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SAAB TIMING CHAIN REPLACEMENT
by Boe Kalinoski, Import Specialist
Saab has always used timing chains in its four-cylinder engine, starting with the British engine back in the early 1970s. Both chain noise and tensioner failure were common problems. I can recall the repairs on that particular engine were the big three - timing chain, head gasket and water pump. I repaired quite a few back then, as I was working in a dealership in Boston as the engine and transmission tech. When Saab merged with Scania in 1972, they came out with an all-new 2.0 L "B" engine, which had a double-row timing chain and stronger-style tensioner. The water pump was still a problem, as the engine block was part of the main housing. The engine had proved to be the basic design for years to come.
In 1981, the 2.0 L "H" engine was introduced. The timing chain was dropped to a single-row design as the tensioner was made of some type of carbon-fiber spring. That tensioner was a problem, and redesigned units using a ratchet design were available. The repair could be accomplished with the engine still in the car.
In 1985, Saab introduced the 16-valve engine only in turbocharger form. The multi-valve engine, which used double camshafts and was an interference engine, was a huge success. In 1986, it also was available in the 900 in a normally aspirated version. The chain tensioner was replaced with a smooth, close-notched unit. The problem with the old-style tensioners was that the teeth on the ratchet were too far apart, making a large gap when trying to get to the next click for some tension. Then the chain rattled and stretched, causing major failure.
The tensioner has two ways of holding pressure on the chain. There is a coil spring that is built into the unit, along with oil pressure that plays a major role in holding tension. There is a small hole in the upper area on the tensioner housing, and sometimes that hole will get plugged up with foreign material and
won't have sufficient hydraulic capability, resulting in chain rattle. Also, when the engine was cold, I found out that chain noise/rattle could be cured just by replacing the small rubber ramp under the valve cover, as it tends to harden and have no dampening effect.
In 1991, the B234 engine was put in the 9000, and also was available in new generation 1994 900 models. It used counter-rotating balance shafts. Note: B stands for gas engine, 2.3 is the displacement, and 4 stands for the amount of shafts - two balance shafts and two camshafts.
The balance shafts are on both sides of the engine to cancel out the vibrations generated by four-cylinder engines. The balance shaft chain also is in time with the crankshaft as there are markings on the sprockets. The engine's basic design is now still in production. The balance shaft chain uses an oil-pressured, spring-loaded tensioner, which is separate from the timing chain, see Photo 1.
The timing chain for the valves could be replaced without removing the timing cover. Saab has developed some special tools for this procedure. Also available from Saab are split chains with press-fit links to ease installation. I don't recommend replacing just the timing chain in the B234 engine, as the noise could be coming from the balance chain area. You can't see the balance shaft chain when taking off the valve cover, as it is covered over with chain ramps and sprockets.
In our shop, we replace the timing chain primarily in the early 900 series - the 2.0 L and the
2.1 L engines. The tools (listed below) can be purchased from any Saab dealer. I just use the chain splitter and recrimping tool, as shown in Photo 2.
CHAIN REMOVAL/REPLACEMENT PROCEDURES
Remove the valve cover and position the camshafts at zero, see Photo 3.
Use wire ties to hold the chain to the sprockets so it won't fall down in the cover.
Check the timing chain for wear by first removing the chain tensioner plug with spring and locating stud (plastic) and then remove the chain tensioner. Do not change the position of the plunger. The maximum measurement is 11mm. If it exceeds this measurement, the chain should be replaced, see Photo 4 on page 41.
Inspect the sprockets and chain guide for wear. The surface between the outer grooves of the chain guides should not indicate any contact marks.
Separate the chain by pressing out a link with special Saab tool #8494637.
Using a Saab chain link, #8394660, join the new chain to the old. Don't let the chain fall down and get entangled. Remove both chain sprockets as shown in Photo 5.
Hold the new chain up and have another technician turn the crankshaft and feed in the new chain as the old one comes out the other side.
Remove the link and install the press fit link with Saab tool #8394645.
Put the crankshaft on zero and reinstall cam sprockets with the chain in position.
Recheck the camshaft marks and install a new tensioner with the special sealing washer.
Remove the rubber valve cover gasket from the cover and clean the surface well. I use spray adhesive glue on the valve cover to hold the gasket in place. Do not use any other type of glue or silicone as it will plug oil passages in the engine.
If the balance shaft chain fails on the B234 engine, most of the time it takes out the timing chain at the same time, causing extreme engine damage. The cost of the repair runs around $3,000-$4,000 and could be more if the cylinder head and pistons are needed during replacement.
We have repaired quite a few early 9000s with chain problems, especially in the 1991-'93 model year vehicles. Saab used a split roller chain in those particular years. Saab has since replaced these with non-split roller chains made by another manufacturer.
Starting in 1994, Saabs were revised with a new style balance chain setup including upgraded tensioners and harder sprockets. None of the parts are interchangeable, other than the chain.
I recommend changing the chains at 75,000 miles. Most of the cars now have well over that amount of mileage. We have found that, in the vast majority of cases, our technicians can hear the chains making noise before they fail. As we discover the stretched and worn out chains, we replace them before a catastrophic engine failure occurs. We warn the customers about the problem and try to make them understand that if they let the problem go, it will cost them more in the long run.
When replacing both chains in the Saab 9000, the engine does not have to be removed, as in the late generation 900. It's like anything done a few times - the more you do the repair, the easier it gets.
1. First remove the A/C compressor with the serpentine belt.
2. Remove the inner fender well.
3. Drain the cooling system and remove the water pump.
4. Remove all of the pulleys and the harmonic balancer.
5. Remove the alternator and the power steering pump.
6. Unbolt the alternator mount bracket and upper mount assembly. Be careful of the crank sensor and wires.
7. Remove all timing cover bolts and pry off the cover.
8. Remove the valve cover and set up the camshaft marks to zero.
9. Inspect all sprockets for worn teeth and replace as needed.
10. Always install new tensioners as they tend to wear in one particular spot.
11. Install all new ramps and guides.
12. Camshaft timing is set with the engine at the
No. 1 cylinder, at TDC. The zero mark on the flywheel should align with the timing mark on the flywheel cover or end plate. The timing marks on the camshafts should align with the marks on the bearing caps. See Fig. 1.
13. Next, fit the chain around the crankshaft sprocket. Make sure that the chain is tight between the intake crankshaft and the camshaft.
14. Fit the chain and sprocket to the exhaust camshaft and tighten the bolts. Make sure that the chain is tight, fit the chain and sprocket to the inlet cam and tighten the bolt.
15. Tension the chain tensioner, fit it and trigger it. Rotate the crankshaft two complete turns in its normal direction and check that the timing marks are again aligned before torque-tightening the camshaft center bolts.
16. Balance shaft timing is set with the engine at the No. 1 cylinder, at TDC. The weights on the balance shafts should be on the bottom. The timing marks on the balance shaft sprockets should align with their respective marks on the bearing holders, see Fig. 2.
17. Fit the balance shaft chain around the crankshaft sprocket. Make sure that the chain is tight, and fit the chain over the exhaust side balance shaft sprocket and loosely around the inlet side balance shaft sprocket.
18. Insert the idler sprocket into the chain and, while maintaining the chain tension, locate it in position.
19. Fit the top chain guide. Fit the chain tensioner and moveable guide, but do not release the tensioner just yet.
20. Check that the alignment is OK. Fit the idler sprocket bolt. Then release the tensioner, rotate the crankshaft one complete turn in its normal direction and check that the timing marks are aligned again.
Note: The timing cover could give you some trouble while it is positioned on the block. I found out that if you file the sharp edges off the top of the cover, it will tend to slide on easier and without destroying the head gasket, see Photo 6. Use Saab anaerobic sealant; it works very well and won't break down and leak.
22. Reassemble in reverse order, taking the time to recheck all bolts and making sure to properly torque the harmonic balancer.
23. It also would be a good time to check the serpentine belt and pulleys. And, don't forget the belt tensioner as it tends to leak out oil and have no holding power.
TIMING CHAIN EVOLUTION
I can remember when my father worked for a company that NASA contracted in the '60s to build special cameras that operated in space. His department was in charge of developing a remote-control platform for the cameras. He told me that they used a small timing belt with a spring-loaded tensioner with cog-type wheels.
As the cameras were subjected to changes in temperature that ranged from very hot to very cold at times, the belt jumped time and failed. The next step was to use a timing chain with sprockets and tensioners. It proved to be trouble-free and was a success. It was also more compact in design and more reliable than using a belt in that application. But it added more weight, so light alloys were used.
As was the case with camera platform technology, timing chains used in engines had to be improved as engines got more complex with their multi-cams and valves. Split-roller chains were dropped and stronger, more refined sprockets are now used.
- Boe Kalinoski