bleeding radiator system

I know this has been touched on before, but during searches I can not find any specifics. So forgive if it is a repeat.

I am trying to figure out how to bleed the air out of my radiator/coolant system.

Hose routing:

Top hose on water pump runs to the top radiator hole
bottom radiator hole goes to lower water pump hole with the thermostat
The steam hose runs to the top of the radiator
the expansion tank hose runs to the lower radiator area

I filled the reservoir up w/ the air inlet hose unhooked until coolant started coming out of the steam hose.
I started the engine and the coolant seems fine, but then the expansion tank over flows.
I dont have a full 3 gallons in it yet

What should I do?

You mean the tank pressurizes to the point that coolant is being jettisoned from the expansion tank overflow tube once the cap pressure is exceeded? Or are you running the engine with the cap off?

When running the engine with the cap off, once the engine reaches the temperature at which the thermostat should open, you should see the level in the expansion tank decrease; meaning the engine coolant system is open and the engine is "drinking-in" the coolant.

If you noticed that the engine has taken no additional coolant, and after the gauge says the engine is up to thermostat-opening temperature, the thermostat may not be opening due to an airpocket. You can try to 'burp' the hoses by hand by sqeezing them which may release the airpocket.

The radiator is quite low as compared to the heads and expansion tank and so once the engine is warmed, in your case, the coolant is not circulating and the air thats caught in the radiator/therostat region has little where to go. The coolant expands and pressurizes the air which is also heating up and expanding and causes your condition. You may also try to jack up the front of the car, run the engine to operating temperature and see if this helps dislodge the air pockets. Also, you should be running the heater system on high which allows coolant to purge the air in the heater core and lines as well.

Okay, I just watched your video "Its Alive" and have to ask....It looks like the hose to the inlet/thermostat housing isnt even there?!?! I also saw that the cap was back on at the end of the video.

Anyway, if coolant is coming out of the steam pipe after warmed, that would suggest that the t-stat is still closed and coolant is boiling up, expanding and busting out anywhere it can. Since you have the steam pipe unconnected, it comes out there.

When properly bled, the only thing that should come out of the steam pipe is.......steam.

Ok. I am working on my temp gauge. I have only had the car running for about 5mins at the longest. I am afraid of the fans not kicking on after the T-stat opens up. I hope to have my temp gauge hooked up tomorrow night and will try going from there.

For those who would like to know how I have my system hooked up, I drew up a picture. Let me know if I need to change my setup. I think I have it done properly but am not sure.
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Looks okay but those are some mighty strong restrictions at the outlet and inlet of the radiator.

Should be fine.

It is the radiator that renegade sells.

Ahh. Yeah, its a bit weird. I dont think Ive ever seen the expansion tank hose routed to the outlet of the radiator before. I know some cars do this is a similar way but they route the expansion tank hose after the thermostat.

The hose coming out of the heater core goes to the expansion tank > out of the expansion tank is another hose routed to the larger 3/4" inlet nipple (one of the two nipples next to the thermostat on the water pump body) > then another hose coming out of the smaller 5/8" outlet nipple is routed to the inlet of the heater core.

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Not saying its wrong. Just that its odd.

So did you run two tanks on yours? All I have is the expansion tank and at the moment I don't have a heater hooked up, I plan on messing with that later.

I got some fittins, I am sure will work for a bleeder setup on the steam hose. I would like to get it to run the trapped air into the expansion tank so it bleeds itself. Anywgow though, this is the way RH has their's ran.

So did you run two tanks on yours? All I have is the expansion tank and at the moment I don't have a heater hooked up, I plan on messing with that later.

No, I just had the one expansion tank. My expansion tank hose ran from the expansion tank to the left tank of the radiator.

I think I have figured a simple way to bleed my system. I am going to plug a brass T into the steam line and have a drain cock on one side to use a a bleeder valve. I will post up on it after I get it together and see how it works.

My biggest worry is that once I bleed the system some air might get trapped again and stay inside either the head or radiator. Like I mentioned before I hope to figure this out at a later date so the system can bleed itself while running for those who will run the RH radiator.

My biggest worry is that once I bleed the system some air might get trapped again and stay inside either the head or radiator. Like I mentioned before I hope to figure this out at a later date so the system can bleed itself while running for those who will run the RH radiator..

Nah, thats the whole point of the steam pipe system! It actively bleeds the air out for you as long as it is connected to the expansion tank (highest point of the system). See, any air in the system will want to go to the highest point of the system whereas the coolant wants to stay low. Any air in the system will cause the engine to slightly overheat causing the coolant (and any air) to expand. This causes the system to pressurize. Pressurized air/steam has a high affinity for the atmosphere. It wants up and out right now! Once the air makes it to the top of the engine, it will exit through those steam vents and then be routed to the expansion tank. Wherever the air pocket was, the coolant takes its place allowing proper cooling.

Once the air is out of the engine and into the expansion tank, it immediately wants to go to the highest point of the expansion tank. The radiator cap is there to welcome it. Once its there and the engine is heated up, the coolant in the system expands as does the steam. The radiator cap then opens (at whatever pressure rating it is) and the first thing expelled is the air/steam; which in turn lowers the pressure of the system thus closing the cap.

So you see, you really dont need to worry about further bleeding once the intial bleeding is done! And, you also see that those who plumb their steam pipes back into say the heater hose is simply returning the air back into the system. This is not a good thing to do at all as it could get stuck at the highest point of the heater core....and then what?!?! You want to plumb that line to the highest point of the cooling system. That place is, in our case, the expansion tank. Thats the only place for the air/steam to escape because thats the only place there's a radiator cap that will allow the escape of the air/steam. Without it, you will always have air in the system......no matter what anyone says.

Oops, just looked at your diagram and noticed you had the steam vent hose going to the radiator. Youre gonna want to cap that port and connect the steam vent to the expansion tank. You could connect the steam pipe there if the radiator was the highest point and had a radiator cap so the steam/air could escape, but that radiator doesnt. That means any air out of the steam pipe and into the radiator tank will be stuck there.

Gotta show the steam the door out.....thats the expansion tanks radiator cap.

There is a nipple at the left rear corner (as you look at it) of the stock 944 expansion tank that used to be used for the 944 radiator vent. This is where to connect your steam line. Heres a picture of the steam line at the expansion tank.

Note that this picture shows a steam vent mod for stock 944's. But it still shows you where that steam nipple is located.

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So can I just add a T setup to the rear tube and plug both the steam vent and the radiator vent to it?
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So can I just add a T setup to the rear tube and plug both the steam vent and the radiator vent to it?

Yeah, I see what your trying to do. If I was going to do that, I would have the tee as close up to the nipple on the expansion tank as possible though. Just like how you see it in the picture above. That way theres little/no chance of steam deciding to take the alternate route back into the system.

I didnt run it that close to the expansion tank due to some clutter but I did manage to get the T above the radiator and almost level with the steam vent. that should work for the most part.
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I have plumbed my engine as shown in 944-LT1's coloured diagram.
Thinking about how do I fill the system?, I believe I need a fill/air bleed port in the top hose.

After searcing the net for a 1 1/2" in line filler I see that they all have standard radiator caps.
I don't want to go this route as the fender header tank has the pressure cap as per the referenced diagram.

Anybody know a source of in line filler with a simple screw in plug?

I filled mine through the expansion tank. Seems to work fine, it took almost four gallons.

There appears to be multiple coolant schematics out there, I planned to use the one below.
Who designed this, does it work, why loop the heater circuit thru the T at the header tank ???

I can add a H valve to control the flow through or around the heater core.

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No idea who drew that, I just used the Porsche system, and put the H-Valve in the heater hose lines near the cruise control module. Very simple, seems to work just fine. That drawing seems overly complex.