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Another stolen document of the Astra Network :lol:

check original link as some pics are missing, CCUK only allow 40 image uploads at a time!

Ok here is a guide I have wrote for you people to refurbish your z20let turbo without going to a specialist and paying high bills.
It can be done at home with the right tools and not cost you a lot.

Firstly anything you see/read in the guide and attempt to do yourself, I take no responsibility in any damage caused doing this. You are following this guide at your own risk!

Before getting onto the guide you’re going to need some supplies,
How to acquire a refurbishment kit:
I purchased mine from eBay, just search K04 have a scroll through the few pages there is you’ll see a few rebuild kits advertised.
The kit I got was this:

10mm Spanner
13mm Spanner
19mm Spanner
E10, E12, E14, E16 Sockets
Socket set
T50 Torx Piece

Few other bits.

Onto the guide;
You’re going to need to take the turbo off the car. I’ve not wrote a guide on this as there is one on the zlet site located here: I will say, I struggled getting 2 nuts off the turbo that are on the underside of the turbo behind the actuator. In order to take these off I didn’t use the E16 socket, I used a T50 torx bit. When removing the turbo and re-attaching it follow the guide on the zlet site and do make sure to torque all bolts correctly.
So once the turbo is off the car your left with this:

We now need to remove the compressor housing and turbine housing in order to get to the CHRA. I just basically unbolted everything off, here are some pictures;

Compressor housing and turbine housing now off, we have the CHRA.

IF you do attempt this you MUST scribe across the compressor wheel, nut and end of shaft before unbolting anything off the CHRA. If you don’t do this there is a high chance when you bolt it all together the turbo will be out of balance.
So now you’ve scribed the turbo, were going to need to remove the compressor wheel nut. To do this you have need 13mm spanner on exhaust compressor, and 10mm on intake. The nut is oppersite threaded so clockwise to undo!
Note - If I were you id first wrap the blades up with a towel or use gloves, because if you slip and your hand hits them it’s going to hurt, along with a high possibility you’ll see a lot of blood.

After you have removed the nut and compressor wheel, you can remove the turbine wheel along with the shaft and heat shield.

Next we remove the seal plate, along with collar.

Inside the seal plate we can see the collar and piston ring; you’ll need to remove all the carbon especially around were the compressor piston ring sits.

Now we have the seal plate removed we can see the entire bearing system. We will now remove all this, removing all carbon ready for clean new components.

First we remove the oil deflector,

Second is the thrust bearing,

Third the flinger sleeve,

Fourth the snap ring,

Fifth the o-ring,

Now, all we need to do is take the lock plate off and we can easily remove the journal bearing.

Lastly remove the Journal bearing, making sure to see if it has 2 small holes or if its twin feed.

First thing, make sure all parts removed are retained until rebuild is complete.

Now the CHRA and bearing system is all removed you need to make sure you remove all the carbon from components. We are also going to need to clean the shaft of all carbon too.

So in order to remove carbon and cleanup the shaft we will need to use some 1200grit sand paper, remove the surface varnish then polish it up with some kind of metal polish. Make sure the shaft shines, with no dull areas or scoring. Next rinse the shaft in water, also rinse the exhaust wheel. Now we need to clean the shaft and exhaust wheel with some thinners to get rid of any contaminants from the water. Soon as this is done coat the shaft only with engine oil to prevent from rust, as it’ll form quickly.

So now all the dissembling is done and cleaning. You’ll need to put a new bearing onto the shaft.

After you’ve cleaned the bearing housing of all carbon, you can install the new journal bearing into the CHRA.

Next we put on the new lock plate.

Make sure this lock plate is locked into place, see above image.

Ok so now its time to put the snap ring into place, this can take some time to do but if you push enough you’ll get it into the groove.

We will be using the original flinger sleeve which we retained.

Now we insert the new thrust bearing.

Next we use the original oil deflector.

Put the new o-ring in place.

So now we need to insert a new compressor piston ring on the collar, make sure you also remove all carbon deposits off the collar.

Place the collar into the seal plate.

This can be quite tight, you may need to push the collar in at a angle and use a small tool to poke the compressor piston ring in.

Now we have the seal plate with the collar and new compressor piston ring in, we need to make sure that the collar will rotate smoothly before placing this onto the bearing housing. So do this by holding the middle and making sure it will turn freely.

Once the seal plate is on the bearing housing after you’ve made sure its all moving freely, we need to clean all carbon off the heat shield. Make sure you clean in the middle of the heat shield as this contacts another piston ring.

Now place the heat shield onto the bottom of the bearing housing.

Place the turbine shaft into the bearing housing, and push this making sure the piston ring is on the central of the groove. You may damage the piston ring if it isn’t central.

Make sure the turbine shaft can rotate freely.
Now place on the compressor wheel and nut.

We are now at the second most important part of the rebuild. Make sure you align the compressor wheel, nut and shaft all correctly up to the scribed line. Just as it was before we took it apart.
Rebuilding the turbo is now complete; reassemble the CHRA into the compressor and turbine housing, connect all pipes and bolt back to the car.

For bolting to the car just follow the guide on the zlet site following it backwards, making sure to use the correct torque settings.

Hopefully this guide has helped you, or either been an interesting read for you.
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