Author Topic: 30mm or 40mm Hub -- Water Pump 1.6L Diesel Rabbit 1984 (Read 8698 times)

RabbitMainiac · « **on:** July 23, 2008, 03:14:44 am »

One of these days, I'm going to replace the water pump on my Rabbit, when I replace the AC compressor. I got a deal on a re-conditioned AC compressor, but, my current AC compressor is working fine... I just purchased it because it was such a good deal. (the "new" one will be sitting, sealed up, until I need it. )

My question concerns which type of water pump I need to buy. I can't seem to find a clear answer. Apparently there are water pumps with a 30mm hub, or a 40mm hub.

Also,... if somone happens to know... when I was changing out the oil pan and oil restrictor plate, I hit a small plastic "plug" in the bottom of the water pump.... it broke in half.... no water came out, so, I'm assuming that there is no great pressure (from inside the water pump) that is "pushing" on this little plug.... so, I just super-glued it back into place, and it is holding fine. question is.... what is this plug for ? Is it kinda like a engine freeze plug that will blow out, if necessary ... to prevent damage ?

Your input / advise is appreciated... thanks

burn_your_money · « **Reply #1 on:** July 23, 2008, 04:47:55 am »

That plug is sometimes what tells you when the WP is junk. They leak from there.

As far as 30 or 40mm, just measure the ID of the pulley on there, that will tell you 30 or 40mm

RabbitMainiac · « **Reply #2 on:** July 23, 2008, 11:53:02 am »

Burn money guy...

I guess I was just being lazy.... I just went out and measured the pulley on the water pump, and it is approx. 120 millimeters across, from outside edge to outside edge. The HUB (in the center of the pulley) is 30mm. .... from what I can tell by reading stuff in various places, the 40mm water pump hub, seems to be used on cars that do not have Air conditioning. ( or maybe different years.... not sure which, but,... I have my answer as to which pump I need. )

About that plastic plug.... since no water was coming out, when I broke it in half... that must mean my impeller is not leaking. If the impeller did fail, ....I'm guessing that hot water would flood into the area of the plug, and (if it got bad enough ) it would blow that plastic plug right out.....

anyway thanks for your input.... it is appreciated.

fatmobile · « **Reply #3 on:** July 23, 2008, 10:04:24 pm »

The center hub, part that sticks out through the center of the pully, is what you measure.
It changed in a certain year, I've seen a 40mm on an '81 but not sure when they quit installing the old 40s.
According to autohaus:
http://www.autohausaz.com/search/product.aspx?sid=3tmqavfxl0cjaq55gbxxyl20&makeid=800026@VW&modelid=1285455@RABBIT%20L&year=1984&cid=16@Cooling%20System&gid=2208@Water%20Pump
30mm is what you should have.
Carefull with the little waterpump bolts,... ya know.

Possum79 · « **Reply #4 on:** July 24, 2008, 09:32:32 am »

From what Ive read on autohaus before if you have the 40 and you buy the 30 you have to change your pulley out too along with the housing. if you have a 40 and want a 40 replacement i think germanautoparts.com sells them.

Im into the same boat of trying to figure out which is better.

fatmobile · « **Reply #5 on:** July 25, 2008, 10:32:32 pm »

If I remember right, going from 40 to 30 means a different diameter pully, that requires you to change the crank pully because they touch.

Quantum TD · « **Reply #6 on:** July 26, 2008, 12:32:08 am »

Quote from: "fatmobile"

If I remember right, going from 40 to 30 means a different diameter pully, that requires you to change the crank pully because they touch.

Not always. I've seen cars with and without AC with both 30 and 40mm hubs, and the OD is the same. I think some early cars had larger ODs on the WP pulley, but from 1981-up, I think that they're all pretty much the same (except for the ECOdiesel pulleys which are specific to that model only).