Dear jd620,

Hope you're well. I'll defer to Amarin, as to the proper lubricant. Soapy water should not be used to find a leak on a piping system, that has no pressure or is under vacuum. The reason - as you noted - is that with a vacuum, soapy water enter that system.

Soapy water should be used only for pressurized systems, where some pressure is known to be present. The reason: any gas escaping will form bubbles in the soap, so showing where there's a leak. If a pressurized system is not under pressure, soapy water is useless to show where there's a leak.

Thus, your comment that the system won't hold a vacuum for long enough to allow a search for a leak suggests that the leak must be very big. I'd guess that adding refrigerant with UV dye will reveal the leak, unless it is in the evaporator, which is enclosed by the surrounding housing, wherein is the heater core. Even so, if no exposed tubing or component shows any sign of leakage, then one could infer the leak must be in the evaporate.

I'll leave further analysis to Amarain.

Hope this helps.

Yours faithfully,

Spook