What's causing o-ring leaks on my '04 Frontier?

[Q451990]

New guy here chasing his tail and writing a book.

So I've had a few years of trouble with the A/C on my 2004 Nissan Frontier. First it was an o-ring on the suction line at the compressor, then a liquid line leak, then the dual pressure switch failed closed, and I blew a charge out of the relief valve on the new liquid line. Then the compressor started leaking at the big o-ring where the two halves of the housing fit together - presumably from the high pressure event. I tried pulling that apart and replacing it's gasket twice, but no luck.

I finally had a "f-it" moment last summer and replaced everything, compressor with a new Valeo, condenser, evaporator, expansion valve, everything. I flushed the lines that were left, pressure tested it with nitrogen using "tightness test" on some Fieldpiece gauges, pulled a really deep vacuum to under 100 microns - and it ran wonderfully all last summer and through the winter.

Fast forward to about a month ago, and it started not cooling so well again. I found two leaking o-rings on the suction flex hose ends. This was the only factory part left, so I ordered a new one, a fresh bottle of PAG46 oil, and yet another drier. I installed those today, filled it to 150 PSI with nitrogen, and had a pretty fast leak. Found it with an ultrasonic leak detector at the condenser where the small metal tube leaves the condenser to make it's journey over to the evaporator. So three blown o-rings. I couldn't see any obvious problems with the o-rings I removed.

I'm at a loss! At this point I've replaced just about everything - be it with Chinese parts from Rock Auto - but that's all that's available for my almost 20 year old truck. Factory parts from Nissan are long gone. So what could cause o-rings to leak? I found one post somewhere where someone blamed blown o-rings on his Frontier on high head pressure caused by a bad fan clutch, but the truck itself is cooling fine. I've let it idle in the sun on a 90 degree day for 10 minutes, and it keeps the engine at about 180 degrees. Besides, wouldn't the newish dual pressure switch protect the system from high head pressure anyway? I know it cycles on and off, but I haven't taken pressure readings yet. I'll do that tomorrow when I recharge it - again.

Any thoughts would be greatly appreciated!

[Cusser]

Wow.

I've had a 1998 Frontier since 2004 (273K miles) and a 2004 Frontier since 2011 (116K miles) and am in Phoenix AZ, home of the 119F July temperatures. So I will relate the complete AC histories of these trucks since I've owned them (and I'm not aware of any AC issues with either before I obtained them).

1998:
One nice 119F day driving 100 miles from northern AZ in 2017, I developed a pinhole in the rubber part of the high pressure line, at a curve/bend. Nissan had discontinued this part, but there is an aftermarket line available, so I got that and installed it. I also replaced the fan clutch (lifetime warranty) that was bad at that time. After evacuation and R134a fill, has been fine since.

I replaced the fan clutch again in 2022, they seem to last about 6 years here.

2004:
The compressor seized up driving to California (vacation) in 2018 in Gila Bend AZ, but it was only 103F that morning. Once back, I installed a brand-new (not rebuilt) compressor, and new condenser with drier (parallel flow condensers cannot be flushed properly), and backflushed the high pressure lines with solvent. Other than the compressor and condenser not arriving with any O-rings (cost savings program), installation was straightforward. So I had to buy an NBR/refrigeration O-ring kit; after evacuation and R134a fill, has been fine since.

I replaced its fan clutch in 2022 (lifetime warranty).


Both my Frontiers are 4-cylinder, 5-speeds, but the AC on a V6 2004 would share most parts. And both cool great even in Arizona summers.

Rock Auto is just a reseller and typically offers several brands of a part; and most auto parts places sell the same stuff, and most stuff is made in China these days due to lower labor costs and pretty-absent pollution controls.

[Cusser]

I found one post somewhere where someone blamed blown o-rings on his Frontier on high head pressure caused by a bad fan clutch, but the truck itself is cooling fine.

Yes, the coolant temperature can still be fine with a bad fan clutch; a properly operating fan clutch definitely helps an AC system. And of course complete radiator/fan shrouding must be in place.

Crap/debris on the outside of the condenser can cause high pressures too.

[bohica2xo]

If only O ring leaks, probably tolerance stack with the new chinese parts.

If you have room in the groove width you can add a split backup ring to improve O ring tension. Most O rings seal on the OD and the ID. If the groove is too wide the ring can go oval and lose tension. Thin backup rings are .053 inch thickness.

But Cusser is right, condensing problems can lead to high pressures - were all of the failures on high side lines?

[Q451990]

Thanks for the responses!

Cusser, my Frontier is also a 2.4L with about 110K miles on it. I'm in central South Carolina, so it's hot - but not AZ hot.

It looks like your fan clutches have failed on both of yours, and I'm curious how you diagnosed them? I've spent more time than I'd like to admit watching youtube videos and searching forums to find out. The Nissan service manual only talk about wobble or play in the bearings. I've checked mine, and it can't be stopped with a rolled up magazine - and the resistance changes depending on if it's hot or cold (based on how many blades I can spin it by hand) but I still can't get a definite answer on how to test one. The fan shroud is fine, but there has been some breakdown in the foam that surrounds the condenser. I'll have to work on that.

bohica2xo, I had two o-ring failures on the low side flex hose fittings, and one on the small metal output tube from the condenser that goes to the evaporator.

So would high head pressure be a possible cause of these failing? I would think the pressure switch would protect the system, but maybe it's a situation where my aftermarket parts tolerances are bad enough that the o-rings are a weaker than the pressures that the switch allows?

[bohica2xo]

In theory the O ring should hold well past the HPCO pressure.

But there are O rings, and there are O rings. Sometimes when working on import hydraulics I find a metric O ring groove with an imperial sized O ring that was "close" but had sealing issues. Offshore suppliers may not hold the same tolerances we do. I can buy softer or harder O rings in many compounds. Lots of variables.

Recently on this site I saw a picture of an O ring in a wide groove, where the used seal was flattened to each side quite a bit. This means it was losing tension against the sealing surfaces. That particular part was a candidate for a backup ring.

Or your aftermarket parts may have a burr or lack a chamfer - which is damaging the new seal as it is installed.

You have the hard parts. It may take some measurement and investigation to get the right seals. For the liquid line connection at the condenser, check with Nissan to see if they happen to have the seal. Nissan has "done their own thing" quite often over the years. It might be special in some way. Just try getting U joints for a Hard Body...

[Q451990]

I'll try to post some pictures of my o-rings on the old low side flex hose I pulled yesterday. That would be a factory Nissan hose mating to it's factory hard pipe connection on one end, and it was leaking bad enough to drip refrigerant oil a day or so after cleanup. Maybe you'll see something I don't. If it's not visibly split or torn, I probably wouldn't know the difference.

[bohica2xo]

Any chance you have the removed components and a pair of calipers to make some comparative measurements?

[Q451990]

I just recharged it. Here are the gauge readings at 1500 RPM. These match almost perfectly to my notes of how it was running in June 2022 when I replaced all of those parts.


At 1500 RPM, I was getting about 52F out of the vents, and the temperature near the intake at the passenger floorboard was 72F. Ambient temperature in the garage was about 97F at 51% humidity. The engine was running at about 200F at this point.

Here's another screenshot at idle (850 RPM)

[Q451990]

I'm a little concerned about the pressure switch, because I never noticed the compressor cycle on and off. However, the high pressure never seemed to get out of range enough to cause it to. The factory service manual has a kind of confusing chart about what it should be doing. If I unplug it, the compressor turns off, so at least the ECU is responding to the signal.

Am I correct in interpreting this to mean that it's only reading the high side of the system (it's attached to the condenser) and that the switch should be open below about 25 PSI, and above about 400 PSI - and on any time time high side pressure is between about 25 PSI and about 400 PSI? I think what's throwing me is the "Low-pressure side" and High Pressure side" labels. I was thinking they referred to the suction and liquid sides of the system, but with it only reading pressure on the condenser, that has to mean where it drops out for low pressure and high pressure on the liquid side of the compressor, right?