Pre-cats: The Official MR2-ROC Information Thread

[bluesmoke]

Metricated I am! Will do this tonight. Then run the car up to temp so that the paste can do its thing.

[Joesson]

Blue smoke and harvey718 I suggest you have a look at the new members section, BillRitson has a 2 with 217k miles since he had it from new.
For the first 120k the oil and filter was changed every 5k!

[bluesmoke]

Blue smoke and harvey718 I suggest you have a look at the new members section, BillRitson has a 2 with 217k miles since he had it from new.
For the first 120k the oil and filter was changed every 5k!

I saw it a few days ago. Amazing!

[Swanseamr2]

I've researched this issue and it seems most failures occur to the pre cats on early pre face lift cars. I have a 2004 with 27000 miles on clock. Don't know whether to remove the pre cats. It appears most people with cars pre 2003 have this issue?

[Joesson]

I suggest that BillRitson ( see newcomers) got it right.
His car must have been regularly used and regularly had an oil and filter change.
I am of the opinion that the precats fail after excessive oil consumption and exhausting the burnt oil via the precats causes there break down.
Your 2004, will have some of the piston and oil control ring modifications that Toyota made post 2003 to end of model manufacture. With reatively low mileage and hopefully regular oil and filter changes your car is less likely than mine (2002/ 54k) to suffer oval bores.
I decided to remove the precats. It was not a difficul process, I refurbed the heat shields while doing it.
There has been no problem with subsequent MOT emission tests and for sure my precats cannot damage my engine.
I wouldn't t advise you to retain or remove your precats.
I would advise that you regularly change the oil and filter.
Whatever your choice enjoy  your 2.

[Swanseamr2]

Thanks for the info. I intend to change my oil regularly and use the car daily . Hopefully all will be ok with the pre cats . I've just had the car serviced. And will ensure it's done often

[dkirkwood89]

Just reading this now for the first time, very good write-up

food for thought...

[dkirkwood89]

Thought I'd read on down through the posts, have a couple of questions now (apologies if they've been answered, I read through the first 2 pages and my eyes are going blurry and better get back to work so thought I'd post):

1 - taking everything into account other than cost, would it be better to remove the precats or buy a new manifold?
2 - If its buying a new manifold, can anyone recommend a few to look at, including performance ones?
3 - If I removed the pre-cats, does it affect any tests and would I have to inform anybody like insurance company, tax etc.?

Dale

[Roadster]

Thought I'd read on down through the posts, have a couple of questions now (apologies if they've been answered, I read through the first 2 pages and my eyes are going blurry and better get back to work so thought I'd post):

1 - taking everything into account other than cost, would it be better to remove the precats or buy a new manifold?
2 - If its buying a new manifold, can anyone recommend a few to look at, including performance ones?
3 - If I removed the pre-cats, does it affect any tests and would I have to inform anybody like insurance company, tax etc.?

Dale

I Just bought a new manifold & Manifold bolts (as some don't come with new bolts), cost me £120 for the manifold and about £30 for the 6 manifold bolts

 m http://www.ebay.co.uk/itm/TOYOTA-MR2-RO ... 483cb398aa m

And I bought the bolts from this site

 l viewtopic.php?f=57&t=50500 l

If you choose to replace the manifold, the heat shield will not go back into the non-genuine manifold, i've never had any problems with this or heard of anyone who has had these problems, been using this manifold for over 6 months without any problems, other tip would be when removing the diaper under the car, you only need to remove the rear diaper, and half of the middle diaper, you don't need to crawl all the way under your car to completely remove the middle diaper

[tricky1138]

I'm hoping that Wabbitkilla will read this and post the pictures that he took, but I've just replaced my manifold and not a moment too soon.

The precats had just started to breakdown and any longer and that would be knackered main cat and possibly knackered engine!

My car doesn't burn any oil, nor did it use any generally,  but the precats we still starting to break down.

Get them out ASAP!

[Swanseamr2]

So do you think that engine begins to burn oil due to poor maintenance and the oil changes not being carried out regularly? I have seen some Mr2s on here with mileage well over 100,000 and still on same engine. Most of these have been serviced regularly

[Ginny]

Having bought my 2 a couple of months ago and added another 2k to the 17 it had already, I saw this thread about pre-cats and the potential damage. Decided to go down the route of an after market manifold.
Getting the old one off . . what a nightmare! Ended up cutting the heat shield on the right hand O2 sensor hole as I didn't have an O2 socket and, having cut my shiny new 22mm DD socket and found it didn't work, I was in a no nonsense mood. Most of the bolts were so rusty they broke off. The bottom flange wasn't too bad and the top was easy. However it took me a good few hours of digging deep in my box of swear words to get it off and out. Five minutes later the new one was in, the O2 sensors removed from the now easily accessible manifold. A short while after that it was all buttoned up . . I say buttoned but quite a few of the bolts holding the plastic bits underneath had also sheared off due to the excessive rust. Never mind, that is what tie wraps are for hey? Off I went down the road smoke pouring out of the engine bay as all the old WD40 burnt off   s:D s:D  As I slowed for the roundabout a horrible noise like something dragging on the ground made itself heard. I pulled over in the petrol station . . smoke still coming from the back   s:flame: :flame: s:flame:   whoops. Anyway nothing to be seen so I slowly drove back home with an awful noise coming from my lovely little car. By this time I was thoroughly sunburnt and hurting so I called it a day.
This morning I carefully got dressed and rigged up a sunshade over the back of the car and slathered myself in factor 40. Removed the plastic stuff from underneath and had a look. The 2 into 1 section's heat shield was right up against the cross member where the bolt hole is. I tried slackening joints and levering to no avail. Right that heat shield is coming off! No I am not says the heat shield. A war ensued. I removed one nut and bolt, cut off three others and left the stupid one in between the two pipes where it was. I managed to wriggle and jiggle the heat shield until I had some daylight showing between it and the cross member. Using a screwdriver as a podger I managed to line up the holes in the tin ware and get a new bolt in. Now the opposite side which had been the offending area . .another bolt. So far so good. The bracket things had lined up reasonably well. Now to the two that join it to the tin ware on the next section rearwards. Podged one set of holes into alignment and bolted. The other was nowhere near lining up so stuff it. It'll have to stay like that.
Checked the clearance was still there . . . . yeah. Off the ramps and a quick blast up the road for a few metres. OK reverse it back . . OK Oooh seems like it might have just enough clearance. Back on the ramps to stick the plastic stuff on again and take it for a blast on the road. Down to the roundabout accelerating hard and braking hard. . . . .sweet sounds. Round the roundabout not quite getting my knee down but hard -ish . . . OK. Back home reverse it hard and brake . . OK. Seems I may have done it.
If I haven't then the next stop for my little car is a visit to the race workshop where I can get the oxy-acetylene onto that fifth bolt. Heat shields off and exhaust wrap on. That will definitely sort it. But for now the main thing is I don't have any pre-cats or any lingering doubts about whether the garage mechs got all the ceramic out of the old manifold   s:D s:D

[Joesson]

That' s a nice low mileage "2" you have found for yourself.
The pre emptive surgery should do no harm other than perhaps aggravate symptoms of moditis !

[Ginny]

Thank you, yes it is a lovely low mileage example. Not the colour I would have chosen and not the trim option I would have chosen. But the mileage! That trumped all other considerations. Well worth the aggravation of the modification to keep it in tip top condition. As for moditis? I am not addicted, I can control it and give up any time I want lol . . . .ooh MAFmod hmmmm

[Reeflodge]

Thanks I'm going to give it a go but I am going to be prepared!

Does anyone know what bolts sizes I will need as I may as well replace them as a go?
Also which gaskets do I need?

Thanks again

[Reeflodge]

Just done mine, one manifold bolt took me 5 fricking hours to get undone!!!

I also noticed that there was no gasket rings between the main cat and manifold!
I have ordered a new manifold gasket and ring gaskets.

Need to get a new stud and bolt thern reassemble,
someone said to dip the studs in copper grease so going to do that.

Question.... Is the plastic under panel  underneath the engine bay in 2 parts as I only seem to have one piece under the oil sump?

[shnazzle]

5hrs?!? One religious figure on a pedaled vehicle.

Good man for sticking with it.

Bottom panel is indeed in 2 parts. The "nappy" on the rear covering the cat and the middle bit covering the sump

[Reeflodge]

Question?

Now that I have done the De-cat mod what if the Main cat started to break up?
It now would have a straight path into the engine!

My main cat was replaced earlier this year as Mr T said there was a rattling from the exhaust (not Manifold) and suspected the main cat was breaking up!

[Bossworld]

Sorry if I've missed it but read pages of this thread. Is there a list of the parts required as part of this process (seen people mention replacement gaskets and bolts)?  Going to tackle it in the next couple of weekends, wish me luck.

Thank you

[shnazzle]

All the exhaust gaskets and if you're lucky the bolts are reusable.

What I would do is spray the crap out of the manifold bolts (at block and top of cat pipe) and see if you can undo them. If they come undone, saves you almost 70 quid in bolts.

[Bossworld]

All the exhaust gaskets and if you're lucky the bolts are reusable.

What I would do is spray the crap out of the manifold bolts (at block and top of cat pipe) and see if you can undo them. If they come undone, saves you almost 70 quid in bolts.

Cheers, just going to take it steady and come back to it, car is in the garage for winter now anyway.

Found a list on Facebook if it's of use for future reference (Credit to Edward Banzan):

T17173-22010 manifold gasket x1 £20.32. The nuts are T90179-08228 x5 £1.14, CAT gasket £4.15 T90917-06066 X2, three amigo nuts T90179-10070 £1.85, burrows Toyota doncaster

[Mod]a quick heads-up - crush gasket part number is 90917-06065, not 06066 as stated.

[shnazzle]

That's it! Also bear in mind your exhaust to cat bolts (with springs) might be too far gone to re-use.
They're a stupid amount per bolt. I believe 12 quid each excluding spring.

[Kitch]

Hi Guys,

I'm new to the site having just bought a mk3, however the first thing I noticed is the precats are well and truly knackered!
The car seems to be running fine however with a slight tapping noise from the engine at over 4000 rpm, would this sound be because of the damaged precat?

Don't know wether to decat it of send it back to the lad in bought it off and look for another.
Cheers

[shnazzle]

Tough one Kitch. But given the evidence suggesting engine damage from pre-cat failure, which is caused by oil control rings failing, there's enough grounds to send it back I reckon. Unless they take it back, rebuild the block, replace the manifold (or knock the pre-cats out) and give it back

[Ben]

I was lucky enough to have been bought an MR2 roadster for a 'special' birthday 6 months ago. It is a 2002 pre-facelift model - a fantastic car and I've loved every minute of driving it.

Like anyone with a new toy, I soon found the mr2oc online and read all about pre-cat failure and piston rings and began to think my car would be a liability. I check the pre-cats regularly (all intact) and it hasn't used a drop of oil in 7,000 miles (now done nearly 100,000). all the online forums and buyers guides state that the piston rings were improved for the facelift model and they all recommend that this is the one to go for. I was worried - was my car a lemon?

The I found the Toyota online parts catalogue (toyota.epc-data.com) and found that the piston rings, pistons, short block and exhaust manifold were all updated well before the facelift model was launched.

For example, the parts number for piston rings for a car built between 12/99 and 11/01 is 13011-22090. The same part for a car built between 11/01 and 09/05 is 13011-22150.  The facelift cars were built from 08/02.

So, basically, a pre-facelift car built from November 2001 has exactly the same piston rings, pistons, short block and exhaust manifold as the facelift model.

This is backed up by the mr2roc log of pre-cat/engine failures.  It has details of 20 cars that have destroyed their engines. 18 of them were first registered 1999-2001. Of only two cars registered 2002/3, one blew up on a track day so I'm not sure that counts...  So at least 90% of engine blow-ups have been in cars built before 2002.

If you're not sure when your car was built, enter your VIN on the toyota.epc-data.com website and it'll give you the build date. If you've got a pre-facelift care built after November 2001, its engine is identical to the facelift model. The only difference is, you probably didn't have to pay as much for it and it's a lot better looking...

I think this is an important point - most buyers guides out there advise that the face-lift is the mechanically stronger car and many pre-facelift cars are undervalued as a result.  It seems most motoring journalists are happy to assume this is true without taking the trouble to investigate a bit further.

I will probably still remove the pre-cats; I get that they're a liability.  So far I've changed the gearbox/diff oil (Redline MT90), engine oil (fully synth 5/30), filters and put new tyres all round.

Great car. Great owners club - but stop dissing the pre-facelift!!