95 E320 new noise from drivebelt - PeachParts Mercedes-Benz Forum

tbenner · #1 08-28-2007, 06:28 PM

This morning, pulling between two cars at the parking lot at work I noticed a new sound from under the hood. Not good. It sounds like something ticking but is irregular. Opening the hood, it sounds like something attached to the drivebelt, but that leaves plenty to choose from:
tandem pump, AC compressor( it was the same with AC on or off) ,
water pump, airpump, alternator and the belt tensioner.

My questions are does anyone have a method for diagnosing this kind of noise? (I like to keep my hands and ears far from the fan)

Which of list list of components is likely to fail first?

Anyone have a similar experience at around 143k miles?

Thanks to all,

tbenner · #2 08-28-2007, 06:37 PM

That was the other thing I noticed. Is this an easy job? I haven'y even been able to trace the wiring yet.

Thanks again

tbenner · #3 08-28-2007, 09:23 PM

I bumped it and it started running. Turned off the AC and they both stopped. Turned it back on and only the right one runs... just touch the left one and it starts. The trouble is, when in stop and go freeway traffic you can't get out and touch it. I'd like to shoot some contact cleaner in there. Is there any way to get to it without removing the radiator and breaching the AC?

The other noise sounds more like a squeaky bearing. Water pump maybe?

John Plut · #4 08-29-2007, 10:35 PM

I had an irregular ticking on my '92 300e that was caused by a loose tensioner shock.

The rubber bushings at the ends of the shock deteriorate and cause metal-to-metal rattle. A quick fix is to remove the bolt and sandwich a rubber washer (like a hose washer) in there.

A264172 · #5 08-29-2007, 10:40 PM

As far as listening to the areas from farther away.. a long bladed screw driver makes a great stethescope{sp?}... just put the blade on a hard surface close to what you want to listen to next and your ear to the handle.

tbenner · #6 08-30-2007, 08:59 AM

I tried the long screwdriver and found that it is not the tandem pump or waterpump. It has the new type tensioner with no shock but I wonder if these develop problems with age. I'll try and get to it with the screwdriver 'listener' when I have more light.

Thanks again,

A264172 · #7 08-30-2007, 09:13 AM

I think your engine has a fan clutch bearing bracket... these tend to go bad.
It's a bearing in a aluminium bracket that the main fan (between the rad and the block) and the fan clutch (on which the fan is mounted) are attached to.
This would be hard to listen to. With the engine off grab ahold of the fan clutch and try to move it front to back... any play would not be good. Also with the engine running try to look down at the pulley and see if it is making contact with the crank pulley below it... that's how mine failed and I could see a little fountain of metal shavings spraying up from where they were being ground off of the fan clutch pulley by the rubbing.

JMaxwell · #8 08-30-2007, 11:30 AM

When my airpump went at 115k, it had the same issues you are reporting.

Long story short, when it did sieze up, not only did I have to replace the pump, but the fan belt had melted into all of the other pulleys as the crankshaft still pulled the belt around the non-rotating air pump pulley.

Not a fun fix!! Especially since everything reeks of burnt rubber. I had to use a little dremmel tool to clean out some of the pulleys, and a couple were so screwed I had to replace them.

I suggest checking the air pump and the air pump pulley asap.

tbenner · #9 08-30-2007, 02:41 PM

It's a quick 20 miles at lunchtime and an hour of stop and go at 5:00. The noise has gotten worse so I didn't want to risk having it come home on a hook.

Since it is louder it should be easier to identify, right? The good news is that the belt still looks OK. I'll try the screwdriver stethescope tonight. If that fails, I'll pull the belt and start shaking things. It really seems like the sound is coming from the left side. The waterpump pulley has a slight wobble to it but no leakage. I can move the fan in and out *very* slightly on its shaft (<1mm)

We'll see what it is tonight... I hope. I'll need to get parts tomorrow or wait until next week. (which would please my wife who wants to start re-doing a bathroom)

TMAllison · #10 08-30-2007, 03:19 PM

If the stethoscope doesnt work, try droppng the tension on the belt and spinning all pulleys driven by it by hand to see if you can find a bad accessory bearing.

You can also fire a COLD engine up and run it w/o the belt for 30-60 seconds to confirm whether or not the noise is from an accessory device or not.

okc329 · #11 08-30-2007, 06:12 PM

is a piece of hard but flexible plactic or rubber tubing. You put one end at your ear and aim the other as close as possible to sources of noise like a pulley bearing. I've also used this to check on the proper functioning of such components as the purge valve in the gas vapor recovery system.

tbenner · #12 08-30-2007, 09:10 PM

I gave up on the stethescope as I was hearing nothing wrong through it. I pulled the belt and checked each pulley.

The airpump, alternator, idler, fan, AC and tensioner pulleys all spun freely and had no play fore and aft, nor any up and down (radial) play.

The tandem pump had .015 play fore and aft but no radial play. It spins pretty smoothly but not too freely as it would be pumping fluid as it spins.

The waterpump had no fore and aft play but the pulley did move up and down. It was dark so I could not find a way to mount my dial indicator to measure it. It spun less freely than the tandem pump.

I have never had a waterpump bearing go bad by itself before. They have always started leaking out of the weep hole before the bearing went. But there is always a first time. Maybe it is weeping and I cannot see it behind the pulley. I am losing no coolant though.

Given that none of the other pulleys had any radial play I am ready to conclude that it is the waterpump.

Could someone more experienced than I give an opinion and/or experience? I would surely appreciate it.

Thanks and Regards

tbenner · #13 08-31-2007, 08:37 PM

I got started tonight, draining coolant and pulling hoses. I local parts house (Foreign Car Parts) had the waterpump priced reasonably. So I decided to give the waterpump pulley another shake just to see how sloppy the bearing was and the slop is now almost imperceptable.

But it WAS moving up and down >1/16" when warm and that can't be right can it?

Ferdman · #14 09-01-2007, 03:21 PM

Tim, I recommend buying a remanufactured water pump from your local MB dealer rather than relying on some aftermarket pump. Replace the thermostat while you're at it.

tbenner · #15 09-06-2007, 08:47 AM

I had some doubts as to whether the noise was the water pump as it was not leaking... never ran in to that before. But after a little more extensive reading here I was not the only one with a leak-free but noisy water pump.

It is all buttoned up and I drove it to work... nice and quiet now. And no leaks anywhere. So the rad and block have been flushed, it has all new hoses and clamps, a new belt and a new waterpump. All of the other pulleys on the belt are checked out and are fine. As a bonus, I got the left side aux fan running. I just gave it a good shot of contact cleaner inside while everything was nice and cold. When I turned the AC on both fans spun up with no assistance for the first time. It took a long time to get all of the air out of the system... if it is all out even now.

The new thermostat must be slightly different than the old. On the highway, the temp needle rests in the top circle of the 8 for the 80 mark. I don't know what temp that actually represents but am guessing close to 90 since it is about halfway between the 80 tick mark and the next one up. Before the new parts the needle stayed in the center of the 8. With the AC on and idling it climbs up to the 100 tick.

I checked the radiator with an infrared thermometer when it was good and hot (needle close to 100). It was reading 93-94 pretty consistently across.

Would I do this job again? Absolutely, now that I have acquired/made the tools needed. I sacrificed a few ball end allen wrenches, using the Dremel to cut them to the length needed to get the waterpump bolts off and to be able to torque them. A few $10 sets of allens is a lot cheaper than 5 hrs labor... and now I have the tools. And the front & left side of the engine are now very clean!

Thanks to all for your help!