Need input from those in the know.

I'm adding refrigerant to an older vehicle of mine, a '97 Land Cruiser. Recently had a head gasket redone, unsure if that would impact it or not, but the air has not been blowing cold and recently stopped cooling except in short spurts. Peekaboo window on the drivers side (in line) shows some bubbling when running, so I set out to recharge with some A/C Pro that I picked up at Autozone.

The instructions say not to go over 55lbs of pressure, and according to the charts on their website if the outside ambient temps are around 90 at the time, I'm okay in that range. However, when I added the refrigerant I noted that the initial pressure was around 49 and I didn't get much in until it hit 55.

My question is, did I need to vacuum the system prior to adding back the refrigerant, or am I being obtuse and the 55 is merely a conservative suggestion? I don't want to cause more damage, but it appears the compressor is kicking in and running and the belts are brand new, so I'm unsure if there is something else I'm missing.

Any input from those who've done this is appreciated, but keep in mind you're dealing with a guy accustomed more to blood and guts than grease here, so speak slowly with monosyllabic words where possible.

I did this with my Honda Civic and almost blew up the compressor according to my mechanic, so I don’t dare touch it anymore. Added WAY too much when I thought I still hadn’t added enough.

Just did this on a 20 year old Explorer with no obvious sign of a leak and enough in the system that it still cooled a bit.

Vacuum is needed if it's been empty, but then you have a bigger problem that needs to be fixed first. If they had disconnected the A/C lines when they did the head work, that would require the system be vacuumed down first.

Otherwise hook it to the low side port and the car needs to be running, A/C on with the fan on high when you do the filling. The outside temperature has an influence and the warmer it is, the higher the low side pressure will be. My kit had a chart showing the temperature vs pressure when full.

I used about 2/3 of the can and stopped when it cooled well and reached the recommended pressure. Better to undercharge just a bit than overcharge as it won't cool well and can cause damage if way too much is put in.

Head gasket probably wouldn't affect it, but 'cooling in spurts' is odd either way. If it wasn't a drastic change right after the head gasket, it's probably not related. If it is cooling at all, you probably can add refrigerant & get it 'cold'. If the compressor won't kick in, you should probably take it to a shop, but if you really want to try it, there are ways to hot-wire the compressor & get it to pull gas in.

There's a relatively fine line between 'almost enough' and 'too much'.

229-9er's advice is solid, but there's a lot of other factors that could change the situation. The 'cooling in spurts' sort of sounds like a blower/blend door motor on the fritz -just to point out that the issue could be unrelated to refrigerant (or in addition to low refrigerant - it's a '97, it probably needs some gas). Or it could be right on the line of setting the safety switch & depending on inside/outside temperature & humidity, it might work sometimes.

I've fixed a few in the driveway & blown 1 up. The blown up one makes my ROI of doing it myself VERY negative.

Head gasket will not affect freon level. Best to vacuum all of the old freon so you can input the correct amount in. Overfilling freon even just a little can burn out your compressor and actually have warmer air blow out. God Bless

The only way the head gasket job would affect it is if they disconnected the AC lines from the compressor to get it out of the way to remove the head or something similar to the AC system that would have been necessary, would have thought they'd tell you about having to refill the AC system or done it and charged you.

Follow the instructions, add the freon in a can see if it stops cycling the compressor on and off and starts cooling.

Manifold garages are not that expensive and lots of y-tubes to help.
add Freon thru suction side and watch high side.
You could have other things going on ,this could depends on age of auto .could be compressor clutch,evap or condensor or expansion valve.
It takes experience to just add freon safely ,do it wrong and it gets costly.
Off my soap box now.

I have a 1996 Land Cruiser, don’t know about your specific question but https://forum.ih8mud.com/forums/80-series-tech.9/ asking here would get you an 80 series Land Cruiser specific answer.

Fellow 97' Land Cruiser owner here. First and foremost: You've OVERCHARGED the system. You may do damage if you continue to run it.

The Toyota Land Cruiser repair manual states the pressure ranges as:

Low Pressure side: 21.7 - 36.2 PSI
High Pressure side: 198.7 - 227.7 PSI

Now, these pressures will vary based on ambient air temperature; essentially, you want to keep the low side under 40 PSI. As for the high side pressure range, good rule of thumb (that I heard from someone on the Ih8mud forum) for R134a equipped car A/C systems is:

Ambient air temperature (in Fahrenheit) multiplied by 2.45 plus 50. This give you the low end of high pressure range. The high end of your high pressure range is calculated: ambient air temperature (in Fahrenheit) multiplied by 2.5 plus 50.

So if it's 90°f outside : 90 x 2.5 = 225 + 50 = 275 PSI (your high side pressure shouldn't be any higher than this)


With all that said, to properly diagnose what your A/C system is doing, you need to buy a set of R134a automotive pressure gauges to see both low & high side pressures. Personally, I would not put much trust in the tiny gauge that comes on refrigerant tanks. You can get a set of gauges from amazon for about $30; worth it if you plan on trying to fix this issue yourself. If you don't want to, then take it to an A/C shop and let them figure it out. Speaking of, the shop didn't need to disconnect any a/c lines when pulling the straight six head from the block during the head gasket job, the A?C lines aren't in the way.
Now, you did say the initial pressure according to the questionable gauge read 49 psi, if it's even remotely accurate, then the reason you have "short spurts of cooling" is because the compressor runs and the air cools until high pressure builds up enough to shut off the compressor via the high pressure switch (at around 450 psi IIRC).

If you want to try and fix it yourself, before emptying the whole system and having to vacuum it down, you should start by putting a set of gauges on it and, if the system appears to be overcharged (both high & low side pressures are reading high), release some refrigerant out until the pressures come down to what I mentioned above. There may be other issues at play here (and I will check back on this thread to answer any questions you have), but this is where you'd need to start.

PS: If you were closer to the Tampa Bay Area, we could do all this in my driveway.

To do it right you need gauges and a vacuum pump. You are taking the chance of getting a cheap, temporary fix that can turn into an expensive repair. A/C systems are sealed, low refrigerant equals a leak. Once it’s leaking it’s not going to get better. And don’t use stop leak, it will make it worse. Take it to a mechanic.

Thanks all for the input. I've not got the gauges but have seen plenty of places to get some. I think I will just let the pros take it from here. I am concerned to see gascan's low side pressure range, since mine was higher than that to start with.

quote:

Originally posted by slabsides45:
Thanks all for the input. I've not got the gauges but have seen plenty of places to get some. I think I will just let the pros take it from here. I am concerned to see gascan's low side pressure range, since mine was higher than that to start with.

You want to purge the system before you start to refill. It's not hard and there are Youtube vids about doing it.

I just did a recharge a couple of week ago and it's very important to have the AC running on high, engine warmed up and air on recirculate. If you don't have the AC running, you'll get weird readings on the PSI.

On my car it plainly says not to exceed 55 psi and I stopped at 45. The PSI readings will be wonky and jump all over the place whenever the compressor starts cycling. Just be patient and try to get an average reading.

It took me about 15 mins and the recharge from AutoZone worked well.

The only way to charge A/C accurately is to recover/evacuate/vacuum the system, then put a known amount, measured with an accurate scale, back in. But with this vehicle there's some room to play with that.

quote:

Recently had a head gasket redone, unsure if that would impact it or not

It might have been necessary to disconnect a refrigerant line or lines, or even remove the compressor altogether, to remove the cylinder head. But if this is the case, why was it not recharged then?

Anyway, if the compressor clutch is engaging (it will be apparent if the front plate is turning along with the compressor), I'm pretty sure this has a sight glass in the receiver-dryer, typically located beside or in front of the radiator. If you see a lot of bubbles swirling around while the system operates, you can slowly meter in cold juice from your can through the low side until the bubbles stop, and no more. Low side pressure is in the 30-50 psi range depending on temp, so it is safe to do so. But if the above conditions are not met, something else is going on, and you should not just add cold juice willy-nilly.