What the hell?

[olds307 and 403]

As said, the closed impeller pumps are far superior than the usual open impeller pumps. GM didn't spend money for fun, the heavy duty cooling models got the closed impeller pump. I wonder if Flowkooler would add their impeller to the Olds diesel reverse rotation water pump? Either way, something plugged or probably and air pocket for those readings. Although cheap thermostat's have caused issues before. Unless you step up to Autometer, probably will end up with a similar gauge quality from nearly any other cheap Chinese gauge.

 

[500/600]

As said, the closed impeller pumps are far superior than the usual open impeller pumps. GM didn't spend money for fun, the heavy duty cooling models got the closed impeller pump. I wonder if Flowkooler would add their impeller to the Olds diesel reverse rotation water pump? Either way, something plugged or probably and air pocket for those readings. Although cheap thermostat's have caused issues before. Unless you step up to Autometer, probably will end up with a similar gauge quality from nearly any other cheap Chinese gauge.

In defense of Buick, which I am a very big fan of (430 and 455 anyway) the water pump cover is a sculpted piece and the veins on the water pump mirror this shape. There is no simple method for adding the 'enclosed' back, nor is there a need to. The waterpump vain to cover clearance is very optimized and I would imagine that the Flowkooler piece is even better.

For the OP, I don't know how you are creating your own problems, but you seem to be doing it nevertheless. Get another cheap water pump and put it together. Take the cheap gauge in the house and put the probe in a pan of water on the stove. Let it run through the range from ambient to boiling. Shut off the stove and let it cool to 125-150 and fire it back up and see if it repeats itself. If it's jumping around then it's junk. THEN replace it. If it acts normal then you have other issues, which maybe the new cheap waterpump fixed. Short trips within 10-15 miles of the house, not 200 mile jaunts unless you just enjoy the punishment. And if that's the case then I'd quit airing out the results every time you do something ridiculous because you are taking a beating on here and it appears that you either like it or don't know that it's happening. All my opinion and I wish you the best.

 

[lilbowtie]

Cheap or not gauges were there and alerted you to a problem before it became catastrophic.

 

[olds307 and 403]

In defense of Buick, which I am a very big fan of (430 and 455 anyway) the water pump cover is a sculpted piece and the veins on the water pump mirror this shape. There is no simple method for adding the 'enclosed' back, nor is there a need to. The waterpump vain to cover clearance is very optimized and I would imagine that the Flowkooler piece is even better.

For the OP, I don't know how you are creating your own problems, but you seem to be doing it nevertheless. Get another cheap water pump and put it together. Take the cheap gauge in the house and put the probe in a pan of water on the stove. Let it run through the range from ambient to boiling. Shut off the stove and let it cool to 125-150 and fire it back up and see if it repeats itself. If it's jumping around then it's junk. THEN replace it. If it acts normal then you have other issues, which maybe the new cheap waterpump fixed. Short trips within 10-15 miles of the house, not 200 mile jaunts unless you just enjoy the punishment. And if that's the case then I'd quit airing out the results every time you do something ridiculous because you are taking a beating on here and it appears that you either like it or don't know that it's happening. All my opinion and I wish you the best.

The factory Olds HD pumps are also nice, sculpted and a closed back that fills the whole cavity. But most replacement pumps have the smaller much smaller open blades, almost half the size. I assumed cheap Buick 3.8 and 350 pumps had that issue. Hopefully a new water pump fixes it, mine did that until it was bled out, now fluctuates 10 degrees. I would pull the thermostat and test, almost anything but the heavy duty thermostats gave issues a few years back.