Author Topic: Vacuum Pump (Read 5616 times)

Trimster · « **on:** June 10, 2007, 09:17:14 am »

Rebuilt the vacuum pump. Now I have 'suck' and break booster and other related stuff now works. But it quit working after about 2 weeks. The lower vent hose into the pump was full of crank oil. I don't think this is normal. How does one fix this? and what might be the cause?

TIA

tylernt · « **Reply #1 on:** June 10, 2007, 11:31:20 am »

Did you perform the alignment procedure on the vacuum pump crankshaft? I made that mistake and ripped it a hole in my diaphragm in short order.

Trimster · « **Reply #2 on:** June 10, 2007, 11:50:09 am »

Uhhh, no... How is that done?

tylernt · « **Reply #3 on:** June 10, 2007, 04:09:46 pm »

Heh, that's just what *I* said!

After you replace the diaphragm, leave all the screws around the circumference loose. If you take the top 5-sided cover off (that's why the diaphragm kit comes with a new gasket), you'll see a little crank and a connecting rod that goes to a white plastic piston. Remove the circlip that holds the conrod onto the crank and lift the conrod up and off the shaft. This takes all the tension off the diaphragm.

Now evenly tighten all those diaphragm screws. That done, push the conrod so the piston is at "TDC" towards the diaphragm, then turn the crank and put the conrod back on with the crank still at TDC. Finally, replace the circlip.

I don't know why it's such a big deal, but my diaphragm is still good several thousand miles later, so I guess it works.

If you pull it apart and your diaphragm is still good, then there are two little valves on the side of the pump that are probably bad. There is another rebuild kit that comes with two valves and a gasket for that side cover, it's a little harder to find but it is out there. I replaced the valves on my pump too, easy to do and not too expensive.

Trimster · « **Reply #4 on:** June 15, 2007, 11:07:08 am »

Oh, cool idea. Which ones will fit? When I call the junk yard, what model/years of VW am I going to find these on?

TIA

rwest1 · « **Reply #5 on:** June 17, 2007, 02:11:47 pm »

Old style V. pumps that waste to the crankcase are a problem on high mileage vehicles with blowby. Blowby overcomes the positive pump pressure and gunks (oils) up the pump valves, efficiency is also lost pumping against crankcase pressure. Need to vent the pump to atmosphere. You can cap the crankcase hole, set up a breather, or T it into upper breather system. I normally use some hose, clamps, and a push-in chevy small block breather. Regards

hipifreq · « **Reply #6 on:** June 17, 2007, 03:01:40 pm »

The n/a diesels get their crankcase pressure from the vacuum pump, so it won't work to vent it anywhere else without putting something else in place to pressurize the oil.

Try it out, with the engine running pull the vac pump line out, and the oil pressure warning light comes on along with the brake warning light.

I would think that blowby wouldn't be problem unless the valves themselves were too old and tired to properly hold pressure. IMHO, if you're putting in a new diaphragm, a new set of valves should be installed at the same time.

Trimster · « **Reply #7 on:** June 17, 2007, 07:20:57 pm »

It seems that the issue is my lack of knowing that the pump needs to be timed to the engine timing. I did rebuild the pump, and the pump valves. All new stuff.

The rotory pump sounds like the way to go/upgrade. Which year, make and model of diesel am I looking for to get this pump?

TIA

bob

tylernt · « **Reply #8 on:** June 17, 2007, 07:39:07 pm »

Quote from: "Trimster"

The rotory pump sounds like the way to go/upgrade. Which year, make and model of diesel am I looking for to get this pump?

As far as I know, it came on all VW diesels '85 to '92. You may also find it on earlier turbodiesels (my '84 Jetta TD engine donor had one).

rwest1 · « **Reply #9 on:** June 18, 2007, 07:14:06 pm »

hipifreq said

Quote

The n/a diesels get their crankcase pressure from the vacuum pump, so it won't work to vent it anywhere else without putting something else in place to pressurize the oil.

I’m guessing your talking about gas pressure (air, oil vapor & combustion byproducts) in the crankcase. Some blowby is always present in a piston motor, there is not a perfect sealing ring (most technical articles on crankcase venting say a little backpressure helps the engine seals do their job). Crankcase pressure will probably drop, on an old motor, when you unplug the pump hose, because your venting the blowby to atmosphere, not because the V. pump was pumping lots of air (put your finger over the pump waste fitting and you will see it doesn’t have much output). Don't see this as peculiar, or a big problem, it's just the way old diesels are. It’s when the pressure and or oil vapor content become excessive that we have problems (pushing oil past seals, engine runaway, V. pump gunking, etc.). Some newer diesel (GM & MB) models have belt driven V. pumps, some Toyota diesels have pump on back of the Alternator, most with no connection to crankcase. Virtually all gassers manage to get by w/o an auxiliary pump pressurizing the crankcase, so I don’t see your comment as particularly relevant to high mileage motors, which was the subject of my previous comments.

Quote

Try it out, with the engine running pull the vac pump line out, and the oil pressure warning light comes on along with the brake warning light.

Sounds kind of scary...not a Dasher man, but in the pre 81 rabbits the oil pressure sw. is set at a little over 2 psig. trigger. Sounds like you have low oil pressure, or a bad sw., if just pulling off the V. pump waste hose turns on OP warning light! Suggest you put a gauge on it to see what’s going on. Regards

Trimster · « **Reply #10 on:** July 07, 2007, 05:53:37 pm »

Soooooo, 2 diphrams later I still have a problem. (I blew one apart no knowing about the engine timing issue, I built one out of sub-standard rubber) I now have a new diaphram and ittle or no vacuum. If I pull the waist tube and plug the pump waist port, the vacuum on the intake side works fine. It seems that if there is NO resistance on the waist tube, then there is no vacuum pressure on the 'suck' side.

I'm tempted to re-direct the crank case to a breather cap on the valve cover and put a 1 way valve on the waist side of the pump.

thoughts?

bob

tylernt · « **Reply #11 on:** July 07, 2007, 07:14:54 pm »

There are two check valves on the side of the pump, under a cover with a gasket. If the valves are bad or the gasket is old and hard and no longer seals the two chambers from each other, you get no vacuum. AutohausAZ.com sells the valve kit, and that's just what cured my vacuum woes. I suspect it will fix your issue too since playing with the waste port makes things better/worse.

Trimster · « **Reply #12 on:** July 07, 2007, 10:01:58 pm »

The valves are new... well, replaced them when I replaced the 1st diaphram about a month ago. The second test homebuilt diaphram worked super for about a week then the rubber failed. Wrong type, low quality.

I did check the valves, one side was full of oil. Cleaned that out and re-assembled.

Sooo, what's the issue with slipping a marble up in the waist tube? It blocks the venting of the pan gases ... that might be bad.

this has been an all-day in the 100 degree heat frustration. I can do this in my sleep now. Nightmares.

bob