Clanking noises when aircon switched OFF in 1996 C220

[KLee]

Hi guys, great to have found this forum. Kicking myself I didn't find it whilst I was in UK. Am now in Sydney and have brought my UK 1996 C220 92k miles along with me. So still feel aligned to the UK.

No doubt car is aging so have few items to be looked at. First obvious one is a loud high velocity clanking coming from the engine when the car is first switched on just before the aircon kicks in. It also comes on again when the aircon is deliberately switched off. It is loud and definitely like a piece of metal hitting fan blades. I see 3 fans in my engine bay - 2 for the aircon and 1 is the large radiator fan. I cannot see any suspect and cannot isolate the sound as it echoes too much everywhere to be pin pointed.

I don't think the cam belt has been replaced in thsi car. There was a bit of shuddering whilst I drove the car back from the ports and on inspection the radiator liquid levels were low so I temp topped up with water until I get it checked. Since then no shuddering just this loud clanking. After the ports I also did get the aircon regassed. Btw when my aircon comes on, I hear a clunk (like a relay thunk) then a hiss almost like a truck's air brakes (but not so loud) - is this normal?

Any ideas guys? Have me v worried.

 

[Robby]

I believe the aircon compressor has a fairly simple clutch on it. I'd guess the clunk is that clutch operating, and after several months of salty sea air it is no longer operating smoothly, just a surge of torque to work the partially seized components. Try giving it a spray of WD40 - be careful not to get any on the belt - and turn ac on and off a few times.

Its a camchain, not a cambelt. Just keep changing the oil and it should stay fresh.

 

[KLee]

Thanks Robby. I will look into it once I figure out where the aircon clutch is. But what about the loud clanking? Any ideas what possibly causes it?

 

[guydewdney]

if the sound only happens when the air con is off - ie the pully on the font of the air con pump is spinning freely - it sounds vey much like the air con clutch is stuck / loose.

at the end of the day its a pretty simple device - remove the belt, and undo the bolt at the front of the pully (it MIGHT be a backwards thread - i have no idea) - the pully itself then comes off. theres a wave washer behind it (acts as a spring)

if this spring was broken / stuck it would allow the pully to flop about - when its powered (ie air con on) the pully is pulled onto the shaft by a big magnet - thus no flopping.

try removing belt / loosening belt and wiggling the pully?


you could double check its this by powering the air con on and off (theres a simple plug on it - you might be able to power it with a bit of wire - ymmv... caveat emptor etc etc)

 

[KLee]

Thanks for your input. I have sent the car in to a mechanic (not main dealer) that the family has known for 10 years - repaired family's 280E and Audi 1.8T with a pedantic long list of things to chk incl comments from this group as well as carry out the 92000mile service. Got a quick report call from him - I'm listing for the benefit of the group in nontech brief translation - we decided to go ahead with repairs in order of priority: WD40ed the aircon parts reduced the clanking; engine mounts weak -> must replace to resolve vibrations when idle and also some of that clanking; found auto transmission oil filter (?) and gasket must be replaced slight leaking discovered; fan belt must be replaced; front shocks sweating and steering ball bearings worn down must be replaced; I had complaint accel was sluggish driving back from the ports -> he chked and replaced v clogged petrol filter (?) and test drove around -> apparently the improvement was like night and day.

he found aircon compressor also leaking -> reduced coldness from aircon - leave alone for now; he found (as did the prev mech) corrosion in rear disc brakes ok to be chged when rear pads go; found rear differential has oil leak (?) - ok for now;

Sorry if I blabbed on but I just wanted to share with others if in similar situation - I know I was looking for some reading like this. Are my above items about what others are experiencing at that mileage or is mine terribly crook?