2008 Altima Not Cooling

[Cusser]

Now onto the next issue. I can't pull a vacuum down to 29.9 Hg. I can only get it down to like 16-17 Hg. I think it may be the vacuum pump because I can't pull down to 29.9 even just using the gauges not hooked up.

I wouldn't change the vacuum pump oil; I'd see if Autozone has a different pump to swap out.

If it won't hold vacuum without the hoses connected, might just be bad O-rings in the hose fitting to the gauge set, or the valves in the gauge set are leaking. Is the gauge set a loaner set also?

What if you connect gauge set to the vacuum pump, start it up, and also temporarily put your fingers over the bare male fittings on the gauge set - does the vacuum increase?

[tbirdtbird]

Umm, you are wasting your time if you charge into a vacuum of 16-17.
Loaner pumps have been used by every Tom, Dick, and Harry imaginable, and exactly what they did to the pump is unimaginable. We had a guy here who flushed his evaporator out with WATER and then vacuumed it down! Ya don't think that pump oil was trash, do you? Not all DIY boys are pros.
If they have another pump to swap, go for it. As stated, check for a leak in your equipment somewhere, or the pump oil is trash. The seals in the ends of your hoses can be changed out for new, especially if they are old or they have been stored in the heat, or if they have been stored with the knurls screwed down real tight. In the off season, we loosen the knurls so as to not destroy the resiliency of the seals. We have been known to test our seals by putting in a small freon charge to the gage set only then using a sniffer when we were perplexed by a low vacuum. You cannot tell by looking at the oil if it is any good, and it DOES make all the difference in the world to the function of the pump

[JohnHere]

I wouldn't change the vacuum pump oil; I'd see if Autozone has a different pump to swap out.

I didn't know the VP was a loaner. But I agree...request another pump and try again.

Lots of good comments in the previous two posts. In particular, I reiterate the comment about not charging it yet until you can evacuate to around 29.9 InHg for at least one hour and preferably longer.

[jtupper]

The saga continues...

The manifold gauges were a loaner set as well. I took the pump back to AutoZone and got a different one from Oreilly's. Same result. I started looking at the o-rings in the hoses and they were pretty gnarly. I ended up picking up a brand new set of gauges. Full disclosure, they are the Harbor Freight set. I hooked up the pump to the new gauges and it vacuumed down to 26 Hg within a minute or so. It wont vacuum down below 26 Hg, but it has only been a few minutes.

Can I assume there are no leaks in the system since it held vacuum overnight? The vacuum actually increased overnight to 20 Hg. I don't understand that (ambient temp?). I'm going to let the pump run for a while to see if it will vacuum down any lower. I'm kind of at a loss here.

BTW...I'm in Houston so I'm at or just above sea level.

[JohnHere]

The manifold gauges were a loaner set as well. I took the pump back to AutoZone and got a different one from Oreilly's. Same result. I started looking at the o-rings in the hoses and they were pretty gnarly. I ended up picking up a brand new set of gauges. Full disclosure, they are the Harbor Freight set. I hooked up the pump to the new gauges and it vacuumed down to 26 Hg within a minute or so. It wont vacuum down below 26 Hg, but it has only been a few minutes.

Well, 26 InHg is better than last time but still inadequate. Since you have a new Manifold Gauge Set connected, that would seem to rule out leakage at the knurled hose ends and the MGS itself. It must still be a weak vacuum pump since the system itself maintains the maximum pump vacuum over time. Try running the VP for about one hour and see whether the vacuum reading drops. If not, I would suspect either the oil again or an abused VP that just will no longer pull an acceptable vacuum.

Can I assume there are no leaks in the system since it held vacuum overnight? The vacuum actually increased overnight to 20 Hg. I don't understand that (ambient temp?). I'm going to let the pump run for a while to see if it will vacuum down any lower. I'm kind of at a loss here. BTW...I'm in Houston so I'm at or just above sea level.

Typo? I think you must have meant 28 InHg and not 20 InHg. I can't explain why the reading would increase slightly overnight.

Sometimes, a system can hold vacuum indefinitely but leak under pressure, and vice-versa. So because it held vacuum overnight is no assurance that it won't leak after charging.

Since you're virtually at sea level, you should see a vacuum of 29.9 InHg or better. But you would need a micron gauge to measure a lower vacuum reading (in microns) because at that reading, you'll be at the practical lower limit of your low-side gauge. For your purposes, 29.9 InHg should suffice, though.

[jtupper]

Typo? I think you must have meant 28 InHg and not 20 InHg. I can't explain why the reading would increase slightly overnight.

Sometimes, a system can hold vacuum indefinitely but leak under pressure, and vice-versa. So because it held vacuum overnight is no assurance that it won't leak after charging.

Since you're virtually at sea level, you should see a vacuum of 29.9 InHg or better. But you would need a micron gauge to measure a lower vacuum reading (in microns) because at that reading, you'll be at the practical lower limit of your low-side gauge. For your purposes, 29.9 InHg should suffice, though.

Yes, I meant 20 inHg. Apologies.

After letting the pump run for about 1.5 hrs, it pulled down to 28 inHg. I was going to pull the gauges off and double check that it is zero'd properly, my low side port is now leaking. This is so incredibly frustrating. Now I'm off the get a new port or schraeder valve.

[tbirdtbird]

AC can be frustrating, we have all been there.
The steps that need to be taken to get AC to work are very exact, precision steps, and with good quality and properly maintained equipment. Seldom is there a cheap way out. Bad schraders are a very common problem. Many of us change the schrader cores every time we open a system. Please remember the schrader design is not the best engineering out there, and when you are done be sure you put the plastic cap back on each port, since they all tend to seep a little. The plastic cap stops that. We also change the seals on our hose ends from time to time.

I actually think you are making progress. If you continue to follow just what JohnHere is advising, to the letter, I am confident you will get it done. He is MACS certified, meaning he is highly qualified, and has probably worked on more than 1000 cars if I were to guess.
And those of us that do this all the time have invested some decent bucks in our equipment.

[jtupper]

All oft he help and guidance has been greatly appreciated.

Back off to the auto parts. The schraeder valves in the service port repair kit that I purchased are much, much smaller than the one I pulled out of the service port. Hoping I can find one that fits.

[jtupper]

IMG_6383.jpg (137.18 KiB) Viewed 4318 times

And we have liftoff...

Low and high port schraeder valves replaced, fresh oil in the pump and back under vacuum. Went to 28 inHg almost immediately. I actually tapped on the gauge a couple of times and it went to 30 inHG. The plan is to let it vacuum for an hour or so, then let it sit for a couple of hours to ensure it stays under vacuum, the charge with refrigerant. Sound about right?

[tbirdtbird]

Yes, sounds about right, good job.
Be careful when you switch your yellow hose from vac to charge that you do not introduce any air!!
Be sure you bleed all your hoses of air.
You are probably using cans even tho that is not the preferred way.
For the first can, turn it upside down and thus rapidly charge liquid into the high side (COMP OFF)with the blue side valved off. This gets a lot of refrigerant in right away so that the comp doesn't start up with a measly charge, because such a charge will carry very little oil, and that is not good for the comp. Then you shut the red side handwheel, and charge the rest of the way with vapor (can upside right) into the blue side with engine running, comp on.
Once you are done charging be sure you have both handwheels closed in order to take pressures. With the comp running, you never want the high side handwheel open.

Once all charging is done, shut the quick coupler to the high side on the car. You now have a red hose with high pressure liquid trapped, and a blue hose with vapor. Now open the red handwheel and allow the high pressure liquid left in the red hose to bleed back into the car. Then you can shut the blue coupler, and remove the hoses entirely.
Read this over several times to get your head around it.
When charging vapor you will likely need to have a warm water bath handy because the can will get very cold and as such will not deliver the full can contents.

Report back with ambient, center vent temp at 1500 RPM, doors open,recirc on, max fan, mac cool, and high and low pressures.
The thread is long and I don't recall if 134 amounts and oil amounts have been discussed.
Also, waaay better to charge when ambient is at least 80. You will get better representation of what is going on. I would NOT charge at less than 80°