Date: Sat, 08 Apr 2000 22:39:02 GMT
From: coxinga <coxinganopsameja.com>
Subject: Re: Timing Chain


Armed with the engine service manual and the Haynes book on SAAB 9000, I undertook the on-car dismantling of the timing chain. Compared to other cars that I have work with in the past, which include a Honda Civic, a Toyota Camry and Volvo 240, the SAAB 9000 is a bear. The 9000 has only one serpertine belt on the side of the crank shaft pulley to drive all accessories. These include water pump, AC compressor, in front, alternator and power steering between the engine and firewall. To get to the timing chain, they all have to be removed since they are all bolted to both the timing chain cover and the engine. The alternator and power steering are especially hard to reach being sandwiched between the motor and the firewall. I started by removing the head cover. Because of engine heat, the cover gasket was sort of stuck on the head. I used a razor blade to scrape around both the inside gasket and the outside one before removing the cover. As expected, after 100k miles, the cam shaft looks excellent. No visible scour at all. The timing chain was tout on the cam shaft sprocket. There is no indication that it is broken. But when I turn over the engine, the camshaft doesn't turn at all. So the timing chain cover is next. I proceeded to remove the passenger side front wheel. After removing the front plastic mud guard, the crank shaft pulley and the serpertine belt is in full view. Water pump, AC compressor, alternator and power steering were taken off in that order. I used a string to hang the AC compressor to the frame because there is no need to unhook the hose. A steel tubing which goes from the water pump wrapping around the engine block on the timing chain side and rear to penetrate the firewall to the heater core is extremely difficult for me to remove. It has to come loose because it is in the way of the timing chain cover. The oil pump is actually on the outside of the timing chain cover, concentric with the crank shaft. It came off too. After the timing chain cover is removed, there are two chains inside. The outside one is likely unique to SAAB 9000, it drives two balance shafts, one for the inlet, another for the exhaust, supposedly reduce engine vibrations. Following removal of the balance shaft chain, to my surprise, the timing chain was intact. Why? Becaust the timing chain sprocket on the crankshaft is free spinning. That's why the crank did not turn the cam shaft. After the timing chain came off. I finally realized what happened. The oil pump, balance shaft chain sprocket, and the timing chain sprocket, are all held on the crank shaft by a Woodriff key. It is a crescent shaped key fitted on a slot on the crank shaft. What happened was the timing chain sprocket, being on the inside, engages on only the tip of the crescent. Overtime, the small area at the tip of the crescent failed in fatigue. (Does SAAB engineers has the wisdom to design the key so it failed just a little ove 100k mile? I wonder.) To confirm engine damage, I quickly turned the timing chain sprocket around (Not only was the key damaged, the slot on the sprocket fitting the key was chipped on one side too. But the other side was not chipped. I also turned the key around when fitting the chains back. With No. 1 piston on TDC and the camshafts marks alligned, I fitted both chains back on but left it uncovered. When I hooked up the battery and turned the engine with a compression gage on each spark plug hole, none show compression. So the engine is confirmed toast. My options. 1) I can get a motor for $1,000. This is of course off of a totaled car. Get it, drop it in. Clean and easy. I know the motor has 66k miles. 2) Remove the head. Rebuild it. This likely costs less. But I am not sure I am ready to deal with the amount or work and the attention to details required. I like 1) better because it gives me an opportunity to examined and may be replace the timing chain on the bought engine. In addition, it allows me to replace the clutch since I need to remove the engine anyway. Your thoughts. coxinga -- Coxinga/ The 17th century warlord, son of a pirate, who was bestowed the last name of Ming emperors. He defeated the Dutch to capture Formosa. A rare victory in the struggle against colonialism by the East. It spelled the beginning of the end for the Dutch East India Co. Sent via Deja.com http://www.deja.com/ Before you buy.

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