Common Turbo Problems / Failures
Highway and Heavy Parts (HHP) presents the latest in our tech tip blog series. This month we will cover lubricating oil in the turbocharger and external turbocharger leaks. Monthly our parts department records the most frequently asked questions, what the answer are, and what did we learn. This not only helps us better answer your questions but also helps keep us updated on the latest industry trends.
In this blog we will cover: Compressor side leaks, Turbine side leaks and possible turbo failures.
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Compressor side leaks -
Plugged air cleaner:
This will cause a vacuum to build in the compressor housing and pull oil past the seal. This will be most noticeable when letting the engine idle for extended periods of time. When the engine is running with a load there is enough pressure in compressor housing to keep the seal seated and the oil from leaking past. Servicing the air cleaner at recommended intervals should keep this problem from occurring.
Excessive crankcase pressure:
When excessive air pressure is coming from the crankcase the oil is actually being pushed past the seals. Many times oil will be noticed in both the compressor housing and the turbine housing with this type of problem. A good place to start when crankcase pressure is suspected is by inspecting the engines crankcase breather. If this becomes plugged it will cause high crankcase pressure. If it is not plugged but appears to flow an excessive amount of air, it may be a sign that the seal between the piston rings and cylinder liner has been compromised and the engine needs to have a rebuild kit installed.
Turbine side leaks –
Drain line restriction:
When the oil drain line has a restriction in it, a possible result is that the oil will back up into the bearing housing. When this happens the oil can push its way past the seals and into the turbine housing. If this is suspected a couple of trouble spots to check are the drain gasket for excessive silicone that may have seeped into the line. A second item to check is if the drain line has a silicon rubber section. Sometimes, if the line has been changed with standard heater hose it may swell due to contact with oil and cause a blockage. It will need to be replaced with oil resistant silicon hose.
Valve guide seals or piston ring failure:
If the valve guide seals in the cylinder head pass oil or if the piston rings allow oil to pass it will be expelled out the exhaust manifold. From the exhaust manifold it then travels through the turbine housing and out the exhaust pipe. This is a very common problem and has led to many un-necessary turbochargers to be changed. The turbo will look very suspect and may appear to be leaking both externally and internally. An excellent way to diagnose this is by adding florescent oil dye to the oil. After letting the engine idle for some time, the turbocharger can be removed and a black light used to see if the dye is present in the exhaust manifold. If it is, the oil is coming from the engine and not the turbo.
Excessive crankcase pressure:
This issue was also covered under oil in the compressor housing, but should also be mentioned here. When excessive air pressure is coming from the crankcase the oil is actually being pushed past the seals. A good place to start when crankcase pressure is suspected is by inspecting the engines crankcase breather. If this becomes plugged it will cause high crankcase pressure. If it is not plugged but appears to flow an excessive amount of air, it may be a sign that the seal between the piston rings and cylinder liner has been compromised and the engine needs to have a rebuild kit installed.
Turbo Problems –
Damaged compressor wheel:
A damaged compressor wheel can be a result of a foreign object getting into the compressor housing. Turbo bearing failure is also a leading cause. This can be diagnosed by removing the intake tubing and examining the compressor wheel. If fins are bent, missing, or even just missing a piece the turbo should be rebuilt or replaced. Also, if pieces are missing it is a good practice to have the charge air cleaner cleaned and inspected. This will insure no further engine damage by one of the pieces entering the intake manifold.
Damaged turbine wheel:
A damaged turbine wheel can be a result of internal engine pieces being expelled out of the engine due to a failure. Turbo bearing failure is also a leading cause. Another known cause is carbon buildup in the turbine housing. This can be diagnosed by removing the exhaust pipe and examining the turbine wheel. As with a damaged compressor wheel, if any of the fins are bent, missing or even just missing a piece the turbo should be replaced or rebuilt. If any pieces are missing, it is a good practice to try and remove them from the exhaust piping.
Turbo bearing failure:
Turbocharger bearings can fail for many reasons. A few of more popular include:
- Poor engine maintenance of oil or air cleaner allowing dirt to come in contact with the bearings.
- Loose turbo clamps allowing the compressor or turbine housing to move.
- Oil starvation on engine startup or when first installing the turbo.
- Wastegate malfunction, removal or wastegate hose pinched.
The best way to diagnose a bearing failure is removal of both the intake piping and exhaust piping. This will allow access to both ends of the rotating assembly. Check the bearings by spinning the rotating assembly to insure it moves freely. Check the end play by pushing and pulling the shaft. If there is any end play the turbo should be rebuilt or replaced. Check the side play by pushing the rotating assembly towards the compressor or turbine housing. Some play here is allowed, and the compressor or turbine wheel may be able to touch the housing depending on how much force is applied. The concern would be if there is excessive side play or “slop” for lack of a better term. If the side play is deemed excessive the turbo should be rebuilt or replaced.
Image Source: Mahle
Originally Posted August 1, 2019; Edited July 29, 2019
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