Tampa 928s

I did use a rebuild kit on it a few months ago now I can see the oil leaking out of the front seal and the 134 is low, hence hot hot hot. Anyone know how to rebuild the seals and have it work and not leak. On an 86 it's a pain to remove and remount I'm not sure to replace it or get a profession to rebuild it any feedback?

Tampa 928s

On at about 85-90 outside temputure what should my readings be, low side is about 38 the high side cannot be tested due to the type of adapter used. When myself and the air shop hooked the high side up when removed it was a full stream 12 inched in the air. Apparently the valve gets pushed into far and sticks open till jiggled with a screw driver. I have yet to find the correct adapter for the high side that works.

dr bob

One thing that the adapter instructs fail to tell you is that you need to remove the valve core from the old fitting before you install the adapter. The adapter tries to push the center pin on the old valve, and unless it's at exactly the right depth it will either not open the old valve at all, or will end up bending/deforming the old valve to the point where it doesn't work. Save yourself the agony later, and just pull the old valve core out in advance.

The partial pressure in the system is low if you have a static of 38 at ambient 85ºf. If the compressor is running and your high side is less than 275 while low side is 38, it's mighty close to good.

dprantl

Where do you see oil leaking? Is it from behind the clutch/pulley?

Dan
'91 928GT S/C

Tampa 928s

Yes behind the pulley going out of the rope weep seal, it has a new seal and was fine for several months.

Tampa 928s

Dr. Bob

Are you saying remove the valve on the Receiver/Dryer with a different type?
I have an old r-12 hose with the larger connection for the gauge assembly on the high side. The normal screw on top piece adapter has no valve, what am I missing?

dr bob

You may have a too-cheap adapter. The better adapters have valves in them. The ones I buy have the valves built in, and a little pin sticking out the bottom that's supposed to continuously depress the pin on the old valve. If the old valve core is too low in the fitting, the adapter pin doesn't open the old valve. That makes evacuating and charging a bit of a challenge. Ifthe old valve core sits a little high in the old fitting, that pin in the adapter will bend the old valve as you tighten it, making it impossible to open and tough to remove.

If for some reason you have to depend on the old valves to make a seal, be sure to replace the cores with new AC-specific cores. The sealing washers will be compatible with the new oil. The older rubber seals used in te original valves will eventually weep if you depend on them alone. You'll want to do this for the schraeder valve under the pressure switch on the drier too, no matter what.

joejoe

Tampa, this is strange indeed. Just had my '81 on the rack for oil change and when finished started car to circulate new oil. when I turned off to check level heard a hissssss. Freon leaking from front of compressor. This leak was big enough that I did not have time to get off lift and to recovery/recycle unit to save freon left. I am getting a rebuilt from 928intl. and will replace when it shows up. I guess 27yr old parts can go bad.

JP Rodkey

When you replace the seal and prep for reinstallation, you will be putting the correct amount of oil (assuming it's a Nippondenso 6E171, you will need 3.7 oz) back into the compressor. Connect the lines, but don't mount the compressor. Hold it as vertical as you can get it, clutch side down, and turn the driven plate on the clutch about 20 times. The seal requires oil to do it's job, and this little procedure is often overlooked leading to failure of the seal. Yes....I did learn this the hard way.

Tampa 928s

Jp

I missed that part all together but did add the oil, that may explain the premature failure!

Tampa 928s

The coldest reading was 54 Degrees after 5 min went to 58 Degrees.

Idle pressure 32-34 its fluctuating low side, high side 220.

At 2k low Pressure 27 still fluctuating a pound or two high, side 275.
This seems ok but not sure about the low side fluctuating and the air is way too warm.
Feedback?

dr bob

It seems like you may still have a lot of air in the system, based on the low sied pressures and temps. 27 PSI on the low side should be freezing the evaporator if there's just refrigerant in there.

Thorough evacuation of the system is absolutely critical to the ultimate performance. Some folks go get a little air eductor type of vacuum 'pump', draw the system down to 22" and call it fine. Others find an inexpensive dry-vane pump, supposedly adeqate fo AC work, and get 28". Serious cold requires serious vacuum, and the bargain pumps aren't adequate. If you can't pull the low-side guage needle hard against the suction pin (assuming you are at or near sea level, safe assumption almost anywhere in Florida...) you are leaving air in the system. Air left in the system causes multiple problems. It consumes compressor, evaporator and condenser capacity. In the condenser, the air never 'condenses', so it passes through to the exoansion valve as a gas. That means it takes up a lot nmore space in the condenser, limiting the amount of effective transfer and therefore the condensing of the refrigerant. At the evaporator, the air passes through the confused expansion valve as gas, and obviously doesn't expand the same as the refrigerant since there's no state change. It's the state change from liquid to gas that requires the addition of heat from the outside of the evaporator, so no state change means almost no heat extracted from the car. So, what's the partial pressure of the air in the charge? In amateur-maintained systems, 5-10% by weight is common. That means that the evap will not cool below about 40 degrees. Pass warm air through the system and you expect to see about 40º of temp drop across the evaporator; less with the air pigging up space and capacity, of course.

If you suspect that you didn't get all the air out, and your presures and temps suggest that you may not have, you may want to have the refrigerant recovered. Then have a good evacuation done, and leave the pump pulling on the system for 24 hours before charging. This will boil oit any stray moisture left in there. Then charge by weight to about 90 to maybe 95% of the original R12 charge. If you are charging to the sight glass, you'll want to still see some bubbles in the glass when you are done. Not a foam of bubbles, but "some". Make extr-sure that your electric fans are working properly too, and consider getting the late GTS-spec pressure safety switch just to be sure you don't overpressure the system on a hot day in slow traffic. It's very cheap insurance.

Tampa 928s

Dr. Bob,

I am going to vacuum my system tomorrow I think you are correct about air in the system. I have a large vacuum pump and will leave it on as you stated. I believe there is a trick to refilling with R-134 as to not introduce air into the system. Do you have a good method to accomplish this? Is there any other hints you may want to share? Now I need to work on the high temperature while in traffic with the air on and yes the fans are all on. I believe the S/C is blocking the air flow by bouncing off of the S/C and am thinking about adding a couple of fans in the front to replace the factory one.
Thanks
Mark

Tampa 928s

Update:

What is going on now that in stop and go my Temp gauge goes above the second bar, it has never been this hot. It will start dropping if a go to a cruzing speed, although the normal range as always been just above the first bar. I wonder if adding a larger fan or 4- smaller fans like in the radiator side will knock the temperature down. My air is all working fine except as I drive the car it starts getting warmer. Could it be that I may have introduced air into the system and as it heats up it becomes less efficient? This morning I did a reading on my air pressures and it was nice and cold. I have access to a 20 Lb can of R-134 but need to use a scale to measure it. I am concerned that using the cans has cause some air to be introduced. I am thinking about a digital bathroom scale any feedback. So I am trying to figure out is it air, heat or a combo of both.

Car not started
Air Temp: 78
Static pressure 84

Car warmed up
Air Temp around 82
Low 33
High 150
Outlet Temp 37.5

Test run for 2-miles outlet temperature 32 feels good

Car shut off static pressure 86

Still waiting on the rain to stop and get it into stop and go drive and an air temperature of 95 like all days here in Florida to measure my pressures.

Tampa 928s

I am using a Robinair vacummaster and notice a lot oil vapor coming out of the handle. I have both the low and high side connected how long should I see this vapor or will it diminish once moisture is gone?