Rebuilding turbo

[OmniGuy123]

Whilst taking apart my turbo off of my turbo coupe, I had to heat up the compressor wheel to free up what I can only immagine to be red locktite that prevented me from removing the turbine shaft/com wheel from the bearing housing.

Is this common in the manufature/rebuild of turbos?

Was it actually locktite?

Should I put more on when I reinstall it?

[OmniGuy123]

I think I might have answered my own question, but I want to hear the feed back of those who have been there and done that.

http://www.gnttype.org/techarea/turbo/turborebuild.html

How to Rebuild Your Turbocharger

Chris Fasulo - cfasulo@cybertours.com.

Introduction

Read ALL of these instructions thoroughly before beginning. They may seem overwhelming, but rebuilding a turbo is actually very easy. The job can be completed in an afternoon or less by anyone with average mechanical skills. There are many suppliers of repair kits and parts for our turbos. I bought my bearings and seals from John Craig for about $70. Other suppliers sell complete kits with additional parts at additional cost.

Pick up any "Turbo" Magazine" and I'm sure you'll find at least a dozen such suppliers! Also, the September 1991 issue of "Turbo Magazine" has an article on rebuilding turbos that has an exploded view of a turbo. I also have another step-by-step article from a "Hot Rod Magazine" engine book. This has excellent pictures. If you want copies of these articles please e-mail me.

Can it Be Rebuilt?
For the most part, if the turbo's compressor wheel still turns and has not hit the compressor housing it should be rebuildable. To be absolutely sure the turbo needs to be disassembled and some internal inspection done. A bound shaft or any compressor or turbine damage/housing contact pretty much constitutes a junk turbo! Don't throw it away! It can be used for a core exchange on new turbo! A core charge on a new turbo is $200 or more. Sometimes people will look for a junk turbo that they can buy for less than the core charge. This allows them to keep their stock turbo. They just send the junker in as the core--which is perfectly acceptable.

Tool List:
1/2" socket
7/16" 12 point socket
5/8" socket
13 mm socket
1/2" boxed/open end wrench
10 mm boxed/open wrench
Internal snap ring pliers
External snap ring pliers
Long Narrow Needle Nose pliers (Craftsman # 45172)
Torque Wrench (in-lb)
A vice is also helpful

General Notes

It is best to remove the turbine housing first. This side is more difficult to remove. By keeping the compressor housing on, it may protect the compressor wheel from possible damage while removing the turbine housing. Spray some WD-40 or Liquid Wrench around the area where the turbine housing mates with the center section. Let it penetrate awhile. The snap rings that hold the shaft bearings in have very small holes. You may need to modify the tips of a set of INTERNAL snap ring pliers so they fit the holes. Just grind the tips down to a good point--proper size tips are probably available.

There are three main pieces of the turbocharger:
the turbine housing, or the hot side;
the center section, or CHRA (Center Housing and Rotating Assembly);
and the compressor housing, or the cold side.
Please take the time to mark or scribe the relationship of these assemblies to each other. I "thought" I'd remember how they went back together but got the bracket that secures the turbo to the engine (I call this bracket the "rabbit ears") off by one bolt. I had to take the hot side all apart to correct this!!!

Disassembly
Remove wastegate elbow from turbine housing (1/2" bolts)

Using a boxed wrench loosen all turbine housings bolts--a socket may fit on some

Remove all of the turbine housing bolts except for the two at the top and bottom of the housing. (across from the oil feed-in line and oil outlet) These two screws will hit the center section and be used as "jacking" screws to push the turbine housing off of the center section.
Back both of the above bolts out until they hit the center section. Continue to alternately turn each bolt about 1/4 turn until the center turbine housing is separated form the center section.

NOTE: The turbine housing needs to come off the center section parallel to the turbine wheel. If allowed to come off crooked it will bind on the turbine wheel and possibly damage it. After EACH 1/4" turn try and turn the turbine/compressor wheel. It will bind a little during this part of disassembly. TAKE YOUR TIME ON THIS STEP. If the binding seems excessive turn the bolts back in and try again. More penetrating lubricant may also be needed.

Remove compressor housing by removing the 13mm bolts and metal retainers. Keep an eye out for an 'O' ring around the outer diameter of the compressor seal plate. This 'O' ring can be re-used if not damaged.

Mark the compressor wheel and turbine wheel so they can be lined back up when reassembled. (The turbine wheel and shaft are one single piece)

A 5/8" socket should fit the turbine wheel "nut". If it does not fit, CAREFULLY secure the wheel by this nut in a vice.

Remove compressor nut using 12 point 7/16" socket then remove compressor wheel.

Remove turbine wheel and shaft from center section-- you may have to tap the end of the shaft to get it out. You should now have the turbo broken down into four pieces:
(a) the compress wheel and nut;
(b) the center section;
(c)the heat shield (also called the dog dish); and
(d) the turbine wheel and shaft.

Next, remove the compressor seal plate by removing the 10mm bolts securing it to the bearing housing. Removing the seal plate will expose the following parts:
(a)the compressor seal;
(b)the thrust collar;
(c) the thrust bearing;
(d)the thrust bearing retainer; and
(e) 'O' ring

NOTE(1): the compressor seal is in the seal plate and has a spring behind it. Use care to prevent the spring form ejecting the seal across the room!!! Also note, the star washer-like thrust bearing retainer is supposed to be FLAT not bowed! Don't be surprised to find yours bowed as this is very common and is caused by thrust loading.

NOTE(2): On New Generation Turbos (TA-49, TE-44, TE-60, ect) built by Limit Engineering, (John Craig) the thrust bearing may/will be held to the center section by two metric pan head screws. This is a modification that John does to help oiling to the thrust bearing. These screws have a thread sealer on them and require a 2.5mm allen wrench to remove them. You may have to apply heat to these screws to remove them. On a STOCK turbo the thrust bearing is just held by two roll pins.

Remove the two turbine shaft journal bearings from the bearing housing by removing the snap rings on each side. The bearings will/should just now fall out from each side of the housing.

NOTE: there are also two other snap rings located inside of the housing. These do not need to be removed. The stock original bearings are made of Aluminum as this is the material that the GM engineers specified to Garrett. Replacement bearings are not usually Aluminum--they are often made from sintered bronze. There should be numbers stamped into the outer edge of the journal bearings. You will need these numbers when ordering new bearings.

[OmniGuy123]

Soak the bearing housing in carb cleaner and check to make sure all oil passages are clear.

Remove the old turbine shaft shaft seal and clean off all carbon around the seal area--this is not easy to do! I used a wire brush on a bench grinder to do this. TAKE CARE NOT TO NICK/DAMAGE THE BEARING SURFACES ON THE SHAFT.

Install the new turbine shaft seal using external snap ring pliers to expand the seal--the same way a piston ring is installed. Try to expand the seal only as much as needed to install it. An over expanded ring will make re-installation of the turbine shaft more difficult. As a side note, contrary to what is often believed, this is NOT an oil seal. The purpose of this seal is to keep the exhaust gases from entering the crankcase via the oil return line.

Turbo Balancing

Turbocharger balancing as it applies to the Buick turbos is somewhat misunderstood. From my conversations with John Craig of Limit Engineering, I have learned that our turbos were balanced to a very low tolerance and the purpose of doing it was to reduce vibrations/harmonics that could induce noise in the exhaust system. Balancing was not done to/will not improve the performance of our turbos. I also learned that Garrett balanced the stock turbos in two different ways.

One way was to balance the turbine wheel and shaft and the compressor wheel as a single unit. The other way was to balance the turbine wheel and shaft the compressor wheel individually. You can tell how the balancing was done by the shape/appearance of the COMPRESSOR nut. If the nut appears to be ground down then the turbine wheel and shaft and the compressor wheel (and nut) were balanced together. If the nut is not ground down then the wheels were done individually. If the wheels were done individually then it is not absolutely necessary to mark them and get them in the same location as they were prior to removal. In the case of the "ground down nut" turbo, it is a good idea to keep the wheels lined up in their original positions. If you mess them up all is not lost! John can re-balance the wheels for under $20!!! Other turbo repair shops should be able to do this as well.

Reassembly Notes
Essentially, everything reassembles in the reverse order.

Use 105 Lubriplate or Torco Assembly lube to pack the journal bearings and shaft. Plain motor oil can also be used.

Make sure ALL journal bearing snap rings are installed and seated in their grooves.

Make sure all 'O' rings are in place on the seal plate.

The only tricky part is compressing the turbine seal ring enough so the shaft will slide into the bearing housing. The turbine housing is tapered and the ring and shaft are *supposed* to just slide in IF the seal ring is centered on the shaft and the seal was not over expanded during installation. Hold center section in one hand, compressor side down. Insert shaft into center section until seal touches housing. Rotate turbine wheel with a firm but gentle pressure. This will center the seal in the housing and on the shaft. Then give a slight pressure and the seal will snap into place. It should not be overly forced as other problems may exist if extra force is needed. With normal conditions, this technique should work every time. This may be the most frustrating step of all or you may get it on the first try! This may be the most frustrating step of all or you may get it on the first try!

Line up the mark on the compressor wheel with the mark on the turbine wheel. Torque the compressor nut to 18-20 in-lb (that's INCH-pounds NOT foot-pounds) Then continue to rotate the nut an ADDITIONAL 90 to 110 degrees. DO NOT use any sealers on the nut or shaft threads--the nut is self locking.Leave the compressor housing bolts and retainer clips loose until the turbo is installed back on the car. The housing will more than likely need to be rotated to get the turbo outlet aligned with the intercooler inlet. Try to get this alignment as straight as possible.

Like a new engine, it can't hurt to oil prime the newly rebuilt turbo. This can be done a number of ways but I always disconnect the orange ECM power feed wire located near the battery. Crank the engine for 15-20 seconds three to for times allowing equal time between cranking to avoid overheating the starter. Plug the ECM power feed back in and start the engine.

[xrattiracer]

that is correct, there is no need for a thread locking compound on the compressor nut, but thats not to say someone didnt put some on it. i have found that the compressor wheel itself often fits very tightly on the shaft, and may even have been compressed slight by the pressure of the nut so that it is even tighter. a bit of heat is a good solution as you found.
I would also add that marking the components for reassembly is not required, reassemble in any orientation.

[OmniGuy123]

Quote:

Originally Posted by xrattiracer that is correct, there is no need for a thread locking compound on the compressor nut, but thats not to say someone didnt put some on it. i have found that the compressor wheel itself often fits very tightly on the shaft, and may even have been compressed slight by the pressure of the nut so that it is even tighter. a bit of heat is a good solution as you found. I would also add that marking the components for reassembly is not required, reassemble in any orientation.

Thanks for the info!

[Tim_K]

Sounds like a good proceedure for a rebuild, I'll have to keep this post in mind for my upcoming Garrett rebuild project.