Precats removed without removing the manifold!

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Topic author
StuUK
Posts: 4
Joined: 19/02/20 14:48

Precats removed without removing the manifold!

Post by StuUK »

I removed my precats while the manifold was still on the car.

Reason was my heatshield bolts were rusted solid and I assumed my manifold studs would have been similar

Well I got it all done today!
It's very messy but definitely do able.
For anyone who is interested here was my basic procedure.
Get backend as high as possible, I have a decent trolley jack and sat the back wheels on car ramps.
Remove the 3 amigo's
i couldn't remove the 2 bolts holding the other end of the main cat to the silencer although completely removing the cat would have been much better.
I removed the rubber hangers from the left side of the silencer on top, the tailpipe and the cat. That way i could swing the manifold end of the cat out of the way and tied it off, I also put a bag over the open pipes.
Remove the O2 sensors from the manifold no need to remove the heatshield.
Wear protective clothing, face mask and goggles.
Forget about attacking the precats from the o2 sensor holes its a waste of time.
I used a 1 inch spade woodbit in my dewalt drill/screwdriver set at screwdriver speed and just attacked the precat from underneath through both holes.
Use a large bucket or tray to catch most of the debris
Work your way around each precat working the drill up and down and side to side. It's messy! Eventually it will all come out along with what looks like a load of cotton wool wadding
I took my time and cleaned up the mess multiple times
Check, check and check again everything is out. I used a garage endoscopy type camera looking from both ends.
Then from the o2 sensor holes I flushed the now empty precat cannisters out multiple times with a hosepipe set to a moderate flow..
Final check with the inspection camera and i was happy
Reassembled everything and job done
Peace of mind that precats are out.

Final thought if the manifold comes off easily then that would be best way to do it simply due to being able to control the mess. But if like me you didnt want to or couldn't remove the manifold for whatever reason then this way certainly works. You just have to be careful with the mess and ceramic dust. I forgot to mention as a final cleanup measure I ran my engine for a minute or two with the main cat still detached just in case any dust was still lingering in the canisters.


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