has anyone used the Harbor Freight pumps - PeachParts Mercedes-Benz Forum

Junkman · #1 05-29-2015, 11:24 AM

AC is out on 3 vehicles that I'm responsible for. One needs a new compressor and the other at least has leaked all of the gas out. Once refurbished, I probably won't do much AC work.

Will any of these pumps & gauges suffice? Are there any that definitely should be avoided?

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BayouFlyFisher · #2 05-29-2015, 01:22 PM

I've used their 2.5 cfm pump for a while now and it works fine. I've used it on my 77 300D twice and two of my grandson's vehicles. I bought the pump with a 25% discount coupon so it has been a great bargain so far. Operationally there has been no surprises or drama. I know nothing about their gauges though.

barry12345 · #3 05-29-2015, 05:52 PM

I think you can grab both items off ebay and other sources new much cheaper than harbour freight. Have a look under hvac equipment. I think I paid about 27.00 including shipping from China for a simular quality set. For no proffessional heavy duty use they are more than adaquate.

I also got a really high quality vacuum pump from ebay very cheap as well. . Can easily pull down to 100 microns fairly quickly.

The example you show is a toy in comparison but will work ok. Up here in Canada things are substantially more expensive in the hvac field.

I did pretty easily aquire everything I felt was needed at reasonable prices from american sources primarily. Even the gear that I felt had to be good quality for certain applications. Generally you do not need the one percent accuracy the expensive gauges claim.

ah-kay · #4 05-29-2015, 06:14 PM

I used the simple one using bernoulli's principle with a compressor. It seems ok for a DIY. Have you ever thought about using the vacuum pump on the engine? I can't see why it wouldn't work.

vstech · #5 05-29-2015, 10:17 PM

The engine pump will pull a vacuum, but only down to 22" at most... To do any moisture removal ya need a full 29.9" and below 1100 microns...

mannys9130 · #6 05-30-2015, 12:25 AM

Quote:

Originally Posted by ah-kay

I used the simple one using bernoulli's principle with a compressor. It seems ok for a DIY. Have you ever thought about using the vacuum pump on the engine? I can't see why it wouldn't work.

Engine vacuum pump could never ever even hope of drawing a vacuum suitable for AC work. It would be full of water and non condensable gases at the end.

barry12345 · #7 05-30-2015, 11:44 AM

I forgot to mention. I aquired a real strong vacuum pump from the ebay listings on vacuum pumps. Usually you have to fit a fitting to modify the connection on them to work with ac hoses. That is minor as the real pumps are designed for continious service in comparison to the average cheaper hvac pump.

Most decent pumps will be two stage as well. The smaller pumps in the real vacuum pump world seem to come up as pretty much surplus from time to time. All I am certain is at the present time you can still get a better cheapie type vacuum pump from ebay for less money. I looked. Same with new gauge sets.

Actually there is a cheap new viot but looks like a two stage on ebay with less than two hours to go. Two stage is not the cheapest model either. Brand new with no bids and starting is .99. At this time it is one in the afternoon here in eastern Canada. May or may not attract any bids and it is listed under vacuum pump on ebay. . Someone should grab it if the original poster does not. Possibly comes out of the same Chinese factory the harbour freight one does. I think it is a better model than their 99.95 edition though.

BillGrissom · #8 06-01-2015, 12:49 PM

You guys are silly. You only need ~10" Hg vacuum (dep. on temperature) to boil off any water in the system, and the one on your car should do that. Good luck reaching 29.9" Hg with any pump. The longer you leave it sitting under vacuum, the better. If you see the pressure creep up, don't fret since it could be stuff out-gassing. You also need a way to isolate your pumping kit, so no leaks there confuse you. My setup has a needle valve (posted photo before). I start w/ the 300D's vac pump, then switch to a HF hand pump. I could only hold it at 22"Hg on my 300D last time I did it, but later found a leak in my setup. I hand-pumped one car down to 29"Hg one time w/ only ~5 min of pumping, but that was just for fun. I also leverage my 300D's pump for AC work on my gas cars. You could be the neighborhood hero that way.

mannys9130 · #9 06-01-2015, 01:02 PM

Quote:

Originally Posted by BillGrissom

You guys are silly. You only need ~10" Hg vacuum (dep. on temperature) to boil off any water in the system, and the one on your car should do that. Good luck reaching 29.9" Hg with any pump. The longer you leave it sitting under vacuum, the better. If you see the pressure creep up, don't fret since it could be stuff out-gassing. You also need a way to isolate your pumping kit, so no leaks there confuse you. My setup has a needle valve (posted photo before). I start w/ the 300D's vac pump, then switch to a HF hand pump. I could only hold it at 22"Hg on my 300D last time I did it, but later found a leak in my setup. I hand-pumped one car down to 29"Hg one time w/ only ~5 min of pumping, but that was just for fun. I also leverage my 300D's pump for AC work on my gas cars. You could be the neighborhood hero that way.

Ummmm....no.

As you pull vacuum the water gets colder and colder which requires a harder and harder vacuum to be pulled in order to boil it off. 10" is not enough. 22" is not even close. Second, if you pull a vacuum on a semihermetic system for more than an hour or so, you'll begin to draw moisture back into the system through the porous areas. Drawing a vacuum and leaving the system with a vacuum is equally bad for the same reason.

Leave the engine driven pump for the power brakes and door locks that it's designed to run, OK?

Get a proper vacuum pump for AC work, vac it down to 29" for an hour, fill with 200psi dry inert gas and let it sit for an hour or 2 to leak check, vacuum it again for an hour, recharge with refrigerant. That's the one and only proper procedure.

BillGrissom · #10 06-01-2015, 01:35 PM

Oops. I recalled 10"Hg from somewhere, but did more research and found at 90 F, you need 28.5"Hg to turn the water into vapor (Air Powered A/C Vacuum Pumps). We can hit 100 F ambient here and a car can get much hotter in the sun, so 110 F is easy, in which case 27.3"Hg will work, and you can get there fast w/ a Mighty-Mite type hand pump after letting the engine pump "rough it". Another technique is to use dry gas to help evaporate water. Some industrial AC guys use N2 (from dry ice). In CA, we could just let our dry air into the system, then re-evacuate. Even at 1 atm pressure, water doesn't stay liquid long here in the summer. I doubt must be perfect in a car since there is also the filter/drier which has dessicant to absorb any remaining water vapor. I replaced that when I did my 300D recently. As mentioned, give it time for everything to warm up after pulling a vacuum.

In olden days, I didn't have a vac pump, so I would just fill w/ freon, then blow off some freon, which I figured should flush air and water vapor out. Freon was $0.25/can then and they sold freon "BB machine guns". We didn't know we were increasing the ozone hole then, as many today don't know you are causing climate change with R-134A (to be outlawed). You can use the blow-off method today if you use HC refrigerant, but it cost $8/can. Doing so is no worse for the environment than a cow fart. The main problem with water in the system is that it can freeze and clog the expansion valve, and promote corrosion.

ah-kay · #11 06-01-2015, 01:38 PM

Quote:

Originally Posted by mannys9130

Ummmm....no.

Get a proper vacuum pump for AC work, vac it down to 29" for an hour, fill with 200psi dry inert gas and let it sit for an hour or 2 to leak check, vacuum it again for an hour, recharge with refrigerant. That's the one and only proper procedure.

If A/C shop follows your recommendation then they would be either out of business or change you 'an arm and a leg' literally to work on your A/C. It ain't going to happen commercially as a business. If you do it yourself and sit on it, then you can do whatever you like.

mannys9130 · #12 06-01-2015, 02:04 PM

I'm sure VStech will be in here shortly...

1st point: ambient temp differs from the temp inside the lines. It gets very cold inside when you pull the vacuum because evaporating water takes phase energy away from its environment to boil into vapor. It doesn't matter if it's 110F outside. It's cold inside the lines where it matters.

2. Letting atmosphere back into the system is the most counterproductive thing you can do. You're trying so hard to remove all the water, and then you put atmosphere back in. I'm in Tucson. The dry air here trumps that of California. Even I wouldn't consider doing what you propose with our "0%" humidity dry AZ summer air. Bottled dry Nitrogen is CHEMICALLY pure, meaning it's lab grade. It can be used to store Sodium metal which reacts with water in the air.

3. Dry ice is made of CO2 not Nitrogen. You can use any nonreactive dry gas you wish but N2 is preferred.

4. Venting of refrigerant is illegal regardless of chemistry. As a 609 tech I cannot vent any refrigerant.

Ahkay, if I was to pay a PROFESSIONAL to do the work, they better do it correctly or I'm not paying. Mind you, I work as an automotive tech, so you're talking to the industry here.

ah-kay · #13 06-01-2015, 02:32 PM

Quote:

Originally Posted by mannys9130

Ahkay, if I was to pay a PROFESSIONAL to do the work, they better do it correctly or I'm not paying. Mind you, I work as an automotive tech, so you're talking to the industry here.

Where is your shop? I will take my car there. How much you think an A/C shop would charge, say, to open up the system to change out the receiver/drier which is a $25 parts give or take? Recharge with freon and oil etc.

"Get a proper vacuum pump for AC work, vac it down to 29" for an hour, fill with 200psi dry inert gas and let it sit for an hour or 2 to leak check, vacuum it again for an hour, recharge with refrigerant. That's the one and only proper procedure."

mannys9130 · #14 06-01-2015, 02:47 PM

If you think I'd tell you over the internet where I work you're dreaming. I most definitely did practice what I preach. That's why I preach it.

Every single AC job I did got proper procedure and protocol. That's part of having a 609 cert. You're bound by law.

If I didn't have the tools, time, or knowledge to perform specific work I sent it down the road. My conscious is clean AhKay.

I stand my ground.

ah-kay · #15 06-01-2015, 04:33 PM

Quote:

Originally Posted by ah-kay

Where is your shop? I will take my car there.

If you think I really meant taking my car to your shop, think again. You have not read my bio. If you practice what you preach and charge reasonable rates then we have a honorable and honest mechanic. The bottom line is that we do not need a VP that can pull down to 29" vacuum or have a N2 tank to pressurize it to do A/C work as a DIY. This is where we diverge. I have nothing to add to this thread.