Best Way to Flush AC system?

[Philoprof]

Well, I just changed the compressor on my 380sl. But, afterwards, when I evacuated the system, I turned the vacuum pump off and left the ports in the manifold gauge open. So, app. 100cc of oil from the Mastercool vacuum pump got sucked into the system, because the pump didn't have a valve to prevent that from happening.

Anyway, as I now have to take the system apart, and flush it, I was wondering if I also have to flush the evaporator coil which, if I'm not mistaken, requires removing the expansion valve first.

So, I was also wondering if anybody has ever done this before and, if so, how difficult it was.

Thanks in advance.


Bill

[Air&Road]

Why were you replacing the compressor? If it was due to catastrophic failure, this might have been a blessing in disguise. Any debris from a failed compressor if not COMPLETELY removed will destroy the new compressor.

Yes, you need to break every connection and thoroughly flush every component making SURE that you remove the flushing agent, preferably with nitrogen or other inert gas. Distribute the proper oil volume in the components. Connect the new filter drier very last thing and don't uncap and install it until the vac pump is connected and ready to evacuate. As soon as you get the connections tight on the drier, start the pump. This keeps the dessicate from getting saturated before it can do its job.

It will not be a trivial job, but if you want long lasting cold air, it will be worth the work. BTW, make sure you close the manifold valves when you finish evacuating next time.

Hope this helps.

[Philoprof]

Originally Posted by Air&Road

Why were you replacing the compressor?.

No. TEe compressor was 30 yrs old and I was trying to avoid the "black death"

Originally Posted by Air&Road

Yes, you need to break every connection and thoroughly flush every component making SURE that you remove the flushing agent, preferably with nitrogen or other inert gas. Distribute the proper oil volume in the components. Connect the new filter drier very last thing and don't uncap and install it until the vac pump is connected and ready to evacuate. As soon as you get the connections tight on the drier, start the pump. This keeps the dessicate from getting saturated before it can do its job.

Since I put a new drier in after I sucked the oil in, do you think the new drier may be salvegable, if I take it off and seal it up before I open the system up?

Originally Posted by Air&Road

It will not be a trivial job, but if you want long lasting cold air, it will be worth the work.

Do you think I can get away with flushing the lines but not the evaporator, as I hate to fool with that thing and the TX valve?

Originally Posted by Air&Road

BTW, make sure you close the manifold valves when you finish evacuating next time.

Yes, I will. Thank for the advice

Bill

[Air&Road]

You can "get by" with most anything and still have AC for the near term.

If it were mine and I wanted to have reliable AC for the long term, I wouldn't cut any corners. There are several reasons to flush the evaporator and replace the drier. It sounds like you don't have to worry about debris, but if you don't flush everything, you will not know how much oil is in the system.

Too little oil wears out compressors. Too much oil can destroy them. The evaporator may very well have lots of oil in it.

If it were mine I would flush well, replace all o-rings and make sure to oil them. Distribute the correct amount of oil throughout the system. Put drier in place last thing and immediately evacuate.

If you can borrow a charging scale and charge by specified weight that would be best.

Hope this helps.