[BTRowan]

I tried reseating and tightening the Schrader valve (loosen it, then tighten it) several times. Didn't work; still bubbling.

I tried pulling, pushing, and rotating the pin in the valve (with ultra-small needle nose pliers). Didn't work; still bubbling.

Now, calling around to parts stores to see if anyone carries a no-refrigerant-loss valve replacement tool. If I can't find one locally, then I'll go online.

Thanks for the info re the Mastercool tool.

 

[webbch]

Car OFF: Left gauge 94 PSI; right gauge 80 PSI.
Car at IDLE + AC on HIGH: Left gauge 150 PSI; right gauge 20.
Car at IDLE + AC OFF: Left gauge 57 PSI; right gauge 60 PSI.

Black and greasy around high-side Schrader valve. When the gauge set was removed, the high-side Schrader valve was bubbling. Diagnosis = the high-side Schrader valve is leaking.

If I can tighten the Schrader valve so it no longer leaks, what pressures do I need to achieve when I add some oil and refrigerant?

Odd. I thought most gauge sets had low side gauge on left, but no matter. You left out the ambient temperature at which these measurements were taken - that affects the range of pressures deemed "normal". Regardless, low side pressure is definitely too low (shouldn't ever get below the 30-40 psi range), and if it was a relatively warm/hot day, the high side looks a little low to me - both indicative of an under-charged system.

You don't need to add any oil unless you're changing major components like evaporator, condensor, compressor, etc. You could add a 1/2 ounce if really concerned, but I wouldn't bother. Black and greasy on the high side schrader sounds like you've found your leak point, provided there's nothing nearby that could've dripped/been flung onto it. There are tools for changing the shrader w/o evacuating. If you want to DIY, you'll need that tool (about $40 I think), and then guess at how much refrigerant to add back in. Alternatively, you could take it in and have it recharged to a known amount, and have the shop change the schrader while they have the system evacuated for the recharge. If I didn't have the evac/recharge equipment, that's the route I'd take. Have them throw in some dye at the same time if it doesn't have any to help find any future leaks.

 

[BTRowan]

Hello nitely2,
How did you get the tool to grab the valve so the valve could be pulled out (after unscrewing the valve)? Wouldn't the valve fall out of the "teeth" of the tool?

 

[BTRowan]

Hello oldskewel,

The "Car OFF" reading was taken first. The van had been driven earlier in the day, but had been sitting for about 3-hours (this is when I took the "Car OFF" readings.

 

[nitely2]

Its fairly easy. Look here...

Just be careful. Don't forget to lock/close the system first before pulling out the old valve core slowly.

 

[nitely2]

Here is the instructions from the mastercool website....https://www.mastercool.com/wp-content/uploads/2014/12/58531-INST.pdf

 

[rbhollabaugh]

Please wear safety glasses when working on the AC.

 

[John Clark]

Wow...this thread has gone a long way today!

I don't think it hurts anything to check your own pressures with a gauge set. However, there is absolutely no way to accurately charge your system using a gauge set. First, the system isn't built to do it that way. If it's low it needs to be evacuated of the remaining refrigerant, vacuumed down, and then recharged with the amount of refrigerant on the sticker under the hood. That's why they put the sticker there. If you could do it with gauge pressures you wouldn't need the sticker and manufacturers definitely wouldn't spend the money to put the sticker on there.

Second, even if you could do it with gauges alone you still have to be really careful not to allow any air into the system. It's easy to do it accidentally by not properly purging hoses, etc. Also it only takes a turn of the wrong valve to run into real problems. Even if you do everything right you can still have major problems. I had an o-ring burst on the high side fitting of a cheap Harbor Freight set of manifold gauges, with the compressor running, which vented a ton of refrigerant and oil until I could get it turned off--very dangerous in and of itself. Instead of evacuating the system I tried to recharge it by using gauge pressures. A month later the compressor started making noise...less than a year later the compressor failed and I had to replace the entire system with exception of the evaporator core which I had to flush. Fortunately, this was on my older 98 Nissan and not on my Ody. Lessons learned? Don't use cheap gauges and never attempt to recharge the system using gauges. I had overcharged it which stressed the compressor. It took a while for it to go bad but it did finally fail.

It sounds like you found your leak. I would take it to a shop and just have them service it. Let them know the valves are leaking and need to be replaced (many AC shops replace them as a matter or routine at service because they all leak.) It'll cost you $100-150 at most and no risk of damage to your system.

 

[bonbonb]

Rear expansion valve! Had same issue last year, fixed it by replacing the rear expansion valve. Good luck!

 

[oldskewel]

Hello oldskewel,

The "Car OFF" reading was taken first. The van had been driven earlier in the day, but had been sitting for about 3-hours (this is when I took the "Car OFF" readings.

Well that seems a little weird, so you might want to keep it in mind. After sitting for 3 hours, the pressure within the system should have equalized, making the high and low pressure readings the same. It might indicate a blockage somewhere. Or, could it be that some gas vented when you were attaching the gauges?

EDIT - I just read the previous suggestion on the rear expansion valve. Definitely something to consider if you think those "Car OFF" measurements are good.

Also, with the compressor not running, you've basically got a system with liquid + gas refrigerant in there. As the temperature of the system (the tubes, the liquid, the gas, etc.) goes up with the temperature of things in the engine bay, the pressure should go up too. So it seemed odd that the pressures after it was sitting for 3 hours (and presumably cooler) were higher than with the engine idling and AC off. I guess it's possible that having the hood up let things cool down and the idling was not creating much heat.

Another measurement that may help is if you have a multimeter with a thermocouple (many have that, even fairly cheap ones), then getting measurements of the cold air coming out of the vents would give you useful info on how it's doing before and after any repairs or adding Freon.

All the warnings given by John Clark are good advice. So proceed with caution if you dare. The AC system must be kept very clean, so for example that grimy valve should have been cleaned carefully before opening. And yes, air in the system can be a problem. So you'll need to think carefully about what is in the manifold, tubes, can, etc. and make sure any air is purged before it has a chance to get in the system. So far, you're fine since the system is pressurized and just taking measurements will let gas out, but not air in. The other major warning to consider is to not overcharge the system. More is not always better. Careful monitoring of the pressures and the outlet temperature might help you avoid overcharging.

As far as adding oil, my recollection is that typically you can buy pure R-134a in cans of like 12oz, or you can buy a 4-oz can containing 2-oz of refrigerant and 2-oz of oil (get the right kind, of course). Then those are both charged the same way. When charging Freon, you want the can upright so you don't hydrolock the compressor - upright will just charge vapor; upside down would charge liquid. When charging the oil/Freon mix, you want to shake it up, and then tip the can back and forth so the oil all comes out. When charging the Freon, the can will get cold due to the expanding gas. This will have the effect of reducing pressure in the can, possibly significantly slowing charge rate. An easy solution is to get a little tub, like a coffee can, filled with hot water. Then put the can in there, which will keep it warm/hot even as the adiabatic gas expansion causes cooling. So with the can staying hot, the pressure will stay high, and charge rate will stay good.

 

[BTRowan]

Was the "Car OFF" reading taken last, after the engine had been running during other tests? That would explain why the pressure had not equalized - takes some time. Also, when the compressor is not running, whether the engine is on or off, the pressure readings will increase with increasing ambient temperature (the temperature in the engine compartment where the AC tubes, etc. are.

That MasterCool kit nitely2 referred to is good. I have the extended version of their kit, which I've used, I think on my '99. But before getting a kit like that, etc., I'd first see if you can tighten / re-seat / adjust the leaking valve as I mentioned in a previous post. Also, you may as well do that before adding Freon.

The numbers you list are a little low. Here are the pages from the manual (for 1999). Be sure to follow the exact specs of how to run the test before you worry about the numbers. E.g., 1500 RPM. Hmm, how to do that without passengers in vehicle ... well you might need to bend the rules a little.


View attachment 110697
View attachment 110705

Hello oldskewel,

In the A/C System Tests pages you posted, there are two charts. One is labeled "Dual A/C" and the other is labeled "Single A/C." I don't want to assume anything, so which chart applies to a Honda Odyssey? Thanks.

 

[stuckpipe]

On my 06' Touring Odyessy, the front center vents had issues. Left one blowing cold air and the right side blowing hot. It seems that a relay switch in the a/c temperature control circuit was stuck. So it may also be the electronics.

 

[oldskewel]

Hello oldskewel,

In the A/C System Tests pages you posted, there are two charts. One is labeled "Dual A/C" and the other is labeled "Single A/C." I don't want to assume anything, so which chart applies to a Honda Odyssey? Thanks.

Those pages are from the service manual for my 1999 Odyssey. I expect yours is the same. I believe in '99 at least, the LX version only had one set of climate controls, at the front; the EX had a separate set of controls, along with a separate HVAC system (blower, evaporator, etc.) in the right rear of the van. So the "Single AC" is for the front-only LX and the "DUAL AC" is for the front-and-rear EX.

So you need the "Dual AC" version if you've got a rear evaporator, etc.

 

[oldskewel]

Hello nitely2,
How did you get the tool to grab the valve so the valve could be pulled out (after unscrewing the valve)? Wouldn't the valve fall out of the "teeth" of the tool?

Short answer ... it is a snug fit between the "teeth" and the valve, so the valve core just stays in there once fully unscrewed.

You can test for the correct snugness of this fit before doing the actual valve core removal - the rod with the "teeth" on the end can be place on the valve core all by itself before the rest of the sealing apparatus is used. If too loose or tight, you can bend the teeth slightly to get a good fit. That part of the Schrader valve is not a high precision dimension. Then after removing the old core, do the same test and adjustment with the new core so it does not fall out as you try to insert it. (but that last thing did happen to me before I figured this part out - it can be recovered if you're careful)

 

[BTRowan]

I going to tackle the job. I ordered a No-Refrigerant-Released Schrader Valve Replacement Tool (none of the local auto parts stores have one). I'll get high- and low-pressure valves, A/C oil, and R-134 from the parts store. I have a loaner OEMTOOLS Manifold Gauge Set from AZ. I have some questions.

Is there an aftermarket Schrader valve that will fit? Or, do these Odyssey's require a proprietary valve from Honda?

How do I purge the air from the three hoses attached to the gauge (red, blue and yellow)?

If I want to put in only 1oz of oil, how do I do this (since most cans contain 2oz of oil)?

Thanks for your help.

 

[oldskewel]

I suspect the rear expansion valve. It might be clogged.

I also suspect the rear heater & cooler motor assembly (the blend door motor).

I will investigate both.

The valve repair and refill are good to do, but that still might not fix your problem. So while you're waiting for parts ...

Have you run the built-in HVAC diagnostics yet? Ignition switch ON, Fan switch OFF, etc.? That might tell you something.

Any progress on looking into those items you mention above?

I think the rear blowing hot might be a good clue. If you have AC turned off, but temp set to cold (this should close the heater control valve at the rear heat exchanger, and the AC compressor clutch should not engage, so AC is not active anywhere), how hot is it back there? Then can you make it hot/cold by adjusting temp with the AC still turned off? If so, that would suggest your rear heater valve, etc. is working fine.

Then set AC off, and set the rear temp back to cold, let it reach steady state. Ambient air blowing out, right? Now turn AC ON, so the compressor clutch engages and the AC is "working." Now does that make the rear air hotter? If that is the case, I will guess the problem is with the rear expansion valve. Basically the compressor compresses the freon, making it very hot, it cools in the condenser, then it is pumped to the rear expansion valve (as well as the front AC system, which sounds like it is fine). At the valve, there is an orifice that should maintain high pressure upstream and allow expansion on the downstream side. This expansion cools the freon and allows the liquid - vapor phase change. So the upstream side of the expansion valve should be hot and the downstream side should be cold.

But if there is a problem in the valve, either a blockage that does not allow much flow, or if the orifice is too big to force the expansion/phase change, there will be little or no cooling. There may actually be HEATING since you're pumping the hot (cooled by the condenser, but still hot) compressed freon through the rear evaporator.

If that's the case, you'll need to fix the rear expansion valve, in addition to the other stuff you're already planning to do. One thing to consider is that, if you do have a valve problem, it will affect your pressure readings (perhaps meaning the single-AC charts are needed, vs. the Dual-AC ones). And if you do need to replace this valve, the whole system will need to be evacuated, etc., so the MasterCool special tool is not so necessary.

Since you found a leaking Schrader valve, you definitely need to replace that and you need to refill the system, so most of what you're already doing is still needed.

In addition to the tests above, if you can access the rear expansion valve, it may be as simple as feeling the upstream and downstream pipes for temperature. Upstream should be hot, downstream should be cold.

 

[John Clark]

Rear expansion valve! Had same issue last year, fixed it by replacing the rear expansion valve. Good luck!

This is always a possibility but, unfortunately, the only way to come to that conclusion is to first have a full refrigerant charge and then diagnose with gauge pressures. If there is any problem in the system then attempting to charge with pressures will never work and you'll likely overcharge the system and ruin the compressor because the system pressures don't even have a chance of being within spec no matter how much refrigerant is in the system.

 

[oldskewel]

I going to tackle the job. I ordered a No-Refrigerant-Released Schrader Valve Replacement Tool (none of the local auto parts stores have one). I'll get high- and low-pressure valves, A/C oil, and R-134 from the parts store. I have a loaner OEMTOOLS Manifold Gauge Set from AZ. I have some questions.

Is there an aftermarket Schrader valve that will fit? Or, do these Odyssey's require a proprietary valve from Honda?

How do I purge the air from the three hoses attached to the gauge (red, blue and yellow)?

If I want to put in only 1oz of oil, how do I do this (since most cans contain 2oz of oil)?

Thanks for your help.

"Proprietary valve from Honda" - LOL, I remember when I was doing this, I went to my local dealer's parts dept., asked for this, they had no idea and sent me to the service dept. They said they didn't really know, and checked with the smartest guy there. He said they'd probably go get one at NAPA, not really sure. After making a mental note about how much the dealer knows, it turned out NAPA didn't have one, but I found a really old school auto parts shop nearby that looked like it was from the 50's. They had them, but weren't sure what exact ones I needed. I did get the right ones, but don't remember the exact part number.

You basically want of course an exact geometric match. But also, you want to be sure the sealing surfaces on there are chemically compatible with AC.

Purging air - understand exactly how the valves in the manifold gauges work, then think carefully as you go through the process. Assume all hoses begin full of air, and gradually let some refrigerant vapor to escape, displacing that air and filling the hoses with refrigerant vapor.

Oil - I'd be much more concerned with oil compatibility - spec is DENSO ND-OIL 8 (so something that matches that) that 1 vs. 2 oz. They have specs for how much oil should be added when replacing certain components, etc., but really this part is very far from an exact science. There is no way to really know how much oil is still in the system. If the leaking valve was oily, I'd put in the 2 oz. But if you really want to just put in half the can, you could weigh it before and during charging. But keep it shaken up so you're getting half oil/half freon out.

 

[John Clark]

I going to tackle the job. I ordered a No-Refrigerant-Released Schrader Valve Replacement Tool (none of the local auto parts stores have one). I'll get high- and low-pressure valves, A/C oil, and R-134 from the parts store. I have a loaner OEMTOOLS Manifold Gauge Set from AZ. I have some questions.

Is there an aftermarket Schrader valve that will fit? Or, do these Odyssey's require a proprietary valve from Honda?

How do I purge the air from the three hoses attached to the gauge (red, blue and yellow)?

If I want to put in only 1oz of oil, how do I do this (since most cans contain 2oz of oil)?

Thanks for your help.

Can you take a close-up pic of the valve inside the port? On my 08, and on most Japanese cars the valves they use are called JRA schraeder valves. In my experience the parts stores won't carry them. The kits they have are for domestics. I bought some genuine schraeder brand valves on eBay. Be careful of cheap Chinese junk ones.

Additionally, there are multiple different sizes of tools to remove them based on the type of valve. Hopefully, the tool you ordered will fit and be the right one.

I really see nothing gained by replacing this valve this way, in your case. The system needs to be evacuated anyway. Just replace the valve when it's empty. When you're done, vacuum the system and then put in the proper amount of refrigerant.

If you attempt to replace it with the tool, you risk using the wrong tool and getting it stuck and possibly not being able to get it back in and have the tool stuck on the service port until you empty the system. Even if you do get it replaced, how are you going to refill the system properly without evacuating the system?

I'm all for learning how AC works and how to fix it, but this vehicle is an expensive system to replace should anything go wrong. I'm trying to respectfully raise a red flag here.

If you're dying to do this yourself, I think the best thing to do is just use your gauge set to let the remaining refrigerant out the yellow hose (VERY slowly so you don't lose much oil,) replace the valve, vacuum it down with a vacuum pump for 30-40 mins, and then use the 12 oz cans of pure R134a from Wal-mart to refill it based on the sticker under the hood. Some will not like the idea of letting it out (yes, it's illegal) but if you do nothing it's all going out anyway. You might need to add 1 ounce of oil, max, if you go slow when you let it out.

To measure the right amount to go back in use a small scale from Wal-mart. Figure out how many cans you need (probably 3) and then empty one can partially so that the partial can, plus the other full cans will add up to the proper charge amount. Then put in the partial can followed by the full cans until they're all empty. Be sure and purge the yellow hose each time you change cans by loosening the yellow hose fitting at the manifold gauge for a couple seconds to purge the air. Then open the blue valve to charge the system.

When charging use the tub of hot water trick described above. You can probably get nearly two cans in with the vehicle off using that method. Then you'll need to start the car, turn on the AC to get the rest of it in. If you can't get the refrigerant in you will need to jump the low pressure valve to turn on the compressor. This can get a bit complicated but it's all do-able.

If you aren't familiar with all this it REALLY is better to just take it in and have it serviced and then troubleshoot the system. If you do have a rear expansion valve that's bad you will never get pressures to the right place and it's impossible to recharge with gauge pressures only.

 

[oldskewel]

Hey, I found my old notes regarding valve cores and the MasterCool tool ...


My '99 Honda uses "Standard" AC Schrader valve cores. Not JRA, Eaton, etc. I bought for ~$1.25 each at Young's in RC. GA1528 is the part number for what I used. The receipt from the ones I bought (I guessed right) says PN 59346, which appears also to be a good PN for Schrader valves.


Replaced using Mastercool 58490 repair kit. Regarding that kit ...
- there are 5 shaft things. They are valve core dependent. "Standard" size uses #1 (marked on end of the knob). When using the tip to this tool, I found that it is important for the tip to grip the core just right. So the slight variation in size of the old vs. new cores was a problem. I ended up needing to carefully adjust (with pliers to tighten or screwdriver to widen) the tip before each task. Not a big problem when doing as few as I do. Best to size up tip vs. old valve core with nothing else attached yet - see how tight it is, start to unscrew core, etc.
- Even with adjusting, having the removed old core fall off the tip and stay inside the mastercool valve is common - I would do it very carefully and would fail a few times before succeeding. I can see how others might find it impossible. Skill is required.
- Good to use bike valve tool to get partially started on the unscrewing (loosened), and also on the final tightening.
- The last screw fitting (last when moving away from the refrigerant line) is basically optional. It helps stabilize and center the shaft (which may be important), but is not needed for sealing.
- Other than the issue with needing to fine tune the #1 tip, the tool worked amazingly well. Refrigerant loss is tiny. No sealing problems.

Following are some pics of my MasterCool kit, including one pic from using it on another car of mine (not Honda). Second pic there has the old valve core on the end of the rod, new valve core sitting on the case.