Schrader Valve Question - PeachParts Mercedes-Benz Forum

shertex · #1 09-06-2018, 10:03 AM

For many years my 91 has had a very slow AC leak....didn't know where and didn't care. Just added refrigerant once a year.

This year I discovered a bad condenser leak, which I assume was separate from the other leak (although no way to be certain). So my indie replaced the condenser and I had ice cold AC once again.

After a few months, AC seemed noticeably weaker, so I assumed original minor leak was rearing its ugly head. When I looked at the low side port, it was covered with dye and bubbling. So there's the source of my leak, I thought. BUT when I added refrigerant and checked the valve again, it wasn't leaking at all. Somehow by opening and closing the valve there was a tight seal once again.

Can old Schrader valves be temperamental that way? Where, if they leak, just opening and closing again seals it? Or does it sound like I need to replace that valve at some point?

With summer almost over in New England, I have little motivation to throw more money at the AC in this car. But, with all the money I've already spent, I want to be leak free before next summer.

Thanks.

Diseasel300 · #2 09-06-2018, 10:15 AM

Schrader valves can and do leak with age. You can replace the cores with a core removal tool which will not disrupt the charge in the A/C system. Replace the caps too. They should have rubber gaskets in them that will protect against minor leakage. The rubber hardens or falls out over time and becomes useless against slow leaks.

TX76513 · #3 09-06-2018, 10:16 AM

Yes they can "stick" like that - but also can be tightened up just like a valve stem. One other item you may have overlooked is to replace the seal in the cap for the valve.

Zulfiqar · #4 09-06-2018, 11:34 AM

my brother's car had shrader valves leaking on both sides (mazda 6), they were actually bent when I removed them (probably from previous techs fault)

new valves have sealed it nicely.

shertex · #5 09-06-2018, 01:28 PM

Quote:

Originally Posted by Diseasel300

Schrader valves can and do leak with age. You can replace the cores with a core removal tool which will not disrupt the charge in the A/C system. Replace the caps too. They should have rubber gaskets in them that will protect against minor leakage. The rubber hardens or falls out over time and becomes useless against slow leaks.

When I remove the core, wouldn't the refrigerant start leaking rapidly?

I picked up a kit that includes two caps, two cores, and the tool.

Mike D · #6 09-06-2018, 01:45 PM

I use one of these: https://www.amazon.com/Mastercool-81490-R134A-Remover-Installer/dp/B000KITSMI

I believe I got it from Tooltopia.

Do you still have R12 or has it been converted to R134? I believe it makes a difference in regards to the tool needed.

Diseasel300 · #7 09-06-2018, 01:55 PM

Quote:

Originally Posted by shertex

When I remove the core, wouldn't the refrigerant start leaking rapidly?

I picked up a kit that includes two caps, two cores, and the tool.

You need a core remover tool, not just the little twisty bit that comes in the kit. They have a plunging rod and a valve so that you can remove the core, shut the valve, then remove the rod with the core attached. You can also try using the generic core tool that comes in your kit to tighten the cores that are already in place, if they're loose they'll leak!

shertex · #8 09-06-2018, 02:11 PM

It's been converted to R134a.

When I removed the cap today, there was a "puff" of released pressure. For now I will try tightening the valve making sure the cap is nice and tight.

shertex · #9 09-06-2018, 02:14 PM

Would the fact the mine has been converted create any issues? Or should that linked tool work just fine?

shertex · #10 09-06-2018, 02:37 PM

So the little tool that came with the kit doesn't seem to fit...don't see how I can use it to tighten the valve.

97 SL320 · #11 09-06-2018, 03:00 PM

If you have a gasketed plastic cap that firmly threads on rather than just pushes on, it will seal enough not to leak. This isn't optimal but it will work.

Make sure the 12 to 134 adapter isn't leaking on the 12 side as replacing the 134 core won't fix this.

shertex · #12 09-06-2018, 03:06 PM

Quote:

Originally Posted by 97 SL320

If you have a gasketed plastic cap that firmly threads on rather than just pushes on, it will seal enough not to leak. This isn't optimal but it will work.

Make sure the 12 to 134 adapter isn't leaking on the 12 side as replacing the 134 core won't fix this.

Good to know...for the time being I'll just add refrigerant and install a new cap. Will have my indie address next time I have the car in for something else.

Zulfiqar · #13 09-06-2018, 04:23 PM

quite odd that the ac tech didnt replace the shrader valves when servicing a component, I thought it was standard practice to prevent comebacks for small reasons.

barry12345 · #14 09-06-2018, 08:31 PM

The tools to change the valves with the system under pressure. Are dirt cheap on ebay from China. On a 134 system I think 15.00 gets a pair of them including shipping that covers the high and low sides.

Not that bad quality for the money. More than adequate for just doing this.

vstech · #15 09-10-2018, 04:35 PM

The issue is, you will need an r12 core tool, and remove the 134adapters, then change cores, then put the adapters back on...