Odd Occurrence - PeachParts Mercedes-Benz Forum

remotemark · #1 06-03-2017, 07:29 PM

Ordinarily, my 84 300D runs like a top. In fact, over Wednesday to Thursday, I went on a 220 mile work trip with a colleague and impressed her with its awesome ride and a/c.

Today, though, I'm sitting in traffic, waiting my turn to go through a stop sign and something odd happened. I stepped on the gas to move up and the car made, from the front end, a very strange howling sound and there was suddenly a large cloud of smoke behind me and the car was surrounded by a burning smell. I immediately pulled off the road, into a parking lot. Before I got to a parking spot, the sound was gone, and no more smoke was coming out the back. I popped the hood with the engine on and there was a fair amount of smoke swirling around the side of the engine compartment where the exhaust manifold is, but no source was apparent. When the smoke blew away, it was like nothing had happened. There was a faint smell of something burnt, but it didn't seem to be fixed. The only thing I saw was oil on top of the valve cover, in a thin film. But even that was only on a small area, next to the air cleaner.

I drove the 3 miles home, and it was like nothing had happened. I went very easy on the engine, so I'm not sure if it was short of power, like maybe the turbo went.

Anyway, any thoughts on what happened or what I should look at?

Diseasel300 · #2 06-03-2017, 09:32 PM

The color of the smoke cloud is pretty important.

jake12tech · #3 06-04-2017, 12:33 AM

Color of smoke. If you suspect it's a turbo, hook up a boost gauge. Otherwise you're just shooting in the dark and so is everyone else here.

remotemark · #4 06-04-2017, 07:15 AM

The smoke was black and I don't have a boost gauge. Is that something I might borrow at mcparts? Or do you mean the kind of thing I would install through to the inside of the car to view at speed and load?

Mxfrank · #5 06-04-2017, 07:15 AM

Does your A/C still work? Could be an AC hose let go. That would certainly create a cloud of compressor oil in the engine compartment.

remotemark · #6 06-04-2017, 10:26 AM

Quote:

Originally Posted by Mxfrank

Does your A/C still work? Could be an AC hose let go. That would certainly create a cloud of compressor oil in the engine compartment.

I think you may have gotten it. I turned it on and then put on the ac and it squeaked like a pig. Shut it off and it went away. Popped the hood and it's definitely coming from the compressor. I'll see if I can find a leak.

remotemark · #7 06-04-2017, 03:15 PM

I looked for a leak but had no luck. I'm wary of running the car with the ac on; that howling makes me wonder if the compressor is toast or at risk of being toast.

Diseasel300 · #8 06-04-2017, 03:16 PM

Try turning the center section of the compressor hub with your hand (engine off obviously). You should be able to turn it with some resistance. If it won't turn at all, you probably have a locked up compressor.

Diseasel300 · #9 06-04-2017, 03:17 PM

Additionally, check belt tension. If the belt is too loose it'll slip and squeal. Can certainly make a cloud of smoke from that situation.

Squiggle Dog · #10 06-04-2017, 04:07 PM

I'm thinking turbo. It's possible the bearings are seizing up (maybe from lack of oil and overheating), or even more likely, the exhaust side of the turbine wheel is clogged up with carbon so the turbine is dragging.

If the turbo is clogged up with carbon and causing it to drag, one thing you can do if you aren't willing to rebuild it, is to get a spray bottle and fill it with water (and maybe add some Seafoam). When the engine is hot, take the lid off the air cleaner and spray the water mixture from the spray bottle into the center of the air cleaner so the engine sucks it in, while revving up the engine.

What will happen is the water mist will turn into steam and it will steam clean the carbon out of your manifolds, pistons, valves, and turbo. It will smoke out the back like crazy until the steam clears up. One bottle worth ought to do the trick. Just don't POUR the water down because there would be a risk of hydrolocking or too much steam pressure.

tdhawk · #11 06-04-2017, 05:47 PM

My car did that twice before the a/c compressor completely froze and the belt broke/burned off. LOTS of smoke and burned rubber smell

85TD daily driver 360,000 plus

remotemark · #12 06-07-2017, 05:56 PM

I cannot move the compressor hub by hand and I think the belt is not turning it either. What are the options for new compressors? Is there anything more suited to R134 than the old compressors?

remotemark · #13 06-10-2017, 08:13 AM

So from what I can tell I have three options: either get another R4 compressor which will work with R134 in a less than ideal manner; get another R4 compressor and convert back to R12; or get a conversion kit to a compressor designed for R134 but which needs hardware to fit, like the Rollguy or Klima Design kits. Option 1 is easiest, cheapest, and makes for easier maintenance with readily available gas in easy to dispense packaging. Option 3 is the most expensive and hardest but perhaps gets the most out of the system. Any other options I'm missing?

ROLLGUY · #14 06-10-2017, 11:18 AM

Quote:

Originally Posted by remotemark

So from what I can tell I have three options: either get another R4 compressor which will work with R134 in a less than ideal manner; get another R4 compressor and convert back to R12; or get a conversion kit to a compressor designed for R134 but which needs hardware to fit, like the Rollguy or Klima Design kits. Option 1 is easiest, cheapest, and makes for easier maintenance with readily available gas in easy to dispense packaging. Option 3 is the most expensive and hardest but perhaps gets the most out of the system. Any other options I'm missing?

Although I am a little biased, I suggest option 3a. But whatever way you choose to go, do yourself a favor and do it right. Many A/C DIYers fail to do so, and the system doesn't last. Every time an R4 goes bad, the entire system should get serviced, not just the compressor. It is my opinion that when changing any compressor, whether factory or retrofit, the remaining parts of the system need to be flushed properly or replaced. If the hoses are original, they probably need replacing, especially if running R134a (smaller molecules than R12). Usually the problem is not the R4, it is leaking hoses. When hoses leak refrigerant, they also leak oil. That same oil is responsible for lubricating the R4, so when the oil goes, the compressor is not far behind. When a compressor fails, it spreads small parts of it's innards throughout the system. If not dealt with properly, the new compressor (R4, Sanden or other) will fail as well. Far too often a DIYer will put on a new compressor, charge it with products from his local parts store, and have another failed compressor in short order. I believe there is no substitute for the professional A/C tech, and they should be employed for at least the leak check and vac and charge. At first I did the same thing as other DIYers, and replaced the R4 with a rebuilt, and then a new, and being disappointed when they failed later that season. That is why I developed the Sanden retrofit. I got so fed up with the poor design of the R4. Yes some have been successful with the R4, and congrats to them. Bottom line: whatever compressor you go with, flush properly what remains (evaporator, condenser) and replace everything else, and have the leak test, vac and charge done by a professional with the proper equipment. This is my opinion, but you are free to do what you please.......Rich

remotemark · #15 06-10-2017, 12:04 PM

Quote:

Originally Posted by ROLLGUY

Although I am a little biased, I suggest option 3a. But whatever way you choose to go, do yourself a favor and do it right. Many A/C DIYers fail to do so, and the system doesn't last. Every time an R4 goes bad, the entire system should get serviced, not just the compressor. It is my opinion that when changing any compressor, whether factory or retrofit, the remaining parts of the system need to be flushed properly or replaced. If the hoses are original, they probably need replacing, especially if running R134a (smaller molecules than R12). Usually the problem is not the R4, it is leaking hoses. When hoses leak refrigerant, they also leak oil. That same oil is responsible for lubricating the R4, so when the oil goes, the compressor is not far behind. When a compressor fails, it spreads small parts of it's innards throughout the system. If not dealt with properly, the new compressor (R4, Sanden or other) will fail as well. Far too often a DIYer will put on a new compressor, charge it with products from his local parts store, and have another failed compressor in short order. I believe there is no substitute for the professional A/C tech, and they should be employed for at least the leak check and vac and charge. At first I did the same thing as other DIYers, and replaced the R4 with a rebuilt, and then a new, and being disappointed when they failed later that season. That is why I developed the Sanden retrofit. I got so fed up with the poor design of the R4. Yes some have been successful with the R4, and congrats to them. Bottom line: whatever compressor you go with, flush properly what remains (evaporator, condenser) and replace everything else, and have the leak test, vac and charge done by a professional with the proper equipment. This is my opinion, but you are free to do what you please.......Rich

Thanks, Rich. This a/c system was redone five or six years ago, with extensive flushing and an overnight vacuum pull, but I think the R134 just uses these systems up faster than the R12 did. What is the overall cost, with new hoses, of a Sanden kit?

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