Disappearing vacuum?

[Salem7]

1982 Westy.
1.6 NA

I have done a search to see if there are any similar problems in any posts. I didn't find any (That doesn't mean they do not exist)

The brake booster seems to have a vacuum for about one press of the brake pedal. The vacuum seems insufficient.

I have tested the system as follows:

Geared vacuum pump(not diaphragm).

Builds vacuum to 20 hg slowly when tested right at the pump, with the engine running.

Vacuum test on the line running to the booster tested, holds 20 hg vacuum.

No hissing sounds or indication of a leak anywhere.

Driving test: Going down a slight hill, the engine in 2nd gear, the first application of brakes- booster assist. 2nd application 10 seconds later, very stiff pedal.

Pretty much the same in other situations. The brake pedal doesn't get "stiff" if holding the brakes on. Bently test of the booster indicates that it is good, pump brakes with engine off to exhaust vacuum and the hold the pedal with slight pressure and start the engine, pedal dips slightly and then holds.

I do not want to go through the time and expense of a booster replacement if I am not sure if it is bad. Pump bad?

Any insight or suggestions will be greatly appreciated
_________________
1982 Westfalia 1.6NA diesel. Converted to Turbo 1.6 and sold.

1995 Eurovan Camper Winnebago, early serial number 5 speed

[?Waldo?]

It's a vane pump, not geared, but I know what you mean.

It's been quite a while since I tested one, but if memory serves, vac rose very quickly.

I have heard that excessive blowby/crankcase pressure can work against the vane style pumps (not so much the diaphragm version). Also any lack of oil supply will seriously hurt the vac pump's function. Without proper oil flow, the vanes do not seal to the body of the pump and it has a much harder time developing vacuum. There is a bushing in the block for the oil pump. If that is overly worn, it could bleed off too much oil flow. There is also a weird seal in the bottom of the vac pump gear to seal it to the oil pump shaft. Similarly, if that is leaking, oil supply to the vac pump could be insufficient. Finally, there is a screen in the vac pump that could get blocked by crud or sludge and inhibit oil flow.
_________________
I am a high-functioning autistic into VW diesels and Vanagons along with other things that are unrelated to this site.

[Salem7]

Thanks for the reply. I will remove the pump and look it over. The PO had rigged up some type of vacuum reservoir to help with the issue. I have disconnected it because it did seem to have any effect. BTW there was no check valve in the system, I installed a new one.

Instrument vacuum pumps in aircraft had a definite lifespan and were replaced after X many hours. Could the vanes be worn on the pump?
_________________
1982 Westfalia 1.6NA diesel. Converted to Turbo 1.6 and sold.

1995 Eurovan Camper Winnebago, early serial number 5 speed

[?Waldo?]

The vane vacuum pumps tend to last for many hundreds of thousands of miles without issue. That said, there are certainly conditions (e.g. long run on dirty oil, etc...) that could cause the pump to wear quickly. You can unbolt the three bolts that hold the lid on and see if the pump body, vanes, or lid seem to be scored. You can remove scoring from the lid by hand lapping.
_________________
I am a high-functioning autistic into VW diesels and Vanagons along with other things that are unrelated to this site.

[Salem7]

The pump is apart. There seemed to be sufficient oil in the pump, nothing excessive. Some scoring on the rotor vane holder, but nothing transferred to the cover. I assume that centrifugal force moves the vanes "out". A couple of them do not move out easily. Fingernail force needed to move them in the slots. Maybe there is not a good seal? I saw no screen as described, or for anywhere for the exhaust air to escape. I will look again. Thanks for your reply.

_________________
1982 Westfalia 1.6NA diesel. Converted to Turbo 1.6 and sold.

1995 Eurovan Camper Winnebago, early serial number 5 speed

[?Waldo?]

That looks like the center hub part is really badly scored. Surprising that it hasn't scored the top also. Regardless that looks like a lack of oil. You pump is missing the screen. It covers the center hole. The oil enters the pump up through the center of the hub, spills over the vanes and the air and oil are evacuated to the crankcase via a slot in the bottom of the pump case that is to the side of the shaft up above the gear. Use a flashlight and you'll see it. If you install that and run it temporarily without the lid, oil should come gushing up out of that center area. Regardless, if that were mine I would source a replacement vac pump.
_________________
I am a high-functioning autistic into VW diesels and Vanagons along with other things that are unrelated to this site.

[Salem7]

Thanks for the diagnosis. Glad that there is someone who has been there before that can give advice. I will be looking for a replacement pump.
_________________
1982 Westfalia 1.6NA diesel. Converted to Turbo 1.6 and sold.

1995 Eurovan Camper Winnebago, early serial number 5 speed

[?Waldo?]

I would double-check the seal in the bottom of the gear. Make sure it is there and looks like it is decent. Then reach into the hole and wiggle the oil pump shaft to see if the bushing is worn out. I would then install that pump without the top (or vanes in place) and run the engine briefly. As mentioned, oil should pour out that center hole. If it doesn't then there is a good chance that there is an oil supply issue and installing a new pump will just lead to the new pump failing very soon.
_________________
I am a high-functioning autistic into VW diesels and Vanagons along with other things that are unrelated to this site.

[Salem7]

Ok, I will check out the seal and shaft and see how it works with the top off and hope to see oil come out!
_________________
1982 Westfalia 1.6NA diesel. Converted to Turbo 1.6 and sold.

1995 Eurovan Camper Winnebago, early serial number 5 speed