[Vwdiesel] Water pump not pumping

[Erik Lane]

Hello all,

I'm looking for some ideas. I've run out, at least for the moment. This is
on a 1981 Jetta with a 1.6NA diesel. No modifications to the system - I
just replace parts when they wear out with the stock replacements.

Driving home from work one day, that also happened to be about the coldest
day around here, I had no heat and the temperature gauge was getting
uncomfortably high as I was getting close to home. I was worried that I had
lost all my coolant or something, but I was close enough to home and it was
rising slowly enough that I was able to make it without getting anything
into danger zones. (Plus it was cold and snowing with no good spot to leave
it.) Though I live near Portland, OR, so our cold is not like most of you.
It was probably mid 20s.

I got home and checked it, and it was full of coolant. After puzzling over
it and letting it cool I took everything apart, thinking that maybe the
impeller had come off the shaft. That wasn't the case, and even using those
rubber band strap wrenches to get a really good grip, I couldn't budge it.
I tried tapping with a punch and hammer to see if the impeller would move
at all on the shaft in or out, and it wouldn't.

I replaced the thermostat, cause I had one on the shelf, and it seemed like
a long shot, but I was running out of ideas. I drove it around a bit after
putting it back together, and it acted up again. I looked at it, and the
coolant bottle was completely full, but it still hadn't even sucked down
any coolant into the radiator. In the past I've always been able to fill
these cars by only putting coolant in the fill bottle and running the
engine a bit to pump it around the system.

I've got it apart again, and I've put the exhaust from a shop vac up to the
hole in the block to see if there were any restrictions, and coolant came
shooting out of every hose that I had open. When I go to drain the system,
I open all three hoses down at the water pump, and water comes out of them
just fine. I also have an inline tee in the hose to the heater core that a
previous owner installed - it's one of those that comes with a radiator
flush kit and has a screw on cap to be able to purge the system. So using
that I know that I have water to the heater core.

I've stood there and watched while the engine was running, and the water
pump spun just fine. (Well, the system was full of coolant, so I only know
that the pulley was spinning. I wasn't directly watching the impeller.) I
revved it up, and there was no hesitation or slipping of the pulley.

I've read an idea about a hose collapsing on the input side of the pump and
restricting the flow, but since there are three of them, I find it hard to
believe that they would all fail at the same time.

My dad has suggested a head gasket failure and air lock that is stopping it
from pumping, which seems possible, but I want to remove all other credible
possibilities before removing the head. I've also dealt with a couple of
these before that had blown head gaskets, and I've never had one stop
pumping like this.

The coolant that came out was pretty ugly black, but not oily. So that
would seem to give some credibility to a head gasket. I've never noticed it
look anything other than green before, but it's been so reliable that I
haven't had to mess with it much lately.

So I think that's all the relevant facts. I'm hoping to learn/benefit from
the combined experience and knowledge of this list. I'm kind of at my wits
end, and with this engine having unknown miles, but I suspect in the
ballpark of 400k, I might get in there and decide it needs to be rebuilt.
With where I am in my life right now, it would be best to be able to wait 6
months or a year before having to tackle such a big job. So even if I open
it up, I'm going to want to do the bare minimum to get by until I have the
time to really do it right, if it gets to that.

Thank you everyone!
Erik