1987 Buick Grand National R12 charge

[tbirdtbird]

So there is no mechanical fan?
If so, is there a shroud in place?
You CANNOT determine level of charge by pressures. The charge must be weighed in.
Are there air dams at the edges of your stack?
Even so all that heat off the intercooler will heat up the condenser. The water misting will tell a lot.
You have more homework to do.

[Ajrothm]

Right..... got ya..

So here is the current test data after a 30 mile drive and straight to testing without shutting it off.

32L/240H at idle, around 95* ambient at the grill. 48* vent temp.

Revved up to 2000 rpms or so, 28L/290H.

Static pressure with the system hot was 75L/75H.

Then I tried to “recover” a small amount, it was all gas, no liquid... from both the high and low side with it not running. Running pressures didn’t change much... maybe down to 30L/245H.... but revved up, it seemed to go to 28L/320H. So it acted like it had higher high side pressure with a little less gas in it. This was at about 98* ambient at the grill and 55* vent temps.

So I’m stumped. Pressures seem in line, but it’s not cooling well. The suction side line is very cold and sweaty. The pressure line is smoking hot. Cant even touch it. But it does sit right on top of the radiator.

So at this point, I’m not sure if it’s over or under charged.

[Ajrothm]

So there is no mechanical fan?
If so, is there a shroud in place?
You CANNOT determine level of charge by pressures. The charge must be weighed in.
Are there air dams at the edges of your stack?
Even so all that heat off the intercooler will heat up the condenser. The water misting will tell a lot.
You have more homework to do.

No mechanical fan at all. Turbo V6s never had a mechanical cooling fan, only a single electric. Mine has dual electrics now though.

I forgot to try the water hose test. I’ll go back and try that next.

No air dams on the sides of the intercooler.

And yes I have a feeling you are onto something about the charge. Initially I thought it was low, then going off of the high side pressure climbing, I thought it may be high...

Then when I recovered some, it was all gas, no liquid, no snow.... just slightly cool gas, and it didn’t really have much pressure behind it. Almost acts like the system is low. The high side pressure at 300+ scares me though.

[JohnHere]

Originally when I charged it 2 years ago, yes, I charged it as close to factory specs as I could get it. 3.25 lbs and as close as I could measure out on the mineral oil. I had used 3 - 12 Oz cans and 1 - 14 oz can with dye. The system worked great initially.. then over time it started to warm up some. I figured it had a slow leak.
Looking at the static pressures by temp charge for R12, the pressure is a little low, indicating under charged but.... after I added Freon yesterday, it definitely got worse.

Like us old-timers used to do back in the day, you could charge an R-12 system using the Sight Glass or by using a graduated, clear, refrigerant charging cylinder.

If using the former, continue adding refrigerant until the bubbles and foam in the SG disappear, and then add a little more, perhaps one more ounce. That will get you close to the correct charge. But even with an R-12 SG system, it's always best to weigh-in the exact charge for proper system functioning using an accurate refrigerant scale or an RRR machine. As already said, you can't charge by pressures alone.

[tbirdtbird]

...Sigh...
those electric pushers are not gonna get you where you want to go with that thick a stack and no dams. You can fab your own dams, but I am sure you know that
Puller fans work much better BTW

All the info you need has been posted, you only need the motivation to respond to it
A condenser w/o good airflow is like having a snow shovel covering it

[Ajrothm]

So I tried the water hose test, idle pressures dropped to 28L/170H. It didn’t even take much water to make the pressures plummet. On the same note, coolant temps also came down 20*...so I’m sure that also affected the condenser performance. Ironically, vent temps did not change much at these lower pressures. I saw about 53* vent temps after cooling it down. Once I hit the condenser for about 5 mins, went and sat in the car another 5 mins, and the vent temps slightly dropped to 48*, but didn’t stay there.

Not sure exactly what this tells us, other then the condenser is over worked and restricted but... vent temps used to be 10* better on average then this. So I still think I have a charge qty problem. Don’t know if I’m high or low.

I guess I’m gonna have to try to hunt someone down that still has R12 recovery equipment... when I checked 2 years ago, I found no one.

Oh and this one doesn’t have a sight glass on the drier to watch the liquid go in. Only the sight glass on the gauges.

[Ajrothm]

...Sigh...
those electric pushers are not gonna get you where you want to go with that thick a stack and no dams. You can fab your own dams, but I am sure you know that
Puller fans work much better BTW

All the info you need has been posted, you only need the motivation to respond to it

These are pullers.

[tbirdtbird]

went and sat in the car another 5 mins, and the vent temps slightly dropped to 48*, but didn’t stay there.
Because the water on the condenser dried up

Not sure exactly what this tells us, other then the condenser is over worked and restricted
YEP

[Ajrothm]

Maybe time to buy a Mastercool recovery machine and tank....

[JohnHere]

Oh and this one doesn’t have a sight glass on the drier to watch the liquid go in. Only the sight glass on the gauges.

The SG on the MGS doesn't tell us much except that refrigerant is flowing. You might want to consider purchasing a professional-quality refrigerant scale, which I think would be your best bet. Check with the Forum sponsor for price and availability.