Public Portfolio Site & Various Posts.

Posts tagged “Opel

Can you make a mild steel exhaust last longer ?


Something else I needed to fit was a new mid silencer on the Zafira, since the rubbish the garage fitted split along its plated seam after less than a year.

Luckily the new section I have is “rolled” instead of “pressed” meaning it only has one  long edge seam instead of two physical sections tacked together. So my plan for this is just to give the product more protection from the elements, it’s mild steel and it will fail eventually but it might help a little…


Versachem is a good product, and it is a strong sealer so I have applied it to all the seam edges on the box, notice how it’s embedded into the small gaps nicely…


Here is another example on the recesses, this only took about five minutes skimming the versachem wearing latex gloves (seriously use gloves as versachem is rather potent stuff).


Spraying is also a rather quick task, since this is matte VHT it tends not to run so bad and even one coat looks rather tidy. Also it can be good to tape the edges to give a cleaner finish (not that anyone will see this work of art lol).


After fifteen minutes I applied another quick coat.


I applied the paint mostly to the ends and on the long seam edge, after five minutes of drying you see it goes to this flat matt colour and does not look too bad at all. To finish I sprayed the hanger sections also just to help protect the welds.

That concludes my little DIY post here on a little rust/corrosion protection for budget exhaust components, have a good day 🙂

Z16Xe Zafira A / Astra G Catalytic Converter Replacement


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:

  1. Get nut/bolt extractors to make removal much easier
  2. 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.

Kenny 🙂

001: Engine Rebuild Task


This was an optional unit but one of the more interesting things to do in the first year. The engine is from an old vectra around 1998 (X18XE) and is pretty stripped down having just the basic main components left to remove, inspect, clean and re-install. The following photos are some of the stages from this task.


Head strip down, cam caps etc…


Head removed.


Valves removed.


Bottom end sump and oil strainer etc coming off.


Trying to keep everything in some sort of order here !



Bottom end components coming out.


Pistons and bottom end caps out.


Cleaning of the bare cylinder head.


Next years students wont need to do much cleaning on the head.


Perhaps this was cleaned too much as well !


Sticking to who knows best (the book).


Pistons back in @ TDC.


Bottom end oil components going back on.


Time to flip back to the head.


Valves going back in.


Valve collets can be a nightmare. Using a compound or grease like this helps drop them back into their recesses with more precision.


Head bolt order (torqued to 25nm for stage 1, then 90 degrees for stage 2, 90 degrees for stage 3, 90 degrees for stage 4 and 15 degrees for stage 5. Cylinder head bolts were torqued in a reverse spiral pattern as shown in the manual)


Cams going back in.


Taking notes from auto-data. Notice the requirement of a cam-lock and how the tensioner functions.


Timing belt refitted and the engine was cranked by hand to see if it was timed correctly. Luckily mine okay first go !

Here is my conclusion taken from my job card:

Conclusion: In the process of stripping down this engine unit i found 1 crucial scew (1x cam bearing torx cap) to be missing and a half valve collet also missing. The cam cover gasket did not look capable of providing a good seal but the head gasket was in a reasonable used condition. The gasket for the bottom end cover appeared to be in good condition. Having observed the piston walls their condition was acceptable but the piston from cylinder 1 had scoring marks on its thrust side.

I looked up online what could be the problem. Resources suggested that scuffing marks on the exhaust side of the skirt without corresponding marks on the intake side means the lubrication film failed under thermal load on the exhaust side of the piston. The possible cause of this could of been the use of poor quality/wrong type/lack of engine oil. I checked the end gaps on one of the pistons and they were all in the required ranges. On the other pistons though some of the compression rings clearly had gaps too large and these would have to be replaced.

For more info on this task go here:!8344