Sanden Compressor Conversion - Hoses, Oil & Refrigerant - PeachParts Mercedes-Benz Forum

mach4 · #1 04-16-2013, 07:53 PM

While I'm waiting for my Sanden compressor to arrive, I'm trying to figure out the best way to go for the rest of the system.

Background: I'm installing a new Sanden SD5H14 compressor that comes with PAG pre-installed. According to the site, the dryer must be replaced and "the Expansion Valve, if equipped, should at least be inspected for proper operation if not replaced". Sanden only recommends PAG oil for their compressors. The compressor is going on an OM617 engine.

The chassis in this instance is a 380SL that came with a blown engine, so there is no way to ascertain the condition of the A/C system aside from inspection. The old compressor appears to be good (turns free, no gunk in the oil) and the old oil is clear. The fittings on the system have been changed to 134a-style fittings, but there is no sticker that documents a change from R12. I think I have to assume that the system was converted, likely not by a shop. I think I need to further assume that the system was not flushed and the majority of the oil is mineral plus whatever ester was added along with subsequent charges.

I know that it's best to change out the expansion valve, but in researching that process and looking at where the valve is, I'd like to avoid that if at all possible... for obvious reasons.

It's a nasty job.

So I'm going to take the chance that based on what I see, that the valve is ok, and am willing to risk needing to rip the dash apart and change the valve at a later time as well as do another charge if it turns out I'm wrong.

I'm assuming therefore that I've got at least some residual mineral oil in the system, and that there is probably some ester oil in the system as well. Since I can't fully flush the evaporator without removing the expansion valve, I'm pretty much stuck with using ester oil at this point. If I could reasonably flush the evaporator I'd go PAG.

I've also decided to use propane for my refrigerant - well actually EnviroSafe, so oil compatibility is not an issue. I've also decided that the risk of fire from a collision is a risk I'm willing to take, so at this point EnviroSafe is to be considered a given, not subject to debate. On a risk-reward basis, I'll be taking the risk.

So here's the plan.

Drain the PAG oil out of the compressor and flush it with ester oil. Add the recommended amount of oil to the compressor. Install a new dryer. Install new hoses from the compressor to the dryer and from the compressor to the existing hose to the evaporator. Leave the evaporator and expansion valve as is. Pull a vacuum and charge with the calculated amount of refrigerant.

Am I missing something obvious, or is there something else I should be considering?

This stuff is so complicated and if you read long enough you can find someone supporting any position. It's worse than the air filter debates, the oil debates, the oil filter debates, the coolant debates and the WVO debates combined

Please accept the two givens - EnviroSave refrigerant and no change of expansion valve.

Fattyman · #2 04-17-2013, 11:08 AM

If you change out the valve now you won't have to later!

daw_two · #3 04-17-2013, 11:30 AM

The FSM as I recall spells out how much oil to put back into the system when a component is being replaced. Since you replacing the compressore and the dryer, I'd put that much back into the system. Are you flushing the condensor?

In addition, you figure, you are going to have some residual oil in the compressor. I guess what I'm suggesting is, you won't need a "full" oil charge on your new, modified system.

Is a little too much oil better or worse than a little too much oil?
Does it even matter if the amounts are within 10%?
Does it matter if the amounts are within 20%?

I hope my contribution was worthwhile. I'm behind you by hopefully only a week or two on a similar conversion on my 1984 Light Ivory unique car.

vstech · #4 04-17-2013, 11:56 AM

Quote:

Originally Posted by daw_two

Is a little too much oil better or worse than a little too much oil?
Does it even matter if the amounts are within 10%?
Does it matter if the amounts are within 20%?

...

a little too much oil is worse than a little too little oil... but a lot too little is much worse than a little too little, and a little too much oil. and it's a little hard to tell when you have a little too little or a little too much or a lot too much...
so I flush it all out and put in the exact amount any time I do much a/c service...

WHIEW!!!
say that 3 times fast!

DeliveryValve · #5 04-17-2013, 12:19 PM

I wouldn't risk an unknown expansion valve. Curious, what is your plan of how to evacuate ES if you end up replacing Valve? Not many shops would evacuate that refrigerant.

mach4 · #6 04-17-2013, 01:19 PM

Quote:

Originally Posted by Fattyman

If you change out the valve now you won't have to later!

Good point, but if I don't change it out and it works, I won't have to change it until later...maybe much later, or with a little luck, ever.

Quote:

Originally Posted by DeliveryValve

I wouldn't risk an unknown expansion valve. Curious, what is your plan of how to evacuate ES if you end up replacing Valve? Not many shops would evacuate that refrigerant.

My plan is to cook hot dogs.

Since ES is mostly propane with a little isobutane, it will cook dogs really nicely. Now, if I decide that ES is just too expensive as a cooking fuel, my plan B is to rig up a Cheap Little Sucker to pump it out to a small propane tank, where I could actually reuse it by fabbing up an adapter.

Either way it won't see the inside of an A/C shop.

vstech · #7 04-17-2013, 01:25 PM

ES is a negligible carbon footprint gas *(1/1 I think...) and it is legal to vent it...
I would not pump it into anything... risk of explosion scares me. venting it into a hot dog broiler may be safe... may not...

either way, vent it outside, not in your garage!!!

Fattyman · #8 04-17-2013, 03:23 PM

I like grilled onions

mach4 · #9 04-17-2013, 03:49 PM

Quote:

Originally Posted by Fattyman

I like grilled onions

I can't believe an air conditioner thread is turning into a menu thread.

If my expansion valve turns out to be bad - I'll personally turn it into an adult beverage thread!

mach4 · #10 04-18-2013, 12:19 PM

In continuing the research and preparation for finishing the Sanden conversion project, I came across a very helpful document related to calculating the amount of oil to add to a system, based on the status of the system. It's shown as a file attachment to this post, or just click on the image below

The key data from the document is shown in the chart below:

In my case, I'm figuring I've got 25ml in the HP line (since I'm replacing a small part of the HP line), 30ml in the LP line (since I'm replacing about half the LP line) and 89ml in the evaporator, or a total of 144ml trapped in unreplaced parts of the system. Since that's less than 177ml, that's the number I need to use.

Since the new compressors are charged with 296ml of oil, I'll need to add 152ml of oil to the compressor after flushing it (296-144).

compu_85 · #11 04-18-2013, 01:55 PM

Does the expansion valve have to be removed to flush the system?

-J

mach4 · #12 04-18-2013, 02:27 PM

Quote:

Originally Posted by compu_85

Does the expansion valve have to be removed to flush the system?

Yes it does. The expansion valve is essentially a tiny orifice that restricts the flow of refrigerant as it enters the evaporator reducing the temperature and pressure in the process.

So there's just no way to flush the evaporator without removing the expansion valve.

Air&Road · #13 04-18-2013, 02:50 PM

Quote:

Originally Posted by vstech

...

a little too much oil is worse than a little too little oil... but a lot too little is much worse than a little too little, and a little too much oil. and it's a little hard to tell when you have a little too little or a little too much or a lot too much...
so I flush it all out and put in the exact amount any time I do much a/c service...

WHIEW!!!
say that 3 times fast!

Too little oil wears out compressors. Too much oil destroys compressors.

I too believe that if you can flush and THOROUGHLY remove the flushing agent you'll be okay.

compu_85 · #14 04-18-2013, 02:55 PM

Thanks. If you've gone through the bother of removing the valve, you may as well replace it I suppose.

-J

mach4 · #15 04-18-2013, 03:15 PM

Quote:

Originally Posted by compu_85

Thanks. If you've gone through the bother of removing the valve, you may as well replace it I suppose.

The ONLY reason I'm not replacing the expansion valve and flushing the lines and evaporator right away is that the expansion valve is in a place that makes the choice of replacing the valve or sliding down a 50ft razor blade into a pool of Iodine pretty much a flip of a coin of which is worse