FAQ by Ben Thompson - Email Contact
Prologue
Head gasket, timing chain replacement - in sitiu - on a 1994 Saab 9000 Aero
I've owned my '94 Aero for about five years now. It's the Saab I've always wanted, and I drove to freakin' Idaho to get it. The previous owner lived a good 3 hours from the nearest Saab mechanic, so I spent the first several years re-doing a variety of JB Weld and bailing wire repairs.
The entire time I've had it, the engine was always a little rattly on the serpentine belt side. I checked the pulleys, changed the top chain guide under the valve cover, and toyed around with different weight oils. Every time I took the car to my indy mechanic, Charlie, for something that I felt was out of my league, I'd ask him about the rattle. He told me some Saabs just are a bit louder than others, so for a while I was comfortable with that. Last month, I had the car into Charlie's to get the drain plug unstuck. I'd successfully made a circle of a hexagon again. He told me that I had a metal on metal sound coming from the chain, and that I should do something about that.
In addition to the persistent chain noise, I'd noticed the car weeping coolant from the right front (when standing in front of the open hood) part of the engine, right at the corner. I'd very slowly loose coolant, needing a top-up every couple of months. I knew I had a hairline fracture in my radiator where the top hose attached, so I figured that accounted for the loss, but I also knew the gasket was on it's way out.
So I did a little research, and decided I should check the extension on the timing chain tensioner. If it was out of limits (over 11mm), I'd pull the head and do the chains. If it were 11mm or less, then I'd leave it be for a while.
Now, one detail is critically important; that is, that I have a tiny garage. Actually, given the urban location of my house, it's lucky to have a garage at all (and in fact, it has a garage plus two carports). Though I have a crane and an engine stand (currently housed at my mother in law's house - that's another project), there simply isn't enough room for the car and the crane in front of it. That meant that whatever procedure I'd be doing, it's happening with the engine still in the car.