Recharged AC - Now loud screeching noise - PeachParts Mercedes-Benz Forum

latief · #1 09-09-2009, 10:27 AM

Hello,

I recharged my AC yesterday, the system was not working (AC did not engage) since i bought the car in July. after the recharge ( a partial recharge as i was just testing to see what the deal is), it worked and it is cooling to my relief......

anyhow, i have a loud screeching noise from the engine belt-driven pulleys once the ac engages...is this an indication of a bigger problem with the compressor? or simply it needs some time to improve since it has been frozen for a while (not working)? could it be an indication of an overtightened serpentine belt?

thanks,

#2 09-09-2009, 11:14 AM

What is your high side pressure? Is the belt tensioner system in good shape and working properly?

IVIuzzy · #3 09-09-2009, 11:19 AM

it would be squealing because the belt isnt tight enough, the ac compressor is the most difficult component to turn. Check the tensioner. It wouldnt hurt to change the belt if it looks worn, if it was turning a compressor that wasnt working for a while, it may be time for a new one....

Is the AC blowing cold? could be a fan clutch if its not

latief · #4 09-09-2009, 11:37 AM

I just went through a head gasket replacement.......and i did inspect the tensioner and changed the piston + tightening rod. I don't think the tensioner is in its best condition, but the belt did tighten down nicely......is there any known test for belt tightness?
as for AC pressure, i am not sure..i just grabbed a can of a134 + leak super sealant. i got the smallest can since i was not sure what will work -if any thing....it worked to my surprise. today i will get one of those readily available kits with a pressure indicator. sure it is not very scientific or the correct procedure, but i am a complete newbie when it comes to AC systems. I did a search and the amount of info is overwhelming.....

any more suggestions?

fan clutch is working fine. the AC used to not engage. yesterday was the first time it did since i got the car.....

tyl604 · #5 09-09-2009, 11:46 AM

You might try belt dressing. It comes in a small container like 3in1 oil and helps the belt to get a grip and stop screeching. But the real answer is probably to tighten up the belt or replace it.

latief · #6 09-09-2009, 11:49 AM

could it be the opposite? an over tightened belt putting too much pressure on the 16 year old pulleys?
could it be rusty pulleys from the all the degressing i did while cleaning the engine during and after the head-gasket replacement?

I will try the belt dresser solution and see ...

thanks

IVIuzzy · #7 09-09-2009, 12:34 PM

if u dont have belt dressing handy, i always use a bar of soap...with the car running just rub the bar against the edge of the belt..... it will help resist the squeal.

also the AC gauges are just generic, see if anyone on here knows what the exact pressure (psi) normally average car takes 2-3lbs.... dont go by the green, yellow, red lines on the generic gauge. sometimes Jiffy Lube or a shop like that does a free AC check for you that'd tell u if u were low.......

#8 09-09-2009, 12:50 PM

You should NOT have used the sealant. It is quite common for this to be the death of an a/c system. The "kits with the pressure regulator," have no pressure regulator at all and they ONLY give a vague pressure reading for the low side. You need to know the HIGH SIDE pressure. Since it now has 134 in it, all bets are off as to what the high side pressure needs to be.

The problem you are looking at now is that no one will recover the charge from your system because it now has leak sealant. It will ruin their multi thousand dollar machine. If you were to drive in my shop, I certainly would not touch it. I wouldn't even connect my gauge set to it since the leak sealant can even ruin my gauges.

I would suggest that you see if you have the noise with the a/c OFF. If you still have the noise, remove the belt and spin all accessories to find which pulley/bearing is locked up. If the squeel DOES go away with the a/c turned off I really don't know what to tell you. The sealant has already been put in and there's no turning back at this point.

latief · #9 09-10-2009, 05:14 PM

Well, it looks like the screeching noise is coming from the smog pump bearing. i guess it was just a coincidence that it happened while i was working on the AC.

any how, i have read a bit about what my options are, and i want to remove it completely as i don't need it florida...

can someone confirm the correct belt size for the m104 engine without the smog pump?

also, what do i do with the valve & Hoses & tubes going into the engine head? where do i block them and how ?

thanks guys

#10 09-10-2009, 06:19 PM

It would be a good thing to develop the habit of spinning all idlers and accessories any time you have the belt off. Check to see that all pulleys spin smoothly and freely. Take advantage of this chance to inspect ANY time that you have the drive belt off.

latief · #11 09-11-2009, 05:40 PM

its not even the smog pump, i took it apart today and it is the fan bearing bracket....I just finished my head gasket last week and only drove the car for a few days and this happned...

the pulley was scraping against the crank pulley , good thing i caught it...

I am trying to save some money, but since i have the fan clutch out, how can i check to see if it working correctly? i would hate to replace it if nothing is wrong with it....

any suggestions?
thanks,

#12 09-11-2009, 10:45 PM

The fan clutch is typically tested while on the car. To do this, simply give the fan a spin. If the fan clutch is in good shape the fan should not spin a full turn, probalby not even a half turn. If the clutch is bad the fan will spin freely with no resitance.

Richard Wooldridge · #13 09-11-2009, 11:21 PM

The fan clutch went out on my '82 380SL- After I replaced it with a good used one, the difference was quite amazing to me. For instance today it was 96 degrees here, and the car cooled right down inside to a nice icy "almost too cold" feel, and the engine temp gauge sat right on 85 or so. Before I replaced it the gauge would shoot up to 110 quite often, especially in slow traffic, even on cool days.

dhjenkins · #14 09-12-2009, 01:03 PM

Get a cheap set of mechanic's ears and put it against the compressor body. If the screaming is coming from there, the compressor is bad (or has no oil in it). You can try an oil shot to see if that quiets it up, but you'll need to make sure and get a PAG oil if you're using 134-a. Chances are, though, even with new oil the compressor has already been damaged.

If it still screams, and you've charged it, you've probably just spread little bits of metal all through the A/C system. You now not only have to replace the compressor, but remove all parts of the entire system (evaporator, condensor, hoses, etc...) and clean them out to insure that those little shavings don't re-introduce themselves into any new compressor you install.

To test if it's the belt, just spray some belt dressing on it - if that gets rid of it, even temporarily, it's belt related.

Good luck!

latief · #15 09-12-2009, 08:25 PM

It was the fan clutch bearing, I am waiting for parts to come in the mail. I will update this once I install them....

thanks for all the feedback guys !!!