Re: gasket is shot! - Saab 9000 Bulletin Board - Saabnet.com


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Re: gasket is shot!
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Posted by sam96CS [Email] (#852) [Profile/Gallery] (more from sam96CS) on Mon, 26 Feb 2018 06:02:43 Share Post by Email
In Reply to: gasket is shot!, Name Left Blank, Sun, 25 Feb 2018 20:14:41
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I use a little cheap-o Pittsburg brand torque wrench from Harbor Freight. It is the kind where you rotate the end of the handle to dial in the torque setting. When the set torque is reached the wrench sorta slips with an audible click.

The valve cover probably will be stuck on after you have removed all the bolts. I smacked the side of the valve cover with a rubber mallet or dead blow hammer to knock it loose.

Take pictures of the top of the engine with the valve cover removed. If it is very clean looking then you know the previous owner used synthetic motor oil. Otherwise the engine has been running dino.

I found an old style distributor plug by looking in the Classified section (linked at the top of this page) for someone parting out a '94 9000. '94 was the last year that had the old style plug.

There are plenty of instructions in the archives. With apologies for the length I'm pasting below the notes I made when I did this job followed by instructions I found in the archives from Ari about the bolt tightening pattern and procedure. Read all the way through before you tackle the job. You should get a tube of Loctite 518, and this is a good time to replace the upper timing chain guide which is a relatively cheap part.

How I did the job:
1. Layout the gasket in the correct shape a few days before so that it doesn't try to twist all out of shape.
2. Drive onto ramps to elevate the front of the car so it isn't such a pain in the back to do this job.
3. Clean the exterior of the cylinder head and the spark plug valley BEFORE changing the gasket so you can see if any leaks develop after you've done the job.
4. There is an upper guide for the timing chain that attaches inside the valve cover. This is a good time to replace it. To remove, use a screwdriver to lift up the end that's toward the rear of the engine. Slid the chain guide about 1/2" toward the rear to clear the 4 retaining tabs. Then the guide will lift out.
5. If any bolts come out soaked in oil, then use a Q-tip to remove the oil from the bolt hole. This typically happens with the bolts around the spark plug valley and also the right rear hole on the perimeter. You can't torque the bolts accurately with oil inside a blind hole.
6. Use a razor blade and Scotchbrite to clean off old gasket material, then acetone to clean off all traces of oil. This part of the job is a PITA. I prepped the head surfaces first. Make sure you keep debris and grit out of the head. A single edge razor blade is much faster/easier to use here than a gasket scraper and less prone to scratch the surface. Keep a rag handy to wipe off the blade. Short back-and-forth strokes with the blade works well. The trickiest place on the head is the corner near the A/C compressor. Get what you can with the razor blade there, then use a gasket scraper for the rest. Scrape first and then rub with the Scotchbrite. A trouble light helps you see what you missed. Acetone on a clean white rag removes the oil residue, but getting all the residue takes 2 or 3 passes (until you don't see much residue on the rag). Prepping the valve cover is more comfortably done on a workbench of counter top. The gasket is wedged into a channel, and with age it will be brittle and stuck to the bottom and sides of the channel. I used a box cutter between the gasket and the sides of the channel where possible to unstick it. The outer gasket can be started at a half moon location, and you'll encounter the most resistance at the bolt holes and corners. The inner gasket is more prone to be stuck to the bottom of the channel. Use the box cutter again to eliminate the sticking along the sides where possible. Use a jeweler's screwdriver at a bolt hole to wedge between the gasket and the channel bottom, then you'll be able to remove most of the gasket by hand. If the gasket breaks, then work the other end or use the screwdriver again to wedge underneath the gasket. It will be especially stuck at the end nearest the timing chain. After removing the gaskets, wipe the channels with folded paper towels. Scotchbrite (I used a generic no-sponge equivalent) will get most of the crud out of the gasket channels. You need something less than 1/4" wide for scraping bit of gasket that Scotchbrite doesn't remove. I used a jeweler's screwdriver. I'm not sure that getting it perfectly clean and shiny is a realistic goal. When finished, clean the channels with a clean white cloth soaked in acetone. This will take about 3 passes. Clean all grit out of the valve cover.
7. Apply a small continuous bead of Loctite 518 on the valve cover (all mating surfaces). Loctite 518 look like red Jello, is thick and requires a firm squeeze. You can smear it around with a screwdriver to fill in voids. Stick on the gasket, working it in with a pencil eraser. Better to have a helper hold one end of the gasket up as you work from the opposite end. Avoid moving the gasket laterally as this is done. Avoid eye and skin contact with Loctite 518 - wash skin thoroughly with soap and water if contact occurs. In the event of eye contact, flush the eye for 15 minutes in water and call a physician. The gasket sealant is tacky enough to hold the gasket in place when you place the valve cover on the head.
8. Apply a small continuous bead of Loctite 518 on the mating surfaces of the head and set the valve cover onto the head.
9. Install all bolts finger tight. Set the torque wrench on 5.5 ft. lbs. which is 66 inch pounds. Following Ari's torque pattern (see below), tighten all bolts. Excess Loctite 518 will squeeze out, so wipe clean with paper towels. Set the torque wrench at 11 ft. lbs. (132 inch pound) and repeat the tightening sequence. Wipe again. Loctite takes 24 hours to cure, and I think it is best to avoid driving until the next day.

Ari's advice about torque sequence:
You need 11 ft-lbs, which is 12*11 = 132 inch-pounds. You can probably pick up a 300 inch-pound beam type wrench for $15. I'd recommend the wrench, because an easy way to guarantee a valve cover gasket leak is to over- or under-torque the bolts. When you tighten the bolts, DON'T start at one end and work your way around. That will cause uneven tightening. Screw the bolts down finger tight, then pick a corner and tighten one bolt down about half torque. (Say upper right) Now go to the opposite (diagonal)corner (lower left) and do the same. Now go to the lower right bolt, then upper left. Now, go to the one next to the one you started with, and keep up the pattern. It's not super critical, but you want to avoid tightening two bolts next to each other. After they're all about half-tight, bring them all to full tight with about the same pattern. This is really critical with head bolts, not as critical but good on a large floppy surface like a valve cover or oil pan.
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