DIY - Exhaust Vibration Fix - Replace Exhaust Hangers
01-18-2019, 07:56 PM
#1
Senior Member
Thread Starter
DIY - Exhaust Vibration Fix - Replace Exhaust Hangers
My 2011 GL-350 developed an annoying resonant vibration in rear of the truck, coming from the exhaust system. This started right after the dealer replaced the DEF tank heater. The vibration and noise started out as a noticable resonant hum coming from the back of the truck that peaked at around 1,800 RPMS. As time passed, the noise got worse - and it also turned into a loud vibration when backing up.
I took it back to the dealer literally 4 times and they could not fix it. They kept looking at the wrong areas - they replaced the engine mounts which had failed, they loosed and re-tightened the exhaust system clamps - the noise would be mostly better when they returned the truck but the vibration was never gone. I would drive it for a while and the vibration and noise would come back. A side note - when they replaced the engine mounts, they saw my oil cooler seal was leaking again, so they replaced it for a second time, all under warranty.
The problem got worse over time, and I was tired of so many trips to the dealer, so I finally got around to diagnosing and fixing. The issue turned out to be that the passenger side muffler was vibrating badly within certain RPM ranges when the transmission was in drive, and across a broader range of RPMs when the transmission was shifted to reverse. You could feel the passenger side muffler vibrating badly.
The problem turned out to be that the exhaust system is supported by rubber hangers that degrade over time. There has also apparently been a redesign of the hangers since the 2011 year. I had mentioned this to my service advisor and he said that they exhaust hangers were not the problem. Whoops for him - had they replaced $75 worth of parts, they would have avoided doing a $5000 re-do of my oil cooler seal, plus the engine mounts.
So here is the fix. It's very easy. The tools you need are a 13MM socket and some blue Locktite and some long nose pliers. The replacement parts are:
164-492-11-44 - Converter and Pipe Bushing - Quantity 1 - Green
164-492-09-44 - Bracket Insulator - Quantity 2 - Purple
251-492-00-44-64 - Suspension Ring - Quantity 2 - Black
Total cost for all parts was about $75 shipped.
Mercedes does a great job of naming each of these three parts that look the same and do the same thing differently. They also all do not show up consistently on exhaust system parts diagrams. All five of these parts are rubber donuts that suspend the exhaust system from the body. There is one rubber hanger on each side of each of the two mufflers - one purple and one black, and one green hanger attaching the the exhaust pipe to the body about two feet behind the engine.
The new rubber hangers are significantly stiffer than the older ones that they replaced. Whether that is a part redesign, or whether the old ones get softer as they age and wear, I don't know.
Replacing them is easy.
Raise the rear of the truck using a jack, and support the truck using jack stands. Look at the mufflers - you will see the obvious purple hanger inboard near the rear bumper, and the black hangar outboard closer to the rear wheel well.
There are arms attached to the body of the truck that run through the top of each rubber hanger. Remove the two 13MM bolts that hold this arm to the truck. This allows you to pivot the hanger down and get a grip on it. Next, with lots of twisting and turning and grunting and other manly noises, you need to pull the rubber hangar off of both the arm you just removed, and then also off of the muffler. I found cutting the old ones off to be easier than man-handing them.
The new ones slide on very easily. It's about 5 minutes off and 2 minutes on for each part. Remember to put a little blue locktite on each bolt before you replace them.
Next jack up the drivers side of the truck, support the truck with your jack stands for safety and go through the same process with the green hangar you will find holding up the exhaust pipe about 3 feet behind the engine.
That's it - the whole repair took about an hour in total and now my exhaust system is rattle and vibration free again.
I took it back to the dealer literally 4 times and they could not fix it. They kept looking at the wrong areas - they replaced the engine mounts which had failed, they loosed and re-tightened the exhaust system clamps - the noise would be mostly better when they returned the truck but the vibration was never gone. I would drive it for a while and the vibration and noise would come back. A side note - when they replaced the engine mounts, they saw my oil cooler seal was leaking again, so they replaced it for a second time, all under warranty.
The problem got worse over time, and I was tired of so many trips to the dealer, so I finally got around to diagnosing and fixing. The issue turned out to be that the passenger side muffler was vibrating badly within certain RPM ranges when the transmission was in drive, and across a broader range of RPMs when the transmission was shifted to reverse. You could feel the passenger side muffler vibrating badly.
The problem turned out to be that the exhaust system is supported by rubber hangers that degrade over time. There has also apparently been a redesign of the hangers since the 2011 year. I had mentioned this to my service advisor and he said that they exhaust hangers were not the problem. Whoops for him - had they replaced $75 worth of parts, they would have avoided doing a $5000 re-do of my oil cooler seal, plus the engine mounts.
So here is the fix. It's very easy. The tools you need are a 13MM socket and some blue Locktite and some long nose pliers. The replacement parts are:
164-492-11-44 - Converter and Pipe Bushing - Quantity 1 - Green
164-492-09-44 - Bracket Insulator - Quantity 2 - Purple
251-492-00-44-64 - Suspension Ring - Quantity 2 - Black
Total cost for all parts was about $75 shipped.
Mercedes does a great job of naming each of these three parts that look the same and do the same thing differently. They also all do not show up consistently on exhaust system parts diagrams. All five of these parts are rubber donuts that suspend the exhaust system from the body. There is one rubber hanger on each side of each of the two mufflers - one purple and one black, and one green hanger attaching the the exhaust pipe to the body about two feet behind the engine.
The new rubber hangers are significantly stiffer than the older ones that they replaced. Whether that is a part redesign, or whether the old ones get softer as they age and wear, I don't know.
Replacing them is easy.
Raise the rear of the truck using a jack, and support the truck using jack stands. Look at the mufflers - you will see the obvious purple hanger inboard near the rear bumper, and the black hangar outboard closer to the rear wheel well.
There are arms attached to the body of the truck that run through the top of each rubber hanger. Remove the two 13MM bolts that hold this arm to the truck. This allows you to pivot the hanger down and get a grip on it. Next, with lots of twisting and turning and grunting and other manly noises, you need to pull the rubber hangar off of both the arm you just removed, and then also off of the muffler. I found cutting the old ones off to be easier than man-handing them.
The new ones slide on very easily. It's about 5 minutes off and 2 minutes on for each part. Remember to put a little blue locktite on each bolt before you replace them.
Next jack up the drivers side of the truck, support the truck with your jack stands for safety and go through the same process with the green hangar you will find holding up the exhaust pipe about 3 feet behind the engine.
That's it - the whole repair took about an hour in total and now my exhaust system is rattle and vibration free again.
10-14-2022, 08:52 PM
#2
My GL320 also developed an annoying vibration at idle after getting the AEM service, which may have required the replacement of the DEF tank. I was able to locate the two rear "holders", black and purple. My purple was so black with dirt that I didn't realize it was purple until I found the other black ones. I will replace them and see if this helps. Thanks for the tip.
Last edited by crypticresponse; 10-14-2022 at 09:23 PM.
