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'How To' replace catalytic convertor on Scenic '99-'03

24K views 10 replies 8 participants last post by  DerrekL 
#1 ·
Bit of a PITA to do this but quite manageable if you have a few basic skills.

Tools required are a half decent socket set, torx bits, 13mm spanner, exhaust paste (which I forgot).

Remove Wiper Arms

Ideally this should be done for access reasons. Each is held on with one nut and then should just pull off (might require special puller tool). I couldn't get mine off so worked around them.

Remove Scuttle Panels

Simple procedure as only held in place with a few torx screws along the front edge and either side. If you haven't managed to remove the wiper arms you'll only be able to remove the passenger side scuttle.

Remove Top Bulkhead Panel

Dunno if that's what it's called but it's the panel hidden underneath the scuttle panels. Again, easily removed as held in with two 10mm bolts either side. Again, if you haven't managed to remove wiper arms you can still move the driver side scuttle panel enough to get to the two bolts that side to remove it.

Remove Air Intake and Resonator

Easy as pie, two torx screws hold the front of the air intake just above the grill. Once these have been removed (or broken like I have done) undo the rubber retaining band before the resonator box and pull the rear of the box off of the air filter housing.

Remove Air Filter Housing

Two torx screws hold the air filter housing at the top. Undo these and pull the top out and up.

Remove Air Box on Rear of Throttle Body

You'll need to unclip the electrical connection at the rear drivers side. There is also a pipe of some description, again on the drivers side that needs pulling off. Then it's a case of two bolts (hidden behind the intake manifold), make sure it's the two smaller ones closest to the bulkhead as the larger ones are for the intake manifold!! Once these are undone you should be able to push the box off of the throttle housing and manoeuvre it up up and away.....or to the passenger side if you haven't managed to remove the wiper arms :rolleyes:

Undo Flange Bolts on exhaust

Once you've removed all the above out of your engine bay you will have enough room to be able to remove two of the 13mm (I think) flange bolts that hold the exhaust to the exhaust manifold. The third bolt is accessible from underneath the car (just).

Undo Exhaust Clamp

Just behind the Lambda (O2) sensor is a clamp that needs undoing to allow the exhaust to separate. Simple case of a couple of 13mm nuts. You can either remove the Lambda probe now or just uncilp the electrical connection and remove once you've got the catalytic convertor off.

Removing catalytic converter

Now, this is the real PITA part. Haynes manual suggests lowering the subframe by 20mm at the front and 40mm at the rear. This method includes undoing the steering rod/rack (something like that) and lowering by use of threaded rods.

My method was to eff and jeff at it for a while and wiggle the darn thing out. I did manage it but it's not easy. It's a case of sort of cork screwing the pipe in all manner of directions to get it over the subframe. Now, if you choose this method the worse damage you will do is to make some dents in the heat shield, baring in mind the heat shield is only thin aluminium or the like I was quite surprised how much abuse it took :rofl:

Obviously, you choose this method at your own peril. If you can be bothered to lower the subframe then I'd suggest you do so ;)

Refit in reverse

You should replace the gasket at the flange and use exhaust paste where the exhaust joins the rest of the system behind the catalytic converter.Hopefully that's been of some help.

I did start taking pictures but the dirtier my hands got and the more effing and jeffing I lost the will to take my phone out.
 
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#8 ·
I'd imagine it's pretty much the same across the range! The reason Haynes suggest lowering the subframe is because the flange on the engine side of the exhaust is shaped as such that it won't easily come out over the subframe! Be warned, it is a real PITA but can be done. The higher you can jack the car up [safely] the easier it will be as you'll have more room/angle to manoeuvre the exhaust ;)
 
#9 ·
I recently did mine coincidentaly by the method you describe above,when tàking good one from 03 to replace onto 00 as I was not going to drive the 03 anymore ( as it is 6 inches shorter on one side now) but easy it was not, ie sheering off studs,putting it onto its new home was don without removeing half the engine bay,not recomended it is quite litteraly only just possible with skin left on knuckles,painstakingly turning each nut about 5 mm at a time,but it must be said the absolute worst part was manouvering the flange past the steering rack so I hope I don't have to do again any time soon
 
#10 ·
Yep, I can confirm the 'wiggle it' method does work having seen this very post and employing a bit of brute force and ignorance on my '01 1600 RXE (a.k.a the mirth mobile) What helped putting the new one on was shaving the Cat's manifold flange a little, that is machining a 5mm sliver off the bottom by removing the 'peak' off the triangular bottom edge, and also nipping a few MM off the top of the flange above the top stud hole..obviously being careful not to remove too much. Then the new cat slid right in without any fuss, and will also come out again the same way... I managed all this on the garage floor with the car jacked up & secured about a foot... So thanks to the original poster!
 
#11 ·
I have a similar issue in replacing the front down-pipe cat on my Scenic mk1 1.4 1999 in that it looks near impossible to put the triangular flange through the gap from steering rack.

Is this the same as the above scenario i.e. the ‘wiggle method’ I'm thinking about grinding a good few MM off the flange before attempting this.

Your thoughts would be appreciated.
 
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