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US Diesel Parts has been professionally rebuilding turbochargers for over 50 years. Today we can offer a variety of factory new and remanufactured turbochargers and turbo accessories for many automotive, agricultural, industrial and marine applications. At this point we only have the most common diesel truck applications listed online. If you are looking for any gas or diesel turbo application that isn't listed on our website, then please send us an e-mail or call us at 1-800-823-4444.

Follow the application links to the left for new and remanufactured stock replacement OEM turbocharger information on Ford, Dodge and Chevy GMC diesel applications. We also offer detailed information about high performance turbos by BD, Industrial Fuel Injection, Gale Banks and more. If you are looking for more power and have already done the basic upgrades (intake, exhaust and chip/tuner) a high performance turbo may be what you are looking for. As always feel free to call us toll free at 1-800-823-4444 to ask the advice of a seasoned turbocharger professional.

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A common problem encountered with turbocharger operations is the "turbocharger oil leak". Often, the assumption is made that the turbo is at fault. This can cause unnecessary maintenance to be performed. In most cases the oil leak is not a turbo problem, rather it is caused by either improper turbo installation or engine maintenance. We feel that if most people understand that most turbocharger leaks are caused by non-turbocharger problems, much unnecessary maintenance, downtime and expense could be saved. To fully understand what causes a turbo to leak oil and how to prevent it, we will cover:

Inside The Turbocharger

Engine oil under pressure enters the bearing housing from the oil inlet line. This oil passes between the bearing and journal surfaces where, as a result of turbulence, air is mixed with the oil. The oil leaves the bearings looking somewhat like a "brown whipped cream", then falls by gravity to the sump at the bottom of the bearing housing. This foamy oil then flows by gravity down the oil drain line and into the engine sump. Anything which prevents this gravity draining will cause the foamy oil to build up in the bearing housing to a height above the oil seals. Under this condition, the oil will leak out into the compressor and turbine housing past the piston ring seals through he piston ring gap.

Types Of Seals / Common Misconceptions

The most common misconception about turbochargers is the purpose of the turbine and compressor seals. The MAIN purpose of the seals at both the turbine and compressor ends of the bearing housing is to prevent the high pressure gases from entering the bearing housing and then to the crankcase! The fact that the seals may aid in preventing oil from  leaking into the turbine and compressor housings is secondary at most. In fact, many turbochargers have been manufactured without a piston ring seal at the turbine side at all. The simple fact is this: Turbocharger oil leaks, in nearly all cases are NOT the result of a failed seal! There are of course some exceptions as you will see as you read further.

Oil At The Compressor Inlet / Outlet

Some leaks are the result of air cleaner problems. A too-small capacity or dirty oil bath air filter will allow the air velocity through the oil in the cleaner to carry oil into the compressor inlet. This type of leakage will show only at the compressor outlet. You can correct this type of leakage by either servicing the oil bath filter by removing and steam cleaning both the upper and lower halves, or installing a larger unit if necessary.

Oil At The Compressor Outlet

A dry type filter, as it accumulates dirt, becomes increasingly restricted and causes a pressure drop across it. A partial vacuum at the compressor inlet will result. This will not affect the engine under load because a positive pressure exists at the seal behind the compressor impeller. During engine idle or extremely low load, a partial vacuum occurs at the compressor inlet and behind the compressor impeller simultaneously. If this condition continues for any length of time, it will cause oil to be sucked from the bearing housing, through the seal, and into the compressor housing and eventually into the pipe between the compressor and intake manifold. Too small of an air filter will cause the same problem.
The solution is simple. A commercially available gauge mounted between the air cleaner and the turbocharger will signal when the inlet restriction is too great and that the air filter should be replaced. To prevent the air intake restriction from becoming too excessive, service the unit on a regular basis. If the air filter capacity is too small, replace the unit with a larger model.
Another problem that can occur may involve the hose between the air filter and compressor inlet. If this hose is too soft, it can collapse under engine acceleration causing an inlet restriction. If this is the case, the hose should be replaced with a more rigid one.

Carbureted Engine Compressor Leaks

Turbochargers operating on carbureted engines where the carburetor is mounted upstream of the compressor should be equipped with a mechanical type seal on the compressor end of the turbocharger. This type of seal will not allow oil to pass through to the compressor even though a sudden closing of the carburetor throttle will cause a high vacuum at the compressor discharge. Any compressor side oil leaks in turbo's with this type oil seal would indicate that the was damaged, incorrectly installed, or is defective. This is one of the few exceptions to the general rule that turbocharger seals are are generally not at fault when an oil leak has occurred.

Oil At Turbine Outlet

Problems with the oil drain system can cause leaks to appear in the turbo. When oil leaks appear at the turbine outlet, it usually indicates a problem in the oil drain system. Something has caused the oily foam to build up in the bearing housing to a height above the seals. Check the following items and correct them to eliminate the problem. Make certain that the turbo drain port is pointing down at not more than a 35 degree swing on either side of a vertical centerline. See that the oil drain line slopes downward its entire length, so that there is no place for the oil to collect inside of the oil line. Especially on new installations, the line should be closely checked and any "sink" traps eliminated. Make sure that the turbocharger drain is connected to some unrestricted place on the engine above the level of the oil in the crankcase. If the oil drain enters the crankcase below the oil level, it will cause the foamy oil to back up in the drain line and the bearing housing sump which will cause a leak. You should also check what type of drain lines you have. Those made form a rubber lined, fabric covered hose may not cause any problems at all after running several years in one location, even though the hose itself has become extremely brittle. When replacing the turbocharger though, it is possible that this type of drain line could be disturbed or bent, causing small pieces of the drain line to break off and partially obstruct the flow of oil. To prevent this from happening, a rubber, fabric type of drain line should always be replaced with a new line when replacing the turbocharger.

Engine Breathers

Also, oil leaks in a turbocharger may be the result of the crankcase breather system. Either atmospheric or positive ventilation systems may not be large enough to handle the somewhat higher "blow by" which exists in turbocharged engines. It is recommended that the engines breather capacity be increased when a turbocharger is added. Even when the systems capacity is adequate, the elements in the systems breather will become partially clogged through use. Also, the breather may become clogged with mud or sludge in winter or under snowy and icy conditions. These conditions will cause positive pressure to build up in the crankcase. If this occurs, it will restrict the oil from flowing down the drain hose and into the crankcase, causing it to back up to the bearing housing.

Internal Crankcase Ventilation

Some naturally aspirated engines have internal positive crankcase ventilation between the crankcase and the intake manifold. These vents must be plugged when a turbocharger is added, otherwise the crankcase will become supercharged and oil leakage will result. Another source of crankcase breather must be provided when these vents are plugged. Some engines have this extra breather, while others may not. In either case, make certain that the breathers capacity is adequate.