Word of caution on changing the water pump.

pruzink

Veteran Member
Joined
Sep 25, 2004
Location
Granbury, Texas
TDI
GLS, 2004, silver
I just changed my 3rd timing belt on my 2004 BEW TDI Jetta. 40,000 miles after changing the 2nd TB, I developed a coolant leak coming from the water pump. When I removed the pump, the leak wasn't coming from the shaft seal leakage hole, it was coming from the o'ring seal between the pump body & the engine block. I was curious to see if they recommended using any silicone sealant on the mating surface (it actually said to use the sealant enclosed with the pump, but there wasn't any); but what I did find in with the instructions was a note that the design of the original pump casing had been changed slightly, and that a small piece of the back plastic cover in that protrudes into where the back of the water pump sits should be removed (this piece can easily be cut away with a dremel). The bottom line is that this small piece of plastic can prevent the water pump from seating properly. My car didn't start leaking until it started getting used as a rural postal vehicle and was being used on a lot of bumpy gravel roads. The other issue that I had after doing the 3rd belt was that the small vacuum line that goes from the tandem pump to the brake booster (this also provides the vacuum to operate the turbo vanes & the EGR valve) cracked such that the car started & ran & idled fine, but couldn't make it up a hill. Luckily, I had read a post about this happening & that the point where this line cracks often cannot be seen without removing it.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Thanks for the heads up!
.................in with the instructions was a note that the design of the original pump casing had been changed slightly, and that a small piece of the back plastic cover in that protrudes into where the back of the water pump sits should be removed....................
That's just NUTS!!
 

Nero Morg

Top Post Dawg
Joined
Oct 19, 2017
Location
OR
TDI
2003 Jetta wagon, 2001 Jetta TDI, 2014 Passat TDI
I wonder if it's just the pump you bought? Where'd you get it? What brand is it?
 

pruzink

Veteran Member
Joined
Sep 25, 2004
Location
Granbury, Texas
TDI
GLS, 2004, silver
I wonder if it's just the pump you bought? Where'd you get it? What brand is it?
The pump that I got with the TB kit this time was a Meyle, it had the metal impeller; however, it was the water pump that I installed 40,000 miles ago & 7 years that started leaking & it's casing was exactly the same as my recent pump. It is the area just to the right of the top mounting screw that had the slight change. Having the plastic timing belt backing dip down into that space doesn't really make sense (its just a small piece that shouldn't be there), the new casing does have a slight recess that may or may not allow a proper fit. The 3 bolts that secure the water pump don't get torqued to a very high value, so even though the casing has a slight recess, it wouldn't take much for the plastic to prevent getting a good seal. Over the years, there has been a lot of discussion on which type of impeller (white plastic, black composite, or aluminum) was best. When I did a TB on my daughter's 2001 Jetta with a gas engine, it had the white plastic which was cracked & ready to fail, they stopped making pumps with the white plastic impellers & the choices became the black composite or aluminum. Personally, I prefer the metal because even though I know that it does not have as good pumping capacity as the black composite, I know that it isn't going to crack & I did replace a pump with the black composite impeller that was cracked.
 

DuraBioPwr

Well-known member
Joined
Jan 28, 2020
Location
Eastern Washington
TDI
2004 BEW Jetta (5spd)
Yeah I never just trust the o-rings on water pumps. I always add a bit of silicone sealant to the outside and the flat surface of the pump. Should not need to but dont trust it.

Had a duramax water pump do the same thing. Failed by leaking past the seal and not the shaft. All day event to change. Not doing that again thus using silicone.
 

PakProtector

Veteran Member
Joined
Jan 5, 2014
Location
AnnArbor, MI
TDI
Mk.4 and the Cummins-es
IDK...O-rings and silicone does not sound like a good idea to me. Quickest way I can think of to make 'em leak. Just like the pushrod tube O-rings on the old air cooled; the only ones that leaked were the ones locked up with silicone.

Not that youse have not got me worried now...LOL
cheers,
Douglas
 
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