WallyP

895 cc is approximately 30 ounces, which is the correct amount of R-134a for the later cars.

The early cars should have 33.5 ounces of R-12 and about 28.4 ounces of R-134a, so you started out slightly overcharged. Then you added 24 ounces, so unless you have a large leak (in which case all your charging effor is wasted) you are now seriously overcharged.

jwillman

I agree that if all that R134 was still there it should be way overcharged but the gauges and sight glass don't indicate that as best as I can tell so I am guesing I have a leak.

I had put in about the 28 OZ the first go around but when I checked the sight glass the next day had the indication of undercharge. Intent was to add only a bit and get the sight glass to clear a bit and then I would be golden.

Guess I am back to square one and need to either take it to a shop, have it evacuated and pressure tested or add some dye and try to work through it myself. I have never done the later. I assume I need a light or a sniffer?

Any thoughts on the temperature indications? Want to make sure I resolve those if they are an issue.

dr bob

Jim--

How well was the system evacuated before you started adding refrigerant? The sight glass is a reasonable indicator of charge at current conditions, but it really depends on having all the air removed prior to charging. If you try to "evacuate" with one of the little Harbor Freight air-powered venturi vacuum pumps for instance, you'll be lucky to get 20" of vacuum. That leaves about a third of the air inside. Since air doesn't condense in the condenser, it will show up as bubbles in the sight glass, and no amount of additional refrigerant will help.


For those playing along at home, air is a serious contaminant in the system. The gas bubbles take up space and transfer capacity in the condenser. Air confuses the expansion valves, which depend on metering liquid mass to keep inlet and outlet pressures correct. The air that passes through the evaporator take up space and transfer capacity in the evaporator, and can actually add heat back in there. Last but certainly not least, air in the system will team up with any moisture left loose in there to corrode the metal parts of the system. Evaporator coil leaks are a sure sign that there is air and moisture left inside. A good multi-stage vacuum pump, with new oil (should be changed very regularly), is capable of boiling the moisture from the system on a reasonably warm day, given time. The better the vacuum, the less air is left in and the less moisture remains trapped. Hip-shot guestimate is that evacuating to 20" probably costs 20-25ºF in evaporator temps at lowest fan speed, more when fan speed in increased.

jwillman

Well the vacuum pump I have was used to evacuate aircraft AC systems, King Air 300's, so I assume it should be able to pull down a car system.

I did put the gauges back on today and I am down to 15 on the low side at idle so I definitely have a leak. Tomorrow I plan to jack it up and look at all the connections. I realized today that one of the lines running from the expanxion valve also has a rubber hose segment. I did not have that one rebuilt. I see some indication of a leak under that line an a drop or two of oil on the bottom of the pump. I need to re-check the lines on the top of the pump.

dr bob

Jim--

There are o-rings in the manifold plate on top of the compressor on my later car. Same symptoms you describe, with low charge and the oil leak. I missed them frist time around when I did my system, and had to pull the compressor (again...) to replace them by day 2 of use. Use the impact driver on the Allen bolts that hold the manifold plate on there to remove, torque wrench after even hand tightening on install.

jwillman

Dr. Bob,

I plan to drop the compressor again to inspect the manifolds and line fittings today.

I had pulled the suction and discharge manifolds off and replaced the orings, schrader valves and put in new hardware when buildong up the compressor. I had the compressor bench tested and assumed they would have seen leaks there but now that I think about it I don't know if they pressurized it.

I found some green orings at pep boys that seemed to be the right size, but maybe they are not. What size should go between the manifolds and compressor?

The schrader valves were standard types with black seals. Is there a special AC seal schrader valve?.

What is the correct torgue for the manifold bolts?

Thanks for all the help.

dr bob

If they are from their AC o-rings box and fit like the originals they should be fine. I don't remember the specific size, and they aren't called out separately in PET. I took the compressor pieces with me to my local auto AC shop and they had the right ones.


AC Schraeder valves are specific to AC service, difference is the seal material at the base. The ones I used have green seals IIRC, from Pep Boys too. Black ones are plastic tire valve seals.

From memory those are 8mm threads, so 15 lbs/ft. Remember that we have different compressors 1979 vs 1989 MY's, so verify the size of the bolts.

jwillman

Well I think I found the leak. There was very little pressure left in the system. Took only about 30 sec to bleed the pressure off at the low side fitting.

The pressure line from the dryer to the expansion valve looks to be leaking from the rubber flex hose piece. It is all moist and had a trail of refridgerant on the fender well. I spent the last couple of hours pulling that line.

I also dropped the compressor again as the suction line felt loose. Does not look to be leaking from the manifolds. I had some oil collecting around the bottom of the compressor at the front and back ends. I am wondering if it was from the loose suction line? I hate to think it is the compressor. It passed a bench test at the place that makde my lines.

Well back to the AC shop to have that line made and have the suction line shortened a bit. I will ask about the compressor test process to make sure it was put under pressure. Otherwise it looks like I should rebuild it to be safe.

One question I have now is if I don't rebuild the compressor how much Ester oil to I add if any since I have had it apart after all the R134 leaked out?

Big

jwillman

I had the suspect leaking line rebuilt and reinstalled. I also inspected the evaporator front side and found it to be free of the gunk seen by many others.

I vacuumed down for 8 hours (-28PSI indicated) and then added 2 cans (680g minus lose for flushing fill hose) using liquid method to the high side with engine off. I waited 10 minutes, started the car (1500 RPM and fan speed 2) and added remaining R134 until about 890g installed and sight glass was just beginning to clear.

Car is putting out cold air. At 100F OAT I had 40 psi LS and 300psi HS. I have checked it every day for the last three days and I still have good sight glass and cold air. Time will tell but thanks to all for the great advice.

Now to attack the HVAC vacuum issues but thats another thread!

fraggle

Way to go! Hope my path is shorter to success!!

izzzzzz6

Hi guys i'm new to this but hoping to repair a leaky system on my girlfriends motor.
It was in a few small accidents so there is apparently more than one leak. I have just bought the tools required, i am planning to empty out as much of the pag 46 as possible (without taking the whole car apart). I will replace with at least the same amount as removed (not much more depending on evidence of oil leaks).
I will purge the manifold gauge lines with the pag oil then fill with r134a (after a deep vacuum session). I'm only going to use one 1kg can and will weigh it to calculate the correct quantity.

I am just curious as to how much the r134a will weigh in the lines, obviously if in gas form it won't weigh a great deal but if it is in liquid form it may weigh quite a bit since the H & L pressure hoses and the charging hose are often quite long and i have read here that one technique of charging is to wait for the air bubbles to stop, personally i'm not sure about this, does that mean that the hoses used for the charging at this moment will be full of liquid r134a? If so where is the gas? has it all turned to liquid and how would this leave space for the gas which runs through the compressor so that it doesn't get damaged by the liquid r134a? I'm assuming that there is still gas space in the high pressure side of the system and once started or over time the gas and liquid will redistribute itself throughout the system.

I am thinking to liquid charge with the can upside down through the high port and with the engine turned off. Then when it takes no more charge on the high side i'll continue to empty gas into the low side with the engine now running. Hope i can fix the leaks, have also ordered a new drier and new schrader valves. May borrow a vacuum pump or toying with the idea of buying one, was thinking to use a fridge pump and connect it for a few hours but i'm not sure if it will pull a good enough vacuum? I didn't order o rings hopefully i'll be ok here, perhaps i'll have to get a set. I was thinking to pressure test and soapy leak test the system with argon as we have some close to hand, since it's going to get vacuumed anyway i don't really see the problem with using any old gas to leak test with soapy water, if someone could point out to me why i have to use nitrogen if just before a vacuum, that would be interesting to me, i was originally thinking to do it with compressed air or co2, but i think argon is closer to the recommended Nitrogen?

I believe it is possible to fill a system with co2 if it has been dried first (r744) I'm not sure if it can be used in a r134a system at a different quantity or if a specially designed system is needed. i'm not sure how dry my co2 or argon is either but hopeful will be good for a flush and for leak testing?
James

izzzzzz6

Mmmmm old thread