_deleted

I'll try to be brief.

On really hot days with my AC on, my car would intermittently bog VERY noticeably (almost like a small parachute was deployed and released) on the freeway and made a weird noise less frequently, but consistently that came from the passenger side foot well. It did this for a few months and now the AC blows hot air and makes a constant noise from the passenger foot well.

I found this on another website (sorry for linking offsite) and his description of the noise (although I wouldn't say it's a squealing noise, more like a dull grinding/growl) matched fairly closely so I bought everything listed below to hopefully fix my problem. Because I've already paid to evacuate the system and I don't want to have it done again and waste money on more refrigerant also, what I want to know is, should I replace anything else while I have everything pulled apart and before I charge the system again?

I'm mainly curious because the thread doesn't say anything about the severe bogging, so I'm not sure what can cause it to be this bad. I know the AC robs the power a little, but it's VERY VERY noticeable. Bogging and noise stopped immediately after AC was turned off too. Any advice on what other parts of that main blower/evaporator assembly I should look at so I don't have to waste time and money later.

Also, probably not important, but occasionally (maybe once a week), I would get the "mist" he described, but after a bit of searching most people think it's just a natural byproduct of cold air hitting hot air, don't want to leave anything out in case it might be relevant lol

Parts/Misc
- Expansion valve
- Receiver/drier
- R-134 refrigerant (w/out additives)
- PAG 46 lubricant

Tools
- manifold gauges
- vacuum pump

Thanks for any and all input guys!
Brandon

acuratech

From your description, I would have a really good look at the compressor. Expansion valves usually make a squeak/squeal, not a grinding/growling. And if the cars really is bogging down more than it should with the compressor on, a compressor could make it feel that way.
But other than that, your list of parts and tools seems adaquate. If you can get them, I'd replace the sealing o rings at each connection you have apart. Almost always they can be reused if you are careful and keep them clean and undamaged.

_deleted

Thanks for the info! I was really hoping it wouldn't be the compressor because that's at least another $350. If I pull the compressor, what should I be looking for?

Also just remembered that I should have mentioned that when the guy evacuated the system, he say it was probably overcharged. What sort of problems could have arisen from that? The last time any refrigerant was added was early July and it was still operating, although with the passenger foot well noise and bogging when the outside temp was over 85 degrees or so.

Not sure if that helps, just forgot to add that info in my initial post.

Gregg Lee

To diagnose and work on A/C you need a gauge set, vacuum pump, UV light to find leaks, etc. And knowledge. A/C is pretty much the same on every car since R134a came in. Some details vary, but diagnosis is similar. This is one case where you don't need anyone with in depth knowledge of the S2000.

Your best bet is to go to a competent A/C service place. They will test the system and diagnose for a reasonable fee (usually waived if you hire them to fix it) and you will know exactly what you are facing. No chasing false leads and buying parts you don't need.

Getting a recommendation for "competent" is the tricky part.

Gregg Lee

I don't remember if the S2000 has a high pressure cut off sensor. If so it will cut off A/C when system pressure is too high. (Almost all cars have a low pressure cut off sensor, to prevent running the compressor when "dry", but not all have high.) Overcharge leads to over pressure on the high pressure side of the circuit. Can fail seals. Can also increase torque required to turn the compressor, thus slip belt - until the seal fails and releases the freon.

You check freon charge from pressure using a pressure gauge. Correct reading varies with ambient temperature. (Table comes with the gauge set.) There is no "probably" or complicated deduction.

If you have to add freon regularly, the system has a leak somewhere, which generally point to some other failure. My cars go years without adding any. And I live in central Texas, where A/C gets a workout in the summer.

cosmomiller

I also am suspicious of the compressor. From your description, it is having issues rotating when the electromagnetic switch is on. Its not unheard of for the compressor to go. Yes, you are going to have to refill the thing if you replace but you can do it yourself. Call around (include the dealer) to see what the cost is to R and R, remove and replace.

Gregg Lee

OK, I read right past the part where you already started pulling parts out before you knew the problem. Definitely check the compressor. Assuming it doesn't grind obviously when you turn it and pieces don't fall out, take it to an AC shop to have it checked.
You will want all new seals for all connections. Aluminum tubing and connectors are easy to twist and bend. Always use backup wrench so the parts themselves never bear the torque. The existing leak might be in hose or tubing, so have a source in mind. I assume you have an A/C manual? If you do have a leak, you may need freon with UV dye and a bright UV light source. Still it can be difficult.

_deleted

I haven't pulled anything yet. Still waiting to get a little more info about what I should be looking for WHEN I pull the compressor and blower/evaporator unit. Cracked this, fried that, loose this, etc. As per the service manual (pg21-46), I'll be checking to make sure the clearances are good among other things.

Any common malfunctions to look for and anything that would be related to the symptoms I described. I will definitely turn the pulley by hand to check for smoothness.

Also, I'm not sure there was ever a leak, even when it was overcharged in early July. My dad was charging his system and I mentioned mine wasn't as cold as it usually is and he opted to add some more to mine while he was at it and I didn't know enough to stop him. Lesson learned I guess. If anybody is going to break my shit, it's going to be me lol

Gregg Lee

The obvious thing that would bog the engine is the compressor. It's the only moving part in the cooling system.

Without checking the manual, I could speculate one other thing. If the filter (just upstream from the evaporator) is blocked, then pressure would built, bogging the compressor and thus engine, until the high pressure cut off sensor, if there is one, turned off the compressor. In this case you would expect the bogging to cycle as the pressure builds, cuts off, pressure slowly drops as high and low side equalize, compressor kicks back on, repeat. If the filter is blocked, no flow so no cool. If the filter is blocked, the trash came from somewhere, and the obvious source of the trash is the compressor.

I'll have to check the manual to see what desigh the S2000 actually has.

A?C can be frustrating. If the system is closed up, I still think your best bet is to go to an A/C shop for diagnosis. Alternatively get an A/C manual that has through diagnostic procedure. I have an old Haynes A/C manual that has worked well enough for me. Hopefully there is a more recent update. System pressure readings while the system runs and cycles, output air temp under different fan speeds, and system behavior (e.g fast cycling) will usually lead you right to the problem. Locating a slow leak, if there is one, may take UV dye, a shop quality UV light, and a practiced eye, especially if it is the compressor.

Gregg Lee

OK, I looked at the manual while I had it out working on my own puzzle.

The compressor has a mechanical high pressure relief valve. One way, dumps to atmosphere. But should prevent overpressure.

Car does not have a high pressure cutoff sensor, but it does have a compressor high temp cutoff sensor, which accomplishes the same thing indirectly, could also cycle as on and off, fairly slowly, since the trip will probably not reset until the temp is well below the original trip temp.

And S2000 does have a traditional expansion valve rather than an orifice tube (which includes a filter screen). So a blockage could be in the expansion valve itself.