Should Schrader Valve Core Be Removed From The Evaporator?

[Squiggle Dog]

Due to the evaporator in my 1980 W116 300SD being corroded from being covered in wet debris for years, I bought a new Four Seasons one (which had to be highly tweaked to fit). I noticed that the Four Seasons one has a Schrader valve in it at one of the fittings where the expansion valve wire attaches.

I assume this Schrader valve is just for pressure testing the evaporator at the factory. If it's kept in place, I assume it will block the flow of refrigerant to the wire coming off of the expansion valve.

Remove the valve core, or keep it in place?



Also, which is preferable; the original, high-quality expansion valve which is nearly forty years old, or a brand-new Chinese-made Four Seasons one? I just don't know about the longevity of a part that's so old.

[engatwork]

Leave it alone. IIRC the exp valve on that model is easy enough to replace so I'd stick with the original if you know it works.

[Squiggle Dog]

Originally Posted by engatwork

Leave it alone. IIRC the exp valve on that model is easy enough to replace so I'd stick with the original if you know it works.

I don't know if it works. The air conditioning has never worked on this car the entire eight years I've owned it. But, I could probably bring it with when I have the air conditioning charged, and if it works, then I'll stick with it. If it doesn't then I'll have the new one installed.

[97 SL320]

Need pics of expansion valve wire ( tube ) and inside connector.

[Diseasel300]

Take a look at the fitting to the expansion valve. If it has a protrusion to depress the core stem, you can leave it in place. If it doesn't, it needs to be removed. What was the story with the original, did it have a schrader core or not?

[Zulfiqar]

Some T shaped expansion valves had a bypass tube as a safety. I believe this is what this certain schrader is for,

I had an old Honda with this, The factory TXV had a bypass, the replacement one bought for it didnt have it and the little package of the TXV had a brass cap for the left over port in the evaporator.

The sensing tail of the TXV has no business with directly touching the gas. It is clipped onto the metal of the evap tubing.

[Squiggle Dog]

Here is the original expansion valve. It just has a copper wire with a flare fitting on the end, which connects to the area where the Schrader valve is.


The original evaporator didn't have a Schrader valve--it was just an open bore. The replacement evaporator came with a Schrader valve and had so much pressure inside the unit that after loosening the plastic caps on the large fittings and letting the air escape for what seemed like a long time, when I removed the first cap, there was still enough pressure to shoot the cap across the room and nearly popped my ear drums.

[Rick76]

Yes, remove the Schrader valve.
The pressure that you experienced was probably a charge of nitrogen to keep a positive pressure to keep out moisture.
Make sure to lubricate with refrigerant oil or Nylog.
And of course change the receiver/dryer.

[97 SL320]

Valve core needs to come out since the line / fitting does not have a valve depressor.

[Squiggle Dog]

Haha, funny how the replies went from "leave it alone" to "remove it". My best guess was to remove it based on the original evaporator not having a Schrader valve.

The new expansion valve doesn't have a depressor, either. I noticed that it has R-134a stamped on it, so the superheat value is set up for R-134a, but I plan to use R-12 because I live where it's HOT and having air conditioning that takes forever to cool the cabin when the car is started, and that doesn't cool well in stop-and-go traffic is unacceptable to me. What might be acceptable in the Pacific Northwest isn't necessarily acceptable here.

Since the original expansion valve is set up for R-12, it would probably make more sense to just stick with the original one. I have several spares, too, if that doesn't work, I just didn't want to reuse a part that might be at the end of its life expectancy.

Every component of the air conditioning system is going to be brand new with the exception of the high pressure nylon hose going from the drier to the evaporator--and maybe now the expansion valve.

[Rick76]

Originally Posted by Squiggle Dog

Haha, funny how the replies went from "leave it alone" to "remove it".

I think the "leave it alone" comment referred to the expansion valve, not the Schrader valve.