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Discussion Starter · #1 · (Edited)
Finally managed to replace my serpentine belt after much research (albeit scarce results).

This guide will walk you through replacing your 1st gen CLA250's worn out serpentine belt. You will spend a LOT of time under your car so safety first! Find a way that your car won't crush you to death in case your jack fails.

Difficulty: Moderate. But not for the faint of heart
Labor: 2-3 hours for first timers. Maybe an hour for repeat performance.

Materials/tools needed:
1. Socket wrench: 8mm, 10mm, 17mm, E12 torx
2. Serpentine belt tool: Amazon.com: JTC AUTO TOOLS Serpentine Belt Replace Tool for Mercedes Benz M270 Engine by JTC 4346: Automotive
3. Serpentine belt: Mercedes Accessory Drive Belt - Contitech 5K1515
4. A hell lot of patience

66790


STEP 1: Jack up the front of the car. Easier to move the wheels this way. You may also jack the passenger side (using two jacks) if you so desire.
STEP 2: Remove the passenger side front wheel.
STEP 3: Remove the retention clips and screws (Encircled in red). The other screws under the car that you need to remove are self explanatory.

66791


STEP 4: Under the car, remove the oil pan cover to have access to the two bolts indicated in step 5.
STEP 5: Unscrew four E12 bolts (2 on the side and 2 under) to remove the bar indicated in the pic below. The 4 bolts may be accessed from the passenger wheel well.

66792


Next steps are done under your safely jacked car and things get tricky and why you need the serpentine belt tool. There is virtually no space to put in any other fat-ass tool to access the tensioner. This is also a good time to inspect for any leaks (coolant or oil) under the engine.

66793


66794


The belt tensioner is #3 in the pic below.

STEP 6: Once you manage to insert the tool, turn clockwise to loosen the belt.
STEP 7: Slide off loosened belt from the guide pulley (# 2s) and belt should come right off.

66795


My OEM belt is 7 years old and this is the first time I replaced it since I bought the car brand new. Dry and extreme weather would render any other belts to fail by 40k or so miles so this OEM @ 89k miles lasted very long.

66796


66797


STEP 8: While holding the tensioner on the "loose" position, put in the new belt using the belt diagram below.

66798


Tip: When putting the belt back, put the guide pulley (#6 above) last. Serpentine belts stretch over time so expect the new belt to be a little tighter.
1. Drive pulley / Vibration damper
2. Belt tensioner
3. Water pump pulley
4. Alternator pulley
5. A/C compressor pulley
6. Guide pulley

STEP 9: Once you successfully installed the new belt, before putting everything back, start the engine and ensure that all drives and pulley rotate properly. There should be no squeaking sounds whatsoever and no leaks anywhere.

STEP 10: Put everything back and congratulations on your DIY!

Tip: Torque spec for the wheel is 96 foot pound.
 

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Good grief that is a helluva lot of fun!
That belt is one tough crook hanger
Great post
 

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Finally managed to replace my serpentine belt after much research (albeit scarce results).

This guide will walk you through replacing your 1st gen CLA250's worn out serpentine belt. You will spend a LOT of time under your car so safety first! Find a way that your car won't crush you to death in case your jack fails.

Difficulty: Moderate. But not for the faint of heart
Labor: 2-3 hours for first timers. Maybe an hour for repeat performance.

Materials/tools needed:
1. Socket wrench: 8mm, 10mm, 17mm, E12 torx
2. Serpentine belt tool: Amazon.com: JTC AUTO TOOLS Serpentine Belt Replace Tool for Mercedes Benz M270 Engine by JTC 4346: Automotive
3. Serpentine belt: Mercedes Accessory Drive Belt - Contitech 5K1515
4. A hell lot of patience

View attachment 66790

STEP 1: Jack up the front of the car. Easier to move the wheels this way. You may also jack the passenger side (using two jacks) if you so desire.
STEP 2: Remove the passenger side front wheel.
STEP 3: Remove the retention clips and screws (Encircled in red). The other screws under the car that you need to remove are self explanatory.

View attachment 66791

STEP 4: Under the car, remove the oil pan cover to have access to the two bolts indicated in step 5.
STEP 5: Unscrew four E12 bolts (2 on the side and 2 under) to remove the bar indicated in the pic below. The 4 bolts may be accessed from the passenger wheel well.

View attachment 66792

Next steps are done under your safely jacked car and things get tricky and why you need the serpentine belt tool. There is virtually no space to put in any other fat-ass tool to access the tensioner. This is also a good time to inspect for any leaks (coolant or oil) under the engine.

View attachment 66793

View attachment 66794

The belt tensioner is #3 in the pic below.

STEP 6: Once you manage to insert the tool, turn clockwise to loosen the belt.
STEP 7: Slide off loosened belt from the guide pulley (# 2s) and belt should come right off.

View attachment 66795

My OEM belt is 7 years old and this is the first time I replaced it since I bought the car brand new. Dry and extreme weather would render any other belts to fail by 40k or so miles so this OEM @ 89k miles lasted very long.

View attachment 66796

View attachment 66797

STEP 8: While holding the tensioner on the "loose" position, put in the new belt using the belt diagram below.

View attachment 66798

Tip: When putting the belt back, put the guide pulley (#6 above) last. Serpentine belts stretch over time so expect the new belt to be a little tighter.
1. Drive pulley / Vibration damper
2. Belt tensioner
3. Water pump pulley
4. Alternator pulley
5. A/C compressor pulley
6. Guide pulley

STEP 9: Once you successfully installed the new belt, before putting everything back, start the engine and ensure that all drives and pulley rotate properly. There should be no squeaking sounds whatsoever and no leaks anywhere.

STEP 10: Put everything back and congratulations on your DIY!

Tip: Torque spec for the wheel is 96 foot pound.
Excellent review..
You have spent a lot of time working on the presentation..
Well done 🍻🍻🍻👍
 

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You guys are going way above and beyond. I’m doing a water pump/ thermostat on a customers car I just used a XXL flathead to put some pressure against tensioner and belt easily slipped right off lower front idler pulley. Went back together just as easy. No special tools no taking all this that and the other apart. Only thing I removed to make it easier was the “ oil pan protection bar”. Took me 2 seconds literally to get belt off.
 

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Discussion Starter · #5 ·
Good you found a way to remove the belt in literally two seconds. We would love for you to post instructional videos. Especially for the water pump and the thermostat replacement.
 

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Interesting variant
Please do post the particulars on using the flat head instead of the tensioner tool
 
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