You can not believe what I have been seeing lately. 9 out of 10 617 Turbos I have been diligently tearing down and inspecting recently do not past muster! In fact the findings have been shocking. I think this is largely due to the age of most of these engines coupled with the lack of preventative maintenance. The results and pictures I will share with you here will not doubt get you thinking TURBO MAINTENANCE.
Maybe you have heard or heard about turbo wine and just thought it was due to "bad bearings" inside the turbo. You may be surprised to learn that these turbos dont use bearings or rubber seals. They use bronze bushings and spring steel dynamic sealing rings to keep the oil inside the turbo center bearing section. Just try to imagine what happens when oil starts leaking out the rear turbine shaft sealing ring. No it does not just burn up and go out the tail pipe. Due to the high heat on the turbine side of the turbo when the oil seeps out it boils quickly and can form carbon or a crust like substance. As more oil leaks out the crust continues to build on itself and can eventually cause some serious problems.
In the picture to the right I have just removed a turbo from a 1981 300TD. I quickly discovered that the turbo shaft was dragging and there was no way I could spin the turbine shaft. Must be bad or seized bearings, right! Wrong - the bushings were actually loose. Upon removing the turbine shaft look what I found under the rear heat shield. And this turbo is NOT alone!
The carbon build up here is so excessive that it formed a super hard crust thick enough on the shield to make contact with the back of the turbine impeller. If you look closely at the following 2 pictures you can actually see the wear marks at the point of contact. This is what creats turbo wine coupled with a significant loss of power.
If you let your turbo go too long without maintenance you can count on having to replace some very expensive internal parts. In the case of this turbo the extra heat created by the friction of the impeller rubbing on the heat shield caused the bushings to actually spin in their races. This one is going to be very expensive to overhaul.
The three key reasons for this type of coking and wear inside a Garrett Turbo are as follows:
If you act early turbo overhaul usually requires only cleaning and replacement of the bushings, thrust washer, and dynamic sealing rings. This can keep the cost at or under $100. Turbos should be removed every 80,000 to 100,000 miles for this type of preventative maintenance. When you do this you will extend the life of the turbo, increase fuel economy and engine power output.
If you think the previous turbo was bad. Take a lot at one I took apart two days later:
The carbon build up was so extreme that it permanently damaged the impeller tips on the exhaust turbine. This one it toast. That is what happens when you go too long not doing any turbo maintenance. This engine had 205,000 miles on it and the turbo had never been opened up.
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