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Saab
Saab Turbo Diagnosis & Rebuild
Edited from an article by Boe Kalinoski, ImportCar, August 2000
While most every automobile manufacturer participated in the turbo craze about 15-20 years ago, Saab has been the leading manufacturer of turbo-powered cars. Refinements in the technology led to the appearance of the first Saab turbo-powered car in 1977. Saab built only seven of these cars for the U.S. for testing purposes. I had a chance to drive one of these rare cars back then when I was working for a dealership in Boston. It was a great new beginning for Saab.
In early form, the turbos were lubricated and cooled with engine oil. Eventually, a water-cooled unit was produced, allowing the turbo to run lower in temperature and increasing seal and bearing life. With the addition of APC (automatic performance control), this very sophisticated boost control system uses a knock sensor to control boost pressure under detonation. This system enabled Saab to increase the compression for more performance. With the aid of an intercooler, the boost pressure could carefully be increased by cooling down the charge. Cooling the charge regains density as well as efficiency.
A turbocharged car that is well maintained by the owner with oil changes every 3,000 miles and periods of cool down after long distance trips could last many trouble-free years. But if dirty oil (or no oil) is directed to the turbo for even a short period of time, there is a good chance that the unit will be short-lived. We have many customers who own Saabs who have more than 160,000 miles on their vehicle, still with the original turbo.
Some customers were afraid to purchase a Saab with a turbocharger because of the high maintenance demands and expensive repairs, even though they liked the vehicle’s inherent performance and smooth acceleration. As a result, the manufacturers designed small displacement engines with multi-valves, hemispherical combustion chambers and sophisticated fuel systems with variable cam timing in an attempt to squeeze more performance without the aid of a turbocharger. But the turbocharged cars made a statement and were still in demand.
PINPOINTING PROBLEM AREAS
Turbochargers won’t actually blow a seal. Most of the time when a cloud of blue smoke is coming out of the exhaust, the problem area is the seal. The seal on the exhaust side, for example, is usually a simple cast ring with a very small gap. The seal on the compressor side is either the same style or a more positive carbon type, similar to a water pump impeller seal.
Before you blame the turbo, consider the fact that even a good turbo will leak oil under certain circumstances. Here are five areas to check out:
• A restricted exhaust;
• Restricted air inlet;
• Any restriction to the oil drain going to the crankcase;
• Crankcase ventilation problems that can increase excessive pressure on all oil seal areas; and
• Cracked or brittle hoses.
On some early Saabs, the head gasket failed, allowing the oil to be injected into the number one cylinder. It was the oil feed to the cam tower that created the blue-smoke syndrome. A compression test would be a good idea to rule out this possibility. The oil drain inside the unit could be restricted with burnt oil or coke deposits, making the only route for the oil to be dumped into the exhaust. Consider the possibility that excessive oil pressure/volume might be fed to the turbo, causing the bearing housing to be flooded with oil and the turbo to leak. Oil must be drained away from the turbo faster than the oil being fed to it.
In this month’s article, I am going to give you some pointers for diagnosing a Saab turbo, and then provide procedures for rebuilding the unit.
TURBO REMOVAL/REBUILD PROCEDURES
Removing the turbo on a 1992 9000 is not a big deal once you’ve done a few. (Saab has used the Garrett T3 or the Mitsubishi TEO5 unit in the 900 and the 9000 series.)
First remove the A/C compressor, then the mounting bracket that is bolted to the cylinder head (see Photo 1). It is not necessary to discharge the gas in the A/C system, as the hoses will still be attached to the compressor.
Place a fender cover under the unit and slide it out of the way on the radiator support (the fender cover will protect the finish on the radiator support).
Remove the cooling fan, then the exhaust head pipe. If the lock nuts on the pipe give you trouble, just use a little heat on them, otherwise they will snap off in the turbo and give you some problems in the removal process.
Next, remove the oil feed and drain tubes, then the coolant lines.
Remove the pressure and suction hoses, and the three APC pressure hoses.
You are going to remove the exhaust manifold with the turbo in one shot. Remove the seven lock nuts that hold the manifold on the head. Note: Be careful not to snap the studs! Place the unit on a workbench and remove the four bolts holding the turbo on the manifold and discard the metal gasket.
Place the turbo in a vise as shown in Photo 2. On a Garrett unit, you must mark the housing before you disassemble it. The Mitsubishi unit has locating pins mounted in the housing. You will want to mark the housings to have the correct alignment for reassembly so all the hoses and connections line up for installation.
Remove the compressor housing, then the exhaust housing/wastegate valve. Very important note: Try to mark the compressor wheel with the exhaust drive wheel so it will be assembled in the same manner as it was balanced from the factory! If this is not done, the compressor will be very loud and noisy, and sound like a siren.
Clean all parts. Use a glass bead cabinet if you can get your hands on one. It will pay off in the long run. All parts must be thoroughly cleaned and rinsed, as residual glass bead would destroy your rebuild in a very short time. If glass bead is not available, a cold carburetor dip is acceptable.
Inspect all worn areas, such as the compressor plate on which the seal ring rides (See Photo 3).
Soak all the parts until clean. Use a soft brush to help remove stubborn deposits. Remember, the cleaner you get the parts, the longer the rebuild will last.
Make sure all of the oil passages are very clean to allow proper oil flow to the bearings.
Inspect all of the parts for signs of abnormal wear. All shaft surfaces should be smooth and pit-free. Sand the turbine shaft smooth with 800-grit paper (See Photo 4). Note: This is a very important step.
Bearing bores in the housing should not be scored or distorted. The turbine seal area in the housing should be flat — no grooves. Blades should not be bent or broken and should not have contacted the housing. Do not try to straighten out the blades! They will crack and fail under pressure.
Inspect the exhaust turbine shaft area for worn out groove depth.
Carbon/oil deposits trapped in the main housing could fool you, as they look like the casting. Poke all around with a sharp object and scrape away all the foreign particles. This is a very important step, as the oil has to drain through the housing without any restrictions (See Photo 5).
On a clean area, lay out the torn down turbo with all the parts ready for assembly.
Install the brass bushings in the housing using engine oil.
Install the small snap rings in the housing in the proper manner — sharp/square side out.
Carefully install the split seal rings on the exhaust-side and the compressor-side turbine shaft. Lube with oil.
Install the turbine shaft into the main housing and don’t forget the heat shield. Make sure the seal is centered in the housing. It will slide in easily when in position. Do not apply force; you could damage the shaft and or the seal.
Slide the compressor wheel on the shaft. Tighten the nut to 18-20 in. lbs., then add one additional quarter turn or shaft stretch of .0055 in to .0065 in. At this time, the turbine wheels should spin freely with no excess play.
Install the compressor housing with clamps and bolts. Tighten the housing to 145-165 in. lbs. and turbine side to 185-200 in. lbs. Make sure the turbine wheels do not contact any of the housing surface.
INSTALLATION TIPS
Reverse the procedure of removing the turbo.
- Replace the exhaust manifold studs, especially the long-end studs, located on the cylinder head before installing the assembly. Since the long-end studs have a tendency to snap off in the head because of high temperatures, replace them with the short-end studs. Remember to use new lock nuts on all studs.
- Change the oil and filter and clean or replace the oil pressure inlet pipe going to the turbo. Oftentimes, the line will be restricted with coked oil.
- Do not use silicone sealer (rtv) on the oil inlet gasket as it may squeeze out into the bearing passages and plug up the oil feeds.
- Do not race up the engine for 4-5 minutes after start up. Just let it idle and check the coolant level.
- Check all connections and hoses for leakage. Also check the turbo bypass valve for leakage (See Photo 6). Replace, if necessary.
The TEO5 Mitsubishi unit is much smaller in design. It has line-up pins built into the main housing to make the rebuild easier to assemble after tear down. Instead of bolts, this small unit has a large snap ring and collar-type clamp holding the main housings together.
The rebuilding procedure for the Mitsubishi unit is similar to that of the Garrett unit. Patience and clean parts, complemented with a careful inspection of worn areas, are the keys to a successful repair.
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