D24TIC vacuumpump pushrod size
 

Hello!
Recently my vacuum pump started making sound, so I ordered a new pump. When it arrived, I noticed, that the pushrod in the pump is longer than on the old pump:

https://live.staticflickr.com/65535/...9ef51092_c.jpg

As I did some research, I found out that there are 2 types of pumps: older and newer style. The older one ( on the right in the picture) has a longer tappet (71mm https://www.brickwerks.co.uk/vacuum-...t-to-1994.html) and the newer one has a shorter tappet (https://www.brickwerks.co.uk/vacuum-...4-lt-late.html).

I ordered a 67,5mm tappet also, but when I installed it, it pumps vacuum, but when i rotate the engine to the point where the vacuum pump cam lobe has zero lift, there is a ca. 3-5mm gap between the tappet and the cam lobe.
Is it normal? Or does it increase cam lobe wear?
With the old pump and old tappet the tappet always touches the cam lobe.

Interesting, seems like the gap you measured happens to be near exactly the difference in length between the two vacuum pump pushrods. Maybe the new vacuum pump uses the same old (longer) rod in this application?

Note that the two ends of the pushrod are different. Reinstalling the wrong way can cause excessive wear on the actuating cam.

I didn't measure the gap, I judged it with my eye :)
When I use the old tappet (longer) with the new pump, I can't turn the engine over as the tappet in the pump will bottom out and it doesn't have anywhere to go.
So the new pump cant be used with the longer tappet.
But my question is: Why doesn't the new pump with its tappet reach the cam?
Very odd, considering that the old type pumps and tappets are out of stock / not made anymore.

A little difficult to definitively tell from your photo but it sure looks like the plunger protrusion looks higher in the newer shorter vac pump.

One way to clear up the mystery would be to measure the plunger protrusion for each pump and use the measured length of the existing rod (for the longer pump) to do the math to extrapolate the needed length rod for the new shorter pump.

Yes, the newer pump protrudes more, thats why it cant be used with the older (longer ) pushrod. But the newer pushrod is shorter so that should compensate it, but with the shorter pushrod, there is a gap between the pushrod and camshaft cam lobe.
As far as I know atm, there are no inbetween lenght pushrods for this engine, only the longer and shorter one.

:eek: :eek: :eek:

Smart thinking on checking this rotating the engine by hand before trying to start it and destroying something!

Seems like this is a new issue we have never heard of before on here. I have had some situations where for whatever reason the vacuum pump pushrod length was too *short* for the pump (in other words it opened up a clearance with the cam, resulting in a tapping noise). I attributed that to a weak piston return spring in the pump though I could have been wrong, but a different pump solved my problem in that case. However I have never heard of this issue where the dimensions are too long and cause the cam to want to lock up.

This style of vacuum pump was used on many engines other than the D24 family (Audi 5cyl gas and diesel, TDI, etc) so maybe some of those other engines used different measurements and now the parts manufacturers are trying to consolidate all the applications into one part that is a poor fit for all of them? Seems to happen with older vehicles like ours sometimes unfortunately.

Can something be done with the pump itself to change the free protrusion of the pushrod?

Well I think that the new pump with the new tappet is too short and probably only suits the VW and audi TDI engines. Strange thing is that spare parts catalouges list it as suitable for VW D24 engines too but who knows...
The good news is that the old style pump is still quite easy to find, artermarket ones aren't expensive too, but the tappet is at least half the price of the pump and hard to find.
I doubt that something can be done to the new pump, but I might take a look at it sometime.

That would comport with v8volvo's suggestion above about parts suppliers consolidating items, sometimes overzealously, ending up with ill-fitting parts across all their applications.

My own experience with parts houses listings for D24-specific items often list lots of items that are obviously applicable to gassers only. Obvious things like spark plugs, radiator hoses, gasser injectors, etc. :confused:

One of my future D24T improvement projects is to replace the mechanical vacuum pump with a blockoff plate and install an electric vac pump (and possibly a reservoir) from a S60.