How can tell if my water pump stopped pumping?

tothemax

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Joined
Aug 7, 2006
Location
Nevada
TDI
TDIs: 2003 Jetta, 2016 Q5 3.0
Car overheated a cpl times when pushing her hard..... noticed the fans will not come on without turning on the AC.... noticed the top water hose going to the radiator is super hot but the bottom hose is cold.

How can tell if the water pump stopped pumping?...

Noticed temperature goes to the 205... 210...range.. at times

The fans both work if the AC is switched on but not otherwise.... I bypassed the fans at the temp switch.. .they both came on... thought it was the switch... changed the switch .... still no fans working after changing out the switch ..

then I changed the thermostat... still no fans working..

The heater in the cab seems to work fine and I get plenty of heat from there....

There does not appear any flow into the expansion tank when the engine is running...

I am suspecting the water pump failed but not 100% sure ... is there a way to find out for sure if it is pumping or not?

Another 20,000 mi or so to the next TB change.... so maybe it's time to change the whole thing our early?

You thoughts?

tnx
 

Ski in NC

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Joined
Jul 7, 2008
Location
Wilmington, NC USA
TDI
2001 Jetta ALH 5sp stock
Open cap on plastic coolant bottle. With engine idling, the top hose should be dribbling coolant into bottle. Get someone to rev motor, dribble should turn into a stream. No flow there and likely impeller is slipped.
 

tothemax

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Joined
Aug 7, 2006
Location
Nevada
TDI
TDIs: 2003 Jetta, 2016 Q5 3.0
will over heat very quickly at idle or on the road
It does not overheat quickly while on idle but if I push is super hard... like in racing.. it does.. also jsut driving it on the freeway normally, it gets up to the 200 to 205...

Also another dumb question... can the pump fail slowly where it still pumps but not as strong as it should? or does it fail suddenly like ... is there only two case .. either it pumps or it does not?

I plan to take the thermostat out again this weekend to check the impeller but would like to know the answer to the above question... I did the test of looking into the expansion tank while someone else is revving the engine and I did see an increase in flow into the bottle but it still appeared pretty weak and there was a lot foam/ small bubbles in there...

It did not look a like a strong flow ... not really sure what it should look like... I guess I should check on my Golf to see what a normal flow looks like... I will as soon as my boys come back w/ the Golf... ;)
 

mlemorie

Veteran Member
Joined
Aug 15, 2009
Location
Romulus Michigan
TDI
2004 Jetta
To make it easier I usually pull the return line off the bottle and hold it over the opening while I have someone start the car and rev it. It makes it a lot easier to tell just what kind of flow you are getting. I have seen a few pumps that cracked around the inside ring where it mounts to the shaft. They would still spin and pump fine at lower RPM ranges, but once the RPM came up and they started spinning faster they would start to slip. Although usually the whole thing just breaks apart.
 

DanG144

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Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
If it is reliably keeping your cabin heater pumping out heat, I don't see it being the water pump.

The water pumps can fail such that they slip intermittently. They will tend to slip more when hot.

When you say the car overheated, what temperatures were you seeing? What were you reading them on? 210 on the head outlet temperature pushing it hard is normal, in my opinion.

But remember the gauge is computer driven; it reads centered (90C or 190F) over a wide range of temperatures - about 167 F to 225 F. So as soon as it goes up off of center it is already at 226F, not 191F.

The fans are typically turned on by the radiator thermoswitch which is halfway down the radiator; if you have any breeze across it the fans will rarely come on as it has cooled below the fan setpoints prior to getting halfway down the radiator.

Bentley fan operating points, from the radiator thermoswitch:
low speed
on - 197-206 F (92-97 C)
off - 183-195 F (84-91 C)

Fast speed
on - 210-221 F (99-105 C)
off - 195 - 208 (91-98 C)

 

tothemax

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Joined
Aug 7, 2006
Location
Nevada
TDI
TDIs: 2003 Jetta, 2016 Q5 3.0
Did you have a chance to check out the water pump's impeller last weekend, Pierre?
I did check and it's tight so I assume it's working... still can't get my fans to get going... oh well .. .just have to not race any more Audi's and I'll be fine..
 

dan kerkstra

Veteran Member
Joined
Jul 6, 2011
Location
ardmore ok 73401
TDI
2009 tdi Jetta 2002 jetta 5spd 2004 Jetta 5spd
Just my 00.2 , due to age make sure the radiator isn't limed up onthe inside restricting the flow, had my dodge diesel start to overheat each time I put it under load, put in a new radiator fixed the problem, long shot, but acted the same as your.
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
I have also seen radiator heat transfer restrictions. The interior passages were clean and open, the exterior looked fine, but corrosion from a salt environment (Hawaii) had caused poor heat transfer at the fin to tube junction.
 
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