Hi

1983 300sd 125,000km or 80,000 miles

Problem:

Rattling noise from front of engine when climate control off or on economy mode. Noise stops when normal or defrost AC modes selected.

How I think I caused it:

I changed the power steering fluid on Sunday, and filter, and purged. Sure needed it - the old filter had separated into three separate parts! When purging I forgot there was a hole in the side of the reservoir as I'd removed the low pressure return hose, and I managed to pour about a cup of ATF through the hole! Stupid, I know......

I assume that the black cylindrical thingy driven by a belt that is below the power steering pump is the AC compressor? And I managed to ATF all over it. Yuk.

I saw one old posting when searching that reported similar noise when the AC was disengaged, and that was due to insufficient belt tension. Do you think that ATF over the belt could cause the same issue? But why when disengaged?? I've always had previous compressor problems when you engage the AC, NOT when you disengage it!

Thanks in advance.... RL

There is a different set of "moving parts" when the clutch is not engaged. It just depends on which set has the problem.

pulley bearing

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

Thank you. So you think it was a coincidence that the noise started at the same time that I did the power steering job.

Can the pulley bearing be replaced without removing the compressor lines so charge is not lost in the AC system?

Sorry, newbie here...

Ritchie Leslie
300sd 1983 80,000 miles

Pulley bearings can be replaced without loosing Freon, accessed from the front of the compressor. You may need to remove the radiator to get enough room to work. But I would think a bad bearing would make noise all the time. And a belt usually make noise only under load, as when the compressor is engaged.

You say the noise stops when the compressor is engaged? Could be a problem with the compressor clutch. When the compressor is not engaged, the pulley and bearing turn, but the clutch plate mounted to the compressor shaft doesn't and just misses the pulley by a small gap. When the compressor is engaged, this plate is sucked against the pulley and turns with the pulley. It is possible that this plate is jiggling and rattling against the pulley, and I think the plate is usually mounted in rubber. Maybe your oil spill lubricated the assembly up and caused the plate to slip in the rubber mount, possibly accelerating an existing problem. Or something broke loose in the plate assembly. The clutch too can be serviced from the front without loosing Freon.

KCM is on the mark here. Two different techs have told me the clutch is flaky. They both want to replace the compressor as a unit (and attendant receiver/dryer,switches, recharge etc - runs about $1500 Cdn parts & labour up here, ouch). An engine shampoo seems to have fixed the problem (!!) and the AC is cold today, so I will wait until the damn thing packs up totally. I will see if I can find a tech who knows how to adjust/repair the clutch in Toronto.