M278 Timing Chain Replacement
Thread Starter
Member
Joined: Aug 2019
Posts: 173
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2014 GL550; 2010 GL450
M278 Timing Chain Replacement
For the M278 and M157 engines in the GL-Class, can the timing chains, tensioners and guides be replaced with engine in the car or it's absolutely an engine-out operation? I don't mean just the upper tensioners and plastic guides at the top, but all the stuff behind the main/lower timing chain cover. Are they accessible by removing front end (radiator, fan, valve and timing covers, accessories, etc.) or engine has to absolutely come out for the operation?
Last edited by tadiguy; Mar 19, 2023 at 02:07 PM.
Super Member
Joined: Jul 2019
Posts: 735
Likes: 298
From: New Orleans
2014 GL450, 1992 W140 300SD, 1993 W140 300SE, 1987 E30 Convertible
You need to remove front cover to do it. It has enough clearance if you take radiators out. You will have to change turbo coolant lines, since plastic on those fragile. Anyway i didn't expect your car to have that much of mileage for timing chain needed to be changed.
Thread Starter
Member
Joined: Aug 2019
Posts: 173
Likes: 36
2014 GL550; 2010 GL450
You need to remove front cover to do it. It has enough clearance if you take radiators out. You will have to change turbo coolant lines, since plastic on those fragile. Anyway i didn't expect your car to have that much of mileage for timing chain needed to be changed.
Newbie
Joined: May 2023
Posts: 5
Likes: 2
2012 Mercedes S550
Trying to replace timing chains with the engine in the car. Need to remove the crankshaft pulley to get the timing cover off.
I've been told not to use an impact wrench on the crank pulley for this engine so I purchased the flywheel locking tool but can't figure out where to use it from the WIS procedure.
Do I remove the starter on the left side or is there access to the flywheel on the right side? The procedure seems to indicate there is a crankcase cover on the right side but I can't spot it from underneath the car.
Any help will be appreciated.
Thanks!
I've been told not to use an impact wrench on the crank pulley for this engine so I purchased the flywheel locking tool but can't figure out where to use it from the WIS procedure.
Do I remove the starter on the left side or is there access to the flywheel on the right side? The procedure seems to indicate there is a crankcase cover on the right side but I can't spot it from underneath the car.
Any help will be appreciated.
Thanks!
Super Member
Joined: Jul 2019
Posts: 735
Likes: 298
From: New Orleans
2014 GL450, 1992 W140 300SD, 1993 W140 300SE, 1987 E30 Convertible
You can absolutely use impact wrench on main bolt. Don't use it to torque. Engine block has opening on both side, other side just closed with cover
