2004 Toyota Sienna Van, a/c has been getting progressively less cooling, obviously a slow leak in the refrigerant.Two questions, 1- what type of refrigerant is used, two- does it have a sight glass on the low side, and if so where is it located. I couldn’t find it on a rather hasty look-see. One more question, what is the proper lowside pressure range? Thanks, Marty


It uses R134 and while I can’t say for sure on this model, my feeling is that it does not have a sight glass. Sight glasses have just about disappeared from all makes of cars.

I put more credence in pressure readings and do not know what the proper low side range is. That can vary depending on ambient temperature, humidity, RPMS, fan speed, etc., etc. At around 1500 RPM one could probably figure on 35-40 PSI - depending.

Some refrigerant loss is normal over time and since the vehicle is about 5 years old it’s probably due.
One thing to look at closely is the service fittings; both high and low side. These can be prone to leakage.
Also inspect the caps for the fittings. They have small rubber seals fitted and these help to stop slow leaks from the fitting Schrader valves. Sometimes when the caps are removed the rubber seal falls out and this may not get noticed. Hope that helps.

Maybe the best bet would be to take it to a A/C professional who can look and correct the leak and properly charge it using the proper gauges, or if necessary, to totally evacuate it and recharge it.


If it has a sight glass, Toyota puts theirs on the accumulator/filter, typically located near the condenser in front of the radiator on the high-side line. Nice thing about the R-134a ports is they are hard to mix up. The high side port is significantly larger than the low side port, and most recharge connections will not come close to fitting on the high side. If you have a slow leak and will add R-134a, consider adding some compressor oil. This tends to leak out through the slow leak, as well.


i will take a look at the fittings.and the rubber seals.andthe schradder valve thanks for the advice


Replace your drier reciever/accumulator every 4 years. Corrosion (moisture in refridgerant) is the largest cause of AC system leaks