Valve Guide Seals or Turbo Leak? - Saab 900 Bulletin Board - Saabnet.com
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Thank you for your post!
The TE05 SAAB turbochargers have been one of our favorite 900 assemblies due to the quality of construction, and ease of servicing. The original turbine oil seal employed is a gapped carbon steel piston ring design allowing for thermal expansion, which has been commonplace for most turbocharger manufacturers for decades. The piston ring gap will always be reduced as temperatures increase, but this will also lower engine oil viscosities. The turbocharger turbine piston ring, however, is subject to wear over mileage wherein the gap will always increase in gap size as this occurs with an engine piston ring. This seal was only designed to combat a standard oil use, but will not be capable of eliminating oil bypassing when experiencing oil levels accumulating within the turbocharger's bearing housing. This may occur when the oil return is being inhibited by means of positive crankcase ventilation problems at the engine's oil sump, an over-filled oil sump, or damaged return pipe from the turbocharger to the oil sump.
To combat positive pressures from entering the crankcase, make certain that the one way check valve at the valve cover is functioning, and replace, if required. These valves are also notorious for tiring over time which will allow for the check valve to begin bypassing at a pressure "threshold" making them difficult diagnose...we typically recommend replacing all vacuum line and valve assemblies if questionable. Most shops test this valve by means of a miti-vac hand pump which will be tested from the check valve assemblies intake manifold connection. At this signal line, there should be an ability to draw vacuum at 15hg, but should seal/check when changing this tool to pos. pressures.
Also, B202 engine valve seal bypassing is very atypical due to the overhead design, and quality of valve guide and seal assemblies. Engine oil bypassing due to the valve seals should show signs within the engine combustion process, and may show as discoloration at a spark plug, when removed. Most valve seal issues would also show symptoms of bypassing upon initial engine start.
Thanks again for your post, and please inform us as to any progress!
Gary K. at SWEDISH DYNAMICS, INC.
->Posting last edited on Wed, 23 Jan 2019 22:19:28.
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