I'm new to the forum and about "one year old" in learning the mechanical design, function, repairs, and maintenance of my '85 300D.

I thank everyone for the support I've gained in reviewing SEVERAL old posts over the past year!


My most recent project is getting my a/c functioning. The a/c compressor belt is missing (since purchasing the vehicle.) I can easily spin the pulley, so my understanding is the compressor is NOT locked.

Is it okay for me simply put a belt on and recharge the system? Although I prefer to restore to original R-12 coolant, with this project I will do the R-134a conversion, for convenience and safety. Cold is okay with me. It doesn't have to be frigid.

The R-134a coolant has 6 ozs of lubricant. With this, and an EASILY spinning pulley, I do not have to add any more lubricant to the compressor do I?

Thank you for any help shared!!

John

I believe you have to suck out the moisture first. If you don't you risk ruining other critical parts.

Harbor Freight sells a vacuum you can use. I saw it on 'Eric the Car Guy' on youtube

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Ben
1987 190d 2.5Turbo

First, a "free spinning pulley" only means that the pulley bearing is ok. You need to actually spin the compressor and see how that feels.

If you go 134a I suspect you'll be disappointed.

You can certainly just recharge, but since you have no idea where you're starting, you'll have trouble figuring out where you need to get to. If you DO go 134a you need to have the system evacuated to recover any R12 in there now. If the system leaked, it could have leaked the oil, so you'll need to replenish some oil.

If the system is empty, you'll definitely want to vacuum the system.

So the bottom line is you don't know if the compressor is good, you don't know if there are any leaks, you don't know how much oil is in the system, you don't know of your evaporator and expansion valve are ok and you don't know if your dryer is still good.

Might be a good time to take it to a shop for an analysis... or possibly start from scratch and consider a Sanden conversion before you throw a lot of good money after bad.

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Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
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• F350 Powerstroke
• Auburn Boattail Speedster replica

Just to add to what mach4 has said, spinning the pulley is easy because the clutch must be engaged before you will be able to spin the compressor. You would likely not be able to spin a good compressor by hand.

I have converted a couple of R-12 systems to 134a, and while I was pleased with the results, it requires an understanding of the system and it's operation. The old oil is not compatible with 134a so the old oil must be removed and new PAG oil added, a new drier is typically used, and new green O-rings used.

Since yours was not being used when you bought it, there is likely a problem with it of some sort. I believe it would be better to take it to someone who can diagnose it and sort of watch, and ask questions, before you work on it yourself.

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'97 E 300 D

The original R4 compressors are notorious for siezing. Read about it both here and on GM web-sites. The one in my 85 300D seized and gave a plume of smoke under the hood as its clutch slid, melting the connector. Inspect your connector. Unsure about the one in my son's 84 300D. When he pulled in last summer after a 400 mi drive, the AC belt was broke and hanging down, and oil was dripping out everywhere. It had tangled in the pwr steering belt, flipping it over so its "teeth" cut into an oil cooler hose like a chainsaw, wearing a small hole in it. That sprayed oil everywhere, but fortunately still 2 qts left in the pan. I suspect his compressor seized then, though now I can turn it over by hand (I don't mean just the pulley).

Instead of R-12, I refill mine with Duracool, a HC mixture (mostly butane). It is compatible with all oils and works slightly better than R-12. I'll let you read the crazy rants from people who have never used it. You must do yourself since the EPA sets bizarre rules for shops, and most shun it for other reasons. However, it is quite easy. To draw a vacuum, I just connect to the manifold of one of my gas engines to draw down to ~20" Hg, then switch to a Mighty Vac hand pump using valves. I can pump it down to almost a pure vacuum (~29" Hg) in a few minutes. I let it sit for 30 min, pumping a bit to eliminate the out-gassing, then hold several hours, before adding refrigerant. If too weak to use a hand pump, you can buy an electric vacuum pump for ~$300, or use the vacuum pump already on your 300D.

I too use duracool, although I'm terrible when it comes to putting vacuum on the system first or anything of that nature, because it all leaks out pretty quickly for me

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1982 300D Turbodiesel, daily driver. Mods so far: Fram 8038 paper filter, 4 brake light mod, Gen II w126 (front) rotors/calipers, boost turned up to 12lbs, non-egr manifolds, water/methanol injection, 4-speed manual
1980 300SD Turbodiesel, project car, nearly ready to hit the street

1974 240D, New paint

this is exactly why i cut the a/c belt with a knife yesterday. no need for automotive drama right now.

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Ben
1987 190d 2.5Turbo

I have to agree with all the naysayers here. if the belt is not on the compressor, it's VERY unlikely the compressor is functional.
if you grab the faceplate on the compressor, and can turn it, at least you know it's not siezed. to go further, requires cleaning, replacing the receiver/dryer and vacuum, then a recharge.
IF there is still R12 in the system (pressing on one of the shrader valves for a second with a small screwdriver should emit a puff of gas pressure) you would not need to drain and recharge, just add in R12. however... it's unlikely to be that lucky, or the PO would have done it.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

All that being said,

help is what we do here, so bring on the questions, and we'll help you get the system working in top shape!

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Thank you everyone for the feedback - all of it!!

I'm looking over everything. I just finished filter & oil changes...also put in new front brake pads and cleaned the banjo bolt related to the ALDA. I had some soot build-up...probably from Winter start-ups (replaced the glow plugs after about 2-3 wks of that.)

....now FINALLY, I can get back to the A/C and your input. Ben, I can definitely understand why you cut the belt.

Mach4, thank you for letting me know that the pulley spinning does NOT mean the compressor isn't seized.

I was also thinking that if the PO didn't replace the belt, that there probably IS a problem. You know I'm hoping for the best.

I will be back with some feedback/questions in a day or two.

Thanks again everyone!!

As VS indicated, you can at the very least see if the compressor is siezed by turning the forward most part in front of the pulley. This is attached to the compressor input shaft. It turns smoothly, but with smooth pulsating resistance, there is a chance that the compressor is okay.

If the belt is gone, the chance is very high that it was removed because of a bad compressor, but it's quick and easy to find out as described.

Test the compressor first, and then we can get on to the next step.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

Ok, I'm back again...longer than intended. Hopefully I can still get some advice to keep me moving along!

I guess before deciding which type of coolant to use, I'll do as VS and Larry suggested...determine my first step regarding the compressor condition.


This morning I spun "the forward most part in front of the pulley" of the compressor as suggested. I WAS able to spin this part (not the pulley) by hand. It spun easily (not freely) and smoothly.

This means the A/C compressor is NOT seized, right?

VS suggested the next steps: cleaning, replacing the receiver/dryer and vacuum, then a recharge.

What should I do for proper cleaning?

Also, I have assumed that the coolant leaked out. To check this I will take VS's suggestion and carefully press on one of the shrader valves for a second.

Honestly, I do not know where the shrader valves are, and I just searched an image to see what they look like. I'm a mechanically-inclined person, but still learning the mechanics! I'm figuring I will find this when I go back to the vehicle, but if it's tough to find, I'd love if someone can describe where to find it.

Thanks again everyone....