2017 GLC 300 Alternator replaced.

recent 3 weeks, i noticed minor bearing noise (mosquito or bee sound) that sounds depends on engine rpm between 1500~2500.

Engine run short time test without serpentine belt. No noise, means that noise is not from the engine inside and turbo, but something at accesory pulleys.

Turning each pulleys by my hand, tried to hear noises from idler, tensioner water pump, alternator, AC.

Initially I could not find except idler pulley's very tiny noise. So I ordered an idler pulley $15 from aliexpress and installed. of course still noisy.

Then more carefully I turned each pulleys and found alternator pulley making minor mosquito sound. And pulley was not easily turn at counter clockwise. I had choice to just change pulley only, or the whole alternator. I chose the whole alternator because I drove 200K km which is about time to replace whole alternator and I was not sure noise might be from bearings inside alternator. Also the regulator brush might be almost worn.

New alternator is priced about $900 for MB oem. Or $300~400 for new at Ali. I ordered the cheap one, and found delivered cheap one also made by Bosch parts. Good quality. Original alternator has OAD pulley, what I bought has OAP pulley. OAD type is a little better, but I can live with OAP type.

Removal and installation was not easy but I could do with my years DIY experience.

Steps;
Remove battery minus terminal/ Tensioner holding with a pin/ Serpentine belt/ idler pulley/ ecu/ intercooler 2 pipes/ put aside intecooler and pipe from turbo/ top plastic cover over the cooling fan

alternator main plus terminal 13mm nut with a cap/ alternator control port connector/ 2 long bolts

take out old alternator / put new one





















noise is gone now.

 

Thanks for your post sn202020. What other interesting replacements have you needed as your mileage has accumulated?
I’ve had three MB, this 2018 glc will need to last another three years. I’ve always kept my cars past 150K so would appreciate just a bit of your experience advice.

 

Hi,
​​These are short list I have done DIY between 100Kkm~150Kkm

With issue;
P052e code -- replaced remanufactured-intake-line ( not easy)
cold starting 2 seconds engine noise -- replaced Cam adjusters for intake and exhaust (not easy, need special tools)
clunking somewhere under hood on uneven road - replaced two engine mounts (not easy)
squeaking suspenson - replaced right lower control arm rearward
Engine auto stop start at brake not working - Battery replaced. H7 size AGM

Preventive replace;
Spark plugs, Serpentine belt, transmission mount.

Fluid;
ATF, rear diff, front diff, brake, coolant