Hi all,

I'm fixin' to flush the evaporator on my 124 before refilling with R12. I am looking for hints or ideas as to removal of the expansion valve, installation of a new expansion valve and not making a mess with flush all over the car. Will a hose on the outlet of the evap take care of it, or is there more?

I am considering the flush gun concept that takes liquid solvent and input from a shop air compressor and blows it thru the system.

Thanks,

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Brian Toscano

Hi Brian -

It's actually surprisingly easy to access the expansion valve. The hi/lo side lines are held to the valve by a single 8mm (I think) nut. It can be undone reasonably well with just a common open ended wrench. Be careful not to drop the nut. I used a magnet to grab it while undoing the last few threads with my fingers.

The hi/lo lines are clamped down near the alarm siren. To get some ease of movement it's best to remove these clamps. I think I unbolted the alarm horn for access.

The expansion valve itself is held on by two 3mm hex screws. A common allen key is all that is necessary. Just unthread them, then again use your magnet (I have a pen style magnet) to extract them without dropping.

There's a heater hose in the vicinity. Unclamping it from the firewall fitting and moving it out of the way makes the task a bit easier.

Once you get the hang of it, it's about 15 minutes work.

I recommend using nylog (or some other o-ring sealer) when reinstalling. The expansion valve can be a bit tricky to get sealed well. It helps to alternately tighten the 3mm hex screws, sorta like torquing head bolts.

I used an aerosol flush. As I recall, it came with a plastic hose containing a rubber fitting. As such there was no need to get the can down to the evaporator tubes. My only concern with a flush gun is whether the gun needs to go all the way to the evaporator tube - that would be a tight fit, to say the least.

Using common plastic tubing to transfer the used solvent to a container worked fine for me. I don't think the tubing even needed to fit all that tightly.

- JimY

Thanks for the great write-up!

Do you know how much flush you used?

Thanks,
Brian

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Brian Toscano

Hmmm. It's been a good year and half since I did that work, so it's getting a bit hazy in my memory. I think I purchased two cans of aerosol solvent and used them exclusively for flushing components which I left installed in the car - namely the evaporator and the hi/lo lines to the evaporator. Everything else I removed from the car and just used a funnel to pour in lacquer thinner.

I recall reading on a web site put together by an a/c shop owner that they use mineral spirits for flushing (cheaper than lacquer thinner, but not as volatile and hence more work to remove). They just introduce it using one of those pointy tipped plastic ketchup dispenser bottles, then use a blow gun with compressed air to blow it out. The flush gun is a nice tool, but I don't think it's really necessary.

Anyways, I think I used a full can of flush just for the evap, a good 12 ounces or so. Lots of black gunk came out of the evap, though there was no visible contamination of the rest of the system.

- JimY