I have a water pump question

Let me add a few details as well.

The LT1/L99 water pump is shaft driven from a cam gear. While this was an innovative idea from GM engineers to eliminate a belt, the coupler design became a weak link instead.

Many failures I've seen involved the outer bearings being completely destroyed. The symptom is seen after removal the WP and the bearing housing is blown apart, or the balls fall out or are visibly ready to fall out. Usually leaking is a side effect of the destroyed bearings.

The root cause is a seized WP drive coupler. The coupler seizes onto one end (or both ends) of the shaft. Any amount of wobble, even a tiny amount, at that point will tear up the WP bearings.

The the solution is to reinstall the WP properly. Meaning replace the o-rings on the both sides (WP and engine side) and repack the coupler with a tacky grease that won't harden. The o-rings are critical to prevent dirt, grime, moisture from entering the coupler. And also to prevent grease from spinning/flinging out. Remember this coupler spins at high speed. As soon as grease flings out, it's not long before it seizes and eats bearings.

They really should have designed a more flexible fitting. Perhaps a small yet more robust CV joint of some sort. Even a tapered coupler to allow for some wobble? I dunno. But that would solve the problem 100%. And likely increase production cost. So there you go. They knew the existing coupler design made it to 36K miles (enough to pass warranty) and called it a day.

Hope this helps.

the WP's were all leaking from weep hole and killing Optis according to dealer as the car was under warranty

What I discovered though is that Mr Goodwrench during one of those swaps, likely the 1st or 2nd one, was the check valve on the vent harness was reversed (assume Gomer pulled vent harness off and FU putting it back on) eliminating any vacuum to purge opti. Crud quickly built up in them thus killing the Opti. Dealer just kept replacing WP & Opti as a pair under warranty. Service Mgr showed mw the crud in opti. Dealership was cool and even sponsored SoCal SS club back then. They would install H/C if you wanted. It was after 500 mi on the last one I discovered the reversed check valve and since the car was out of warranty, I just went EWP and to this day that EWP has been on 2 motors without issue.

There was never a coupler alignment issue. If you ever gut a mechanical pump you will see what a cheap bearing/seal that is in it. Unfortunately, the weep hole position coolant is then pissed on Opti.

BALLSS said:

There was never a coupler alignment issue.

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And this was determined how?

BALLSS said:

f you ever gut a mechanical pump you will see what a cheap bearing/seal that is in it.

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I agree. I have taken apart WPs, both early GM ones that failed and later remans. Yes they aren't made great. But no cheaper than any other belt driven 350 SBC pump I've ever taken apart. My point being is that some of us, with proper installation techniques, get reasonable life out of the water pump.

In the early days, I didn't know better to do these steps (and of course WPs failed or leaked every 30K or less):

• Replace the shaft O-rings.
• Properly clean and grease the coupler and shafts.
• Check position on the alignment pins during reinstall (sometimes remans didn't fit properly).
• Clean the threads, apply thread sealant, and properly torque the bolts to FSM specs (over tightening bolts and over crushing the gasket will also ruin the bearings).
• Add 1-2 tablets to the cooling system (especially if doing a drain and flush).

Once I got better at doing the job correctly to include every step above, the problems decreased significantly. My daily drivers are B-Bodies.

Sorry, I didn't jump on the electric WP bandwagon. On the contrary, I worked with guys at the track back in the day who had overheating problems with electric WPs -- and it left a bad taste in my mouth. Granted that was decades ago, like I said, pros and cons. Don't need to turn this into a "which is better" argument. Just saying it's not all doom and gloom just because someone runs a mechanical WP.

95wagon said:

Interesting note , I have seen two types of bearings in OE LT1 pumps.
One had an inner race like a typical ball bearing set up and a straight shaft.
The other, the shaft WAS the inner race.
Anyone know which was first , which was second type ?

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I don't know off the top of my head. I haven't taken them all apart. They usually just get thrown back in the box for core return.

But what I do know is that my Impala SS has ~20K miles on it and still has the original WP from the factory. So when it does go (if it goes in my lifetime before I ever sell it), I'll let you know what design it uses.

I'm think one design is chosen over the other for reman reasons. Common sense tells me that the remans may have the version with discrete off-the-shelf bearings. The remans also got polished steel heater hose tubes versus stainless steel of the originals. You can tell by which ones rust in the rust-belt areas. There are other differences, but those are the two main ones. I wonder if the so-called "new" ones (non-GM, non-Gates) use stainless tubes? Or is everyone cheaping out now. Curious to know what bearings those use. Last one I did was a Gates and I didn't pay attention. Car got totaled a few months later and the engine is sitting in my garage. I'll give the tubes a magnet test (albeit not a guarantee that's stainless or not).

The

95wagon said:

The one pump I rebuilt ( long time ago a guy wanted a ceramic coated pump ) the jobber kit I got, the bearing and shaft were integral to each other.

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only time I ever did have anyone work on my Impala was when it was under new car warranty (other than alignments and rear gears after it was out of warranty). Unfortunately, as a result Mr Goodwrench caused the problem of failing Opti's until I discovered the blue/white check valve was reversed (they are one-way valves). All WP's there were replaced, along with Opti and vent harness, were factory or AC Delco parts installed by dealer. The 6th WP was the one I gutted, dealer installed, and that bearing had no ball bearings.

Agree on points made about a clean and greased spline coupler and new O rings on respective Opti & WP drive splines. I keep both those in my parts stash.

Every other car I have ever had uses a mechanical and I have swapped several of those over the years bt consider their life spans normal.

I also was "skeptical" of using an EWP on a street car in terms of longevity so I have the coupler in console if it ever crapped on long drive as I could just put a mechanical back on. 15+ years ago I chose to buy a 2nd EWP as spare to keep in trunk as I could just replace it on the side of the road in 10 min wearing a Tux. That spare has never left the trunk in over 15 years but with over 90k mi on current one, I assume at some point it will fail. No idiot light or buzzer needed. I have a temp gauge, among others, I monitor just like my other cars.

I will note I regularly drag raced the car and spun motor to 6k rpm back when the SoCalSS club would go to Pomona when the car still had mechanical WP. IDK if those higher than normal RPM's "contributed" to any premature failure which was leaking from weep hole. For me, the EWP has proved to be considerably more reliable. YMMV