OM602 Turbo Rebuild
 

Anyone know of any resources to help with rebuilding of the Garrett T25 in the 300D 2.5? I've seen plenty of kits on the interwebz, but haven't seen anyplace to pick up new impeller shafts. I've contacted Garrett for any info, still waiting to hear back. Also haven't come across any write ups on the forums of anyone that has actually done this (with this particular turbo).

Next question, is this truly a DIY? Some reading I've done suggests a "balance" is mandatory (not sure what that requires), other say it's not mandatory.

Thoughts?

What do you think is wrong with the old impeller shaft?

People claim that the compressor wheel and the turbine wheel are balanced seperatly. If that is the case the balance when swapping parts is not an issue.

If you are reusing the compressor wheel and the turbine wheel scribe the position the compressor is on compared to the shaft and simply make sure it is in the same position when you torque the shaft nut.

Turbo Rebuild kits Has Pics of Different Turbo Seals
» Garrett T3, T4, T3/T4 Rebuild Kits

Should be info on rebuilding here: Repair Links
Fast navigation http://www.peachparts.com/shopforum/diy-links-parts-category/146034-fast-navigation-do-yourself-links.html

I don't necessarily think anything is wrong with the impeller shaft, but I'm a little worried about wear given my mileage (~230K).

I'm planning on having the turbo out of the car in the not too distant future to hunt down an oil leak, as well as for easier access to the wastegate actuator I'm planning to swap, so it got me thinking about a rebuild. According to K.B. of Merc Source fame, you should expect to replace the impeller shaft during a rebuild on turbos with >200K miles - of course, this coming from a guy who will conveniently sell you said shaft for your turbo (for an OM617, that is).

Thanks for the links!

From what I've read and understand, the Garrett turbos have the compressor and turbine sections balanced independently. You can mix and match all you want on these turbos. If you have the KKK, the turbine and compressor are balanced together as an assembly.

I will say that the impeller shaft can be a source of oil consumption if the grooves are worn. If you aren't consuming oil or smoking and there isn't a bunch of oil slobber in the compressor housing, I wouldn't worry too much about doing a turbo rebuild.

Well what people have been doing is installing new bearings and seals and they get away with that most of the time. If you are doing that yourself you only risk the cost of the bearing and seal kit.

During a real turbo rebuild you are supposed to measure the bearing area on the turbine shaft and the groove that the piston ring seal rids in. For a do-it-youselfer either one of those worn beyond spec would indicate a new turbine shaft.
However, if your turbo presently is not leaking Oil into the exhaust side cleaning the Turbine seal area and installing a new seal has a high chance of working. It is sort of the same with the bearing journals. If they are causing no issue now putting new bearings in will make it a little better.

The Turbine Shaft journal areas can be polished a little with 1200 grit paper.

In a real rebuild the bearing bores inside of the turbo would also be measured and inspected for condition. But, again if your Turbo was working OK installng new bearings is likely to work fine.

The thrust washer and thrust bearing are a different story. But, you get new ones in the Kit so that take care of that.

I only know about the turbos that use piston ring type seals (as are on the Turbine Wheel) on the Compressore side. If the bore that the rings go into on the compressore end plate are worn you need to replace that whole plate (made of aluminum with a steel sleeve).

Concerning the balance of the Turbine shaft and compressor wheels. As long as the fins are not damaged you can usually re-use them with out balancing.
If either of the Wheels has dents or metal removed from the fins then the balnce is suspect and even if the wheel looks like it can be reused it should be re-balanced.
Unfotunately border line cases are a matter of experience to determine if it can be reused or not.
I have some pics I attached.

One of the pics shows what the turbo can look like when there is an oil leak at the Turbine Shaft Seal. Notice lots of carbon and that it is shiny and wet looking.

One of the pics is of an aluminum compressor wheel that has some fin damage. Once the wheel is out it can be inspected and dressed with a jewelers file but it would need re-balancing before reuse. With the damage show it would be slightly less effecient however, you can adjust the waste gate to bring up the max turbo pressure.
Also you need to campare the cost of a new wheel to the cost of re-balancing the old wheel.

There is another issue that seldom comes up.
But, one member of one of the Forums did not know it but his car had a turbo that had previously been replaced by an exchanged rebuilt turbo.

Garrette/Air Research makes undersized ID bearings so that worn Turbine Shafts can be reground and reused and oversized OD bearings so that the Turbochager Bearing Housing can be bored oversized and reused.
That guy got one of those that did not have the standard bearings in it so that the standard bearings kit he bought would not work.

Can't remember any one posting specs on journal or bearing bore sizes that would help determine if you have oversized or undersized.
Also there is several versions of torquing the shaft nut which differ from each other.

Not a whole lot on that side of the engine to leak maybe valve gasket or turbo drain. Access to the waste gate is ok from below a lot less effort than removing the turbo. Guess you could drop the exhaust and check for oil in exhaust and that may free up more room for you.

Thanks again for all the info. Some of those pictures make me want to pull the turbo just so I can have a better look at it and inspect it for damage.

VCG is new, I think I may be dealing with a turbo oil drain leak. Last time I looked from below, it looked like there was quite a bit of old oil caked on the wastegate actuator, as well as on the lower frame on that side of the engine bay.

If you find anything interesting post some pictures.

If its messed up inside consider putting in T28 parts to move more air.

For sure, but probably 3-5 months away from actually doing this. Just wrapping up an injector rebuild on the W124, and about to move into a house we just bought. Plus the BMW is sort of acting up, and I expect to have the valve cover off to replace a stupid sensor. I definitely want to tear into this OM602 a little more over the summer, though.

I had thought about that, but had a few concerns, namely:

i think about the only gain you could hope to get by upgrading the turbo only would be better/faster "spool" time

I recently rebuilt the Garrett AirResearch turbo from my 1985 CA 300D failed engine. This is to swap w/ the turbo on my 1984 300D (when son swaps cars), which appears to be leaking oil from the compressor side. I know the 1985 CA is clocked different, but otherwise appears the same and the clocking just depends on where you tighten it. I forgot to mark the compressor and turbine wheels before disassembling. I doubt it matters since afterwards I spun it w/ air and didn't feel any vibrations. Also, there is nothing other than friction to hold the two aligned, so doubt Garrett would rely on that. People say the wheels are balanced individually. The compressor wheel is thin aluminum, so treat it very carefully, and a replacement isn't affordable.

Rebuild was fairly simple and cheap ($18 kit from China) and there are many web instructions and youtubes. The new bearings didn't feel any tighter than the old. I have no way to measure <1 mil bores accurately, but I think one can feel the clearance. The main useful thing I did was to clean the oil crud under the exhaust-side cap and clean totally gunked compressor wheel. 1985 CA engines plumb blow-by gas thru the turbo, which seems ill-advised (re-plumbed my engine). The main short-coming is that the kit doesn't have a seal that fits the compressor housing. It has a too-large O-ring. One guy here bought correct diameter O-rings at McMaster-Carr. I made a thin O-ring from a "cut & glue" kit (put gap at the top). But, there is no O-ring groove so I think it should instead have a thin flat gasket, which seems to be the remnants of what I scrapped off. Perhaps a thin bead of RTV would work OK. My O-ring wanted to splay out the first few times I slid on the compressor housing, and hard to tell when it does that.

MORE PERFORMANCE as result of Larger Turbo
 

Will only result IF FUEL FLOW IS INCREASED Proportionally...

AND if y'all try that without a baseline TIT (Turbo Inlet Temperature)
AKA Exhaust Pyro-meter Reading
AND a properly installed Pyro (Ongoing)

You'll be looking for a new engine shortly...

anyone know if our garret turbos are ball bearing or journal bearing? Most modern garret turbos are ball bearing.