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Re: Water Pump Stress Posted by DougM [Email] (#211) [Profile/Gallery] (more from DougM) on Sat, 15 May 2021 03:26:23
In Reply to: Water Pump Stress, Paul D, Fri, 14 May 2021 07:46:58 Members do not see ads below this line. - Help Keep This Site Online - Signup
Rust and improper water pump installs - the 2 biggest killers of Saab 99's.
I've been around 99's for 36 years but am still confused about what years changes were made in water pump designs. If I had to make an educated guess, type 1 pumps(8 cog) were used through 1975, then sometime in 1976 they started using 12 cog type 2 pumps, and in 1977 went to 12 cog type 3 pumps. Your '77 should have the brittle cast 12 cog type 3 pump, and the threaded portion on top of the shaft was not used with a nut, but the threads were only there for extraction and install.
I'd be wary of just sourcing a "new" pump shaft. The perfect combo would be to source an idler shaft and pump shaft which have been happily mated for the past 40 years, but those aren't so easy to come by. I was excited to find a new pump shaft on ebay 15 years ago, and the install I thought went OK, but a week later the idler shaft stripped all its teeth off and the engine got hot within a minute of start up. I have no idea if the new shaft was improperly machined, or there was a problem while I was pressing it in, but it killed that engine. My solution was to install a '75 engine block and everything has been fine since then. Ideally that would be your best option too if you never want to worry about the water pump again.
Everything 12 cog I have at home is broken, but I have every variety of 8 cog design pumps. I do have a '73 engine block I would sell, but I know for a fact it would need the pistons replaced as there's a hole in the top of one of them. I have no idea how to ship it, unless you were close and could pick it up in person.
You might want to take Jimmy's advice and pull the engine, remove the idler shaft, then use a slide hammer to get the pump out.
Gary might have some 12 cog pump shafts, but he's at Carlisle this weekend so he probably won't be chiming in for a few days.
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