for that. Much appreciated. I take all of what you have said very seriously can see where you are coming from on all points. Like I said before, I am not questioning your knowedge or judgement, I just want to know all the facts before I make what seems to ME a very drastic (regardless of whether you think it is or not) measure.

My car is standard, with no mods (do the side vents count? ) and has only ever had the oil that MrT themselves have put in it at services. It doesn't use oil at any rate (I hardly have to touch it between services. In fact, I don't actually remember having to top it up at all in my time as yet as it has always been full or thereabouts), the car is driven hard-ish, but not thrashed at all.........I would say I take good care of my car. So, maybe what I am asking is am I t risk, regardless of driving style and maintainance? I think maybe this is my main paranoia. I have had suggested to me that I seek an extended warranty to cover me for any engine failure or pre-cat destruction and this seems a very sensible suggestion, as it would have the bonus of covering other things on the car too. As the car is getting to that milage where these things could happen, then it does heighten my worries......

Are there any figures going about on the number of failures compared to sales? Just out of interest? And does this mean that maybe in 1 ir 2 years time MrT is going to have a whole HEAP of cars going back to them with the same problem? Or is it more likely than not that the car will be Ok?

Your info on the "less desirable" materials makes for interesting reading. Does make me wonder why companies like MrT would use usch materials if they know it is going to come back and bite them at a later date? Would they be so calculating, clever and cynical to do this KNOWING that this kind of thing is going to happen after most warranties are out so they know they can make a WHOLE heap of more money repairing what is essentially a problem casued by them in the first place? Would be interesting to know wouldn't it? But that kind of info would NEVER be divulged..........

I think I am going to take your latter bit of advice and get them to check pre-cats on services and have it written on the service report. I may also go down the extended warranty route too. If I had the practical skills and the logistics to do it, then I may consider taking out the pre-cats. At this moment, its not an option I could take, so will have to make all the preventative measures I can...........

I think this is a dilemma that is going to run on for me personally for some time. In the meantime, I am going to be careful, but all I want to do is just enjoy driving my car. can't be too much to ask can it?

Thanks a bunch for all your info Mark. Much appreciated and all taken very much on board..........

[GSB]

[edit] Wrong end of stick... [/edit]

[markiii]

no problem John.

If you go the extended warranty route though, i would check the small print and get in writing whether it covers emmisions gear and consequential damage. In theory you'd expect it too, in practice it will be a bit of a bitch if you cough up £500 or so and then find it isn't.

[John Woodward]

Yeah, you're right there Mark. A family member was bitten by something similar with household appliances. I temd to be VERY careful of what these things cover nowadays.......checking both MrT's and the AA's extended warranties and won't bother with either if they don't cover that kind of thing. Thanks for the reminder........

[keninski]

beginning to wonder if i dare drive my car after reading all this

[markiii]

drive it, enjoy it.

take what pre-cautions you can, and if it does go, it's not earth shattering money to fix.

mine gets redlined regularly thst what I bought t for and thats how it gets driven.

If it all goes the way of the pear such is life.

[GSB]

drive it, enjoy it.

take what pre-cautions you can, and if it does go, it's not earth shattering money to fix.

mine gets redlined regularly thst what I bought t for and thats how it gets driven.

If it all goes the way of the pear such is life.

Couldn't agree more. This is by no means a new problem, but its one you can manage with additional maintenance checks. Its not the end of the earth if it does go bang, but if you carry out some regular inspections, you'll at least have the oppertunity to avert disaster at some point in the future, and save yourself a few hundred quid into the bargain... Otherwise, its business as usual...

[John Woodward]

Beginning to think your way Mark!!! I didn't buy the thing to worry about it going bang. I bought it cos I knew the Mk1s were good (shame about the Mk2s) and I fancied something I could thrash around. Drive it mate. Worry about it later...........