Screechy turbo after 5SPI? No shaft play by hand.

[TERRA Operative]

A mate of mine and I have been installing a Garret T25 turbo onto his Patrol.
He has just had all the piping welded and intercooler plumbed up (awesome work by Extreme Custom Engineering!) and apart from needing a fuel tune, it is all working ok, apart from one thing.

The turbo starts to make a scraping sound once you hit 5PSI. We looked into the intake side of the turbo and saw nothing obvious, there is no shaft play at all, and the turbo spins perfectly freely.
It sounds fine up to 5PSI though, with no problems at all until then.

We are going to pull the turbo off and have a look at it in the next few days, but does anyone have any ideas what we should be expecting?
I am thinking that the boost is pushing on the impeller, making it contact something inside, and it needs at least 5PSI for this to occur.
We are prepared to stick a bearing kit through it, but it would be nice if we could avoid it.


Pic of the setup:

[NME308]

Hi there,
A bent or broken fin of some sort will do that. So will a damaged/failing thrust bearing... I've tried one of each on the lil T25's!

Hope there is a simple and cheap fix for this one!

Cheers,
Jason

[TERRA Operative]

Yea, I'm hoping it's the bearing at most, as that's easy to replace. The fins looked fine when we had it open to machine the intake side and ceramic coated the exhaust side.

[pandaah]

Dunno where you are but in perth mtq will spin up nd diagnose turbos for like $70 or around that, sounds like a problem thats caused by air passing between the wheels and housing and at a certain pressure enough air volume will cause it, keen to hear the fix

[BenAw11]

had a very similar thing happen in my mates wrx we swear it came from the turbo but it was a small air leak near the cooler that made a screatching sound when it came on boost, prick of a thing to find.

[TERRA Operative]

Well, we checked oil feed to the turbo and that's ok, so we pulled it off and had a look. No coolant or oil where it shouldn't be, and no obvious signs of self destruction so far.

Tomorrow the turbo will be opened up to see what's inside......

[thechuckster]

is that a petrol or diesel Patrol? Just curious whether it might be a mismatch with turbo designed for petrol engine being used on a diesel and being over-sped by the uber amounts of exhaust flow you get from oil burners.

[TERRA Operative]

Diesel Patrol, but apparently the turbo is used quite often on these engines. My mate did the research into that side of things, I'm a supercharger whore, so I just messed around with the fitment etc of the selected turbo.

[TERRA Operative]

Got the details on the turbo and engine. I'll teach myself how to read compressor maps and see how the two match up.


Engine is a TD42. 4.2L inline 6 diesel, cross flow head.

Turbo is a garrett t25 numbers on plate are:

VF 2031J
14411-50F00
466113-1

[SHEPPO3930]

The fins looked fine when we had it open to machine the intake side

what was "machined" on the intake side of the turbo?

[TERRA Operative]

Just the intake side of the compressor snail where the flange for the silicone hose attaches, so the actual compressor clearances were untouched.

[SHEPPO3930]

ok. best to pull the turbo off and remove the housings then. i've got a t25 with about 3mm of play in the shaft and it made a horrid noise when on boost, but that was the wheels touching the housings.

[JDM hachi]

could the o-ring around the compressor be stuffed and be letting air leak out at cert. psi? does the screaching get louder with higher boost?
Thats all I've got, other than a parrot has been ingested by the turbo!
Hope you find a cheap solution, let us know what the problem was when you solve it.

cheers,
matty.

[TERRA Operative]

We're going to pull down the turbo this weekend (I got a wedding to attend today... )
I found it's basically a sleeve bearing version of the GT2554R which when run at about 10PSI on this engine, sits almost bang on the centre of the compressor map (it almost looks perfect if I am reading the chart right) so I don't expect it to be a surge or choke problem.
I'll check out the o-rings. Could it be possible that boost is leaking past and flowing into the oil chamber on the turbo? My mate did mention that it looked a little dry (but oil supply has been confirmed), unless our oil drain is just working really well.

Anyway, it looks like my mate is resigning himself to 'stuff it' and wants to upgrade to a GT2860RS already... Should be good for up to about 18PSI if he ends up getting one.


I'll update with the autopsy of the t25g when I have news.

[boxh34d]

The turbo certainly isn't huge - I haven't seen any T25G's on 6 cyl diesels, they are however quite common on 4 cylinder hilux's and navaras etc. Most cruiser (and I assume patrol TD42's would be pretty much the same) tend to go to the likes of a T2860 for the greater flow potential.

My calcs suggest it is going to be bloody close to running out of compressor at 5psi, and I'm guessing that the turbine is going to be working bloody hard to keep it spinning as well.
Out of curiousity, what assumptions have you made when working out airflow and reading the compressor map?