Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
21
Lowe’s or Home Depot sell pipe insulation tape, a black foam tape about 2" wide that is peel-and-stick. You can use that wherever you can get it in there, but that area around the expansion valve is fiddly at best.
The fluid inside the pipe is at some temperature, and the air in the engine compartment is at some other temperature – probably about 100 degrees hotter! Without insulation, the wall of the pipe itself will have some temperature gradient across it, and there will be a boundary layer of air around the pipe that will also be a bit cooler than the rest of the engine compartment, but any sensor strapped to the side of the pipe is likely to be many, many degrees warmer than the fluid within the pipe. A/C performance will suffer in a big way. The insulation around the sensor is intended to keep the engine compartment heat off it so it will read that much closer to the actual temp of the fluid in the pipe. It is important.
The caps do nothing, or very close to nothing to slow down a leaking shrader valve. Perhaps on a home condenser unit where metal caps are used with o-rings, but I’ve never seen a car use one.
Perhaps it’s cause if a cap has pressure behind it in a car, it can cause safety issues? At home it’ll fire up and it’s over.
In any case, if you’re relying on a cap to help your AC to maintain pressure, you’re gonna be disappointed….and sweaty.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
24
Worked on my '83 for years. The Schrader worked fine for charging, but once the hood was down and the car was being driven, apparently the engine vibrations caused the Schrader to leak. Installed the bolt, O-ring and washer, and it never leaked again. IMHO, that scheme is far more reliable than a Schrader.
The best place to judge how well your A/C is working is a thermometer placed at the central air vent. As far as the expansion valve is concerned, this is how it works. It is connected to the inlet of the evaporator and controls the flow of refrigerant by sensing the temperature of the refrigerant leaving the evaporator, using the bulb clamped to the outlet. Not enough refrigerant = poor cooling, and too much refrigerant = really poor cooling.
If the insulation around the sensing bulb allows engine heat to get to the bulb, the bulb “thinks” that more refrigerant is needed, and opens up the expansion valve accordingly. Excess liquid refrigerant entering the evaporator floods the evaporator, and the system stops working, and cooling your car. Hope that helps.
