Determining if a turbo is good.
04-24-2003, 02:55 PM
#1
3.0 BAR
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Join Date: Dec 2002
Posts: 3,396
Determining if a turbo is good.
ok request for this post. i will try to cover everything if i miss some stuff just post and i shall add it
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1. Check for cracking around the exhaust housing and cracked or stripped bolts, cracked exhaust housing are common the TD models (14b, 12a.. etc) but not usually a problem.
2. Grab the end of the shaft and wiggle it up and down, do this very hard, sometimes the shaft play is sticky. it should have about like 1mm of play, or less. (again i have found the TD models have alot more shaft play then KKK's)
3. grab both ends of the shaft and try to move it in and out, axial play. any axial play is terrible for a turbo, if this is enough for the fins to hit the housing the turbo is garbage. usually caused by the thrust bearing/washer grinding on the half moon oil disk, can be cured by a rebuild if the fins havent hit the housing. (make sure u get the thrust bearing/washer with the rebuild kit)
4. depending on how much oil is caked on the blades of the turbine will tell you if its leaking badly, dry oil on the fins is usually always common on an old car. this is caused by years of the turbo running, and the seals are just a big maze for the oil so sometimes oil will penetrate this and leak a bit. no worries. but if there is wet oil on on the turbine or in the turbing housing lookout, rebuild time.
5. how smooth it spins, i have found every turbo but the KKK's will spin very smoothly if spun, the KKK's have a bit of resistance, i duno why. the turbo should keep spinning if you give it a good spin.
6. check to make sure the wastegate isnt jammed. (they are hard as hell to pull out yank HARD)
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now when u open the turbo here are a few things u can look for.
1. when u pull off the compressor housing (coldside) u will be able to tell if any of the fins are damaged.
2. unbolt the turbine from the shaft (make sure u mark the shaft and the turbine for re-assembly) sometimes the turbine is very tite on the shaft, u might have to give it a few taps to get it off. now remove the entire shaft. by the color on where the bearing are you can usually tell if the bearings have been cooked, itll be brown or black. if this is the case just take some 1000 grit wet sandpaper and sand it off, not to much though.
3. take a look at the bearings inside the turbo with a flashlite and u should see the bearings being a bronze color, not black.
4. i had a 14b where the bearing came out of the turbo on the shaft, this is because somehow whoever rebuilt this forgot to put the snap ring inside to hold the bearing in. might be a problem u could encounter.
5. check for cracking and contact on the exhaust turbine also.
6. there will be caked on black oil on the exhaust seal side of the shaft that can be cleaned up with some carb cleaner and some paper towel.
*** when assembling the turbo back toghther make sure when u tighten the nut on the turbine that u grab the ratchet near the middle to prevent from bending the shaft. also make sure u have lined up the marks u have made ealier on the turbine and shaft, this keeps the turbo balanced. ****
ok thats my writeup. any more suggestions and comments are wanted. thanks!
------------------------------------------------
1. Check for cracking around the exhaust housing and cracked or stripped bolts, cracked exhaust housing are common the TD models (14b, 12a.. etc) but not usually a problem.
2. Grab the end of the shaft and wiggle it up and down, do this very hard, sometimes the shaft play is sticky. it should have about like 1mm of play, or less. (again i have found the TD models have alot more shaft play then KKK's)
3. grab both ends of the shaft and try to move it in and out, axial play. any axial play is terrible for a turbo, if this is enough for the fins to hit the housing the turbo is garbage. usually caused by the thrust bearing/washer grinding on the half moon oil disk, can be cured by a rebuild if the fins havent hit the housing. (make sure u get the thrust bearing/washer with the rebuild kit)
4. depending on how much oil is caked on the blades of the turbine will tell you if its leaking badly, dry oil on the fins is usually always common on an old car. this is caused by years of the turbo running, and the seals are just a big maze for the oil so sometimes oil will penetrate this and leak a bit. no worries. but if there is wet oil on on the turbine or in the turbing housing lookout, rebuild time.
5. how smooth it spins, i have found every turbo but the KKK's will spin very smoothly if spun, the KKK's have a bit of resistance, i duno why. the turbo should keep spinning if you give it a good spin.
6. check to make sure the wastegate isnt jammed. (they are hard as hell to pull out yank HARD)
------------------------------------------------
now when u open the turbo here are a few things u can look for.
1. when u pull off the compressor housing (coldside) u will be able to tell if any of the fins are damaged.
2. unbolt the turbine from the shaft (make sure u mark the shaft and the turbine for re-assembly) sometimes the turbine is very tite on the shaft, u might have to give it a few taps to get it off. now remove the entire shaft. by the color on where the bearing are you can usually tell if the bearings have been cooked, itll be brown or black. if this is the case just take some 1000 grit wet sandpaper and sand it off, not to much though.
3. take a look at the bearings inside the turbo with a flashlite and u should see the bearings being a bronze color, not black.
4. i had a 14b where the bearing came out of the turbo on the shaft, this is because somehow whoever rebuilt this forgot to put the snap ring inside to hold the bearing in. might be a problem u could encounter.
5. check for cracking and contact on the exhaust turbine also.
6. there will be caked on black oil on the exhaust seal side of the shaft that can be cleaned up with some carb cleaner and some paper towel.
*** when assembling the turbo back toghther make sure when u tighten the nut on the turbine that u grab the ratchet near the middle to prevent from bending the shaft. also make sure u have lined up the marks u have made ealier on the turbine and shaft, this keeps the turbo balanced. ****
ok thats my writeup. any more suggestions and comments are wanted. thanks!
05-28-2003, 05:34 PM
#2
3.0 BAR
Thread Starter
Join Date: Dec 2002
Posts: 3,396
Re:Determining if a turbo is good.
heres another write up the guy did from www.dune-buggy.com
ill add this on cause its very in-depth.
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When you go to the the junkyard, do an overall assessment of the turbo vehicles. Look at their mileage, pop the hoods and focus on the best one. Check to make sure there is oil in the motor, and look for signs of obvious engine damage. In my opinion, it's better to find a car with obvious body damage because that will tell you why the car is likely in the junkyard.
Remember, the turbo charger was typically an afterthought to the auto manufacturers so it will be stuck wherever they could find a little bit of space. Before you bust your knuckles taking it off, pull off the air intake and put your fingers on the shaft. It should rotate smoothly all the way around without the blades rubbing on the housing. Now move the turbo shaft side to side. A little tolerance is built into the oil bearings so it should have slightly noticeable play. For sleeve type bearings, look for less than .022" side play which is a noticeable wiggle, and less than .008" end play which is not very noticeable. (A match cover is about .015" thick to give you an idea) If there is too much play, the turbo is either shot or needs a rebuild. Also check for signs of the blades rubbing on the housings, chips and rough edges on the blades and check the turbo outlets for signs of oil leaking past the seals.
Disconnect the wastegate rod and check the operation of the wastegate valve. Look for signs of major cracks on the wastegate port and check for a good sealing valve. Small cracks are to be expected on the wastegate port but if they are opening then scrap the unit or buy it for parts.
Pull off the oil lines and look for heavy deposits of charred oil in the ports. Heavy deposits may indicate that the turbo has had a rough life. Watercooled turbos will probably be in better condition.
The turbo will usually be tucked away in a tight space and the exhaust nuts may be rusted tight. Now would be a good time to spray the nuts with penetrating oil and look for other parts in the yard. When you remove the turbo, keep the oil lines on because they will help keep the dirt out. Whether you use them is up to you, however keep this in mind: That small line on the top of the turbo is the life blood of the turbo. You do not want a cheap or worn line to fail.
Depending on the application, some turbos may have an exhaust outlet that makes a hard bend toward the exhaust pipe. The housing I have seen are cast steel not cast iron so they can be cut and re-welded if need be.
While I'm thinking about it, remember to take a look at the ports where the intake air and exhaust flow through the turbo. If you see any roughness from casting marks or other defects, polish them out before installing the turbo and get a little more free performance.
Expect to pay between $35 and $100 for a used turbo at a junkyard.
ill add this on cause its very in-depth.
----------------------------------------------------------
When you go to the the junkyard, do an overall assessment of the turbo vehicles. Look at their mileage, pop the hoods and focus on the best one. Check to make sure there is oil in the motor, and look for signs of obvious engine damage. In my opinion, it's better to find a car with obvious body damage because that will tell you why the car is likely in the junkyard.
Remember, the turbo charger was typically an afterthought to the auto manufacturers so it will be stuck wherever they could find a little bit of space. Before you bust your knuckles taking it off, pull off the air intake and put your fingers on the shaft. It should rotate smoothly all the way around without the blades rubbing on the housing. Now move the turbo shaft side to side. A little tolerance is built into the oil bearings so it should have slightly noticeable play. For sleeve type bearings, look for less than .022" side play which is a noticeable wiggle, and less than .008" end play which is not very noticeable. (A match cover is about .015" thick to give you an idea) If there is too much play, the turbo is either shot or needs a rebuild. Also check for signs of the blades rubbing on the housings, chips and rough edges on the blades and check the turbo outlets for signs of oil leaking past the seals.
Disconnect the wastegate rod and check the operation of the wastegate valve. Look for signs of major cracks on the wastegate port and check for a good sealing valve. Small cracks are to be expected on the wastegate port but if they are opening then scrap the unit or buy it for parts.
Pull off the oil lines and look for heavy deposits of charred oil in the ports. Heavy deposits may indicate that the turbo has had a rough life. Watercooled turbos will probably be in better condition.
The turbo will usually be tucked away in a tight space and the exhaust nuts may be rusted tight. Now would be a good time to spray the nuts with penetrating oil and look for other parts in the yard. When you remove the turbo, keep the oil lines on because they will help keep the dirt out. Whether you use them is up to you, however keep this in mind: That small line on the top of the turbo is the life blood of the turbo. You do not want a cheap or worn line to fail.
Depending on the application, some turbos may have an exhaust outlet that makes a hard bend toward the exhaust pipe. The housing I have seen are cast steel not cast iron so they can be cut and re-welded if need be.
While I'm thinking about it, remember to take a look at the ports where the intake air and exhaust flow through the turbo. If you see any roughness from casting marks or other defects, polish them out before installing the turbo and get a little more free performance.
Expect to pay between $35 and $100 for a used turbo at a junkyard.
08-31-2003, 04:35 PM
#5
3.0 BAR
Thread Starter
Join Date: Dec 2002
Posts: 3,396
Re:Determining if a turbo is good.
anything thats hit the turbine would probably comprimise the strength of that blade because when it hits that piece of sand its going like 50 000 rpm. its up to you, i have seen MANGLED exhaust turbines create great boost.
if its cheap enough go for it, who ever your buying it off of haggle them.
if its cheap enough go for it, who ever your buying it off of haggle them.
10-27-2003, 08:00 PM
#6
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Join Date: Mar 2003
Posts: 21,479
Re:Determining if a turbo is good.
Now added to "USER FAQ"
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02-16-2006, 01:38 PM
#7
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Join Date: May 2005
Posts: 378
Re: Determining if a turbo is good.
Originally Posted by shortyz
4. i had a 14b where the bearing came out of the turbo on the shaft, this is because somehow whoever rebuilt this forgot to put the snap ring inside to hold the bearing in. might be a problem u could encounter.
Also, you guys make reference to "tapping" or "hit the shaft slightly with a hammer" and this is a horrible idea especially if you're going to include "you don't want to bend the shaft" in the next sentence.
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