Schrader valve high pressure side

Moderators: Nacho, Tom Greenleaf, ACProf, acsource

Schrader valve high pressure side

Postby Van Diest » Thu Apr 06, 2017 9:49 pm

I have a 95 Silverado C1500, 5.7, extended cab with factory A/C, 134a. My sniffer picked up a small leak in the center of the high pressure side port. I can not see a schrader valve but I can see what looks like a flat piece of black plastic? It also looks like you can possibly unscrew the nipple. Is this a serviceable item or is it something best not to mess with?

On a vacume pump do you use mineral oil or what type of oil? The oil level is almost 1/8" under the "oil level" mark on the pump or would running it this way hurt anything?

Thank you for your time, Van
Van Diest
 
Posts: 37
Joined: Mon Jun 26, 2006 3:00 am
Location: So Calif

Re: Schrader valve high pressure side

Postby Tom Greenleaf » Fri Apr 07, 2017 9:46 am

It's a ball valve known to leak and highly depends on a good cap. If it still leaks actively you can discharge and replace those whole at the risk of stripping threads that look welded and are not if all OE and what I think.

Where are you with this guessing low on charge and this alone if it's the only leak wouldn't lose much oil. The OE Delphi compressor is known for "belly leaks" and those ports leaking. Low charge is deadly - so disable it until you can figure out a plan.

It should be a charge of 32 oz. 134a and about 8 oz of PAG 150. Stickers underhood may be on the original accumulator only or radiator support.

Again - don't let it run low on charge expessed as a rattle. Top hoses high side should be warm/hot + return cold when compressor engaged or it's low FYI.

Only charge this or anything from known well held vacuum to known exact amount. These can tolerate being off of perfect by 10% maybe a little more but no more. Avoid overcharging,

T
(Edit: Crew cab if so the capacity is 36 not 32 Oz.)
MetroWest, Boston
Image
______________________________
User avatar
Tom Greenleaf
 
Posts: 4549
Joined: Tue Jun 28, 2005 8:40 am
Location: Marlborough, MA. USA
Favorite Refrigerant: R-12+134a

Re: Schrader valve high pressure side

Postby Tom Greenleaf » Fri Apr 07, 2017 10:13 am

Sorry - re-read that oil was for vacuum pump not the truck. IDK - If a sight glass how low is it really? Check after a blank run of it while it's running if that type.

Oil type should be listed if you wish to add or change it or just ask for vacuum pump oil. One I have I don't recall but think was a synthetic for the pump's sake not to do with the vehicle it's working on.

With just gauges attached you should be able to pull a full vacuum without a vehicle at all and do so, Tom
MetroWest, Boston
Image
______________________________
User avatar
Tom Greenleaf
 
Posts: 4549
Joined: Tue Jun 28, 2005 8:40 am
Location: Marlborough, MA. USA
Favorite Refrigerant: R-12+134a

Re: Schrader valve high pressure side

Postby Van Diest » Sat Apr 08, 2017 1:00 am

I pulled vacuum for 45 min and it held fine. I got interrupted while I was charging. So instead of putting in the 32 oz it calls for, I accidentally put in 34 oz. I do have a R12 recovery tank that is empty that I could flush, pull vacuum and put the 134 in, but I wouldn't know how much oil came with it. I have a TIF digital scale.

74 ambient temp, low side 24, high side 180, center vent temp 39, at idle.

Any suggestions?

Tom, thanks again.
Van Diest
 
Posts: 37
Joined: Mon Jun 26, 2006 3:00 am
Location: So Calif

Re: Schrader valve high pressure side

Postby Van Diest » Sat Apr 08, 2017 1:05 am

After charging, sniffer still picked up a small leak on the high side without the cap on, but did not pick up a leak with cap on at static pressure.

Thanks again.
Van Diest
 
Posts: 37
Joined: Mon Jun 26, 2006 3:00 am
Location: So Calif

Re: Schrader valve high pressure side

Postby Tom Greenleaf » Sat Apr 08, 2017 7:57 am

OK - Still a leak with cap on? Check your sniffer. My own will pick up signals from any sprays used or if dirty in the area or windy goes bonkers.

R-12 tank would work - just vacuum it out if empty but there are easier choices.

This may hold 36 oz not the 32 oz I mentioned and changed if you look back. IMO that 4 ounces isn't going to make or break this truck's A/C it will or should work and your performance results are fine for that ambient temp.

Note on that: Ambient to the truck is the temp of the air coming in thru the grille NOT the day's forecast or a thermos on a wall thing. It's usually warmer than you think right in front of the grille of the truck is all it knows.

Check if you wish the charge to be super on target if it's 36 oz. that's 3 of the small cans but do weight them first new. OMG - I find them off new!

What to expect for pressures is highly dependent on air flow, RPM and how effective fan clutch is on this. Water on condenser will dramatically drop pressures just FYI to help or check max performance. Takes a lot of thermos placed around.

The high side pressure should reflect a multiple of the temp of air coming in X 2.5 or so for 134a at a raised RPM of about 1500 or a bit higher.

Here's a great link also above at this site for good basic info on charging...............

http://aircondition.com/tech/questions/ ... Procedures

Notes: Vacuum at sea level is 29.92 or close - real close. How long a pump needs to run to get to that varies but once there you can shut the pump off and just let time pass while it holds. If anything leaking or more moisture either as liquid, in desiccant or as ice for any reason is will rise by itself and run again to see if it holds. No need to run the pump for an hour unless it's seriously too slow or defective. All connections are also always suspect too.

Back to the leak. Just get a high quality new cap is probably the solution for high side. It's getting old but might find one in stock new at dealer or even a great one used. Some cheap stuff will just fail right away and it does count on it.

BTW - know a tad more for this than others as I've owned a 96 Suburban and currently 97 C/K 2500 the difference is Vortec 5.7 engines not much else.

Chat: Going to be warm here soon and on my list (I'm done actively doing much of this) check all vehicles after Winter that they are working properly now old catching them early has saved them for decades on end by NOT allowing them to run while low and old enough can go a few years and need some not enough of a loss to require a repair on them yet as too slow to be credible,

T
MetroWest, Boston
Image
______________________________
User avatar
Tom Greenleaf
 
Posts: 4549
Joined: Tue Jun 28, 2005 8:40 am
Location: Marlborough, MA. USA
Favorite Refrigerant: R-12+134a

Re: Schrader valve high pressure side

Postby Van Diest » Tue Apr 18, 2017 9:38 pm

[quote="Tom Greenleaf"]It's a ball valve known to leak and highly depends on a good cap. If it still leaks actively you can discharge and replace those whole at the risk of stripping threads that look welded and are not if all OE and what I think.

What should be done prior to removing the ball valve to prevent doing any damage to the threads?
Van Diest
 
Posts: 37
Joined: Mon Jun 26, 2006 3:00 am
Location: So Calif

Re: Schrader valve high pressure side

Postby Van Diest » Tue Apr 18, 2017 10:37 pm

[quote="Van Diest"] I got interrupted while I was charging. So instead of putting in the 32 oz it calls for, I accidentally put in 34 oz. I do have a R12 recovery tank that is empty that I could pull vacuum and put the 134 in, but I wouldn't know how much oil came with it. I have a TIF digital scale.

74 ambient temp, low side 24, high side 180, center vent temp 39, at idle. [quote]

I did find a sticker on the truck that calls for 32 oz. I didn't think to weigh the cans of R134a before I charged the system.

What would be the best way to remove the 2 oz overcharge to put in the recovery tank?

Can I pull vacuum on recovery tank and remove overcharge thru the high or low side?

At idle w/ ac on the comp clutch is engaged, when I rev the motor to 1500 rpm the clutch will start cycling on and off. Should this system's clutch be engaged whenever the a/c is on or might this be from the overcharge? (95 Silverado, 5.7, extended cab, factory R134a)

Thank you for your time.
Van Diest
 
Posts: 37
Joined: Mon Jun 26, 2006 3:00 am
Location: So Calif

Re: Schrader valve high pressure side

Postby Tom Greenleaf » Wed Apr 19, 2017 4:30 am

Quote you ">What would be the best way to remove the 2 oz overcharge to put in the recovery tank? <"

Leave it in there. 2oz isn't going to wreck the project in this. In fact hard to know it's exactly that without costly equipment to remove it and count then put back exactly 32.

If the amount over was a problem performance would drop off and you would see the belt struggle. That isn't enough to do that for this vehicle,

Tom
MetroWest, Boston
Image
______________________________
User avatar
Tom Greenleaf
 
Posts: 4549
Joined: Tue Jun 28, 2005 8:40 am
Location: Marlborough, MA. USA
Favorite Refrigerant: R-12+134a


Return to A/C Questions and Opinions

Who is online

Users browsing this forum: Bing [Bot], The Google [Bot] and 11 guests

cron