One of the most challenging jobs on the SL will be the timing chain. You will also gain a great deal of knowledge on how your Mercedes Sl really works and how Mercedes did things. NOTE: a few model years came with single row chains that were prone to break. You will be presented with one of three options. First, you will do it yourself, second you will take it to a shop to do it for you, or if you are fortunate, you will help a friend do the deed who has a shop.
Second Evaluation: Regardless of whether or not the chain has been replaced, if you have recently acquired a SL check the timing for your self. The following is a step by step procedure on how to check the timing:.
Step 1: Remove righthand valve cover. That will be the left cover if you are in front, facing the car. It is the plug closest to the front of the engine. Do not tighten, just snug to stopping point. NOTE: In order to turn the engine over with the radiator, fan and shroud still in place, you will need to utilize the bolt on the power steering pulley.
Otherwise, you will turn the engine by the crankshaft pulley bolt. Turn slowly.
When pressure begins to build, start watching for your timing marks to align. When the timing marks align at this stage, the engine is at TDC. NOTE: Should you continue past the timing marks, your gauge would begin to register on the vacuum side. If you do miss the mark, start over.
The image shows the marks you will need to look for on the top of your camshaft and gear. The marks are in increments of 5. In this case, my odometer hasmiles recorded and I know the timing chain has not been replaced.While traditionally the timing belt has been preferred to a timing chain, manufacturers have made the switch to using timing chains in the past few years.
Replacing the timing chain is a complicated job, and the labor costs can be quite high. Below are some sample costs for having the timing chain replaced at some of the leading garage chains in the country. Prices will vary from state to state and from car to car, but they should give you a rough idea of what you can expect to pay.
The timing chain works as the connection between the camshaft and the crankshaft, and the main responsibility of the chain is to operate the inlet and exhaust valve gear during the stroke cycle of the piston. The chain keeps these valves opening and closing at specific intervals, helping the engine to function properly.
Until recently, the vast majority of cars were built to use a timing belt instead of a timing chain. Using a timing belt was usually more cost effective than using a timing chain, with the only cars opting for the chain being higher-end sports cars.
Recently this trend has actually been in the opposite direction, with the timing chain taking over as the preferred option. A timing chain will need replaced far less frequently than a timing belt, resulting in a lower cost to maintain the car for the owner. While a timing chain will usually last far longer than a timing belt, it will suffer from wear and tear and will need replaced at some point during the life cycle of the vehicle.
Manufacturers were being increasingly blamed for these problems, which has led many to make the switch from belt to chain. As a result, car owners need to more aware of what the timing chain is, how to spot a potential problem with it and how often it should be inspected and replaced. Replacing a timing belt is a fairly costly repair, so many people would simply sell or trade in their car instead of having it repaired.
In many cases this would result in someone else buying the car and not being aware of the timing belt problem until it was too late. There are usually a few signs that the timing chain on your car should be replaced, some more subtle than others.
Poor fuel economy and occasional misfires could be caused by a timing chain issue, as could difficulty starting the car or the engine making a rattling sound regularly. If you notice any unusual sounds from the engine or anything out of the ordinary then you should take the car to your mechanic.
By taking the financial hit early you can avoid major engine damage which can cost thousands of dollars to repair. Replacing the timing chain is something which should be carried out by a qualified professional rather than a repair you attempt at home. The best way of saving money on timing chain replacement is to have the work done early before it causes any further damage to your engine.
Get a few quotes from garages in your area to see what you can expect to pay, and go with the place that offers a fair price and which has a good reputation. Below are some example costs for replacing the timing chain on some of the most popular models in the country.Our timing chain three part series concludes with the installation of the chain.
It is of utmost importance to be thorough and to check everything two and three times. Once the engine is at TDC you will need to mark all your positions with a yellow automotive marker. Next, remove the camshaft hub using a puller, oil pan and oil pump followed by front timing cover front of engine. Also, when pulling the crankshaft hub, do not lose the small woodruff key.
Most of the bolts will have been removed prior while removing all the accessories. Once the cover is off, you will see what is indicated in the photo above. This is critical as it has a fractionally small I.
If you install a non-repair seal, you will most likely end up with an oil leak. As you can see clean shop rags were used for this purpose. As you can see in this photo, the yellow marks prior to pulling them for replacement. Everything must line up exactly as it came off. Timing marks, etc. If your gears do not go back properly you will be unable to time your engine.
It is now time to remove the chain guides. For this job you will make the job easier if you have the correct tool or you can use a slide hammer. The image show the Mercedes-Benz guide rail pin puller. Each guide has a threaded center that the cain guide puller or slide hammer will thread into.
Read all directions for either tool carefully before using.
Once all the guides have been removed along with the two camshaft gears the chain will easily removed by pulling both sides down through the head. Now remove your chain. This part will simply bolt on. Do not try to make any adjustments to this part as they are pre-loaded and set at the factory. Remember this part also contains the threaded end for the air pump. Image to right is chain tensioner for a SL.
According to my mechanic there are two choices at this point. The chain can either be linked off the engine or after it is put on. In this case, we decided to link the chain off the engine as it would provide more flexibility in maneuvering while using the link compression tool.
Under no condition do you want your chain to fly apart while the motor is running.One would think that when the engine is at speed there is a higher incidence of wear and eventual failure.
This isn't necessarily true in the case of certain components, namely the timing chain. Chains, sprockets, gears and even bearings experience the most wear upon startup. The timing chain and the various components guide rails, tensioning rail, chain tensioner wear out aftermiles and should be replaced.
The sprockets should also be replaced. The chains can stretch but they also wear. As each rolling element of the link begins to experience wear it sets up for increased vibration and movement of the chain links and pins against the sprocket surface.
Replacing the Timing Chain Top Guide Rails
As many teeth as the sprocket has, the chain has many more links. The sprocket surface wears down contributing to more movement as the chain passes over the sprocket surfaces. This creates an even greater opportunity for chain breakage. The SL engine was considered robust yet like so many engines, there are issues that must be addressed.
The engines can accumulate enormous mileage given proper maintenance and with careful attention to the timing chain health. A chain or chain guide problem is the usual culprit that will destroy these engines. This issue is not exclusive to the SL but crosses all engine technology that uses timing chains. Timing belts are far more susceptible to breaking but chains can stretch leading to other issues. In many examples there are unacceptable degrees of chain slack and worn or broken guides.
These need to be replaced. Neglecting the chain can lead to catastrophic results. The usual scenario involves a broken guide being dragged up the chain and wedging between the cam gear leading to chain slippage or breakage. This will allow the pistons to contact valve heads.The systems on your engine rely on a timing chain or belt to control the engine's timing. Most modern vehicles use a cheaper timing belt, but for high-end vehicles, like Mercedes SLs, a timing chain is used.
This is because the timing chain lasts much longer because it is more durable. Occasionally, you may need to replace the timing chain due to a problem caused on the chain by a faulty tensioner.WHY YOU MUST REPLACE YOUR TIMING CHAIN
If your Mercedes is idling roughly, making loud noises, has a drop in the fuel efficiency or is backfiring in the intake manifold, you might need a new timing chain. If your auto part starts wearing out, the sensible solution is finding a top-notch replacement Timing Chain to maintain your car in like-new shape. Your Mercedes is a high-quality machine, and you can get it running like a champ with our online collection of reliable automotive parts from www.
They are available for the following Mercedes SL years:, 80, 79, 78, 77, 76, 75, 74, The price for this OEM part was the lowest I could find. Half of what the local Benz dealer wanted. Delivery time was 4 days with the weekend in between. PartsGeek is where I will be shopping for my Mercedes Benz.
Close X. To return a part, simply submit a support ticket within 30 days of ordering and we will issue you an RMA number to return your product. See customer service page for refund and return details. We scour the web to make sure PartsGeek always has low prices. You can buy with confidence! Click to Enlarge. Product SKU: W Shipping Options: Ground, Overnight, 2 Day. Product SKU: 76 Read more reviews. Ordered on Friday and received on Monday with standard shipping.
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Interesting thanks Tim. Yes it's a one piece sump. I think the main problem is getting to the sump bolts, so I was thinking I could jack the engine up, undo the sump bolts, lower it again, remove the sump, then do all the rest. No idea if this will work but I might give it a shot. My method was slightly different in that I used cable ties instead of the vice grips.
Symptoms of a Broken Timing Chain
I loosened the plugs cant remember if I removed them altogether but I didnt remove the valve lifters, so be careful when turning as the crank can "overshoot". As a word of warning, my upper guides were very brown, and the end of one had broken off and was rattling around in there, with teeth marks on it from the sprocket. Blessed there wasnt more damage. I had meant to re-check the chain this winter, and purchase a set of offset woodruff keys to improve the timing, but alas, the car has been sold.
Yikes, that has run through under the chain. Lucky there wasn't a catastrophe. I've done the job on a few cars now, including MT's as mentioned.
Once it is done properly, the peace of mind is very rewarding. Just thought I'd update with my progress I decided to do one side of the engine at a time, as follows: Left side with the engine in front of you first: Rotate engine so that master link if present is accessible on that side.
Plug gap with rag so nothing can fall down there. Use cable ties to secure chain in tension, without obstructing access to guides. Loosen nut on camshaft, putting wheel nut wrench handle through holes to stop cam turning.
Remove master link. Remove cam gear lightly tap off with hammer. Remove tensioner rail pin should slide out, don't worry you can't push it through! Remove tensioner rail. That's where I'm at so far. Have a look at my pictures to see how I used the cable ties, and check out the state of my tensioner rail!
At least the tensioner was doing it's job.There are two main types of connections used in automobile engines to synchronize the operation of the valve train with the rotation of the crankshaft. Smaller import vehicles tend to use rubber and fiberglass timing belts to make this connection, while larger American automobiles more commonly use metal timing chains.
Regardless of the type used, the symptoms of a broken timing chain or belt are similar because they both perform the same function. A timing chain that has broken completely will no longer connect the crankshaft to the camshaft.
This will result in the camshaft no longer opening and closing the valves, and the engine will not run. This is usually noticed as a sudden failure of the engine while in operation as if the engine was suddenly shut off. Attempts to restart a vehicle after the timing chain has broken will be unsuccessful. A broken timing chain can create slack in the connection between the crankshaft and camshaft.
This will cause the valves to open and close later than they should, causing reduced combustion chamber pressures and incomplete ignition of the fuel and air mixture. The result is misfiring and rough idling of the engine. A timing chain that has stretched enough to skip a couple of teeth on the sprocket will not allow the combustion chambers to draw in the proper amount of fuel and air mixture, because the valves will not be opening and closing at the right times.
This causes a significant reduction in power and diminishes the responsiveness of the engine to input from the accelerator pedal. A broken timing chain may move around excessively and contact the timing chain cover, or jump around on the crank and camshaft gears causing rattling and knocking noise to come from the front of the engine.
In severe failures on some engine models, a broken timing chain will cause the valves to come into contact with the pistons, resulting in very loud knocking and banging noises, catastrophic engine failure, and destruction of the valves and pistons. This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information.
To submit your questions or ideas, or to simply learn more about It Still Runs, contact us. Reduced power A timing chain that has stretched enough to skip a couple of teeth on the sprocket will not allow the combustion chambers to draw in the proper amount of fuel and air mixture, because the valves will not be opening and closing at the right times.
Noise A broken timing chain may move around excessively and contact the timing chain cover, or jump around on the crank and camshaft gears causing rattling and knocking noise to come from the front of the engine. About the Author This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information.
Photo Credits rusty chain image by Leonid Nyshko from Fotolia.