Metal fan blade hits A/C compressor at higher RPMs, how do I fix it?

[JMURiz]

All,

My '74 280C with the M110 engine has an issue where the metal radiator fan blade hits the A/C compressor when running higher RPMs.

Is this due to the fan blades flexing as they spin faster or something more serious?

Thanks for any ideas.
Nathan

[daidnik]

I assume that you do. It seems surprising that the fan is that close to begin with, but I've never owned a 6-cyl W114.

What I do know is that the visco-clutches can develop a significant amount of axial play (fore-aft wobble at the tips) in later age. You can feel for this with the motor off.

The visco-clutches aren't real cheap anymore either ~$150 for a Behr unit.

They will also become 'softer' in the viscous coupling which leads to hotter running at low speeds esp stop & go traffic.

Check for the axial play first and see if that is a problem.

A bent fan blade is also a somewhat remote possibility. You should be able to see where the blade(s) have been contacting the compressor on the back side. See if all blades show evidence of contact or only some of them show it.

[t walgamuth]

I would say something is not right there. Either wrong fan blade, wrong fan clutch or something. If the fan is actually bending that much with the other items being correct I would say the fan is about to fail.

[engatwork]

I would say something is not right there.

x2

metal or plastic blades? Is the metal fatigued/cracked and flexing outside it's design layout? Try to do a good visual inspection with good lighting to see if anything is out of alignment between the pulleys. Turn the engine over some and look at all the different pulleys it different positions to try to determine what is changing. Are you seeing anything flex/move while it is running?

[JMURiz]

I know not all of the blades hit, but I'll check for fore/aft play and report back.

[daidnik]

This should be between the the short center armature of the visco-clutch and the fan belt pulley on the front of the water pump.

P/N: 114 201 0052

No clue how thick it is, but you should be able to see it between that armature & the pulley.

Judging from the very shallow fan shroud, the front of that fan probably sits very close to the back of the radiator.

This clearance would be another thing to check.

[JMURiz]

OK, scratch my higher RPM comments, tried to take the car for a spin last night and it was clanging at high and low RPM...so I'm guessing something is shot in the fan-clutch assembly.

All the fan blades have made contact now.

Would it be better to get a new fan clutch or to just go electric fan running on a thermostatic switch?

[daw_two]

Are you sure it is hitting the AC compressor?

I remember way back when........when a certain diesel I own needed motor mounts and her fan blade was hitting the fan shroud.

[sjefke]

Ditto. Are you sure it is the compressor that is being hit?

The fan blades may be hitting the radiator (causing a metallic sound). I had this happen on a 114 250C when the radiator rubbers that hold the radiator in the channels were old and the radiator was able to move back a bit (especially of the rubber rings are still installed on the top). Yanking the radiator forward solved it, until I got new rubber channel inserts.

Check for fresh metal scrape marks (and make sure the engine is off!!)

Good luck,

Bert

[JMURiz]

Oh yeah, it's hitting the A/C...the wear marks on the fan correspond to the rivet heads on the front of the compressor. it's not anywhere near the radiator or shroud...maybe that's why it's a problem...possibly sitting way too close to the engine.

[kraakevik]

It may be that the spacing between the fan assembly and the fan clutch has been tampered with, effectively moving the fan arc backwards toward the cabin--there should be about 3/8-inch clearance between the fan and the A/C pulley and about 5/8-inch clearance with the compressor clutch


Tim Kraakevik
kraakevik@voyager.net

[t walgamuth]

Originally Posted by kraakevik

It may be that the spacing between the fan assembly and the fan clutch has been tampered with, effectively moving the fan arc backwards toward the cabin--there should be about 3/8-inch clearance between the fan and the A/C pulley and about 5/8-inch clearance with the compressor clutch


Tim Kraakevik
kraakevik@voyager.net

x2 worth checking.

[Mike D]

On the '74 W114 with the M110 you'll need to use either a "thin-line" puller fan or remove the existing auxiliary fan and install it in front of the radiator as a "pusher". You don't have enough clearance for a standard electric fan between the radiator and the water pump pulley.

I use a pusher fan on my '74 280C here in the desert. I get a little concerned sitting in heavy traffic in the middle of the day but otherwise it is working fine. Do plan on using the heavy duty battery and a possible alternator upgrade.

[JMURiz]

Good info everyone...maybe the PO removed something. I'll dig into it this week sometimes.

Also good info Mike D, I'll look into doing an electric conversion in place of the A/C condenser fan if I can't make a spacer on the engine-mounted fan.

[JMURiz]

OK, I went out to the garage and snapped some pictures:

As you can see the fan blade is really close to the A/C compressor pulley even when cool. The fan blade does spin freely when the engine is off though.

Do you think the fan so far from the radiator shroud may also lead to my car running a bit hot?

I have also attached a picture of a later model M110 where the fan seems to sit MUCH further into the radiator shroud than mine: Note the picture directly below is not my engine


Thanks for any further advice...and if there is someone local that knows these motors, feel free to contact me to see if something looks wrong on my car.

Nathan