When you live in the heat I live in, you are pushing the upper end of a cars cooling capability and some times have some hard times dealling with wierd or what appears to be wierd problems.
My Saturn has had a history of >appearing< to run hot. This started with basically, here, it is hot! It is over 100 degrees 1/3 of the year. If things are iffy in the cooling department it will run warm/hot and either be a problem or normal
depending on how well you trust the heat gauge which in a 94 Saturn is a function of;
The improper factory installed heat sensors, which gave the wrong readings.
Which due to wrong control of the fan
caused things to run warm on certain days,
compounded by a defective catalytic converter which
causes things to run warm or maybe hot on any given day
depending on how hot things are and whether you are climbing 7%grades as fast as you can go
or not
or stuck in traffic with the A/C running
and any combination of the above spread over time to just confuse the issues
Fast forwarding to;
Today
which is shortly after which I replaced the over flow tank which on this car is pressurized as part of the upper radiator fill tank which has it's own sensors in it which brings up?
Why did I change it?
Because; it had a pin hole leak in it that for about 2 years I assumed was the radiator plastic tanks leaking so just sort of ignored things if it did not cause a problem and I kept the radiator topped up.
Of course given all of the above, periodically the car would run hot, water would piddle out more than normal, I'd swear and add water and promist to buy a radiator and didn't.
Good thing, because it was not the radiatore but the over low tank. It had a teeny pin hole leak in it apparently caused by rubbing on something are it wore a hole in it. That of course would leak out water untill it got below the hole at which point it would top leaking, water level was adequate and I would ignore things.
Not there is an interesting phenomina taking place now.Modren, and Saturn S series cars do represnt that, run with a thermostat really close to the boiling termperature, but with a 16 or so # radiator cap, I forget exactly what it is, but the # rating is high, boiling takes place at a much higer temperature so HOT as I think of it, actually is normal, it has to run hotter before it is hot. And it is radiator pressure that keeps things from boiling and that is the magic term or terms.
Because with a pin hole leak that is below water level, you are also leaking off pressure.
Now the engine is running close to or at boiling and water bubbles are beginning to develop. The engine is no hotter than normal, but with out pressure it is starting to boil. And once you get water boiling with bubbles in it, then the water pump can not deal with those bubbles so it start to cavitate. That is a term which means it starts stopping pumping water. So it what? Pumps slow maybe. In any case with the water or coolant not being pumped correctly, than it does not cool correctly which causes it to run hotter and this you can see from watching the heat gauge. It is now climbing, but due to what ever YOUR driving conditions may be it is not really running excessivley, at least not enough to worry about. The water is not boiling out of the cooling sytem in any quantity that you can see, but when it cools down you see it needs a little so you add it and the cycle starts again.
Untill you move something when working on the thing and you discover it was not the radiator that was leaking but that stupid tank.
Thrilled you don't hve to replace the radiator, you by a tank and replace it. Discover the pin hole where it was leaking from which explains why not a whole bunch ever got out, but it also explains with no pressure, why things APPEARED a little strange which comes to tonight and the reason for this missive!
I rand the car hard tonight and noticed for the first time in years!!!!!!
The heat gauge that I do not trust any further than I can pick up and throw a Buick is not longer rising as I drive the car. Which means it is developing pressure in the cooling system which keeps the water from boiling so the cooling pump no longer cavitates so the car does not run hot!
Dang That is the long way around. I wonder how long the pin hole was in that stupid tank messing with my mind?

And as a related side conversation. FLOWKOOLER makes and modifies stock pumps to eliminate cavitation which improves water flow at slow or low rpms which helps engines run kooler at slow speeds but does not have a negative side effect at higher rpms and speeds. I have used those on a couple of street racers and they do exactly as claimed.

 

I wonder how much more it would cost for one of those FLOWKOOLER pumps designed for Saturn service ???

 

I haven't looked at their web site for quite some time so just did;
http://www.flowkoolerwaterpumps.com/
and checked their product line up.
Like many aftermarket product suppliers that are in actuality a niche market supplier that can actually make a profitable product providing that;
1. there is a large enough core group that will spend the money for something that is a better mouse trap
AND
2. You do not have to stock a huge inventory of parts that take up expensive floor space as they wait for some one to buy pieces that take up expensive tooling to make.

A current look at product line pretty much says popular hot rod motors can be a good bet.

So looking at the GM line up, think a bit! The small block Chevy engine has been the corporate engine since 1975 and the leading source of Hot Rod motors. There has only been two of any significance, the Flat Head Ford V8 made from 1932 through 1953 in 3 basic engine sizes, and this includes the current source of "new" ones that were manufactured by Simca of France up through the 60's some where and the Small Block Chevy, still being made, first used in 1955 and who knows how many "Hybred" applications it has been in. And then a few engines that actually had niche popularity for a while. AMC being one of them. And it was used by Jeep Racers for a long time, Grey Marine and International.
The water pump for the AMC is simplicity in it self. It is a flat plate, pop rivited to one side of the impeller which reduces cavitation. Think about a those V8 water pumps (or some in-line 6's) they were little more than an impeller on a shaft. Put a backing plate on one side and efficeincy is improved as to pumping water and you have a cheap up graded part.
The urban legend of "You are pumping water to fast to cool it as it runs through the radiator" is pretty much bogus. A legend that generally starts with remove the thermostat and the engine will over heat.
The probability of that happening is in general based on the fact that you are messing with the cooling system that is overheating allready due to a problem with the radiator you don't want to fix by actually spending the money to buy a new radiator with. Removing the thermostat did not help so in the long run, it becomes the problem when you get a second opinion and that person finds out the thermostat has been removed so the blame is placed there.
Actually the concept of increasing water flow to get better cooling has been an inexpensive modification on circle track racing for years and is dond by drilling holes in the round plate surrounding the thermostat to increase the flow of water through it when open.
When closed it maintains a minimum temperature of what ever the setting is so that the HEATER in the car supplies heat to the passenger compartment as quickly as possible. And the flow through it when open is adequate for the design, but change the application of the engine by creating a "cooking" version and it can use more flow when hot and needs a minimum temperature for efficiency when cold, drill holes in the plate of the thermostat provides a marginal but measurable improvement in cooling efficiency.
In fact if you spend the money to buy a HI FLOW thermostat, basically that is what you are getting.
So their application chart to some extent represents popular hot rod or racing engines that also represent an era of time (AMC) where they were heavily raced and still are and/or also includes an engine that has multiple applications. Such as some Ford and Mopar engines that use water pumps that can be modified cheap and easy. Water pumps in small overhead cam engines are generally better designed and longer lasting anyway in comparison.
I really don't see where a Saturn Water Pump would be cost justifiable for things such as the S series cars as it was a model unique engine in the first place with little or no aftermarket usage and all of the others being some form of corporate block with both limited Saturn sales and pretty much the same thing for other applications too. Or frankly that a Saturn actually needs it.
My long term fight with mine was largly based not on a water pump problem but false readings due improper sensors used by the factory and out side problems such as a bad catalytic converter and a leaking overflow tank.
The sensor problem went undiscovered for a long time. The service bulletin I have reference too was printed some where around the year 2000 indicating it had been in existance since the introduction of the product line and generally had not caused a major dealer service problem which is where the tracking data base for problems is derived from.