rebuilt t25, spoolup sounds like siren

[KingTurd]

Greetings all. Its been a while.

Anyways, my car (91 with sr20det) was in an accident a while back, and I finally got some time to put it back together. I figured while it was down, I might as well rebuild the turbo--the stock t25. It was burning oil like crazy.

So I bought a rebuild kit from ebay and rebuilt it according to the instructions, keeping note of the balancing. I reassembled everything and got the car up and running. The spoolup was great, sounded nice and made boost seemingly faster than before. Did not burn one drop of oil, which is why I rebuilt it to begin with. It was a complete success.

I drove it around stock psi (pressure source hooked directly to wastegate) for about 300 miles, then I decided to hook up my MBC once again. Well, for some reason my MBC went whack and spiked the turbo to around 15 psi. I thought maybe it was in my mind (heh), so I tried it again--15 psi. So, I hooked it back up to the wastegate directly.

Well, while driving after this incident, the turbocharger would spool up and sound like a siren, almost like a supercharger. Louder with higher psi, etc After doing a little research, I found out that its probably out of balance. This seemed odd because it sounded absolutely fine before that day. So I inspected a little more--turns out that the compressor wheel shaft nut came finger loose! However, it did not come all the way off but it was enough to cause the wheel to spin slightly out of balance.

I disassembled the turbocharger and inspected it a little more. The compressor wheel just ever so slightly scraped the compressor housing. The wheel did not crack nor bend as far as I could tell, but some of the fins were grinded a little bit. So I realigned my marks, loctited and torqued down the nut and everything else, and threw it back on the car. After letting the loctite cure, I took it for a drive again--same siren/howling noise. It still made boost, but the noise just doesnt sound right. It sounded neat, but I knew something was incorrect.

So, I removed it *again* (in record time for me--24 minutes from start to finish, and about 10 minutes to tear it all down). The marks were still lined up properly, and the shaft nut was nowhere near being loose. It still spun freely.

In conclusion, my question is this: Is the siren/howling noise due to the imbalance? Did this maybe hammer out a bearing internally? I did rebuild the entire thing, with new bearing and all. Is this even salvageable? The shaft still spun freely without any hangups, and there was very minute play in the shaft moving it up and down (but not pushing it in and out).

Any information appreciated!Thanks in advance,Brady

[vocationalzero]

it might be because of the fins had been grinded down a little bit...

[KingTurd]

I was thinking that too. I understand that it does not take much to throw these things off. My problem would be finding a compressor wheel and a rebalance for cheaper than finding a used t25 somewhere. I dont plan on keeping the t25 forever, but I really dont want to upgrade at the moment either since I would be paying alot more for supporting mods.

[IanS]

Did you break in the turbo properly? Have you replaced the turbo to manifold gasket every time you have the turbo off? The noise you speak of sounds like an exhaust leak. Ive seen it before, replace the gasket, torque the bolts, drive it, and retorque.

[KingTurd]

Here are the pictures of the compressor wheel (clickable to view larger image):







As far as breaking it in, I cranked the car without fuel for a little while before actually starting it up. Then I kept boost to a minimum for about 50 miles or so, then proceeded to drive as usual (which isnt heavy footed, usually).

I reused the same exhaust gaskets, but the only one I replaced was the exhaust manifold gasket (that sits between the manifold and the head). Like I said, it sounded completely fine till I overboosted and the compressor nut came loose. After that, even after realigning everything it still made the same noise. In fact, when I realigned it the second time, I didnt even break loose the manifold from the turbine exhaust housing--i just removed the exhaust housing + manifold + o2 housing in one piece.

I, too, have also heard that it could be loose piping, but I really dont think this is the case here, especially since the only thing that really changed was the compressor wheel becoming loose and rubbing against the housing. When I reassembled everything, I did a boost leak check just to be sure. No leaks at all as far as the pressurized system is concerned. It very well may be an exhaust leak, but I would be clueless as to figure out where its coming from.

[KingTurd]

I just had a thought--what if the o-ring that sits around the outer edge of the chra (where the compressor housing touches when re-assembled) is not making complete contact? I used a brand new o-ring and cleaned up the contacting area on the housing as much as possible. Something like that might be a culprit though, when speaking of leaks. The boost leak test should have caught that, however.

Does anyone have a description as to what an out-of-balance turbocharger sounds like? If I feel non-lethargic and brave enough, Ill reassemble everything and try to get a capture of the noise. It does make the turbine whistling noise as usual, but its drowned out by the whole "siren" noise. Almost sounds like a miniature vacuum cleaner inside.

[Tulsa_S-13]

Sounds like it may still be out of balance and is consequently scrapping against the inside of the compressor housing.

I suggest holding off on reassembling it and taking it to a shop that can inspect it for you. You should be able to contact a diesel shop and see who they suggest locally to rebuild and VSR balance it for you.

I had my T25 rebuilt by the people at GPOP Shop in Arkansas. They did a great job, but that may cost you more than you're willing to spend on your T25.

[KingTurd]

I am talking to a person now from TurboCity that says they can rebalance it. He claims that the compressor wheel is ultimately no good, but they should be able to find another and rebalance it for me.

I dont know if they use VSR, as I didnt think to ask but I havent sent it out yet either. He said he can rebalance it with just the turbine wheel + shaft shipped only, no CHRA required. I thought it was part of the rebalancing process...

I plan on upgrading to a different turbo eventually, which is why I dont want to pump a lot of money into a t25. I still want it to work correctly so I can at least re-sell it, however.