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#4781422 - 06/08/18 03:47 PM Turbo repair: new bypass valve + wastegate adjust
VeryNoisyPoet Online   content


Registered: 12/16/17
Posts: 291
Loc: Massachusetts
Been chasing some performance issues on my car now that I have a boost gauge. The whole point of the tiny turbo is to spool up quick and give a fat mesa of a torque curve from 2000 rpm up to 5000 rpm. But the car was a slug off the line, and even once the revs were up it felt weak. Gauge confirmed boost was very slow to build and peaked at barely 3.5 psi whereas the claimed spec is 6 psi.

Took the heat shield off and checked the wastegate linkage - darn thing was WAY loose and the pivot point had formed an oval from wear. It never closed completely, letting exhaust just fly past the turbine! No wonder boost was low and really laggy. As expected from two decades in the northeast the adjustment nut had corroded into an unrecognizable lump. I needed to get creative using a hose clamp and some steel wire to get everything back to where it should be. The white stuff on the linkage is anti-seize, and the white stuff on the flange is exhaust cement since it does leak a bit there.



This brought back a great deal of throttle response, but peak boost only went up to maybe 4.5 psi. I've had all the tubing apart just recently, and there were no symptoms of a leak to atmosphere. A leak of that size would murder my fuel economy and allow enough pirate air to throw codes. It had to be an internal leak at the compressor bypass valve (recirculating blowoff valve). This would let boost leak back to the inlet of the turbo, robbing performance without the computer seeing that anything is wrong. There was also signs of oil seeping out in the area, which only could have come from the bypass valve, as the turbo oil supply and drain lines were completely dry.

Rebuild kits are cheap so I ordered one and took the old unit apart. Annoying to access but I think I found my problem. Holy boostleak, Batman:


You are not supposed to see light shine through cracks in the diaphragm...


All the oil slime is from the PCV system, which means I probably should inspect and clean that soon. I did clean the housing, intake tube, and PCV solenoid while I had them apart.



Got the new kit installed, which was even more troublesome than the disassembly as I had to fight the spring to get the bolts started while also keeping the diaphragm seated. Since the intake tube needed to come off to give me access to the bypass valve, I also inspected the compressor wheel and checked for play. Very slight vertical play, even less horizontal play, and zero discernible axial play. After 187k miles this turbo feels brand new! Little bit of wear on the compressor leading edges but otherwise looks good in there.



Got it all back together and all I can say is wow. I had no idea how much grunt was missing. Even a quick part throttle burst brings the boost up to 4 psi. The manifold comes up to atmospheric more often and the car just pulls with barely any throttle. Once I do some more testing I'll see if I can put up a side by side comparison of the graphs from my data logger before the repair, after the wastegate adjustment, and after the bypass replacement.

If you have an older turbo car, I urge you to check these items, as you could be down a lot of boost without even realizing it.
_________________________
1998 V70 GLT / 187k miles

"Use yah blinkah!"

"Be nice. The alternative involves an air horn and 7000 lumens of high beam."

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#4781437 - 06/08/18 04:01 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: VeryNoisyPoet]
wemay Offline


Registered: 04/04/12
Posts: 8898
Loc: Southeast Florida
Nice write up. Feels great when you take on a project and see the end results come out so well.

BTW, my favorite car of all time is the 850 T5-R wagon. Like the one Rickard Rydell drove in the BTCC
_________________________
2017 Hyundai Sonata Sport 2.4L
2013 Hyundai Santa Fe Sport 2.0T
Valvoline

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#4781447 - 06/08/18 04:13 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: VeryNoisyPoet]
sleddriver Offline


Registered: 02/06/10
Posts: 4609
Loc: Central Texas
Nice work! I found my wastegate adjustment rod way out of spec. Sure made a difference when properly adjusted. Still using the original diaphram. When I checked it last, it did hold a vacuum so I left it alone. They're also a PITA to get to. Where did you order a replacement from?

BTW, is that a crack (lower right hand corner)?
_________________________
1998 Volvo V70 T5 226,808 mi. Original Owner.
M1 10W-30 HM
"It's never a mistake to buy tools, defined broadly. They're not a cost, they're an investment." - J.B. Peterson

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#4781454 - 06/08/18 04:19 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: VeryNoisyPoet]
VeryNoisyPoet Online   content


Registered: 12/16/17
Posts: 291
Loc: Massachusetts
Originally Posted By: sleddriver
Nice work! I found my wastegate adjustment rod way out of spec. Sure made a difference when properly adjusted. Still using the original diaphram. When I checked it last, it did hold a vacuum so I left it alone. They're also a PITA to get to. Where did you order a replacement from?

Your car is as old as mine with even more miles, so I'd get a quality digital boost gauge on it to see if you are in fact getting full power. If your bypass isn't leaking, it will leak soon after so much heat and time and flexing. I ordered mine from IPD for $25. They have the standard replacement good for 12 psi, but also offer kits with heavier springs if you are turning the boost up, since the stock spring will bypass too early on a tuned car.

Quote:
BTW, is that a crack (lower right hand corner)?


Which pic are you referring to?
_________________________
1998 V70 GLT / 187k miles

"Use yah blinkah!"

"Be nice. The alternative involves an air horn and 7000 lumens of high beam."

Top
#4781458 - 06/08/18 04:26 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: wemay]
VeryNoisyPoet Online   content


Registered: 12/16/17
Posts: 291
Loc: Massachusetts
Originally Posted By: wemay
Nice write up. Feels great when you take on a project and see the end results come out so well.

BTW, my favorite car of all time is the 850 T5-R wagon. Like the one Rickard Rydell drove in the BTCC


I'd really love a T5-R, but I don't think my time machine would let me go back to when my parents were shopping for new station wagons back in 1997 LOL
The GLT has served me well, and things are looking up now that I'm making my way through these "Stage 0" type repairs and tuneups.
_________________________
1998 V70 GLT / 187k miles

"Use yah blinkah!"

"Be nice. The alternative involves an air horn and 7000 lumens of high beam."

Top
#4781460 - 06/08/18 04:27 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: VeryNoisyPoet]
9050lx Offline


Registered: 11/07/08
Posts: 118
Loc: FL
How durable should a turbo be expected to last in a typical fashion? Scared off from buying a turbocharged vehicle so far.

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#4781467 - 06/08/18 04:35 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: 9050lx]
VeryNoisyPoet Online   content


Registered: 12/16/17
Posts: 291
Loc: Massachusetts
Originally Posted By: 9050lx
How durable should a turbo be expected to last in a typical fashion? Scared off from buying a turbocharged vehicle so far.


Well, you're looking at a turbo engine with 187,291 miles and two decades under its belt. Original turbo in good shape, and relatively low oil consumption of a quart in 2000 miles (including leaks that I've been slowly taking care of, so actual oil burning may be much lower). No blue smoke at all, and it pulls hard especially now that maintenance items are taken care of.

The big thing with turbo cars is using good oil and running midgrade or higher fuel, even if it claims to work fine on regular grade. Other than that it's basic maintenance like replacing vacuum lines that rot out after so many years, never letting it overheat or run low on oil, etc.

Some of it does depend on the car, since even the best maintenance can't compensate for faulty designs. These Volvos along with many other models and brands can easily live as long or longer than their naturally aspirated counterparts if properly cared for.
_________________________
1998 V70 GLT / 187k miles

"Use yah blinkah!"

"Be nice. The alternative involves an air horn and 7000 lumens of high beam."

Top
#4781474 - 06/08/18 04:42 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: 9050lx]
123Saab Offline


Registered: 10/27/10
Posts: 1585
Loc: PA
Originally Posted By: 9050lx
How durable should a turbo be expected to last in a typical fashion? Scared off from buying a turbocharged vehicle so far.


Modern Turbo's are very reliable. I don't consider it any more fail prone than any other mechanical part on a car.

I think people who are afraid of turbo's are in the "It's one more thing that can break" camp.
I don't have any phobia's like that.

In typical fashion I expect a turbo these days to last 150-200k.
_________________________
Twenty-twenty-twenty four hours to go I wanna be sedated
Nothin' to do and no where to go-o-oh I wanna be sedated

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#4781485 - 06/08/18 04:56 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: VeryNoisyPoet]
Srt20 Offline


Registered: 07/14/14
Posts: 495
Loc: Wisconsin
That turbo looks rough. Blades are chewed. Also any vertical play at all is bad.

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#4781497 - 06/08/18 05:09 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: Srt20]
VeryNoisyPoet Online   content


Registered: 12/16/17
Posts: 291
Loc: Massachusetts
Originally Posted By: Srt20
That turbo looks rough. Blades are chewed. Also any vertical play at all is bad.


I read that journal bearing turbos can be expected to have a small amount of vertical play because without oil pressure the bearings are not suspended in the correct location. Once there is oil pressure the shaft floats on a layer of pressurized oil like a crank bearing, which will hold it centered. Horizontal play may indicate a problem, and axial play means the turbo is toast. Here there is the tiniest bit of vertical, even less horizontal, and no axial that I can feel. I can't see the assembly move, just feel a click when I gently lift up on it. No matter which direction I apply pressure, the assembly turns easily with no signs of rubbing.

A ball bearing turbo on the other hand should have essentially zero play in any direction since the ball bearings keep the shaft centered even without oil pressure. Any play there means the bearings are fried.

I wouldn't expect the impeller to look brand new considering the age, and I also don't have plans to crank the boost up without a future rebuild / replacement / upgrade.
_________________________
1998 V70 GLT / 187k miles

"Use yah blinkah!"

"Be nice. The alternative involves an air horn and 7000 lumens of high beam."

Top
#4781730 - 06/08/18 09:11 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: 9050lx]
Astro14 Offline


Registered: 10/10/10
Posts: 8545
Loc: Virginia Beach
Originally Posted By: 9050lx
How durable should a turbo be expected to last in a typical fashion? Scared off from buying a turbocharged vehicle so far.


I've got 238,000 miles on the 2002 Volvo XC in my signature. Original turbo.

I've got 194,000 miles on the 2002 Volvo V70 in my signature. Original turbo.

Both have had the wastegate adjusted, and the compression bypass valve replaced (thanks to IPD).

A turbo will last about the life of the engine. My recommendation: good oil, idle for 30 seconds before driving off, drive gently for the last five minutes, and idle for 30 seconds, before shutdown.
_________________________
32 Packard 15W40
02 Volvo V70 T5 0W40 M1
02 Volvo V70 XC 0W40 Edge
05 MB S600 0W40 M1
16 Tundra 1794 5W30 Valvoline

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#4781776 - 06/08/18 10:16 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: VeryNoisyPoet]
sleddriver Offline


Registered: 02/06/10
Posts: 4609
Loc: Central Texas
Originally Posted By: VeryNoisyPoet
Originally Posted By: sleddriver
Nice work! I found my wastegate adjustment rod way out of spec. Sure made a difference when properly adjusted. Still using the original diaphram. When I checked it last, it did hold a vacuum so I left it alone. They're also a PITA to get to. Where did you order a replacement from?

Your car is as old as mine with even more miles, so I'd get a quality digital boost gauge on it to see if you are in fact getting full power. If your bypass isn't leaking, it will leak soon after so much heat and time and flexing. I ordered mine from IPD for $25. They have the standard replacement good for 12 psi, but also offer kits with heavier springs if you are turning the boost up, since the stock spring will bypass too early on a tuned car.

Quote:
BTW, is that a crack (lower right hand corner)?


Which pic are you referring to?


Here's my write-up @ MVS: Wastegate Rod Adjustment

The photo showing the wastgate/exhaust manifold
_________________________
1998 Volvo V70 T5 226,808 mi. Original Owner.
M1 10W-30 HM
"It's never a mistake to buy tools, defined broadly. They're not a cost, they're an investment." - J.B. Peterson

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#4781780 - 06/08/18 10:23 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: 9050lx]
sleddriver Offline


Registered: 02/06/10
Posts: 4609
Loc: Central Texas
Originally Posted By: 9050lx
How durable should a turbo be expected to last in a typical fashion? Scared off from buying a turbocharged vehicle so far.
My overall experience has been fine.

1985 SAAB 900T bought new. Spindle bushing not water cooled. Original turbo replaced at 205,000mi. If I'd used synthetic from day one, it probably would have lasted even longer.

1998 Volvo V70 T5. Bought from dealer @ 11,000 mi. Spindle bushing is water cooled. Current mileage close to 229,000 mi. Original turbocharger.

The Swede's have had turbocharged cars for many, many decades. Everyone else is finally catching up...

No worries!
_________________________
1998 Volvo V70 T5 226,808 mi. Original Owner.
M1 10W-30 HM
"It's never a mistake to buy tools, defined broadly. They're not a cost, they're an investment." - J.B. Peterson

Top
#4781785 - 06/08/18 10:30 PM Re: Turbo repair: new bypass valve + wastegate adjust [Re: sleddriver]
VeryNoisyPoet Online   content


Registered: 12/16/17
Posts: 291
Loc: Massachusetts
Originally Posted By: sleddriver
The photo showing the wastgate/exhaust manifold


I think that's a trick of the light and shadow. Next time I'm under there I can take a closer look but I don't have any signs of a exhaust leak besides the flange that I cemented up.

Cool write-up! Looks like you had some meddling in yours, whereas mine just wore out and got sloppy. If you are getting a full 13 psi your bypass valve is miraculously still intact. Seems like a likely failure point now that these cars are getting old, though. Mine only punched through where I showed in the pic, but there were those little cracks everywhere the diaphragm flexed so other spots were going to open up soon.

I'll see if I can rig up my pressure gauge and an air source to test the wastegate actuator sometime. It obviously appears to mostly work since I'm not suddenly overboosting with the linkage and bypass repaired.
_________________________
1998 V70 GLT / 187k miles

"Use yah blinkah!"

"Be nice. The alternative involves an air horn and 7000 lumens of high beam."

Top