OverFlow System Information
 

Hey guys, I recently purchased a thermostat cap and body with an overflow nipple on it for my 1987 n/a . After seeing several pictures and getting information from different sources, I cannot find a clear cut answer. Is it better to have the overflow tube coming from the Tstat Neck or the radiator? I see in some pictures ( actually a lot of pictures) the overflow tube that goes to the tank is coming from the radiator. But then I see some coming from the tSTAT neck which is how my car was when I bought it. Which is better for your coolant system ? Also fyi My radiator does not have a radiator cap.. its closed. Why do I see some with it on there and some without ?

Any information is appreciated . I already ordered a new level sensor and have the overflow tube currently running from the tstat neck to the overflow tank which is located in front of my radiator( not on the right hand side like some I have seen).

The system doesn't care where the overflow is located.

Sounds like the only option you have is from the Tstat neck as you are currently set up. I'm no expert on the S4 but it seems like Mazda was constantly changing how they did it on the S4 cars. S5 all had it on the radiator with no provisions for it on the Tstat neck.

Mazda had some initial trouble getting the air bubbles out of the cooling system, so there were a bunch of changes to the overflow setup from 85 to 88. the later setup has he radiator growing a radiator cap, and then the overflow hose gots over to it, and then there is a fill cap on the engine. early setup has the radiator cap and overflow on the engine.

one really isn't any better than the other except you can mix and match parts and end up with no radiator cap, and things like this

Ok Ill just stick with the overflow coming from the tneck. Thank you guys... I guess when I fill the system Ill just burp the Upper hose untill all the bubbles come out if i need to. I should be fine tho, thanks guys.

I would look into purchasing a spill free funnel to assist in bleeding the cooling system if you do not have a cooling system re-filler
Its a very effective way of doing the job without making a big mess. I use one and love the thing!