Serpentine Belt Noise on Full Lock/Vibration, Also Temp Gauge running too hot? W202

[JohnnyW202]

Hi there, today in the heat about 26c.

My car started to make a horrible vibration/squeeling noise on full lock... literally just started, so I'd assume the Aux belt at the front of the car is starting to slip. It'll be easy enough to change I assume, crack a nut, push over a tensioner, new belt and on?

I've just changed the oil... strangely with the filter change and a good drain it took 6l when only 5.7l is listed it's a M111 and I changed out the filter with a Fram Element, and AC Delco 5w 40 Fully Synthetic so I didn't skimp. Reset the Service interval. K and N panel filter on it's way as the paper element is a little dirty.

New Original Bosch Plugs on their way too.

One of my concerns is the temperature guage seems to be getting to the fourth stop out of five and I've heard the M111 in my C200 is supposed to run at a constant 85c it's getting as much as 100c+ it never gets into the red and also runs around 80c on the motorway, but it's creeping up in traffic so I'm a little concerned, the coolant level is at the max and never drops, plus it looks a good blue colour, so no headgasket problems.

 

[BillyW124]

When changing the belt make sure the tensioner is ok. Its spring loaded so if its slipping the tensioner may be the cause. If its anything like the face lift 124's with m111 it should have a damper on it too.

The temp should stay around the 80-85 degree mark stuck in traffic even on a hot day.

my E200 saloon once had this same issue. It was a switch or the fan clutch that wasnt working i.e. the fan wasnt coming on. I think the correct term is called viscous fan coupling.

its worth changing the thermostat too. One of the easy things to start with in relation to temp issues..

 

[grober]

Good advice on the viscous coupling being faulty and not locking up as the temperature rises in slow moving traffic. I am VERY surprised that you managed to get 6 litres of oil into the engine without over filling since there is usually always some left in the engine galleries. Are you sure the engine is not over filled- What's the reading on the dipstick? I am not keen on the practice of filling right to the MAX mark unless the engine has a history of using oil. I always recommend the level to aim for on refill is 1/2 way between the min and max levels.

 

[JohnnyW202]

Hi there, the oil stick reads about 1mm under the max line on the bottom of the orange plastic marked max.

This is a Facelift W202... i.e no fan on the engine, it's electric, so no coupling? However I noticed all my other cars with A/C had two fans which ran slow when the A/C was turned on and sped up as the temperature increased, as the temp increased I never heard the fans come on full!

 

[Grahamcol]

Hi there. You won't have a visco fan, just an electric one as I think you've discovered. My 1996 C200 runs between about 80/90 degrees in similar conditions. I'm not aware of the fan speed varying according to whether the air con's on or off but maybe it should ? Seems to me it could possibly be the thermostat in your case as suggested earlier.

 

[JohnnyW202]

Hi there, I'll stick some radiator flush in and replace the antifreeze. Does MB require anything special or will the Carplan Red which is suitable for aluminium blocks do as I used in my Mondeo?

Thermostat just bolts out it's housing and drops in, right?

 

[grober]

I think the thermostat now comes mounted in its housing as a complete unit. 3 bolts and a large O ring to fit it .
ps for all the difference in price I would use MB antifreeze. 50/50 mix with water. If you are going to flush the radiator take it out and back flush it.