Precat removal - How I did it...

[shnazzle]

I've just bought an MR2 roadster on an 04 plate (facelift) and I have a couple of questions regarding the precats:

If I want to check the precats, which O2 sensor do I remove? Or is it both? Left or right when facing the engine from the back of the car?

Also, presumably I could just replace the precats with one of the de-catted pipes that are available online, rather than hacking out the ceramic material from the old one?
If so, does anyone have a link to a de-catted pipe that they have used and definitely fits OK?

And finally, can anyone on here reassure me that they have removed the precats and then passed a UK MOT?

Many thanks for any comments!

Hi Phil.
Have you had a look at this page? :  l viewtopic.php?f=11&t=11393 l

Check both o2 sensor holes, and yes you can remove it for an ebay manifold (the 89 pound one) with no issues in MOT.
Many many of us have passed MOTs since  s:) s:)

[CrazySX]

Yep as above, remove both, check.
Buy the eBay mani.

I smashed mine through and the car went through MOT less than a month ago

[PhilzMR2]

Thanks for the comments. I think I will replace the mani rather than removing the material from the old one.

I haven't seen one on eBay for £89, other than one from the States with £30 postage. The going rate seems to be around £120

Obviously I will need new gaskets. Do I need sealer of some sort or are the gaskets sufficient on their own? I haven't played with exhaust manifolds before..

[Joesson]

As you say, you will need new gaskets. The general consensus seems to be that OE/ Mr T ' s gasket should be used.
Some on here have reused the original gasket , others have tried the one supplied with the eBay manifold but the surest way is a new OE gasket. No sealant will be required with that gasket, nor should it be used on the head to manifold joint, you would be starting a problem for any future work.
You should also replace the manifold to head nuts as these are an ovoid section locking nut and are not designed for reuse.
A new, crush type gasket is also  required between the bottom of the manifold and the main cat pipe work.
If you can have your 2 off the road for a few days I would suggest you take off all the parts you need to and then buy the gaskets and nuts that you need to replace. You may find that other items such as manifold to head studs will need replacement.
Invest in a can of Plus Gas and soak your nuts for as long as you can before you start!!

[PhilzMR2]

That's very helpful - thank you.   s:) s:)

[mat]

I recently de-catted the manifold on my MR2 but had one spare to play with.  Most of the nuts seized so I had to drill about 5 of them out.  The heat shield bolts are standard  M8, which you drill out with a 6.5mm drill and then tap M8x1.5.  However the '3 amigo' studs are metric fine (M10x1.25) and I struggled to find a tap for these.
One of the studs came out, so I went to Toyota and got a replacement which went straight in.  The other 2 I drilled out with an 8.5mm drill to suit a normal M10x1.5 tap.  I found some studs to suit and hey presto, a lovely spare de-catted manifold with all nuts and studs back in place.

I'm going to spray the heatshields with hi-temp paint then fit all this lot on one fine weekend.
Good luck to others replacing these manifolds - it just takes time.  Even if you have to drill out the studs, it only takes a couple of hours and about 5 drill bits!
By the way, if you do tap out the holes back to metric fine, an 11/32 inch drill bit is a good substitute for the recommended 8.8mm bit you would need for that size tap.

[chris goldson]

Have any of you had engine management light problems after this mod?

[Ardent]

It is fairly/reasonably/not unheard of. That when you disturb the sensors. Remove and put back. That can throw a code. Delicate little things. Does not take much to upset them.

If you have a light. Most likely the sensor related. Irritating but not tragic. Have you got a code reader?

[chris goldson]

Many thanks

Yes it read Bank1 took it into local garage and they renewed two sensors, but 20 miles later light back on again

[Ardent]

Did it show 2 codes?
What were the code(s)?
What did they replace with?
Bank 1 is only half the info

Bank 1 sensor 1?
Bank 1 sensor 2?

[Ardent]

for clarity

Bank 1 Sensor 1 is the top, pre-cat sensor on the right hand side of the manifold (when you are standing at the back of the car looking forward with the engine in front of you)
DTC Codes:
P0135 Oxygen Sensor Heater Circuit Malfunction(Bank 1 Sensor 1),
P0130 Oxygen Sensor Circuit Malfunction (Bank 1Sensor 1)
P0133 Oxygen Sensor Circuit Slow Response (Bank 1 Sensor 1)

Bank 2 Sensor 1 is the top, pre-cat sensor on the left hand side of the manifold (when you are standing at the back of the car looking forward with the engine in front of you)
DTC Codes:
P0155 Oxygen Sensor Heater Circuit Malfunction(Bank 2 Sensor 1)
P0150 Oxygen Sensor Circuit Malfunction (Bank 2 Sensor 1)
P0153 Oxygen Sensor Circuit Slow Response (Bank 2 Sensor 1)

Bank 1 Sensor 2 is the post cat sensor accessible from the bottom of the car just after the main cat. And by the way is a be-ach to get out.
DTC Codes:
P0141 Oxygen Sensor Heater Circuit Malfunction(Bank 1 Sensor 2)
P0136 Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)

[Reeflodge]

Please confirm I have got this right..

x5 Nuts Manifold to Cylinder Head 44NM
x3 Nuts Manifold to Cat 62NM
x2 Nuts Manifold Supprt to Engine Block 37NM
O2 Sensors 44NM

Please correct me if I am wrong!

[Reeflodge]

One of the 3 studs (middle one) from the manifold to the cat snapped when undoing the nut,
Anyone know best was to get out broken stud and what size is the replacement I needs to put in?

[ad_car_08]

I borrowed a stud extractor tool from one of the techys at work.
It was very similar to a drill, where you twist the collar and 3 prongs extend out and tighten. There's then a wrench fitment, or hex on the otherside, which you turn to unscrew the offending stud.


Works like a charm!!

[Bossworld]

Had a quick look in the engine bay while doing other work today.

The car still has the precats at 126k miles and I want them out.  But, it looks as though one bolt is missing, and another appears to be snapped already (picture is of the manifold heat shield).

Am I on a hiding to nothing and what needs to be replaced please?

Thanks

[Joesson]

This query " slipped under the radar"!!
However, if you are still wondering -   The two top fixings are through clearance holes and the fixing enters a thread formed in the manifold. With the two top fixings missing/ sheared it should still be possible to remove the heat shield by removing the two 02 sensors and the lower fixings of the heat shield.
An inspection of the pre cats can be made through the sensor holes when removed.
Plus Gas is your friend when doing this job.
When refitting the broken fixing can ground flat and drilled out and retapped  and replacement M8 stainless steel hex head machine screws used.

[Fredy]

Hy guys, i have a problem for a month, check engine light apears am obd says that is the o2 sensor.
By gutting the precat will it go ? the sensors are new.

[Ardent]

What code?
Which sensors repalced?

[tperry2x]

I know this is an old thread, and sorry to resurrect it, but do you still have the pictures of the precat removal steps as need to do mine. Also, anyone know what OBD2 reader works with a year 2000 MR2 roadster? Many thanks.

[Call the midlife!]

I know this is an old thread, and sorry to resurrect it, but do you still have the pictures of the precat removal steps as need to do mine. Also, anyone know what OBD2 reader works with a year 2000 MR2 roadster? Many thanks.

I use this one but any OBD2 should work as long as yours isn't an import.
You don't really need the photo stream for the pre cats, it's fairly self explanatory once you get the manifold off. Just smash them to bits with a hammer and long screwdriver or similar and make sure you get all the bits out.
There's wadding under the ceramic honeycomb, pull that out with long nose pliers. Be mindful of the threads for the O2 sensors and either blow or suck everything out and Bobs your Uncle!
Or splash out circa £120 on a new, stainless one [emoji2]



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[Treboeth]

 m http://www.mr2oc.co.uk/forums/42/153897.html m
MR2OC has a thread with pics.

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[tperry2x]

Brilliant. Thank you for the replies. Here's where I'm up to (is it OK to link to another bit on this forum) Hope so, sorry if not.
http://www.mr2roc.org/phpBB3/viewtopic.php?f=11&t=63470&p=741949#p741949

I'm really having problems with it being a year 2000 non imported UK car. JOBD instead of OBD2 as far as I can tell?   s:roll: :roll: s:roll:

[Treboeth]

Brilliant. Thank you for the replies. Here's where I'm up to (is it OK to link to another bit on this forum) Hope so, sorry if not.
http://www.mr2roc.org/phpBB3/viewtopic.php?f=11&t=63470&p=741949#p741949

I'm really having problems with it being a year 2000 non imported UK car. JOBD instead of OBD2 as far as I can tell?   s:roll: :roll: s:roll:

Yes it`s fine   s:D s:D  
As long as you promise to keep doing it   s:wink: :wink: s:wink:

[MattB]

  I followed this process and knocked mine out when rebuilding my engine. Relatively straight forward to smash out, then pressure wash to remove the dust etc. No subsequent problems passing MoT

[shnazzle]

I have amended the first post in light of new information provided by Kevin from Zero Exhausts about the stock manifold and gutting the pre-cats and what that (theoretically, although reliably accurately) does to decrease low and mid range performance