Vacuum Pump AAZ

[TonyTDTruck]

The brakes on my truck seem to be a little bit weak. I think it could be the brake booster but I'm suspicious about the vacuum pump. How can I test it and has anybody had any problems with the one way valve on the vacuum line just after the pump?
Is there a higher capacity pump on the market? And if not, can these be bought new or rebuilt?
Thanks
Tony
1995 Jetta AAZ in a 91 Transporter Truck


 The vacuum valve looks like this one.
http://www.amazon.com/MTC-4278-Pump-Check-Valve/dp/B006X2GZTO/ref=pd_sim_auto_4

[theman53]

vacuum gauge and see how much it is pulling. Bentley should have a spec, if nothing else for a gas car and what they should pull. I would think anything over 20 would be ok.

[alexgingles]

I looked in a mk2 bentley the other day for vacuum pump specs and came up with nothing.

[TonyTDTruck]

I can't find anything either but I remember on my Golf 1.8 gasser the gauge read 15" to 20" of vac. at idle.
I'll target that. I need to buy a gauge, but if I do, it will become part of the instrument group for my truck. Not a bad idea if you feel you need to know if your vacuum pump is working ok.

[TylerDurden]

FWIW, I recently bought a cheap "mighty-vac" knockoff, to bleed brakes and test dashpots. I'm thinking it could also be useful for checking vacuum issues around the engine: fuel lines, brake servo etc.  Just a thought...

[FunkTron]

good idea!

[Syncroincity]

I was having the same problems; check my Samba thread for troubleshooting suggestions. Basically make sure the pump is getting fresh oil thru the center of the shaft, that the screen is clear, and that the shaft seal is is decent shape. Check the inside of the lid for wear, and the vanes for scoring, chips or being stuck. Lap the lid and/or vanes w/ fine sandpaper to clear up any boogers.

I changed my pump, but ended up getting the same vac readings on the replacement. My brakes improved with use, but the pedal still seems low to me. Just been sitting too long... I think just driving it some more might improve your situation as things seat in and learn to behave. Re-bleed the system helps too.

[TonyTDTruck]

Very cool Jerry. I'll check the pump for wear and bleed the brakes again. I can't find the thread to the vacuum pump repair on samba.
Can you post a link? And what were the readings you were getting on the gauge?
Thanks
Tony

[Syncroincity]

Not sure of the actual reading... I was using my Mity-Vac, and the gauge is very faded, and the needle was fluctuating. I thought it was about 5"hg, but I think I was misreading it. In any event a different pump gave the exact same reading.  so I guess it's normal ops.

There are some suggestions about the pump in my build thread, there's not a separate thread.

My power assist seems to be working fine, but I hadn't driven the van for years, and coming from the stellar brakes in the Passat back to the van's marginal system was a bit of a shock. I'm not happy with 'em... and I have the South African big brake kit up front. The increased weight of my new wheel/tire combo has a lot to do with the way it feels, I think... I'm gearing up to do the Jaguar disk / Toyota truck caliper front brake mod eventually and combine that with the BMW booster can that I had previously removed due to incompetence ( I forgot to shorten the pushrod). I have a rear disk brake kit in the parts bin as well, still not sure if that's going on or not. First thing I'm going to try is a new set of EBC Greenstuff pads on the SA brakes.

[scrounger]

My POV: Most gas engines have about 20"hg at idle. When you look at a gas engine at idle you will see it bounce around. The lowest number say -20 would be the one that would be what you would go by. On a diesel the pump should do something close to that. If the max was at -5" I would think it to be low but might still work. 

You might just get a boost/vacuum gauge and install it in your dash. You can plumb it for diagnostics on the vacuum pump. and once it is satisfactory you can use it to monitor the boost as you drive.