The plastic guide rail in your Mercedes (also known as the timing chain guide) looks like a rectangular piece of plastic that is found in your engine. However, it is actually a critical component that you can use to learn about your engine’s overall condition. Below, let’s take a closer look at the plastic guard rail and discuss where to go to fix any issues with it.

What does the plastic guide rail do?

The main purpose of your Mercedes’ timing chain is to ensure that the camshaft and crankshaft rotate in perfect synchronization. The guide rail helps with this, as it keeps the chain aligned on its track, and therefore helps to prevent engine misfires.

The guide rail in your Mercedes is made from strong plastic. As we all know, the engine produces a lot of heat. Since this part is made from plastic, over time, the guide rail can start to become worn down due to intense heat.

You might wonder why Mercedes and other manufacturers have chosen to use plastic. While at first it may seem like a poor choice, the softer plastic of the rail prevents damage to the timing chain. The timing chain is a more expensive part to replace and repair. Using plastic for the guard rail also helps to lower manufacturing costs, meaning your Mercedes model of choice remains affordable.

The guide rail is not only handy for keeping your car in sync, it can also be used to paint a picture of your engine’s health. Erratic wear to the rail can indicate timing chain troubles, and wear to the surface of the rail itself can indicate expired oil in the system. However, it is most important to remember the chief purpose of the guide rail, which is to keep the timing chain working correctly.

Tips to Fix Plastic Guide Rail Failure

As it is a small, unassuming piece of plastic, the guide rail is a very inexpensive part to buy, costing only around $15. However, the true cost of this part comes in labor, which is a little tricky and requires some know-how. However, you shouldn’t rush into making a purchase and doing the repairs right away. Instead, you could double check that the rail is to blame by paying attention to the following symptoms:

  1. Clicking or rattling sounds coming from the engine
  2. Grinding sounds when first starting the engine
  3. Squealing caused by the tensioner
  4. Rough engine running

Repairing the Guide Rail

As previously mentioned, purchasing the guide rail isn’t the hard part. Installing it is. To reach this part, you need to undertake quite a lot of engine disassembly. So before rushing into repairs, you need to consider if you have the time to undertake correct repairs and if you have the mechanical skill to correctly complete the repairs. If it’s a no to either or both of these questions, then will need to leave it to the professionals and call your trusted repair shop.

Other Issues

The guide rail is well known for causing resulting issues when it breaks. Therefore, when repairing or replacing a guide rail, you should check for the following resultant problems.

  1. Timing Chain is Loose: A loose timing chain can result in engine backfires and power loss.
  2. Wear to Parts Around the Timing Chain: If the timing chain has become misaligned due to guide rail failure, it can deposit metal shavings throughout the engine or rub against other engine parts and cause damage.
  3. Plastic Debris: If the plastic guide rail has broken or even suddenly shattered, you will  need to search for the pieces. If left unchecked, these plastic shards can get into your oil pan, causing clogs and oil contamination.

The Benz Shop

If you drive a BMW, Porsche, Mercedes Timing Chain Check Audi, Volkswagen, or Mercedes and live in or around Scottsdale, Glendale, Tempe, Chandler and Paradise Valley, come to The Benz Shop for your Mercedes repair and maintenance needs. From oil changes to wheel alignments and general servicing, no issue is too big or too small for our dedicated team of experts. Contact our team today to find out how we can help you get back on the road safely at an affordable cost with repairs you can trust.

* Mercedes-Benz Car image credit goes to: y_carfan.

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