Pulling an A/C System Vacuum - Page 3 - PeachParts Mercedes-Benz Forum

Ken300D · #31 06-09-2009, 02:49 PM

I'm getting most of the parts and tools lined up now.

The compressor and expansion valve came yesterday. I got the receiver/dryer through the WorldPac system, but I think when I do this job over again for the 1982 300D I'll just order all three from the same place and take the discount:

http://www.discountacparts.com/addtocart~year~1984~make~Mercedes%20Benz~model~300SD~descript~A-C_Compressor~part~60-00934.asp

I went with their recommended (new) compressor at $245 including shipping. You can't tell that much from the outside of the case, but it looks to be a quality manufactured part.

Has anyone else bought their compressor from these people?

I would like to take manual control over the air recirculation flap. I presume it is controlled by a vacuum pod. Does anyone have any guidance on where it is located?

Ken300D

Ken300D · #32 06-14-2009, 11:11 AM

The previous retrofit to R-134 included a Four Seasons compressor with no marking about R-134a readiness. I was getting a little noise out of the compressor, and the main problem with it was the clutch was starting to slip on engagement - longer and longer before it locked. So with the decision to replace the condensor (leak at a seam) and the compressor came the decision to revert back to R-12 and have good cooling capacity again.

I think I have found the air recirculation flap behind the glove compartment. That's where I looked for the expansion valve first. But the expansion valve on a 1984 300SD is on the driver's side above the accelerator pedal. A real pain to get to and appears to require crow's feet wrenches for the top two (evaporator) fittings.

The new compressor did come without oil so I won't have to flush it out with large quantities of mineral oil. There is a nice replaceable port seal on it so I can put oil in for the initial lubrication and then seal it back up for mounting. I want to oil the compressor and turn it over by hand a few times.

The old compressor has an obviously worn clutch, but the compressor itself does not seem to grind when being turned. The noise may have been mount vibration, because I found the bolt missing that works with the belt adjustor. I guess I forgot to tighten that one down on the last belt replacement..... For now I can get the bolt/washer/spacer from the 1982 300D with non-functional compressor and find junkyard parts later.

So I'm stuck for now until I get 19mm and 22mm crow's foot wrenches for the expansion valve replacement.

Ken300D

compress ignite · #33 06-14-2009, 06:16 PM

Ken300D,

You are ,painstakingly, going about correctly "ReJuevenating" your A/C system.

BG has two versions

"Frigi-Quiet"

AND

"Universal Frigi-Quiet"

You WANT the original "Frigi-Quiet"

("Topping Up" Refrigerants is Always a HACK
Job...The only proper way involves Fixing/Repairing the leaking component and
then (After proper Vacuuming and Pressure Testing with Nitrogen
AND Vacuuming AGAIN) measuring out
the proper amount of BOTH lubricants (By the Liquid Ounce) AND Refrigerant
(By Weight)
ALWAYS replace the Receiver/Dryer EVERY time the the system is opened!

Ken300D · #34 06-14-2009, 08:01 PM

Thanks, I appreciate the input on the Frigi-Quiet vs. Frigi-Quiet II issue. I find it confusing that the BG web site lists FQ but I couldn't find FQ2. You would think FQ2 is the current product.

What is the difference between FQ and FQ2?

The higher grade receiver/dryer from the WorldPac system looks like a well constructed part. It also includes a sight glass. Made in Germany.

Ken300D

compress ignite · #35 06-14-2009, 11:52 PM

I Mis-read your post.
You're going with R134a ...Then you'd want the Universal Frigi Quiet

[The Universal is for R134a ...AND I think the original is for R12]

(I've corrected my earlier post)

Ken300D · #36 06-19-2009, 01:04 PM

While waiting for the 22mm Crowfoot wrench to arrive to complete taking out the old Expansion valve, I am starting to flush out all the lines. I bought liquid (unpressurized) AC flush solvent/solution and a quart-sized pressure container designed for AC flushing. You put the liquid solution in and pressurize the container, then draw off the contents from the bottom of the contained with something that looks like an air blowgun attachment. You stick the nose of this blowgun on the AC line and squirt flush solution into the line.

What I get in doing this is a pressurized liquid stream going through the line. I expected some kind of foaming action but that's not happening. I can see a lot of the old yellow PAG oil coming out and I know the lines are flushing out. My question is, with just a liquid stream, how is the upper 1/3 to 1/2 of a flat horizontal run of AC line flushed? Wouldn't the liquid flush solution just run along the bottom of the pipe? I realize that's where most of the old oil has collected, but what about dirt residue? Is the pressurized flush solution flowing hard and fast enough to adequately flush out such a flat run of AC line?

Understanding how the Evaporator gets flushed out is easy, because it is entirely below the flush entry and exit ports, so it will get completely filled with flush. Its the straight line sections (or portions of a line) that I don't understand how the flush can completely clean.

Does the blast of shop air through the lines to purge them take care of this?

Ken300D

leathermang · #37 06-19-2009, 03:02 PM

That is a good question.... with only one quart of flush... and no way to recycle it like the factory MB flush station... if there is any way to stopper the end and fill it up... and let it sit before the flush is all I can think of to help from a quality standpoint. I would suggest splitting the stuff up into first and last use containers... you can reuse one container.. getting out the main amounts by repeatedly using it... then the last flush should be with the first time use clean stuff in the other container.. so you have a ' gross' jar and a ' final' jar to put through each set of parts being flushed.

Ken300D · #38 06-20-2009, 01:38 AM

Putting a stopper or seal on the low end of the line is a good idea. I'll take that suggestion. Then drain and then blow out with shop air.

I bought only one quart of flush because I read about other people using a can or two of the aerosol flush to clean a system, and I was expecting it to turn to foam. I had some experience with aerosol transmission line flush before that did that.

So I need to be conservative with the flush unless I want to order again.

On the other hand, I thought I was going to have to purge PAG oil from the new compressor with mineral oil and bought four quarts. But the compressor came essentially dry. I guess I'll be using no more than eight ounces now.

The compressor turned over very stiffly at first until the fresh mineral oil was circulated. Then it turned much more easily. Glad I did the initial oil circulation by hand at slow speed rather than at engine speed on the car.

Ken300D

leathermang · #39 06-20-2009, 09:56 AM

OK, so that newbies do not get confused on this... even though you put the smilie after that sentence on using more than the 8 oz of oil....
The R-4 compressor he is using does not have a sump....
The total amount of recommended oil in the system did not change due to the R-4 arriving ' dry ' .. it only means he will need to use some of the oil he bought for adding to the flushed system to make sure the compressor is lubed... but he will not pour in enough that he takes a chance on ' hydro locking ' his compressor... he will just be pouring enough in slowly while moving the compressor by hand until he is sure it will not be starting up dry.....
Having too much oil in an AC system can really degrade the cooling capacity. Spread around the oil , typically 6-8 oz total , at several locations.... this is particularly important with our non sump R-4 compressors...

Matt L · #40 06-20-2009, 11:29 AM

I used six quarts of solvent (at about $10/qt) to flush my system.

compress ignite · #41 06-20-2009, 04:52 PM

When I "Converted" the Golf1.6 D to R134a,I just used Cheap non-clorinated
brake parts cleaner to flush out everything except the Compressor.
(15 160z cans)
['Hooked hoses up to the Evaporator nipples to lead the waste away
from the bodywork]
I knowingly sinned against the HVAC gods (And was not punished)

Of course I'd never do that to a Mercedes.

Ken300D · #42 06-21-2009, 08:50 AM

Quote:

I used six quarts of solvent (at about $10/qt) to flush my system.

Thanks for the guidance on the amount of flush involved.

I'm flushing out the two relatively short lines attached to the compressor manifold first. I decided not to be stingy with the flush and used the whole quart on just this, and glad I did. I finally got completely clear flush output.

One thing I came up with in regard to filling the line with flush is to use the flush gun from the low end of the line up - that is, flush from the bottom. That guarantees the line is filled with flush.

After I flushed the lines nicely and blew them out with shop air, I ran a few ounces of mineral oil through them to see what I'd get. Perfectly clean oil was the result. So I think I've got those sections flushed.

Now I am ordering a gallon more flush to finish off the system. Best price I could find is Amazon for FJC 2404 flush at $42/gallon. I thought about NAPA as a chance to get the flush more quickly, but they want $33/quart.

Is there a torque spec on the A/C compressor bolts?

Ken300D

Ken300D · #43 06-23-2009, 05:03 AM

The 22mm crowfoot wrench arrived and that made short work of the last line on the expansion valve.

The new expansion valve is not Egelhoff like the ones on the WorldPac system. An Egelhoff came off the car - I'd recommend getting the expansion valve and the receiver/dryer through WorldPac/Fastlane.

The new expansion valve I bought is marked R-134a. I did some research and I get some general idea that this will work with R-12. Also, the valve I bought does not have the short section of sensor line outside the "bulb" at the end. It simply has the bulb.

When assembled back on the car, how much of the expansion valve should be insulated? The whole thing? Or just the block section, leaving the "bulb" exposed to air? The unit installed upon the earlier R-134 conversion was left completely open to air.

Ken300D

tangofox007 · #44 06-23-2009, 09:04 AM

Quote:

Originally Posted by Ken300D

When assembled back on the car, how much of the expansion valve should be insulated? The whole thing? Or just the block section, leaving the "bulb" exposed to air?

The OE insulation covers the entire valve, with cutouts for only the four hose fittings.

Quote:

Originally Posted by Ken300D

The 22mm crowfoot wrench arrived and that made short work of the last line on the expansion valve.

No one wants to beleive it, but those fittings are actually SAE, not metric.

leathermang · #45 06-23-2009, 10:12 AM

Quote:

Originally Posted by tangofox007

No one wants to beleive it, but those fittings are actually SAE, not metric.

I believe it because it is true. There is nothing worse than rounding off a flare nut outside deep up in a tight space which has no way to get ' remedial ' help to..like an emergency visegrip.