[NOSIRRAH]

I would bet an ice cream cone that the spline shaft was not moved from the old water pump to the new one. I have had it happen before, by a GM Technician. Without that spline shaft the impellers are NOT turning and the coolant is not circulating.

Tell me more about this.
What do you mean that the spline shaft was not moved?

 

[1slow96]

Look on old water pump for the coupler that belongs on new pump.

 

[Marky Dissod]

LT1 (& LT4 & L99) H2Opumps are driven by the camshaft ... sort of.
Protruding from the engine is a splined driveshaft.
Protruding from the H2Opump is another splined drive shaft.
Joining the two requires connecting them with a splined sleeve.
Without it, the H2Opump is UNdriven.

If the sleeve is installed backwards, it will eventually wear itself smooth, and need to be replaced.

 

[storm9c1]

I would bet an ice cream cone that the spline shaft was not moved from the old water pump to the new one. I have had it happen before, by a GM Technician. Without that spline shaft the impellers are NOT turning and the coolant is not circulating.

Hold on. Let's read post #7:

Dash temperature gauge rises quick and high to 125c (257f), the gauge rises and falls depending on driving or accelerating hard.

Then post #16:

Spline shaft coupler missing on waterpump??

This has already been addressed. Not saying we shouldn't re-address it (again). But without the WP turning, it would go to hot and stay hot. Not rise and fall. So are we saying that post #7 (from OP) would be rendered invalid information? Do we have new information? Or are we beating a dead horse?

 

[NOSIRRAH]

Hold on. Let's read post #7:


Then post #16:


This has already been addressed. Not saying we shouldn't re-address it (again). But without the WP turning, it would go to hot and stay hot. Not rise and fall. So are we saying that post #7 (from OP) would be rendered invalid information? Do we have new information? Or are we beating a dead horse?

Let me take all of this amazing content and work on the car. I will report back on this thread when I can get to it.
The winter weather has slowed me down to working on it.

Talk soon, Thank you
Robin

 

[NiteOp]

Tell me more about this.
What do you mean that the spline shaft was not moved?

When the water pump is working, there is a shaft that connects the water pump to the engine. On the back of the water pump there is a spline gear that protrudes out of the water pump. There is a matching spline shaft that protrudes from the front of the engine. When the water pump is replaced, the spline shaft that mates the 2 spline gears needs to be taken off of the 'old' water pump, and installed onto the 'new' water pump. When installing the water pump, this spline shaft slips spline gear that sticks out of the front of the engine. This is what turns the impeller to move the coolant throughout the engine.

You can see it in this video at the 12:34 mark. THis particular one stayed on the engine, but mine came off with the pump.

 

[Z09B4U]

..How about sliping impeller?

Maybe. That's possible.

without the WP turning, it would go to hot and stay hot. Not rise and fall. So are we saying that post #7 (from OP) would be rendered invalid information? Do we have new information? Or are we beating a dead horse?

BUT... The car sitting in the driveway OVERHEATS!! I also put a new thermostat in then bled the system The entire time the seconday fan NEVER came on.. So do I have a defective "new" water pump? that may explain the overheat while test driving, even with the fans on it overheats???

I took the plate off and the impeller was loose inside the pump, not even attached.. Took it back got another, checked it before installing..Mistery solved!

Cooling Fans not working

Was not a good weekend for me or my 95 SS.. My son calls me to tell me the “car broke down” so I get there and the AC compressor went, sheared the rivets off the clutch. Make a long story short I replaced ALL the AC components. When under the car noticed the water pump is leaking, replaced the...

www.impalassforum.com

It may be possible to run a LT1 without a water pump impeller and have it heat up slowly as without coolant circulation the gauge sensor on heads may have a delayed response. The PCM temperature sensor without flow will also take some time to "see" hot coolant.

pull over to cool down, drive back home, again overheat.

The OP seems to experience the same issues as the poster in the thread I just quoted.

No heat coming out of the heater inside the car.

This may have nothing to do with the problems that have resulted after the water pump replacement.

 

[storm9c1]

It may be possible to run a LT1 without a water pump impeller and have it heat up slowly as without coolant circulation the gauge sensor on heads may have a delayed response.

Could you please elaborate on this? In my experience, the heads are the first thing to heat up (and overheat) when there is no coolant flow. It will take a while at cold start but once it gets hot, that's it. Heads will not cool down without flow. With stagnant coolant, it will heat up and the gauge will work fine. Eventually the coolant will flash to steam. But even with zero coolant in the system, a sensor in the head will still read hot from radiant heat or steam. I guess it's possible for the gauge to fluctuate on the hot side in this state, but I can't imagine it ever moving into a normal range since the entire head will be heat soaked including the metal sensor itself. Plus if the heat is hot enough to be flashing coolant to steam, there will be lots of other symptoms. May even blow a hose or at least be venting at the cap.

Same can't be said for a sensor in the intake or waterpump though. Intake and WP will take much longer to heat soak than the heads.

There's also a question if the sensor and gauge are working properly (may not be!).

I do agree though that we could have a slipping impeller. Good call there.

I think we are at the point where we all agree to move to next steps. One could remove the front plate on the WP. Might be easier than pulling the whole pump. Try to turn the impeller by hand. It should not turn, wiggle or move. Start the engine for a moment and see if it spins, etc.

 

[Marky Dissod]

Could you please elaborate on this?
In my experience, the heads are the first thing to heat up (and overheat) when there is no coolant flow.
It will take a while at cold start but once it gets hot, that's it.
Heads will not cool down without flow.
With stagnant coolant, it will heat up and the gauge will work fine.
Eventually the coolant will flash to steam.
But even with zero coolant in the system, a sensor in the head will still read hot from radiant heat or steam.
I guess it's possible for the gauge to fluctuate on the hot side in this state, but I can't imagine it ever moving into a normal range since the entire head will be heat soaked including the metal sensor itself ...

Same can't be said for a sensor in the intake or waterpump though.
Intake and WP will take much longer to heat soak than the heads ...

One of the dumbest things I've ever done - and documented here on the ISSF - was made much easier with an electric H2Opump.
On a day that peaked under 23F, I started my LT1 wagon with the HDMeziere disconnected and unpowered.
Wanted to see how long it'd take the LT1 to go from an ice cold start to close-to-overheat.
Once I started it, I drove conservatively (northbound on Woodhaven).
After 7min cruising 30MpH, the dash temp gauge needle showed hotter than I'd seen it in many years.
I reconnected the HDMeziere; my friend said the needle never touched / crossed the white line.
Important to note: H2Opump temp sensor did not heat up until after the HDMeziere was reconnected.

One of the ISSF elders admonished my folly; 'could've thermally shocked the engine', something like that.
Maybe he even remembers ...
Got lucky, it ran fine for several years after, despite my continuing to abuse it in more mundane ways, long enough to begin researching how to make LT1s run differently once 'hotter than necessary'.

 

[NiteOp]

Could you please elaborate on this? In my experience, the heads are the first thing to heat up (and overheat) when there is no coolant flow. It will take a while at cold start but once it gets hot, that's it. Heads will not cool down without flow. With stagnant coolant, it will heat up and the gauge will work fine. Eventually the coolant will flash to steam. But even with zero coolant in the system, a sensor in the head will still read hot from radiant heat or steam. I guess it's possible for the gauge to fluctuate on the hot side in this state, but I can't imagine it ever moving into a normal range since the entire head will be heat soaked including the metal sensor itself. Plus if the heat is hot enough to be flashing coolant to steam, there will be lots of other symptoms. May even blow a hose or at least be venting at the cap.

Same can't be said for a sensor in the intake or waterpump though. Intake and WP will take much longer to heat soak than the heads.

There's also a question if the sensor and gauge are working properly (may not be!).

I do agree though that we could have a slipping impeller. Good call there.

I think we are at the point where we all agree to move to next steps. One could remove the front plate on the WP. Might be easier than pulling the whole pump. Try to turn the impeller by hand. It should not turn, wiggle or move. Start the engine for a moment and see if it spins, etc.

Pull the pump, grab the protruding gear on the backside of the pump, and turn it with your hand. If it turns, it is probably good. If it turns but takes a lot of oomph to turn it, I would vote bad pump. Any way you go, you need to do some actual work away from the keyboard.