Turbo Rebuild

Last updated: September 21, 2000

Date: Fri, 26 Dec 1997 19:20:35 EST
From: EDRX7 (EDRX7@aol.com)

Well I did the rebuild on my turbos today and thought I'd pass along my experience for those who may be considering doing it themselves but not sure what kind of job it is.

First of all it's really quite simple and there's not a whole lot too it. In fact, I was surprised on how "unprecision" it was overall. I expected much closer tolerance components with a bit higher complexity than a couple bronze bearings and a couple simple seals.

I bought my kits from Turbo City. You need two kits ($150.00 each) and they have a video as well that is worth the $16.95 when purchased with the rebuild kits. It's genaric and our assembly is slightly differant, but it's good to give you a good understanding of what you're going to encounter before you start disassembly. The seal plate and the bearing housing need to be tunked apart with a hammer and that may not be obvious if you hadn't reviewed the video.

Tools you'll need:

	10mm wrench
	4mm allen wrench
	pointed probe/dental pick
	snap ring pliers with .030 tips
	large snap ring pliers
	small screwdriver
	softface hammer
	marking pen
	glass bead blaster
	carb cleaner
	wash tank
	compressed air

Expect it to take the better part of a day unless you've done it before. I'ts probably only a couple hour job if you've got everything together and know what you're doing. Getting the snap rings in and out took me as much time as anything, but most of your time will be spent cleaning parts. I would recommend if you don't have access to a glass bead machine that you don't do this yourself. I did the whole job at Precision Systems Inc. (the machine shop I manage). You need lots of compressed air too.

Glass beading all the parts and then getting them clean and free from the glass bead can take a while. Get yourself a couple cans of Gumout Carb Cleaner to get the glass beads out of your parts. This can be the death of the turbos if there is any residue left behind. That's the only cleaner I've found that will get the beads out for sure.

If you don't have the right snap ring tips get them first or you'll spend all day trying to get them in and out. Don't let the video fool you when the guy seems to effortlessly snap them in and out with a probe and his finger. If he can do that on these tubos he's my hero!

You'll notice the carbon seal is a complete assembly that needs to be pressed in and out instead of seperate pieces like shown in the video too. The seal is a little differant than the one you'll be taking out.

Remember to mark your parts for alignment before you disassemble and keep things CLEAN. Once you've taken one apart it goes together in about 10 minutes.

The total cost was $320.00. In my opinion anyone with access to a shop and a little mechanical knowledge can do this. It's a piece of cake. Put all those hundred dollar bills into something else rather than pay someone else to do it. It's a hell of a lot harder getting the turbo out of the car than rebuilding it. All the other procedures people have mentioned to me that the turbo rebuilders do don't add up to a hill of beans IMHO. If you do it yourself at least you know it's done right! (?)

Now that it's done it spins like a top and looks like a million bucks! Maybe I'll just put it on my mantle and spare myself all the headaches of getting it back onto the engine! :-)


Date: Sat, 27 Dec 1997 17:37:56 EST
From: EDRX7 (EDRX7@aol.com)

>I'm curious about how your turbo's looked *before* you took
>'em apart. Were there symptoms, and how did the old parts look?
>Did you see any obvious signs of failure in the seals?

There was a lot of gunk and black crap all over one of the turbo and compressor housings. It appeared to me that the leaking was coming from the large o-ring and the turbine seal. The turbine shaft seal was very gunked up with carbon and scale.

I was concerned with the big snapring that holds it all together too. That's all that keeps the oring compressed properly and it's hard to tell if it is seated well. I put two small clamps against the compressor housing and the bearing housing squeezing them together while I pushed the large snapring in a bit further just to be sure.

>Did the rebuild kit include instructions for compressor
>wheel nut torque?


>What about cautions to help prevent damage to the shaft or
>bearing surfaces? Did you do you do the shaft polishing with
>fine paper? In a drill press or a lathe?>>

I cleaned the shaft with some very fine scotch-brite and then a very hard white stone. It really didn't require much. I did them in a drill chuck on a mill. The cleaning was in the area that holds the turbine shaft seal. I carefully glassbeaded that with 40 psi along with the finsstaying away from the shaft itself.

>Any thoughts on getting the rotating assembly balanced, or
>doing any grinding/polishing in the turbine housing to prevent
>hot spots and cracking?

There's no need to rebalance the assembly. It was balanced when built and as long as you mark the compressor wheel and the turbine wheel before you reassemble it will still be just as balanced as it was originally. There was a tiny number 6 on one of the wheels. I just used marking pen to mark the opposing wheel lined up with the 6. You don't want to make scribe marks on the wheels.

>Did you see any signs of cracking? Any signs of heat damage
>to the compressor wheel?

My wheels had no sign of any damage or hot spots. A very low pressure glass bead took the gunk off the one that was leaking and the others looked like they were brand new.

>Did you use straight oil for the bearing/shaft reassembly

Just smeared a little motor oil on them. You just don't want them spinning up the first time dry.

>I think it's also recommended that the oil feed lines get
>replaced, not cleaned, as I've read that it's very hard to get
>them perfectly clean. Nothing sucks more than running some dirt
into your nice clean turbo.

That's probably reasonable advice. I personally sprayed quite a bit of carb cleaner through the oil line while I rotated it around and blew it out and repeated that a couple of times. I see no need to replace it. You stand more chance getting something in you oil every time you do an oil change if you ask me.

>It would probably be a good idea to make sure the turbo's
>are fully oiled before first running the engine by doing some
>cranking with the fuel pump fuse removed.

I agree.

I will add that the 4mm allen wrench was really a 2.5mm and you need a torx wrench as well to get the stock screws out of the thrust bearing.

Also, I didn't glassbead the cast iron turbine housing. I cleaned the outside of that with a wire wheel and then soaked it in a solvent tank and then cleaned it with carb cleaner. I felt it would be too much of a chance to take not gettting the glass out of the little oil holes in that. You also want to be sure you use some scotch-brite or fine paper to clean the buildup out of the seat where the turbine shaft seal mates.


From: djh61187@email.msn.com
Date: May 3, 1999

I just read your page on rebuilding RX7 turbos and though you should know some important tips on RX7s. You are correct when you said that the shaft and compressor wheels are balanced when they are new , but to be rebuilt properly they MUST be rebalanced to regain that ' like new performance ' .001-003gm is factory spec.

After rebuilding 50 plus sets of twins and 100s of other turbos every year,getting a shaft and wheel that doesn"t need balancing is about as rare as winning the lottery and getting hit by lightning all in the same day!

Will they work not rebalanced ? Yes.

Will they last as long ? No. The bearing wear in a uneven pattern causing the wheels to contact the housings and bend the shaft which will make the turbo fail taking the bearing housing with it {not cheap}.

Areas to check when rebuilding RX7 twins or any other turbo for that matter are:

(1) bearing surfaces on the shaft and bearing housing must be free of any imperfections(remember these things turn 125000+rpm"s),

(2)shaft runout measured with a dial indicator of .001 or less,

(3) piston ring seal area in the bearing housing,

(4) piston ring groove on the shaft must be square and tight,

(5)clean, the turbine wheel, bearing housing, and compressor wheel must be glassbeaded so they are spotless.

It also helps to get a accurate balance. These are just some basic things to look for hope this you on your next rebuild!

P.S. i see you paid 150.00 for each kit , where i work we sell rebuilt rotating assemblys for 225.00 , just bolt them in your compressor and exhaust housings and go.


Date: Fri, 15 Sep 2000 22:05:06 -0700
From: "Derek Vanditmars" (dvandit@istar.ca)

>What is the issue with the exhaust side oil seal? Is this something
> that requires professional intervention?

Yup. The re-build kit has nothing for the exhaust side. Talking with the local turbo re-builders, they had to machine the shaft on the exhaust side and use and "over-sized" exhaust seal.

It may be that the compressor side seals are what needs to be replaced, but in my case it was the exhaust seals that were causing most of the oil smoke out the exhaust.


Date: Mon, 18 Sep 2000 08:35:37 -0500
From: "Westbrook, Chuck E." (CWestbrook@tmh.tmc.edu)
Subject: RE: (rx7) [3] Turbo Manifold Leak... need more help ;)

If the turbo assemble (three pieces not counting the turbo cartridges) was dismantled, then most likely the front and rear housings are out of alignment.

Lay a straight edge diagonally across the mating surfaces (try both ways).

There should not be any gaps between the straight edge and the mating surfaces. If this is OK, then either your gaskets are bad or the exhaust manifold is warped. This alignment is a most important task when reassembling the unit after it has dismantled.


Date: Wed, 28 Mar 2001 21:11:32 -0800 (PST)
From: Chuck Westbrook (cewrx7r1@yahoo.com)

Pre removal notes:

  1. For each turbo cartridge, make matching punch marks on the cartridge and housing so that they can be aligned at that point where the cartridge goes into the housing.

  2. For each turbo cartridge, on the back side of the compressor housing, where the retaining "C" clip does not cover the surface where the aluminum housing meets the steel turbo plate, I ground a matching slot in the aluminum to a small dimple on the steel plate. On the aluminum housing with a Magic Marker, I pointed to it and wrote (for the rebuilder to see), "Here is the alignment mark". Also mention this to them in a letter.

  3. When you get them back, make sure that #2 marks are aligned or at least 1/16" within alignment. If not, the "C" clip has to be compressed and the housings rotated until aligned. This takes two people. Insert the cartridges into the housing, align the two punch marks, and bolt them up.

  4. Turbo housing alignment does not use any marks. This is only needed if it is taken apart for WG enlargement. Best to do it on the exhaust manifold. Loosely assemble the housing and loosely bolt it to the exhaust manifold. Hand tighten the housing nuts. This aligns the mating surfaces of the housing to the surface of the exhaust manifold. Remove the housing and finish tightening the assembly nuts. Another way requires using a straight edge across the housing mating surfaces to insure that both sides are in the same plane. This way is less accurate.

If these steps were not taken or if the complete turbo assembly is badly mis-aligned, then you have to do:

Loosely attached both turbos to the housing so they can be rotated. Only attach the oil inlet line to them but only hand tighten. The exhaust manifold has to be already on the motor. Place assembly on the manifold and hand tighten with a few nuts. Rotate the turbos together until the oil inlet line connectors match up properly. Hand tighten them together. Tighten at lease one of the 6 bolts for each cartridge so they will not rotate. Take turbo assemble off, loosen oil inlet line, totally tighten all 12 turbo attaching bolts, then properly torque the oil inlet line to both turbo cartridges.

Place it all back on the engine again. Only attach the front half of the "Y" pipe to the #1 turbo. Try attaching the connecting pipe between the "Y" pipe and IC. If the #1 turbo outlet is too far off alignment, then you will have problems here. If misaligned, try to judge by how much off it is. Remove all, loosen the #1 turbo compressor housing "C" clip and rotate the compressor housing by your prior noted judgment. Repeat the process until the "Y" pipe to IC pipe alignment is correct.

Remove the assembly again. Now install and check how the rear half of the "Y" pipe aligns with the front half. If it doesn't, then you have to loosen the #2 turbo "C" clip and rotate it's compressor housing until the "Y" pipe aligns correctly.

Now you can attach the oil return lines, water lines, and heat shield. You have completed a perfect fit!

Date: Mon, 11 May 1998 14:24:00 -0500 From: "Westbrook, Chuck"

>From: Stephen J Lee
>Now what am I going to do about my turbos?  ... I'm talking about 
>rebuilds and no mods other than non-sequential. Some have sent 
>them to Majestic City (Brad, I think) and others said to avoid 
>Turbo City.

I sent mine to Pettit for their blue-print rebuild with about 8-10% increase flow capacity due to opening the outlets around the compressor blade. Works fine.

Carlos "Julio" Iglesias

Preventing Diagnostic Error Codes when removing solenoids:

330 ohm (1/2 watt) resistors will fool the ECU into thinking that a solenoid connection is valid (i.e. still attached). The 33 ohm resistance of the actual solenoids can be used, but they require a FIVE watt resistor ( 12v / 33ohms * 12v = 4.36...Watts). 10K ohms resistors provided to low a voltage to fool the system.

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