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940 Smoking on decel (a LOT)

O

ortho stice

Member
Joined
Feb 9, 2015
Location
Braddock, PA
1994 940 Turbo, ~245k miles, 16T junkyard turbo off a wrecked T5 that I reclocked myself.

The car uses oil; maybe a quart every 500-1000 miles or so. Occasionally at stoplights it will smoke randomly for a few seconds and then stop. The other night I was driving down the hill I live on and accidentally put the car in 2 instead of D and laid a massive smokescreen behind me.

So I figure either valve stem seals or the turbo must be bad, right? Anyone experienced this before? I built this car as a younger, broker man and could certainly afford a rebuilt turbo this time around (but where to find the time). Anyway, just curious what other people's experience has been.
 
Servicing the PCV as suggested will help stop the oil seepage and lower consumption. It may also be time to remove the intercooler and drain it. They get full of PCV goop.
 
When it smokes at high manifold vacuum I would suspect valve seals. But the basics mentioned above definitely need to be sorted out first.
May want to add a breather because at 245K you probably get a lot of blow by.
 
PCH said:
When it smokes at high manifold vacuum I would suspect valve seals. But the basics mentioned above definitely need to be sorted out first.
May want to add a breather because at 245K you probably get a lot of blow by.
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This is generally the case, but it's not very often I see heavily worn guides on 530 heads ( maybe ever?). Seals will only keep so much oil out, every time I've replaced seals thinking I could band aid the guides it didn't help. The guides need to be in tip top shape. Make sure the crankcase breather box is not plugged, clean flame trap. Turbo would smoke all the time, that's purely oil pressure dependent.
 
It's funny because I thought I had removed and cleaned the PCV system on this car but as I'm thinking about it I realize that was on my old 245. I'll start there and see what happens, thanks for the pointers, all.
 
you could do a leakdown test. That'll likely be the most conclusive thing you can do, quickly and easily.
 
Bumping this to say doing a PCV service fixed an oil LEAK (my oil separator box was broken where it goes into the drain tube) but the smoking continues.
 
Now it's time to remove the turbo intake hose and check the turbo for play. Most of the time it's the turbo. Valve stem seals happen rarely on a Volvo but it can happen.

Also the oil makes a big difference. These engines like thicker oil at the higher temps as they age ime. So moving up to something like a 10-40 synthetic is a good idea. A high mileage full synthetic like M1 would be something I'd suggest. Or Rotella T6 as a cheaper alternative.
 
doucheNozzle said:
You live in Braddock? WTF? I'm just over the hill from you
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Technically Braddock Hills these days, up near the borough building.

I'll try and find a way to do a leakdown test but I don't have compressed air any more or access to a shop space that does. I've been using T6 5w40 but maybe I'll try 15w40...
 
In the turbo fail aspect don't forget to check the turbo for play. Also another turbo failure cause is the oil feed. Over the years the oil feed pipe can get coked oil inside eventually restricting the oil flow to the turbo.
 
dl242gt said:
In the turbo fail aspect don't forget to check the turbo for play. Also another turbo failure cause is the oil feed. Over the years the oil feed pipe can get coked oil inside eventually restricting the oil flow to the turbo.
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Yeah I'll pull the intake hose off tomorrow and check. It did come off a junkyard T5 S70, but it was nice when I put it on (three years ago).
 
ortho stice said:
Technically Braddock Hills these days, up near the borough building.

I'll try and find a way to do a leakdown test but I don't have compressed air any more or access to a shop space that does. I've been using T6 5w40 but maybe I'll try 15w40...
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I'll be back in town the beginning of April. We can hook it up to air at my house if you want to.

Just remember when checking the turbo, slight up and down is fine, back and forth is bad.
 
No excessive shaft play that I can tell. One thing I did notice was that the last oil change I did I put 5w40 in. Just did an oil and filter change and used 15w40 so we'll see how that does.
 
5W-40 is probably a little on the light side. I had a Volvo reman watercooled T3 on my original 242T that did this. No excessive play, but I'd leave a wall of smoke if I did any prolonged engine braking. Ran 15W-50 M1 in it at the time, so the oil was thick enough. Probably didn't help that the turbo came off a B21FT that grenaded itself due to lack of oil.
 
ortho stice said:
No excessive shaft play that I can tell. One thing I did notice was that the last oil change I did I put 5w40 in. Just did an oil and filter change and used 15w40 so we'll see how that does.
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Well I don't know what I was talking about when I posted this. There is significant side-to-side play. This junkyard 16t is toast I think. Or at least the center-section.
 
ortho stice said:
Well I don't know what I was talking about when I posted this. There is significant side-to-side play. This junkyard 16t is toast I think. Or at least the center-section.
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So the first time I checked was right after a drive, gloveless. The turbo was HOT and I just gave it a cursory spin and thought it was fine. It definitely moves up and down beyond what is acceptable.

What's the advisable course of action on a daily driven beater? It looks like there's a turbo S70 in the yard currently if I want to run yet another junkyard turbo...
 
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