Replacing the timing chain guides in a Mercedes-Benz can be a significant undertaking. This guide is designed for individuals with a solid understanding of automotive mechanics who are considering tackling this job themselves. It’s crucial to understand that this is not a task for beginners, and mistakes can be costly. A fractured timing chain guide can lead to severe engine damage, as illustrated below.
Image: A close-up of a broken timing chain guide removed from a Mercedes-Benz engine, highlighting the fracture point.
The image above shows a typical fractured timing chain guide. Often, the broken piece can fall into the path of the timing chain, causing it to jump timing. In approximately 90% of such cases, this results in valve damage due to interference between the valves and pistons.
Beyond the easily accessible cylinder head guides and tensioner guide, there are additional lower timing chain guides located behind the timing cover, along with an oil pump chain tensioner guide. Accessing these lower guides is labor-intensive, often requiring engine removal. Due to the extensive work involved, these lower guides are frequently left untouched unless the engine is being completely overhauled. Fortunately, these lower guides are generally less prone to failure compared to the upper guides and tensioner guide. However, for thorough maintenance, replacing them is recommended, which often necessitates cylinder head removal for easier timing cover reinstallation.
Many DIY mechanics opt to replace only the upper three cylinder head guides, the tensioner guide, the tensioner itself, and the timing chain. For this critical repair, using genuine OE (Original Equipment) Mercedes-Benz parts or parts approved by reputable suppliers is strongly recommended.
This guide demonstrates the replacement process on a 1989 Mercedes-Benz 560 SL, and the procedure is largely similar for other 560 models, with minor variations depending on engine accessories. While the intake manifold is removed in some of the photos for other maintenance tasks, it is not necessary to remove it specifically for timing chain guide replacement.
The following steps assume that you have already removed the valve covers, power steering pump and bracket, and alternator and bracket. In many cases, the power steering pump and alternator can simply be moved aside without complete disconnection.
Image: Precise alignment of timing marks on the driver’s side camshaft of a Mercedes-Benz engine during timing chain guide replacement.
In the image above, we are aligning the timing marks and marking the position on the driver’s side camshaft. Note the small marks in the center of the camshaft that are aligned for accurate timing.
Image: Close-up view of the timing marks aligned on the passenger’s side camshaft of a Mercedes-Benz engine during the repair procedure.
This image shows the aligned timing marks on the passenger’s side camshaft, ensuring correct engine timing before proceeding with the repair.
Image: The engine set to Top Dead Center (TDC) with timing marks aligned and tie-wraps used to secure the chain and sprocket.
Here, the engine is set to TDC (Top Dead Center). When working alone, tie-wraps can be helpful to secure the chain and sprocket when removing them. This also assists when using an impact wrench to loosen the center camshaft bolt. Exercise caution when removing these bolts to prevent them from falling into the engine.
Image: The driver’s side camshaft is marked and secured with tie-wraps before the camshaft sprocket bolt is removed for timing chain guide replacement.
This photo illustrates the driver’s side camshaft marked and secured before the camshaft sprocket bolt is removed, preventing unwanted camshaft rotation.
Image: Detailed view of the crankshaft timing marks aligned at the Zero position, indicating TDC for timing chain service on a Mercedes-Benz engine.
The image above shows the crankshaft timing marks aligned at the Zero position, confirming TDC. Additionally, ensure the ignition distributor rotor is pointing to the #1 cylinder position. With the crankshaft at zero, distributor rotor at #1, and camshaft marks aligned, you are ready to begin the guide replacement.
Image: Using an impact wrench to loosen the camshaft bolt while securing the camshaft with channel locks during Mercedes-Benz timing chain guide replacement.
Using an impact wrench, apply a quick burst to loosen the camshaft bolt. It’s advisable to secure the camshaft with channel locks, using the nubs in the center of the cam for grip. Be mindful of the camshaft oiling tube and its plastic clips, which are easily broken. Once loosened, the bolt should unthread by hand. Set the bolt aside and use a wire from the hood to suspend the timing chain, ensuring enough slack. Use the wooden end of a hammer to gently tap the backside of the sprocket, just below the timing chain. Avoid using the steel part of a hammer or a rubber mallet, as rubber bits can fall off. A few taps should start to move the sprocket. Wiggle and pull it towards you, being careful with the chain.
Image: Removing the camshaft sprocket while carefully holding the timing chain to prevent it from dropping into the engine during Mercedes-Benz timing chain guide replacement.
As the camshaft sprocket comes off, hold the chain up and carefully work the gear out. Crucially, DO NOT let the timing chain fall into the engine. It must remain taut. Use the wire to keep it suspended while you proceed to replace the guides.
Image: A washer visible on the camshaft after sprocket removal, a small part that needs to be carefully handled during Mercedes-Benz timing chain guide service.
Be mindful of this washer, as it can easily fall into the engine. Reinstall the bolt by hand to prevent the washer from falling into the engine.
Image: The camshaft bolt is hand-tightened to secure the sprocket washer and timing mark after sprocket removal in a Mercedes-Benz engine.
Here, the bolt is hand-tightened to keep the sprocket washer and timing mark in place.
Image: Removing timing chain guide pins using a fabricated puller tool made from valve cover bolts, socket, and washers during Mercedes-Benz engine repair.
Removing the guide pins becomes easier with experience. While specialized tools exist, a DIY puller can be fashioned using valve cover bolts, a socket, and washers. When using a homemade puller, be extremely careful not to jam the pin while pulling, especially in uneven areas. Stripping or bending the pins is possible if they lack clearance. Even with a tool, caution is needed to avoid stripping the threads in the pin. If a pin’s threads are stripped, a strong steel screw and pry bar might be needed for removal, requiring a replacement pin.
Image: A timing chain guide pin partially extracted from the cylinder head using a puller tool during Mercedes-Benz timing chain maintenance.
This image shows a pin partially pulled out. From this point, you should be able to remove the pin by hand.
Image: The last pin holding the timing chain guide, requiring careful removal to prevent the guide from falling into the engine during Mercedes-Benz repair.
This is the last pin securing the guide. Hold the guide to prevent it from falling into the engine once this pin is removed.
Image: A side-by-side comparison showing an old, brittle timing chain guide next to a new, genuine Mercedes-Benz replacement guide.
Here’s a comparison of an old guide and a new genuine Mercedes-Benz guide. You can feel the brittleness of the old part compared to the new one.
Image: Installing a new timing chain guide by sliding it into place and aligning the pin holes in a Mercedes-Benz engine cylinder head.
Slide the new guide into position and push the pins through, aligning the holes in the guide with those in the cylinder head. Light tapping might be needed to overcome plastic resistance, but tap gently. Ensure the pins are slightly started in their bores before fully driving them in. Apply sealant to the pin ends to prevent oil seepage, as shown in the next image.
Image: Application of sealant to the ends of timing chain guide pins to prevent oil seepage after installation in a Mercedes-Benz engine.
