Putting R134a Refrigerant In A 1991 W126 350SDL--Use A Different Expansion Valve? - Page 3 - PeachParts Mercedes-Benz Forum

leathermang · #1 08-06-2016, 09:31 AM

Good information and a lesson on the need for both patience and persistence....

funola · #2 08-06-2016, 01:45 PM

Quote:

Originally Posted by leathermang

Good information and a lesson on the need for both patience and persistence....

True, but one must also have the tools or ability to make custom tools like adapters. I want to be able to pressure test each component individually. I am glad I pulled many of the AC hoses (except the TXV hoses) and parts off a 240D and 300D. The fittings from the hoses allow me to make adapters for component testing.

The shiny #10 to the TXV came in the mail this morning and was easy to make an adapter from by taping a 1/8 NPT thread in it and screwing in a 1/4 SAE flare.

Here it is being used to pressure test the evaporator by itself at 1.001 MPa (145 psi) Argon. Last night's test of the evap with the hose on the TXV adapter was encouraging. This test will be definitive whether my evaporator leaks or not. I'll know in a day or 2.

Squiggle Dog · #3 08-07-2016, 12:31 PM

Thanks for all the advice.

Fine, you guys forced me to flush the evaporator. What I did was drill a hole through the smaller holes of the old expansion valve and blew it out and cleaned it with flush. Then I installed it and the hoses.

I ran the thick hose through the firewall and fitted a funnel to it, while routing the thin long hose through the cabin and into a gallon water bottle. I poured in some AC flush from a bottle through the funnel so that it would fill up the evaporator and I let it soak for half an hour. During this time I hung the catch bottle off the turn signal stalk.

After this I moved the catch bottle down onto the ground outside the car with the long, thin hose still attached. I then blew compressed air through the thick hose in the firewall as it drained into the catch bottle.

The flush is a clear liquid. What came out into the bottle was bright orange and not a speck of dirt. I'm not sure if the orange color is from a leak dye or the color of the old oil. I flushed until the fluid came out clear. I then blew compressed air through until nothing was coming out, then disconnected the hoses and then blew compressed air through the evaporator again from inside the car. Then it will be left open to dry out for a few days. The old expansion valve was held together with JB Weld.

leathermang · #4 08-07-2016, 12:46 PM

Heck, we had forgotten you were working on your AC... we were just in ' talk amongst yourselves ' mode.... trying to figure out the fSm combined with ' what is possible'....
But I am sure you will sleep better now that yours is cleaned out....and the pictures will help others tackle theirs also...

ROLLGUY · #5 08-07-2016, 02:47 PM

I have seen that color before when flushing, and I believe it is the oil that made it that color.
EDIT: by the way, that looks like the twin to my car!

Squiggle Dog · #6 08-07-2016, 06:06 PM

Yeah, it's a white 1991 350SDL with grey interior.

Here's another question--is the little tube at the saucer end of the expansion valve supposed to touch anything? It looks like it floats out in nowhere land.

The expansion valve came from the local auto parts store. It was listed as Murray brand, but the stock photo showed an Englehof made in France. When we looked at the box, the box was labeled Made in China. The valve had a big sticker over the original sticker. So I peeled that sticker off, revealing an Englehof R134a sticker underneath. No indication of where it was made, though, but probably China.

leathermang · #7 08-07-2016, 06:18 PM

' Little tube' ... how long is the tube you are talking about ?

Squiggle Dog · #8 08-07-2016, 06:33 PM

Quote:

Originally Posted by leathermang

' Little tube' ... how long is the tube you are talking about ?

It's this little tube thing on the end.

leathermang · #9 08-07-2016, 06:39 PM

My impression is that it is a ' reference' temperature 'gauge' or reference pressure based on temperature .... the longer tube in the system should be in contact with part of the evaporator I think.... OR.. is that TXvalve situated so close that THAT could be the sensing tube in contact with the evaporator ?

http://www.achrnews.com/articles/85048-tech-tips-for-thermostatic-expansion-valves

http://www.tpub.com/ase2/69.htm

Zulfiqar · #10 08-08-2016, 04:22 PM

Quote:

Originally Posted by leathermang

My impression is that it is a ' reference' temperature 'gauge' or reference pressure based on temperature .... the longer tube in the system should be in contact with part of the evaporator I think.... OR.. is that TXvalve situated so close that THAT could be the sensing tube in contact with the evaporator ?

Tech Tips for Thermostatic Expansion Valves

Thermostatic Expansion Valve

You are writing for a T shaped expansion valve with the sensing capillary tube, Which you are 100% correct for.

This one is an H block. and the sensing tube passes through the suction port in it. This one is actually showing a little tail of the same capilary sticking out - I think its used for something on the production line - some dont even have it anymore - all you see is a flat rivet.

compu_85 · #11 08-07-2016, 08:58 PM

Some expansion valves have a sensing bulb on the end of a tube. Our cars use a block type expansion valve so the sensing bulb is built into the valve. That's why it gets wrapped in insulation, and why the suction line runs through it.

-J

lorainfurniture · #12 08-07-2016, 09:00 PM

So in other words, leave it alone.

Squiggle Dog · #13 08-07-2016, 10:50 PM

Okay, I will just put the new insulation halves over it and call it good. I remember reading somewhere about an expansion valve having a sensing bulb that was supposed to touch the upper part of the refrigerant pipe so it senses the gas temperature and not the liquid or something. Sounds good to me.

leathermang · #14 08-07-2016, 11:11 PM

If you look at those url's I posted you will see a bunch of those types..

Demothen · #15 08-08-2016, 09:00 AM

Insulation over the txv? I was not aware of that. Anyone have a part number for a w123?

Edit: just read the FSM again and noticed it mentions opening the insulation. Did a bit of research and it seems like I could just wrap it with some foam tape if necessary, but it would be nice if I had the correct part.