Water pump autopsy!

[stormforge]

It seems to me that our waterpumps are nowhere near as reliable as we should expect them to be... I've had 2 Hepus fail in less than a year and friends with Vanagons tell many similar stories. What's going on? Is it something we can improve?

I grabbed an old pump and performed a quick autopsy:

There is a cast aluminum pump body and an a steel shaft. Everything is press-fit onto the shaft, the pump body, or both. The bearing certainly seems pretty substantial. The seal is a 2-part affair. One part (on the left) is press-fit into the pump body. This is a bit fancy and has a rubber bellows connecting this ring to the seal itself. A spring integrated with this piece provides the load on the seal. The second half of the seal is press-fit onto the shaft and rotates against the first part. Both seals seem to be graphite or some other hard material.

There are 4 ways for this pump to leak:

1. Leak between pump body and press-fit flange of left-hand seal
2. Bellows fails and leaks
3. Leak at spinning seal itself
4. Leak between shaft seal and shaft (another press-fit)

I'm wildly guessing that most of these pumps fail due to #3 - due to wear in the graphite seal surfaces. Once they become anything less than perfectly smooth you're going to start leaking. A tiny bit of grit or metal or calcification in your coolant and that seal will start to wear quickly. So my first suggestion is that maybe you can make your pump live longer with frequent coolant changes and thorough cooling system flushing?

Of course, there could be something else going on here. If any of the various parts move on the shaft you may see that seal open up. Or maybe the manufacturer isn't assembling things quite right (too little spring tension?). It would be interesting to do some careful measurements next time I pull one of these apart....

Any thoughts?

Cheers,
-Bill
'89 Syncro

[Alaric.H]

I replaced the water pump in my other car with a 12v pump it can be rebuilt in 20 minutes that's on and off plus it can be slowed down or speed up or even left running on a timer to cool the engine. They are tested up to 10000 hours of continuous duty.

http://www.race-mart.com/items/products/csr/CSR925C-detail.htm

[IdahoDoug]

Is your other car a daily driver, or something used for specialty purpose? The mechanical water pump seems to be a safer design to prevent overheat, which can happen in seconds if the elec quit. A mechanical pump may leak and show signs of dying over weeks or months, but at least there's the fact that when the engine's turning there is water circulating.

DougM
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[yggdrasil]

Not to jack the thread but sort of in the vein here.
I purchased the nice waterpump from van cafe, took it to my mechanic and had him install it.
He neglected to put on a hose clamp and I was driving the hell out of it and all the c oolant blew out and I fried the engine.
I now have a new ,used engine in my rig , I got to keep the old engine and it still has the new waterpump on it.
I decided not to use this because I suspect it may have been damaged, I know that the coolant lubricates the bearings and stuff in there, It was ran without coolant since the hose blew off due to no hose clamp.
Im in the process of stripping the old cooked engine down for useable parts and that waterpump keeps catching my eye.
My gut is to pull it off and toss it.
What does everyone else think?
I drove the van about 100 miles on that water pump , maybe 5 of wich were without coolant.

[?Waldo?]

[Alaric.H]

[stormforge]

Yggdrasil - I'd guess it's worth keeping - at least as a spare. Bearing should be fine (coolant does not lube it - at least not until the seal fails!). That seal could be damaged but probably not...?

Cheers,
-Bill
'89 Syncro

[IdahoDoug]

With the arrival of powerful electric motors at reasonable prices, we're going to see a lot more functions handled this way. I guess I'd be OK with one myself as long as it had some instant alarm or engine shutdown in the event of failure.

Neat system.
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[Alaric.H]

[J Charlton]

Where did you get the pump from? It sounds inteesting.
_________________
NAHT hightop availability May 18 2023 -
Bend Oregon - for Oregon, California- (7 tot , 3 available), Kennewick Wa (6 tot, 1 available), Small Car Performance Fife Wa. (7 tot 4 avail ), Fairbanks Alaska (1 tot 0 avail)
Future availability TBD : Springfield Mass. Staunton Va, Florida, Colorado, Grand Junction Co., SLC probably late 2024

[Alaric.H]

[stormforge]

Here's more data. I spent some time examining the pump with a magnifier. Everything looks pretty good although there is some corrosion around the interface between the shaft and the fixed seal closest to the impeller. I can't tell if it was leaking there or not...

On closer inspection of the sealing surfaces, however, I did notice fairly significant gunk buildup or glazing of some sort:

In the center of this picture you see the surface of the floating seal (the one attached to the pump body and further away from the impeller). There are little patches of hardened gunk of some sort which can easily be scraped away, but which I suspect were preventing a proper seal in this pump.

Where did this gunk come from? Presumably from the coolant?

Other than this gunk I can't really find anything actually wrong with this very leaky pump... If this is the common cause of many pump failures maybe it could be solved by putting some sort of cleaner in and doing a good cooling flush while running the engine? Perhaps this points to certain types of coolant we should stay away from?

Cheers,
-Bill
'89 Syncro

[Doug Wakeman]

I replaced the water pump on my 86 syncro at 135,000 and am about to do it again at 222,200. The first time and this time it is not leaking but the bearing makes alot of noise. I agree with past posts: not a hard job but a real pain in the arse! I think I still have the modified tools. Any tips or new thoughts on which pump to get. I am also considering replacing some hoses while it's drained.