Basic Coolant Routing Question

I've been looking at all these coolant fittings... and I wonder if I even need the in-hose filler. Why not just build a small manifold and connect the following:

Main water pump outlet -> 4-way-fitting -> Radiator

The other two fittings on the 4way:
1) Steam vent to head
2) 944 Overflow tank


I started thinking about this because the original 944 design seems to call for the coolant tank to be pressurized with an overflow that just drops coolant on the ground. Why not just use that and dump the idea of a in-hose filler that'll be buried under the intake hoses anyway and introduces a 2nd pressure cap/valve?

Might make it easier to bleed air out, too.

I dont know about any in-line filler for these conversions; nor have I seen anyone make use of one (that I can remember). Why do you think you need one? It really wouldn't help you at all due to the main coolant hoses being close to/below the midline of the engine itself.

I agree with you in questioning the use of an inline filler. The reason for any filler/cap, beyond the worst case scenarios, is to blow off any steam from the system as well as to fill the system. However, if a coolant system becomes too hot, the first thing it does is try to release steam (the system has become over-pressurized by excessive engine heat causing an expansion of coolant thus a lesser area for air and ....well... coolant) and if it continues to increase in temperature, the next thing it does is either expel excess expanding coolant into a reservoir, blow expanded coolant through the cap or finally, blow a hose to shreads. This is precisely why a filler is normally the highest part of the cooling system. If your system becomes too hot, and you have an in-line filler in such placement, the steam has no where to go. Actually....it will find a way out.

The things you need: 1) a 944 NA expansion tank... It has one coolant tube that exits the reservoir and into the radiator near the radiators top unlike the turbo models which had two. The location of the stock 944 expansion tank is at the highest it can possibly be in the 944 engine bay. 2) Also try and obtain the Ready-Aire PN: 5930 H-valve from your local parts house to circulate the coolant back to the waterpump when the heater is not in use; to prevent a dead-head situation. 3) There is also part numbers for the main I/O and heater hoses here on the board. Theres really nothing else you should need. well, unless you have a situation I dont know about.

The other two fittings on the 4way:
1) Steam vent to head

The hose designated steam comes from the head and attaches to the 944 expansion tank to pressurize the coolant system to 18 psi. It wouldn't be good to attach the steam pipe to anything other than the expansion tank (hence its name). Introducing steam from the top of the engine to a manifold in-line with heater hose and main coolant hose/s will cause air to circulate continuously throughout the engine which could seriously damage it. The steam must go to the highest point of the coolant system which is the expansion tank.

the original 944 design seems to call for the coolant tank to be pressurized with an overflow that just drops coolant on the ground

The only time any coolant is "weeped" out of the overflow tube is when either the system has become unsuitably hot or when the system is overfilled. When either of these conditions are met, the expansion tank cap opens up and coolant escapes through a relief hole to the overflow tube that is otherwise sealed by the cap under normal conditions.

I hope this helps???

You know... it didnt look that long when I wrote it. Sorry.

Vorsche has the in-hose filler, obvious in the gallery.

Anyway you confirmed what I was thinking. Mine is a 944 NA, so the tank has just the one outlet. I just need to assemble all the proper hoses and fittings, but clearly the steam line needs to exit near the 944 overflow tank outlet, outside the normal pressure flow and I need to replace the in-hose filler with a straight tube.

Right now I have a loop (U) hose on the heater. I ain't fightin the firewall side clamps and cutting to length until the main hoses are worked out and I'm fairly sure I don't have to remove the engine from the car again.

We used an inline filler cap on Vorsche's car. Although next time I will use something more along the lines as this.
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It will give us the highest possible point in the system and we can still get rid of the assume looking yellow "thing" they call an over flow tank.....

You guys need to seriously take a good look at this article. LOTS of great info to set the record straight. And yes the four way H-valve can be installed incorrectly. I also dont see why you would ever want to remove the expansion tank!
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Very informative write up.
Thanks, That also makes my new radiator look like a really good choice for our builds. 

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