Thread: HyChill in 2.7 or 3.0

I've used HyChill in VAG Sanden variable displacement (and conventional fixed displacement of many different makes) compressors for years. The only possible thing I can think of is the hydrocarbon thins out the PAG oil to a point it loses lubrication, generates some Aluminium grunge that makes its way around to jam the valve. Actually, in most cases it's even mobilised the lubricant enough to staunch compressor shaft seal leaks that were prevalent with R134a.

Having said that, every system I've put HC in had a stuffed valved from r134a already. In most cases the HC extended the system life a few years before the valve needed replacing. Maybe it did that by affecting the lubricity of the oil, but I'd be surprised.

The recommendation is to remove/flush the PAG oil and replace it with a POA or Mineral oil if you are moving to HC's, but probably only because PAG is a **** lubricant that is horrifically hygroscopic. The only reason they use that crap is because it's one of the only lubricants that r134 will actually move.

Originally Posted by DiscoJeffster

Why not just get him to change it to 134 while he’s there and lose the guesswork?

He declined a request to charge the D4 in October because he doesn't know Land Rovers, so I will be attempting to get him to agree this time while on site. He may not come with the required 600g of R134a to spare or he may be too busy on the day to stay the extra time, but I will do my best to convince him that I need the Hychill replaced by R134a. I can show him live values with the IIDtool - I've read the manual (if all else fails then RTFM) and now have a favourites defined to get to the display quickly.

Originally Posted by Graeme

He declined a request to charge the D4 in October because he doesn't know Land Rovers

It is just a vehicle A/C system, same as any other modern vehicle. There is _nothing_ Land Rover specific in there. It's a Compressor, Condenser, Dryer, TXV & Evaporator (in that order). No different to anything else. Heck, swap the TXV for a capillary tube and it's just like your fridge. Just vac it down and drop the measured charge of gas in there.

The high side pressure sensor is there for protection only. Outside of protective extremes the displacement valve is controlled to maintain evaporator temperature, the high side pressure isn't really involved. No different to any Volkswagen from the last 20 years either.

I suspect that he hasn't worked on an a/c system in a modern vehicle and if not then I hope to educate him about the displacement valve. I consider that I now know enough about the D4's a/c system to get him to trust me. He only has to vacuum out the system then fill with the stipulated weight of R134a and the appropriate quantity of oil.

Be careful with the "oil" thing. Unless you've pulled out the compressor, condenser and evaporator and drained them into a measuring cylinder then you have very little idea how much actual oil is in the system. Most manuals will say, put oil in the compressor, install and run for x minutes, then pull the compressor and drain it. There will be x oil in the other components.

That was easy to do on old cars where getting the compressor out, or getting a dipstick into the top fill hole was easy/possible. Probably not so much on the D3/4. Provided you didn't completely flush all the old oil from the condenser (which you put in new) and evaporator, there should be enough oil in the new compressor. They come "oiled up". Usually the book says "drain the oil from the new compressor and only put back as much as you drained from the old compressor". Don't go adding a significant quantity unless you know you lost a pile.

Again, too little is always bad and too much is inefficient. To a point. Don't add oil unless you really know you need to.

I didn't drain the new condenser/dryer. The fitted plugs were removed once the condenser was installed and the pipes which had been plugged with clean rag were then quickly attached.

Considering what you wrote earlier about oils, I suspect that the oil added when the Hychill was installed might not be compatible with R134. Does this mean that the system has to be flushed before vacuuming?

Edit: When I released the Hychill prior to changing the valve, I released it slowly into a tall plastic jug so as to catch the oil, which wouldn't have been more than about 10cc.