Vacuum pump suction readings.

Rapidrob

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96' Passat Wagon
I cannot find anywhere what the Vacuum pumps suction readings should be?
Some post show as much as 29" of mercury.
What is considered normal with no leaks?
 

\/\/0J0

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Knoxville, TN
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Sadly, none anymore
29 inHg would be ideal but a reading over 20 inHg is certainly acceptable

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Mongler98

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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
in order to get a real reading on the vaccum you need a micrometer, the cheep ones are junk and you will pay about $500 at the very least for a GOOD one that will actually work. Rule of thumb is, vacuum it down for 1 hour and turn off all the valves and let it sit overnight or for a full day. if the needle moves AT ALL, you have a leak. To truly get down to a level you should be at for a perfect job, you need to flush all your lines out and change the oil in the compressor and new dryer because of contaminates. In a nut shell, just vac it down for 1-2 hours and let it sit for 1 full day. if nothing changes than your golden. if the system always had a good charge on it than just weigh in new refrigerant, dont do this any other way. If its in need of service, change all your o rings, the valve, dryer, and flush all the lines and evaporator with AC flush followed with nitrogen purge. Pull a vacuum for 1 hour and let it rest, if good, fill with nitrogen and do a bubble test with soap water than vacuum it again. Now weigh it back in and enjoy. there is more to meet the eye about this stuff and if you want you can PM me and i will help you out. My father is an Master HVAC and know too much about this for my own good.
 

\/\/0J0

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Sadly, none anymore
Nothing. What type of $500 micrometer do you need for air conditioning service?
Yeah, I'm trying to figure that one out too. I mean you could buy a nice starret for about 125, but I fail to see how it will measure vacuum, or be affected by it for that matter.

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Rapidrob

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Edgewood,New Mexico
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96' Passat Wagon
I bought a used one from a member here and am still waiting for it to show up.
To test the pump I was going to use a drill motor or chuck it in my lathe to do a quick test of the vacuum.
Does the pump spin CW or CCW?
 

KLXD

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CW As viewed from the shaft end.

I wouldn't test it that way. It normally gets a constant oil supply from the engine. A brief spin with a drill probably wouldn't damage it if it has residual oil in it but I doubt you'd get a true reading of its output.

Edit:

Oops. I was thinking of the ALH pump. The AHU is gear driven by the accessory shaft. You could probably tell by looking at the wear on the pump gear which direction it turns.

I think the accessory shaft turns CCW since it's driven by the back of the belt. That and the angle of the gear teeth would tell you.

Again, the vanes rely on a nice layer of oil to effect a seal with their bore...
 
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Ol'Rattler

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The best way to test it would be to connect a vacuum gauge directly to it and just run the engine.
 

Vince Waldon

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If you remember that it spins at half engine speed and make sure there's some clean oil on the pump shaft I think a quick spin at 500-1000 RPM is probably not too risky.

You will know in seconds if it works or not... as long as you get 20+ inches of vacuum you're good to go.

The vacuum supply is used to power the brake booster and also the turbo actuator and EGR valves... fed-back systems for the most part, so the actual value is not super critical.
 

Windex

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If you are evaluating the performance of the vac pump, test it by itself, as well as hooked up to the booster - a perceived faulty pump may just be a vacuum leak somewhere.
 

Vince Waldon

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Good point.

Always tricky to lend constructive help without knowing the context... aka... the actual issue at hand. :)
 

Mongler98

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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
What's all that got to do with the vacuum pump on the engine?
I cannot find anywhere what the Vacuum pumps suction readings should be?
Some post show as much as 29" of mercury.
What is considered normal with no leaks?
When i hear "vacuum pump" i hear HVAC. i did not know that the vac pump on out TDI's had issues. Either it has a bad vac line or it works right? I guess not. I did not think it matters how much vacuum it pulls as its all based off of pressure or no pressure ie it does not matter if 27 or 29 inch Hg

My bad, i was talking about HVAC, you dont need a micron gauge and btw they are $500+ or crap. So ignore my last post.
 

Heinrich D W

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May 1, 2008
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Linwood,ON Canada
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VW Jetta 2003 & 2001
I have tried and check everything I think of, but my 01 Jetta TDI is having problems with vacuum. The gauge registered at 8hg and 10 after cleaning it. So I'm wondering if it is the pump that's the problem. Has anyone had to change the pump to fix this problem? Does anyone have an answer to this.
 

\/\/0J0

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Apr 27, 2010
Location
Knoxville, TN
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Sadly, none anymore
I have tried and check everything I think of, but my 01 Jetta TDI is having problems with vacuum. The gauge registered at 8hg and 10 after cleaning it. So I'm wondering if it is the pump that's the problem. Has anyone had to change the pump to fix this problem? Does anyone have an answer to this.
Yes, the ALH vacuum pumps can have issues, usually with the seal for the nipple on it, but this is the mk3 section. You will be better off poking around in the mk4 section or starting a new thread there.

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Rapidrob

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Edgewood,New Mexico
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The used pump showed up late today and I put it in the car. I hooked my vacuum gauge directly to the pump and with nothing else hooked up the pump is providing 18" HG. Exactly the same as my original pump.
I'm back to square one.
The "flapper will cycle if I run a LARGER I.D hose than the VW tube directly to the vacuum solenoid.
If I hook up to the white plastic vacuum line at the firewall,BYPASSING the line going into the cabin and running the same test line that does cycle the "flapper", it will not cycle even though there is 18" HG at the vacuum solenoid. (same at the engine)
The ONLY difference is the smaller white plastic line and the 12 VDC solenoid, which works and is opening as it should. I took it apart and cleaned it,it wasn't really dirty inside.
Both, the 12 VDC solenoid and the white plastic line when turned ON, provide 18"HG every time and HOLD the vacuum. No leak up.
Perhaps both pumps are worn out. Others have posted 20+ inches of HG vacuum with their pumps.
 

Windex

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Does the actuator hold vacuum if you test it directly with a hand vac pump like a mighty-vac?
 

Rapidrob

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Edgewood,New Mexico
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96' Passat Wagon
The Handy Vac does not have enough volume to operated the device. I tried two types of hand vacuum pumps and neither will move the flapper. The volume is just too large.
The flapper moves like crazy if I put 18" of vacuum on it directly from the engine with a large I.D hose. It moves instantly,not a slow movement. Trying to push down on the closed flap takes a lot of force to move it if the vacuum is on.*
If down, the flapper needs just a little help to push it up one inch or so and it takes off if hooked to the cars original vacuum line.
*I could try that again and pinch the hose off and kill the engine to see if it holds the vacuum and flapper up.
The pump holds a vacuum with the engine off for a long time.
 

Windex

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The Handy Vac does not have enough volume to operated the device. I tried two types of hand vacuum pumps and neither will move the flapper. The volume is just too large.
The flapper moves like crazy if I put 18" of vacuum on it directly from the engine with a large I.D hose. It moves instantly,not a slow movement. Trying to push down on the closed flap takes a lot of force to move it if the vacuum is on.*
If down, the flapper needs just a little help to push it up one inch or so and it takes off if hooked to the cars original vacuum line.
*I could try that again and pinch the hose off and kill the engine to see if it holds the vacuum and flapper up.
The pump holds a vacuum with the engine off for a long time.
If it's as you describe, I suspect your actuator diaphragm is leaking...

I would tee in the vacuum gauge into the line going to the actuator, with the engine running and see what working vacuum you have.

Another alternative is to add a vacuum reservoir into the circuit before the solenoid - the vacuum storage may be enough to give the actuator a "nudge" open.
 

Rapidrob

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Edgewood,New Mexico
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I've been looking around for a reservoir that will fit. It would need to be before the electric solenoid valve as the vacuum has to be dumped in order to cycle the flapper.
I may have to double-back the vacuum lines in order to get one to fit in the engine bay.
 

KLXD

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Hose size should not make a difference in whether the actuator moves or not, only in speed. You may have a leak in the actuator as Windex suggests.

Or the valve may be leaking internally. You may have ruled this out if you tested directly between the pump and actuator.

The big fitting on the pumps likes to leak when they get old. Maybe smear some sillycone around it and see if you get a better vacuum.
 

kooyajerms

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The flapper actuator that is located on the passenger side definitely operates with a hand mity vac. I tested both actuators when I pulled them out. One held vacuum, one did not.

I got a replacement actuator and it fixed my flapper issues. If a big enough vac line is closing the actuator diaphragm, but a mityvac is not strong enough then it must be a leak.

Nice job testing all the difficult firewall connnections, but the actuator could have been tested fairly early on.
 

Steve Addy

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I've been looking around for a reservoir that will fit. It would need to be before the electric solenoid valve as the vacuum has to be dumped in order to cycle the flapper.
I may have to double-back the vacuum lines in order to get one to fit in the engine bay.
On my B3V project, which started life as a 16v 2.0L gas car, there was a reservoir in the rear of the driver side front inner fender. When I reinstalled the fender liner after getting all the suspension and intercooler work done I went ahead and reinstalled the reservoir because it seemed easier to just leave that system alone.

I think the parts catalog schematic shows the reservoir and piping.

Steve
 

iluvmydiesels

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phila area
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AHU
The flapper actuator that is located on the passenger side definitely operates with a hand mity vac. I tested both actuators when I pulled them out. One held vacuum, one did not.
I got a replacement actuator and it fixed my flapper issues. If a big enough vac line is closing the actuator diaphragm, but a mityvac is not strong enough then it must be a leak.
if its the vent recirc vac line(to clarify), thats quite a small vac line, wont take much to work 'flapper'.
 

Windex

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Cambridge
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Stupid question - does the recirc solenoid have two or three vac line connections?

If three, the actuator should absolutely hold vacuum, and should move by a mityvac.

If two, then there may be a calibrated bleed in the actuator that allows it to close once the vac source is turned off.
 

iluvmydiesels

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Stupid question - does the recirc solenoid have two or three vac line connections?
stupid reply, i have an A3, all i know i have one tube going to vent recirc(as i call it, recirculation,vent). it comes off the vac pump hose/adaptor. seems since mk2s this vac hose/line that goes to brake booster(primarily) has two nipples for usage. we as mk3s use both, as far as i know. one goes to vac module for ecm, timing, engine management. the other goes to the vent recirc, the 'flapper' it would seem your describing. i only have the one *tube, that now goes in the vent box area. i never have had a problem yet, so kind of *stupid(to it). thats an A3, (outer, visual). if there is a major vac leak i have found the crankcase can get to much pressure, the easy solution is the rubber, cloth hose that transitions the nipple(from vac pump) to tubing. it would need to be replaced(every so often, like 15yrs or more). or you can cap nipple, till you find a fix/time to fix('flapper' or otherwise further down the vacuum 'line(s)'.).
 
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