| NJGuy |
Earlier this year my A/C system had started to develop a "hissing" noise while in operation. It only happens when the HVAC system is on "Auto" or when the A/C is "On".
I usually drive with the A/C off but with the vent fans running, so I'm pretty sure that it's not a problem with the fan. The hissing noise is somewhat cyclical, but I think it varies depending on how frequent the A/C cycles on and off. I could hear the compressor/cooling fan cycle on for a while, and then when they shut off the hissing noise starts. From what I've read so far, the noise is probably the expansion valve. However, since I don't recall the noise happening prior to this year, I do suspect that there is some sort of problem. I'm guessing that my refrigerent is a bit low. The Pilot still cools down, but do I percieve that the cooling performance has faded a bit.
I took a photo of of the compressor last weekend while doing maintenance. It looks like there's a light coating of oil. I know that the oil could come from anywhere, but I'm guessing it's a sign of a small leak of refrigerant nearby. I plan on making an appointment with the dealer on Friday to have it checked. In the meantime, I want to stop by the local auto parts store and buy a recharge kit to see if it helps cure the problem. I figure I could at least try a band aid fix before shelling out money to the dealer. I do have a few questions before I proceed.
1. Can someone confirm that what I've wrote above is correct or makes sense?
2. Has anyone else here tried one of the recharge kits and would recommend them? How easy or hard are they to use?
3. Is the opening for discharging/refilling the refrigerant on the passenger side of the engine bay with the blue cap?
4. Does anyone have the specifications for the Pilot for the proper pressure for a fully charged system of refrigerant?
Thanks in advance.
Here's the photo I took. |
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| phil17 |
My family has a 2003 Pilot with around 80,000 KMS on it. the AC has been making a "hissing" noise behind the passenger glove box since Day 1. I have always though it was weird but the dealers always told me its normal (even though i've never heard it on any other car before).
last summer the AC stopped pumping cold air and they said they found a leak which was patched up for a couple hundred dollars including a recharge. The car still makes the hissing sound so i'm thinking its normal because i originally though it would stop making the noise after the fix. Hope it works out for you though :) |
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| N_Jay |
Many AC systems make a slight hissing sound as the cycle on and off.
A system that has never does it and starts is usually a little low on refrigerant. |
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| NJGuy |
Thanks for the replies.
In first two years of ownership, I never noticed any hissing noises when the A/C was on (including the Auto setting). If there was any hissing before, it was never loud enough to notice and it is much more pronounced now.
I picked up some R134 and will try to refill the system. I chose the cans that had no additives. Has anyone had any experience or knowledge regarding the refrigerant products with "Stop Leak"? My co-worker recommended to avoid using these types of products because they just add extra gunk to the system. However the companies claims in their "marketing" that the product will not clog up the A/C system. |
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| N_Jay |
Honda AC systems are VERY susceptible to over-filling.
An overfilled system is likely to destroy the compressor.
If it is working fine, I would ignore the noise.
If it is not cooling well enough, I would have GOOD AC shop test and refill the system. |
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| belundy |
First, find out if the oil on the compressor is motor oil or compressor oil--the latter smells different. If compressor oil, have it looked at. Otherwise, proceed.
The hissing noise is probably coming from the expansion valve, located under the dash. If the hissing is mild and lasts only a few seconds here and there when the compressor is running AND the cooling performance is fine, then leave it alone.
If this hissing lasts longer or is continuous when the compressor is running, then it is low on refrigerant (likely) or the valve is malfunctioning (less likely).
If you are confident of being able to add only a few ounces of R134 at a time, then add 2 ounces and run it for a few days. If it isn't better, add 2 more. If that doesn't reduce the hissing as described above, take it in an have it looked at. N-jay is spot on--overfilling these newer systems is begging for a compressor failure.
Note: purge the fill hose of air before you hook it to the low side port--these systems will lose cooling performance quickly with a small amount of air in them. |
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| belundy |
Oh, don't know about cap color, but the refill port is the larger hose that runs COOL to the touch. Plus, the low and high side R134 fittings are different--consumers can only buy refill hoses with low-side fittings.
Stay away from products with sealant--it may clog the receiver, condenser, evaporator and cause the expansion valve to malfunction. Same advice for "blended" refrigerants that claim colder temps or higher efficiency.
The only valid additive is dye so that you can find leaks. |
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| tangotango99 |
quote:
Originally posted by N_Jay
Honda AC systems are VERY susceptible to over-filling.
An overfilled system is likely to destroy the compressor.
If it is working fine, I would ignore the noise.
If it is not cooling well enough, I would have GOOD AC shop test and refill the system.
AS usual you are right on the money. |
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| NJGuy |
The oil on the compressor looks a bit thinner than motor oil, but I did not note the odor when I looked at it; I'll try to swab some off later and get a whiff. It did look like the oil was isolated to the compressor but I'll check again.
I wouldn't say that the hissing noise is mild; it is quite noticeable and I don't recall hearing it in the past. But it only lasts probably no more than 8-10 seconds at a time. I don't believe it happens while the compressor is running. Cooling performance seems slightly reduced but its hard to compare between this year and last year and the hot spell we had this weekend didn't help. Like most people, I don't keep a daily log of daily temperature, humidity, & cooling performance :) . I didn't think it was a big deal, but once my wife noticed the noise yesterday it became a "problem" that needs investigation & fixing.
The refrigerant I picked up was the DuPont R134a; no dyes, leak stoppers, or oil added.
If I had a good in-line pressure gauge hooked up to the fill hose, would that hugely help in preventing overfill? I couldn't find any refill kits at the store with a gauge that didn't include the refrigerant with additives. I also saw this in the store, but didn't think I needed it:
http://www.efproducts.com/proddetail.php?prod=425
It also seems like some of you have or know of someone who's overfilled a Honda A/C system, resulting in a ruined compressor... anyone care to elaborate? |
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| rocky |
quote:
Originally posted by N_Jay
Honda AC systems are VERY susceptible to over-filling.
An overfilled system is likely to destroy the compressor.
If it is working fine, I would ignore the noise.
If it is not cooling well enough, I would have GOOD AC shop test and refill the system.
Overfilling ANY ac system, home office or car will cause the system to fail prematurely. |
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| N_Jay |
quote:
Originally posted by NJGuy
It also seems like some of you have or know of someone who's overfilled a Honda A/C system, resulting in a ruined compressor... anyone care to elaborate?
Refrigerant is measured in OZ or LB of product.
The PSI on the high and low side are an indication of how the system is working but a poor indication of proper fill.
The systems are very small so there is very little room for overfilling without having some residual liquid on the vapor side.
The compressor is incapable of compressing any liquid, and any attempt to will cause severe damage. |
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| belundy |
Well, can't say I've heard expansion valve hissing right when the compressor disengages or after.
The compressor oil will look and smell differently than engine oil, trans or power steering fluid.
A low side gauge can provide a general indication of charge, however an exact charge for these small capacity systems without sight portals is done by refrigerant weight/volume.
A concurrent high & low reading can tell you a lot. A low only reading can still be informative. AutoZone in Texas will rent or let you borrow a set of gauges. See graphic for "normal" readings.
a couple of basic tests might help;
- TEST CONDITION: with A/C on manual and highest blower setting, lowest temp, RECIRC, front doors wide open, raise engine RPM's up to 2500 or so. If compressor kicks off, then refrig charge is low--how low, you can't easily tell.
- the low side hose & pipe should be cool to cold with mild to moderate sweating (depends on humidity) . If the hose or pipe has frost anywhere on it, you have low refrig, or an internal restriction.
-The high side pipe should be hot--probably too hot to hold onto.
- if it passes both touch tests, the system probably has nothing seriously wrong with it. Next....
- if you have a low side gauge, with the test condition above and ambient temps in the 90's, it ought to hover between 30 to 50 psi. Upon compressor engage, if it quickly drops to the teens or lower and the compressor kicks out, you've probably verified low refrig level. You could then add a few ounces, check the pressure under test conditions and keep adding two ounces at a time until the compressor stays engaged and the pressure stays between 30 and 40 psi. Check the hissing--I'll bet it has lessened or is gone.
If you have added 8 ounces and it hasn't improved, STOP and take it somewhere.
This is not an exhaustive guide...
last, if it starts hissing again before next summer, you have a fairly fast leak--need to find it. |
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| sblvro |
| most of these cans that are sold retail have less pressure compared to an industrial type tank where you really have to worry about overfilling them. unfortunately these cans doesn't come with any pressure gauge and the only piece you can buy is a tap and hose connector. against most of the advise here, I will just try and connect and fill it. In my "limited" experience, there should be no ill effects unless you connect it to the high side and the can might explode causing harm. I have converted my mitsubishi galant sigma with the R134 from R12 with no problems. I just replaced the seals(per instruction and everything works normally. It had the original oem compressor still and at 215,000 miles with no failure. It also has auto climate control. I had to replace a leak on the evaporator though. |
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| N_Jay |
quote:
Originally posted by sblvro
most of these cans that are sold retail have less pressure compared to an industrial type tank where you really have to worry about overfilling them.
Hu? Nope!
Since the can is filled with liquid above its vapor pressure, the pressure in the can is defined by the temperature.
quote:
Originally posted by sblvro
unfortunately these cans doesn't come with any pressure gauge
Maybe because it would do no good??
quote:
Originally posted by sblvro
against most of the advise here, I will just try and connect and fill it.
Yes, I would guess you would give advice against most here, even if it is based on a misunderstanding of the principles in play.
quote:
Originally posted by sblvro
I will just try and connect and fill it. In my "limited" experience, there should be no ill effects unless you connect it to the high side and the can might explode causing harm.
Lets keep that "experience" limited, because the "understanding" certainly is.
If you somehow actually get the can hooked to the high side of a modern system you have really gone above and beyond.
If the can does not explode when hooked to the high side, you have a problem.
quote:
Originally posted by sblvro
I have converted my mitsubishi galant sigma with the R134 from R12 with no problems. I just replaced the seals(per instruction and everything works normally. It had the original oem compressor still and at 215,000 miles with no failure. It also has auto climate control. I had to replace a leak on the evaporator though.
Ah, the good old system with lots of reserve capacity.
They are very tolerant of over filling and worked fairly well slightly under-filled.
All you needed was a sight-glass on the dryer to get the right amount of refrigerant.
P.S. Sorry about the attitude, just having a little fun at the expense of sblvro |
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| sblvro |
quote:
Originally posted by N_Jay
Hu? Nope!
Since the can is filled with liquid above its vapor pressure, the pressure in the can is defined by the temperature.
Maybe because it would do no good??
Yes, I would guess you would give advice against most here, even if it is based on a misunderstanding of the principles in play.
Lets keep that "experience" limited, because the "understanding" certainly is.
If you somehow actually get the can hooked to the high side of a modern system you have really gone above and beyond.
If the can does not explode when hooked to the high side, you have a problem.
Ah, the good old system with lots of reserve capacity.
They are very tolerant of over filling and worked fairly well slightly under-filled.
All you needed was a sight-glass on the dryer to get the right amount of refrigerant.
P.S. Sorry about the attitude, just having a little fun at the expense of sblvro
you forgot to take your medicine again today huh! |
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| NJGuy |
Again, thanks for all the replies. They are quite helpful and provide some good insight.
I don't have much time available to look at my Pilot, but I'll at least check the oil residue. I definitely know how motor oil smells, and tranny fluid has a "sweeter" scent similar to VTM fluid. I'm not sure how the power steering fluid smells, but I can always pop open the reservoir :) . I'll also observe compressor behavior and do the touch tests. If the results show that the system seems to be working normally, I'll probably hold off on doing a recharge.
If it tests hint at a low refrigerant level, I may try to do a recharge. The Autozone website doesn't show A/C pressure gauges in their tool loaner program, so I'll have to call the local store to find out if they have them. If I can't get my hands on a decent pressure gauge, I'll refrain from performing a recharge.
Time and weather may be a factor for me as well. There are thunderstorms forecast here for the next few days and my appointment with the dealer is Friday. It looks like I'll be paying the service dept. for a little bit of peace of mind. We plan on taking a weekend trip to VA with the toddler and grandparents in tow in a couple of weeks; a suspect A/C system now that fails at that time would make things unpleasant to say the least. |
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| NJGuy |
During my lunch break I ran the simple tests that belundy recommended.
1. I tried to smell the oily residue that I saw on the compressor. It had no discernable scent or odor. I got a good amount of it on my fingers and the only thing I could conclude was that it smelled like normal engine gunk that I typically get on my hands and arms when working in a car's engine compartment. By the way, now I know what Honda power steering fluid smells like: melted plastic.
2. Ran the A/C on at lowest temp setting with highest fan setting, front doors wide open. Ran engine up to ~2500 RPM. Compressor seemed to stay on. Condenser/radiator fan definitely stayed on. The Pilot's outside temperature display said 85F, weather.com says 88F, 47% humidity.
3. Did the touch test. Low pressure side was cool to the touch. The rubber hose did not feel especially cool, but maybe because it was rubber. The metal pipe on the low pressure side was cooler than the rubber, but not cold enough to condense the humidity in the air or frost up. The metal line on the high pressure side was pretty hot after I touched it for about 1-1.5 seconds.
4. I called Autozone. They don't loan out A/C pressure gauges, they only sell them.
Based on all that, it looks like I won't be doing the recharge. I'm not sure if I'll still bring the Pilot to the dealership so I'll consult with my wife and see what she thinks. I'm starting to have a feeling that this "problem" is just an issue of perception. I guess if my A/C is working ok, I should be happy, right? :mblah: |
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| belundy |
N-Jay can confirm if his meds kick in, but I'll venture the system is slightly low on refrig given the feel test, compressor stays engaged, cooling performance is adequate, but the continuous hissing. More annoying that any pending doom.
I thought Walmart sold a kit with a can of R134 and a small gauge, somewhat calibrated with psi markings (not low, good, high). The running pressure measurement will confirm whether the charge is low and safe to add up to 6 oz.
The overfill warning is often for old timers who used to "add a can" (12 oz) to their R12 system that held 4 or 5 pounds to begin with, just for good measure.
The compressor oil--it is very thin viscosity-- may have lost its scent after being out for a while. Blip off a quick shot of R134, sniff and rub between your fingers the spray for ref. |
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| NJGuy |
All of the R134 kits I saw with the built in gauge (w/ psi markings) said that they included most of the additives (stop leak, oil, performance enhancers, dyes etc.) so I didn't get them. If I have a chance I'll swing by Wal-Mart but I doubt they'll have anything that I'm looking for.
I may go back to the auto parts store (Advance auto parts) and pick up that electronic tool I saw (link in previous post), since its hard to find a cheap but effective gauge. I think it was around $20 or so. There's also an instructional video on that site. Seems to be an almost idiot-proof device.
quote:
Originally posted by N_Jay
Turn the radio up!
I found that a bit funny, because my wife & I used to always do that when listening to music. I guess we've "matured" a bit and turn the volume lower now and don't listen to the radio as much. :)
Anyway, just wanted to let you all know that I appreciate the information you have given me so far. I'll be sure to update everyone with what I do and what happens next. Stay tuned. |
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| sblvro |
quote:
Originally posted by NJGuy
Stay tuned.
? radio! |
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| belundy |
I see N_Jay is still coming out of his funk...
hmm, I've also seen in the past the hose, gauge and the can adapter for around $15--Walmart, Autozone, Carquest-- but haven't exactly paid attention to the offerings in recent years.
I looked at the smart charge link--it could be handy, but is just measuring system pressure and ambient temperature to determine charge--all that can be done with the chart I provided and an reasonably accurate outdoor thermometer. I personally don't care for go/no go status but an actual pressure reading.
Have fun. |
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| NJGuy |
I also would prefer to have an actual psi reading; but given my time constraints and tools available I picked up that electronic A/C smartgauge to do the job.
When I hooked it up to the A/C low pressure line, the "low charge" indicator light flashed. So basically it confirmed the diagnosis that you guys gave. After a couple of short bursts, the "proper charge" green light started blinking. I didn't want to overfill so I unhooked the unit after that.
I tried to replicate the hissing noise. Since the noise would also come on when the A/C was turned off, I shut off the system. I swear I didn't hear it anymore.
I was talking to my co-worker about re-charging and he said he thought he saw some cans at wal-mart w/ the built in gauge but no additives. Unfortunately, I didn't have a chance to go there.
Shhhh... don't tell the EPA what I did. First of all, I'm not "authorized" by them to handle and discharge refrigerant. There was alot of R134a left in the can, so I just let it all evaporate into the atmosphere. I don't want to be paying any fines :D .
Thanks to you all for your help. It's what makes this site so great :29: . |
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| NJGuy |
I must have jinxed myself with that last post :( . The noise has returned. The Pilot is at the dealer as we speak.
I do feel good that I at least put in an effort to try to resolve the problem myself. But now is the time for me to follow N_Jay's advice by having a professional take care of the problem.
Again, I'll update everyone with the next chapter in this saga. |
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| NJGuy |
For anyone who cares, here's what happened.
The dealership confirmed the low refrigerant level. They evacuated the old refrigerant and refilled the system with "R134-32" (32oz?) and a UV leak detection dye. They did not find any leaks though. They also said they cleaned the drain in the vent system. Cost about $160 in all, of which $50 went to the refrigerant.
The noise was gone when I took the Pilot home and on a 2 hour round trip drive on Saturday. I thought I faintly heard the noise again on Sunday afternoon, but I'll continue to observe it. I thought that they would have totally solved the problem by finding a leak, but the leak might be so slow that it'll take a little while before it shows up. In the meantime, I'll be a bit paranoid listening for the noise while driving around. |
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| belundy |
thanks for posting the solution.
Remember that R134 systems have been known to "hiss" slightly once in a while, but it shouldn't be very loud or last long. I noticed just tonight that my Toyota Highlander hissed a few seconds; had the radio off and fan was at lowest speed. Seemed to be related to low cooling demand. |
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| tangotango99 |
quote:
Originally posted by sblvro
most of these cans that are sold retail have less pressure compared to an industrial type tank where you really have to worry about overfilling them. unfortunately these cans doesn't come with any pressure gauge and the only piece you can buy is a tap and hose connector.
Ambient temperature control pressure in refrigerant cans or tanks. |
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| N_Jay |
quote:
Originally posted by tangotango99
Ambient temperature control pressure in refrigerant cans or tanks.
Yea, I kind of told him that a few posts up.
Some people just don't understand everything they "know"! :rolleyes:
;) ;) ;)
Careful, he will start suggesting Meds for you! |
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| sblvro |
quote:
Originally posted by tangotango99
Ambient temperature control pressure in refrigerant cans or tanks.
yup, got it. it was just a knee jerk spur of the moment response at that time.:o |
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| belundy |
Well, he is right in principle, even if inarticulate with his comments. A 12 oz can does drop in temp & vapor pressure quickly after the valve is opened, where the small fluid volume/mass cools rapidly; why some instructions have you hold the can in a pan of warm water to keep vapor pressure up.
The 20lb canisters maintain much higher vapor pressure for a number of minutes, and indeed deliver refrig much faster, and *really* fast if the canister was left in the sun or hot storage area. |
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| N_Jay |
quote:
Originally posted by sblvro
yup, got it. it was just a knee jerk spur of the moment response at that time.:o
As was this?:rolleyes:
quote:
Originally posted by sblvro
you forgot to take your medicine again today huh!
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| N_Jay |
quote:
Originally posted by belundy
Well, he is right in principle, even if inarticulate with his comments. A 12 oz can does drop in temp & vapor pressure quickly after the valve is opened, where the small fluid volume/mass cools rapidly; why some instructions have you hold the can in a pan of warm water to keep vapor pressure up.
The 20lb canisters maintain much higher vapor pressure for a number of minutes, and indeed deliver refrig much faster, and *really* fast if the canister was left in the sun or hot storage area.
But the issue is not the pressure under which you deliver the product, it is the total volume of product in the system.
You can overfill any AC system with the smallest can, if it does not need more product. |
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| belundy |
All you say is true, but his context was how easy it was to overfill, and with 20lb canisters, it is quite easy to deliver a pound of refrig in a very short time and not realize you've way overfilled a small system, where the 12 oz can take 4 or 5 minutes or longer to empty, and you can see the sweat line to gauge aprox how much charge you delivered.
Obviously an academic for the backyard mechanic who can't get the 20 lb canisters, but thought is was interesting. |
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