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Old 07-11-2018, 05:09 AM   #1
dans77b
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Default rebuilding turbo on 940 wagon

***Hi all, new to this forum so not familiar with search facility - hope Im not asking something which has already been discussed-to-death.***

recently bough a '94 940 2.0 turbo for next to nothing. runs pretty well, seems fast enough but has failed its emisions test on blue smoke. Compression seems ok (Ive not got figures to hand right now)

I took off the discharge hose on the compressor end of the turbocharger and found it had quite a bit of oil in it.

this leads me to suspect the turbo seals are leaking.

Has anybody had any experience of rebuilding these? kits seem to be available - how do I know which model of turbo I have (or are they all the same??)

Does anybody have any other recommendations? I found a buildup of crud in the crankcase breather box - and will investigate tonight whether there is a blockage in the oil return from the turbo..

Thanks in advance!!
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Old 07-11-2018, 06:40 AM   #2
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Quote:
Originally Posted by dans77b View Post
this leads me to suspect the turbo seals are leaking.
The Turbo does not really have "seals".

Check for shaft play first (LOTS of information on the internet).
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Old 07-11-2018, 09:22 AM   #3
dans77b
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Originally Posted by Brotkasten View Post
The Turbo does not really have "seals".

Check for shaft play first (LOTS of information on the internet).
Thanks, the shaft has no noticeable play. I will put a dial indicator on it if I can find endfloat specs.

regarding the seals - surely there are flat surfaces which prevent oil getting from the bearings to the turbine/compressor housings which are serviceable - not necessarily rubber seals like the sort of thing on crankshafts etc...

I will take your advice and try a little harder with the google searches.

Thanks
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Old 07-11-2018, 10:54 AM   #4
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I think the turbo seal is actually just a ‘piston ring’ on the shaft. It gets worn down (just like piston rings) and then the turbo burns oil. That’s how I’ve seen it at least.
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Old 07-11-2018, 11:17 AM   #5
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The seals are for gases and not primarily for oil (https://www.dieselnet.com/tech/air_turbocharger.php).

As long as there is no severe physical damage there are a number of things more likely to cause the oil leaking:

- BlowBy gases or a blocked crankcase ventilation
- A blockage in the return line/oil feed through the turbo
- The radial shaft play is too big (which we ruled out)
- The pressure differential is wrong (leaks in exhaust, intercooler, piping, blockage in exhaust...)
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Old 07-11-2018, 11:28 AM   #6
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If the turbine housing is held onto the cartridge (the center of the turbo where the oil / water lines connect) by a large clamp, it's most likely a Mitsubishi TD04-13c. If the turbine housing is held on by bolts, it's most likely a Garrett T25. I only know of the Garrett T25 being used on the '91 940 SE in the US. It seemed to randomly show up on some other 7/9 series turbo cars, but I don't know if there's a year range or reason for when it was used. I don't know what might have ended up on a '94 940 2.0 in the UK...we didn't get the 2.0 in the US, so I'd expect the Mitsubishi turbo.

http://gpopshop.com/products-page/mi...-rebuild-kits/
http://gpopshop.com/wp-content/uploa...r-649x1024.jpg

The two bearings are the gold colored tubes with small holes around the perimeter. When they get worn, you have noticeable radial shaft play.

The two small rings that look like piston rings (rings with small gap between the ends) are used to control oil. My understanding of oil control within turbos is that these seal rings can only do so much...so when the bearings are worn, more oil gets to the rings, and some gets by. The bearings are also controlling oil flow through the turbo. You'll find wear of the rings and/or wear in the groove on the turbine shaft where the ring sits next to the turbine wheel on high mileage turbos. Sometimes a rebuild kit will work on the original turbine shaft...but if there's excessive wear in the groove, or scoring on the shaft (or both), you'll need to replace the turbine shaft.

The big gold colored piece at the lower left of the picture is the thrust bearing. When this wears you'll have axial play (in/out when pushing/pulling on the end of the shaft with the inlet hose removed).

I've had good luck "rebuilding" Garrett T3 turbos. But it wasn't my primary transportation, and I took apart a few used turbos first to learn how they come apart and go back together. It also gave me some spare parts to incorporate into my one rebuilt turbo. If you've never done it before and only have the turbo on the car to rely on, then you might be better off having it professionally rebuilt. They'll know if any additional parts need to be replaced besides the wear items included in a rebuild kit.
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Old 07-11-2018, 11:37 AM   #7
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Rule out the crankcase vent hose as the source of oil in the compressor housing first. Is the intake side as oily as discharge?
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Old 07-11-2018, 01:38 PM   #8
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Quote:
Originally Posted by Brotkasten View Post
The seals are for gases and not primarily for oil (https://www.dieselnet.com/tech/air_turbocharger.php).

As long as there is no severe physical damage there are a number of things more likely to cause the oil leaking:

- BlowBy gases or a blocked crankcase ventilation
- A blockage in the return line/oil feed through the turbo
- The radial shaft play is too big (which we ruled out)
- The pressure differential is wrong (leaks in exhaust, intercooler, piping, blockage in exhaust...)
Thanks.
my crankcase breather was full of a carbon build-up (im soaking the old breather box because cant seem to find replacements for sale in UK..)

I will be checking for blockages in drain line next

the car has got a temporary side-pipe straight after cat, but no leaks from around manifold area (that i can sense) I have a new exhaust waiting to be put on.
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Old 07-11-2018, 01:41 PM   #9
dans77b
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Quote:
Originally Posted by towerymt View Post
If the turbine housing is held onto the cartridge (the center of the turbo where the oil / water lines connect) by a large clamp, it's most likely a Mitsubishi TD04-13c. If the turbine housing is held on by bolts, it's most likely a Garrett T25. I only know of the Garrett T25 being used on the '91 940 SE in the US. It seemed to randomly show up on some other 7/9 series turbo cars, but I don't know if there's a year range or reason for when it was used. I don't know what might have ended up on a '94 940 2.0 in the UK...we didn't get the 2.0 in the US, so I'd expect the Mitsubishi turbo.

http://gpopshop.com/products-page/mi...-rebuild-kits/
http://gpopshop.com/wp-content/uploa...r-649x1024.jpg

The two bearings are the gold colored tubes with small holes around the perimeter. When they get worn, you have noticeable radial shaft play.

The two small rings that look like piston rings (rings with small gap between the ends) are used to control oil. My understanding of oil control within turbos is that these seal rings can only do so much...so when the bearings are worn, more oil gets to the rings, and some gets by. The bearings are also controlling oil flow through the turbo. You'll find wear of the rings and/or wear in the groove on the turbine shaft where the ring sits next to the turbine wheel on high mileage turbos. Sometimes a rebuild kit will work on the original turbine shaft...but if there's excessive wear in the groove, or scoring on the shaft (or both), you'll need to replace the turbine shaft.

The big gold colored piece at the lower left of the picture is the thrust bearing. When this wears you'll have axial play (in/out when pushing/pulling on the end of the shaft with the inlet hose removed).

I've had good luck "rebuilding" Garrett T3 turbos. But it wasn't my primary transportation, and I took apart a few used turbos first to learn how they come apart and go back together. It also gave me some spare parts to incorporate into my one rebuilt turbo. If you've never done it before and only have the turbo on the car to rely on, then you might be better off having it professionally rebuilt. They'll know if any additional parts need to be replaced besides the wear items included in a rebuild kit.
Thanks for the info!

This car is just one of a few projects so no real rush to get it done. I think a turbo rebuild would be an interesting project, but following the advice on this thread Ill check a few other things first..
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Old 07-11-2018, 01:49 PM   #10
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Quote:
Originally Posted by PCH View Post
Rule out the crankcase vent hose as the source of oil in the compressor housing first. Is the intake side as oily as discharge?
Yeah, the intake hose is pretty filthy with sludgy looking oil. the discharge side is oily, but not sludgy.

might as well add that this car came with a chinese looking cone 'performance' air filter, I wouldnt expect this to cause trouble - let me know if you disagree..

thanks
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Old 07-11-2018, 02:05 PM   #11
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Since you're in the UK, you have many options available. If the turbo does need to be replaced, you can just buy a rebuilt center cartridge like this:

https://www.ebay.co.uk/itm/Turbochar...kAAOxyPLpRfgrj

Swapping out the chra can be done in a few hours. I would also replace the oil breather box. The part number is 3501160. You can order from a Volvo dealer or an online parts dealer like Scandix.

http://www.skandix.de/en/spare-parts...ather/1022161/
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Old 07-14-2018, 07:03 AM   #12
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Do not buy the aftermarket crankcase breather box, I put one of those from skandix and blew the top off in 2 months, get the OEM one.
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Old 07-18-2018, 09:03 AM   #13
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Originally Posted by Roman_Turbo View Post
Do not buy the aftermarket crankcase breather box, I put one of those from skandix and blew the top off in 2 months, get the OEM one.
this, I just blew one up too. not as fun time
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Old 07-18-2018, 12:37 PM   #14
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If the OP has a MITSUBISHI turbo 13c likely; an excellent rebuild video from ARD Tuning exists which shows a full TD04 family overhaul. I rebuilt a 15g into a 19t using and ARD kit and their video. You will learn a good deal and gain satisfaction. Tally ho!
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Old 07-19-2018, 03:12 PM   #15
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Well, I finally got round to pulling off the old oil drain pipe, it was clear (can blow through it no problem), the hole in the crankcase was clear and the hole in the bottom of the turbo bearing housing looked clear.

Guess my next step will be rebuilding the turbo.

Interestingly, when I got the drain pipe off, I got the feeling I wasnt the first person there - there were four o rings and a load of silicone sealant on the engine-end of the pipe.
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