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Thread: How To: Rebuild a T25/T28 Turbo (PIC HEAVY)

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2009-08-16 02:26:20
How To: Rebuild a T25/T28 Turbo (PIC HEAVY)
Okay guys, this will be my first "How To", so it may not be as pretty as some of you guys are doing. This informational thread will be for you to learn how to tear down and rebuild a turbo, without needing to send it off to be re-balanced. This will save you TONS of money in the long run, since most genuine garrett rebuild kits run you around $90 plus shipping on sites like eBay.

I'm using Jensen's turbo to demonstrate, as his CLEARLY needs a rebuild. A quick look at the turbine's exterior indicates that the exhaust seal is gone, completely.

Before you begin disassembling everything, make sure to mark the positions of the exhaust and compressor housings, relative to the center cartridge. This will only make reassembly easier in the long run, so that you're not frustrated when you have to re-clock the turbo after re-installing.

Here you can see that I've removed the compressor housing (13mm or 1/2" wrench and BIG set of 90* snap ring pliers,) and marked the nut/compressor wheel. This is CRITICAL, if you don't want to have to send the turbine off to be rebalanced. It's a little difficult to see where I've marked due to the flash. I marked the nut relative to the wheel in three different locations, one mark being wider than the others. I chose three marks because you may inadvertently rub one of the marks off during tear-down.

After removing the compressor housing, it was time to remove the exhaust housing. The exhaust housing was damn near impossible to remove. Apparently this turbo has had a bad exhaust seal for a LOOONG time. After soaking overnight, I still wasn't able to get it freed, so I went to my friend's shop to use their BFH. When you're removing it, use the 13MM wrench again, but don't remove the bolts all the way. They may not come out all the way anyway, because of the center housing. Take a decent sized hammer (5lb. is what we used), and hold the compressor side up, and hit down directly on the exhaust housing. It will eventually break free. This is what we were looking at:

Moving along... Time to separate the wheels from eachother. The thread for the nut on the compressor wheel is LEFT HAND, so lefty tighty, righty loosey . Use a 5/16" (IIRC) 12pt socket for the nut, and vise grips for the exhaust side. CAREFULLY break the nut loose, then ensure that you still haven't moved the wheels out of balance via the marks that you created. (remember that when you broke the nut loose, that it should be a LITTLE off from where it should have been.) When you remove the nut, be careful not to disturb the wheels. Mark the shaft again when the nut has been removed, so that when you reassemble you're 100% sure that you're still maintaining the balalance.

Here you see all the markings I did with respect to the shaft (shaft not shown) and with respect to the nut.

Once the wheel has been removed, you'll see a snap ring holding on a plate:

Next up, removal of the wheel assembly. if you cannot tap the whole wheel assembly out by tapping on the top of the shaft (compressor wheel side), then just turn the turbo so that the exh. wheel is up, and gently tap the whole assembly onto the work surface, forcing the shaft up.

What the shaft will look like when removed (hopefully not THIS bad)

Now you're left with this:

After removal of the wheel assembly, you can start disassembling the "guts" from the center cartridge. Flip the cartridge back over so that you have access to the compressor side. Remove the snap-ring, then the top plate.

2009-08-16 02:26:40
Continued from last picture. You'll see above in the last picture, that this turbo is a DYNAMICALLY SEALED turbo, and not CARBON SEALED. From what I have gathered, small frame turbochargers before 1990 were carbon sealed, and not dynamically sealed. The carbon seals look A TON different than dynamic seals. Remove the thrust collar by simply moving it towards the cartridge housing. It's slotted and sits in the thrust bearing. (The thrust bearing is the funky looking thing with three torx head screws holding it in the cartridge).

Once you have removed the thrust collar, you can remove the thrust bearing itself.
Use a T-15 torx socket, or one of these handy multi-size torx kits.

Now to remove the bearing (Bearing is the LONG type, 9mm in length. This is IMPORTANT). The bearing has several holes in it, that will allow you to grab with an awl (dental pick), and pull out. Depending on the wear of the bearing, you may have a harder time than I did, removing the bearing. This one came out without ANY issues. It actually fell out when I turned the cartridge.

Directly below the bearing is a circlip. If you have snap ring pliers that are small enough and long enough, you can use those. I just used two awls and was able to pull it out relatively easy. It's pretty flimsy, so use caution if you plan to re-use it.

Note, you can see the rubber seal above. Go ahead and remove that now.

You're now finished with the compressor side of the center cartridge.
2009-08-16 02:27:25
Now to break down the turbine (exhaust) side of the cartridge. First things first, there's a piston ring that's rather difficult to get out. I didn't waste too much time since I'm getting a full rebuild kit. This piston ring is a double wrapped o-ring, meaning it's like a compressed spring. You can lift up the corner and try to counter-rotate it until it comes out, or you can do what I did and just yank it out with a dental pick.

Underneath this, you have a washer. Go ahead and remove that now.

Next you need to remove the other bearing, which will be the same as above (the LONG bearing).

Now you've got yet another circlip (a total of two for the entire turbocharger). Yep, you guessed it. That needs to be removed too.

Once you're done, that pretty much wraps up the tear-down. I took the opportunity to clean up the center cartridge with a brass wheel on my dremel tool. I'm also taking the time to soak the exhaust wheel assembly in parts cleaner. There's tons of carbon/oil deposits that should be cleaned off (not completely necessary, but why not???). A picture or two of the center cartridge after cleaning:

Other posts reserved for the rebuild, once I receive it and start the process. I'll take a pic or two of the exhaust wheel assembly once it's all nice and clean for before/after comparison.
2009-08-16 02:27:46
Rebuild procedures:

Here you will see the kit that was used. There are some parts that will not be utilized, you can keep them or toss them. I will send them back with the rebuilt turbo to Jen, and he can determine what he wants to do with them:

Note the dental pick's location. I'm pointing to one of the gasket-rings that was not removed during disassembly. As previously mentioned, I'd post that they need to be replaced before we get to in depth with the build.

Old left, new right:

It's a little bit tricky to remove, so be careful! Replacing with the new one isn't nearly as painful. It took me almost 5 minutes just to remove it, taking care not to damage the wheel.

***Key Note: Use plenty of Assembly Lube during installation.***
Exhaust side:
First, installing the circlips. You probably noticed that I didn't receive the funky looking circlips. That's okay, because I prefer the heavier duty ones compared to the old cheapie OEM's. They're an anodized blue, in color.

Next, insert a new bearing (Note, they're the LONG type of bearing for this particular T28. YTMV)

After the bearing is installed take the new washer from the kit, and install it. Followed by the washer, install the spring type "piston" ring that acts as a retainer.

Done with the exhaust (turbine) side for now. On to the compressor side.
First things first, install your other circlip.

After you install the circlip, install your second new bearing (Again, the long one was used with this turbine. YTMV)

Once the bearing is installed, go ahead and install the small o-ring.

Side by side comparison of the old 270 degree thrust bearing, and the new 360 degree thrust bearing:

New Thrust collar (cannot re-use the old one due to the design of the 360 degree bearing): NOTE: The c ring as shown needs to be installed on the thrust collar, at the top section in the picture shown. The washer in the picture is what you will use next.

Using the washer from the previous picture, install on top of the bearing:

Please pay close attention to the position of the bearing! It MUST be installed correctly, or it will fail immediately and your work up to this point will have been in vain.
2009-08-16 02:28:10
In the below picture, you'll see that the thrust collar basically sits down on top of the 360 degree thrust bearing. See that the C ring is installed. At this time, you can re-use your torx T-15 screws to secure the thrust bearing, or you can use the newly supplied ALLEN key head screws. I chose to use the new bolts (sorry, not pictured). It's easier to install the bolts and secure the thrust bearing, THEN to install the thrust collar in the thrust bearing.

Here you'll see the seal plate. Note the orientation. You will need to provide slight pressure, as the C ring compresses against the seal plate:

Once that's installed, time to install the small snap ring. In the picture, you'll see that it has a beveled edge. The beveled edge needs to be up, or away from the seal plate. Otherwise you'll probably just fuss alot when it doesn't want to seat properly. I chose to use the older one, rather than the new one.


Whew, almost there!

Now we're done with the compressor side of the CHRA, for now. Time to flip the CHRA back over and install the exhaust wheel and shaft assembly:

First, re-install the cover plate:

Installing the shaft may seem tedious, but it's really pretty simple. Once you situate it by carefully navigating the shaft thru the CHRA, the C ring should be resting on the top portion of the exhaust side of the CHRA. Take the CHRA in your non-dominant hand, and grab a RUBBER mallot in the other. Gently tap the top of the turbine wheel (on the nut) until the turbine "clicks" into the CHRA. To verify it's seated correctly, give it a very gentle pull and it shouldn't move.

Thought I'd take a moment to post a picture of the compressor wheel. When the wheel is balanced to the shaft/turbine wheel, this is that they're referring to by the cutting of the wheel:

Next, it's time to install the compressor wheel. Just place the wheel over the shaft and apply even pressure to move it down to the base of the shaft. It will probably click a slight bit when it mates against the rest of the CHRA. That's actually the wheel resting on the base of the shaft that is stepped. You'll see a little bit of the markings on the shaft itself and plenty of markings on the wheel. I didn't mark the OUTER DIAMETER of the wheel enough with respect to the cartridge, I highly recommend you do this! The more markings you make, the more you're sure it's 100% balanced. Don't forget to mark the shaft, the nut, and mark the turbine wheel with respect to the exhaust housings before disassembly.

Nut installed and tightened (remember lefty tighty, righty loosey for left hand threaded items)

Time to re-install the exhaust housing. It may be wise to situate the snap ring onto the CHRA before installing the exhaust housing. Otherwise you'll have issues trying to install it. This ring is also beveled like the ring above, make note of that.

C clamp installed, and housing clamp plates installed.

Now, install the smaller o-ring of the two you have left onto the compressor side of the turbo.

Last stop, compressor housing! I failed to take a picture of this portion (sorry!). What you'll be looking for is the portion of the aluminum plate that mates to the rest of the turbo. Along the outside edge and facing towards the compressor housing, there will be a paper gasket. It's probably half way destroyed by now, so go ahead and remove the rest of it. You don't want boost leaks from the compressor housing. That's what the final LARGE o-ring is for It's a PITA to install correctly, so take your time with it. Once you think you have it to where it won't pop off during re-install of the compressor housing, get the housing on before the o-ring comes off

Once you have the compressor housing installed, flip the whole turbocharger over and re-install the c clamps that you took off in order to remove the housing. Keep in mind (mark if necessary) which section of the compressor housing contained the bracket for your wastegate actuator.

The caution bracket

2009-08-16 02:28:39
I hope this gives more of you a better understanding of the turbine assembly, itself. I know there are many that are weary of rebuilding a turbine on their own, and would rather spend $350 to have one rebuilt, or $350 to buy another used turbo that could end up giving you the same grief. I'd personally rather spend $90 and some change for shipping, and spend time doing it myself.
2009-08-16 02:57:27
Looking good.

Moving this to the How To Section after your done. I will remove my post after too, or any post that gets in the way of the flow.
2009-08-16 03:01:21
Don't think I'll have any issues with the flow, I reserved some space for just that reason Thanks for looking out!
2009-08-16 03:31:28
Sweet moved
2009-08-16 03:41:20
Thanks As soon as the kit comes in, I'll start the re-build and finish up the how-to
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