In principal this is quite a simple job and you don’t really need to be mechanically minded to do this at all, what makes it a pain is rusty nuts ! Be prepared for those rusty nuts from hell ! In this post I will just outline some tips when it comes to replacing the cat for this specific vehicle as it might come in useful for others out there.
So it’s been fifteen years and 65k miles for my Dad’s Zafira, I guess it’s going through the “bits are wearing out” kinda stage. The vehicle has been flawless but in the last year the following have happened:
Exhaust muffler blow – Replaced
Exhaust mid silencer blow – Replaced
Downpipe flex collapse – Replaced
Primary and Secondary o2 sensor failure – Replaced (use genuine NTK/GM/Bosch/Denso or you might get EML issues!)
And now the latest addition: “P0420 – Catalyst System Low Efficiency” ! Eeekk
So this is the best answer I found to removing all the manifold nuts. This is a tool known as a “nut/bolt extractor” and is essentially a sharp spiral teething socket that grips into rusted nuts or bolts and gets them loose ! The ones I went for are the “Irwin Bolt Grip Expansion Set” which has the correct 10mm fitment for the Zafra/Astra G. I would not of got the job done without these they are perfect for this job. It is possible to do the nuts off with a chisel and a hammer but the “Irwin’s” save loads of time and risk of damaging the stud threads.
Would you like to see what happened to the old catalytic converter ? Well here you are, no wonder it wasn’t do it’s job most of the monolith element was gone ! As you can see it is a really chalky colour which is a sign of fatigue and heat damage, 17 years though cannot complain !
There is not much else to mention apart from some tips regarding the new cat. I purchased an “eBay approved cat” costing £100 but there are some differences to note against the OEM GM cat !
Firstly as you can see in the photograph the bottom down pipe connection has bolt holes instead of integrated studs. This is fine apart from the Screws/Nuts supplied are absolute rubbish ! I don’t know what they are but the nuts have weird dipped threads so when you are putting the nuts on they suddenly go extremely tight, and it’s impossible to do laying under the car using a socket in one hand and a spanner in the other !
My advice is ditch the provided Screws/Nuts and pick up the Halfords M8 assortment pack for £3.48 they are perfect for the job and save a lot of hassle !
Also another mention which is unavoidable really but still a bummer and that’s the manifold casting shape. Basically the new one has slightly shallower header branches, if you look carefully on the photo above you will see the far right branch is a fatter shape and this makes the far right bottom nut really damn hard to fit ! The only way I could get it done was to remove the oil filter, and even after that it took about half an hour to fit the damn nut with an open end spanner !
So just to conclude this task:
- Get nut/bolt extractors to make removal much easier
- If you can pickup a new or very good genuine OEM GM cat it will be easier to fit !
Hope this help anyone out there, leave a comment if you have any questions.
The year seems to be going super fast, and finally the weather in the UK is getting better. I’ve mainly been out cycling which has felt somewhat beneficial, and over the break we had an awesome trip at the Go Ape course near Leeds Castle. I’ll be honest I was a little nervous at first since I had no real idea what to do, but after working out the equipment it was really amazing. I want to do a similar course perhaps bigger and more dangerous, probably have to go half way round the world for that !
Here is one of the Folkestone students that was in my group, the zip lines are pretty big, around 250m long and guessing probably around 100ft high.
I tried to use my camera on the big zip line and get a 1/15th shot to show the speed of motion, but I Kinda ended up in a spin… I was holding the cam with two hands and using the viewfinder when I’m supposed to be holding onto the safety harness ! Why did I not use live view you might well ask ? I use the view finder so damn much I forgot about it to be honest. Basically it didn’t work out but I still like the effect…
Like I said with cycling I’ve been doing a lot of that, and the Hope Pro 2 hub I’ve fitted to the bike has really improved the drive pickup, though I’m still getting used to the sound ! Here I’ve parked up at Sandy Lanes just checking it out, a couple of bricks and sticks to move otherwise some of trails seem okay. I want to rebuild the front wheel as well now it seems too weak in comparison. After 16 years I decided to renew the bottom bracket also, it didn’t need one but they are not expensive so I’ve fitted an UN55 in place of the UN52 and it seems good.
In the workshop I’ve completed a few more tasks and only have one left to do now ! Recent ones have been diagnosing a turbo charger pressure fault, audio equipment fault, and a steering related fault. I got to do some kind of pre-MOT inspection so I’m not sure when that is happening because it will have to be done in the other workshop, using the necessary testing facilities like the brake roller.
Here is an example of the evidence I have to submit with diagnosing audio equipment. Although the problem was damage to the component speaker wiring in the door I still have to show a methodical approach, so going to the stereo fuse first, then moving on to checking the output from the head unit amplifier etc. until getting to the component speaker in the door and no signal after entering the door indicates a wiring damage/high resistance.
I got my LV07 assignment passed a few weeks back which is good. This assignment is about describing an electronic fuel injection system and outlining an in depth diagnosis of a specific problem that can occur on the system. I did my investigation about solder breaks on the PCB for a Fuel Pump Relay. I have Mark Lamond with his great website to thank for the in depth look at the Honda CRX.
With this I was able to base my own essay off the scenario and pin it onto a newer vehicle. This fault is only common on 80’s / 90’s era cars but it still poses some relativity with vehicles that often cross climates from cold winters to hot summers.
LV07 engine and LV08 chassis exams have both been passed first time as usual. I was not totally impressed with the engine LV07 exam, getting questions about variable valve timing and just generally old stuff really. There was nothing on electric cars, hybrids, common rail diesel, direct injection, variable turbo geometry etc… I was not really expecting these things to come up, but I think the exams should focus on much newer tech because it gets quite boring covering stuff I learned in my first year.
I end the post on a rather tragic note, and that was the team I participated with did not win the skills competition over at the Broadstairs campus, we came second by half a point ! Well done to EKC Broadstairs for getting 1st place and to the other colleges that took part in the event, it was a good laugh and I leaned a fair bit on the day.