The previous owner of my car replaced all of the rubber under the hood and left the overflow tube on the plastic thermostat housing fill neck blocked off instead of replacing the hose. I've tried searching and I can't figure out just where it is supposed to be routed to. Is it supposed to be routed to the overflow tank or some other random place in the cooling system. If it isn't something simple, pictures would help.

 

Yes, it's supposed to go into an overflow tank.


-Ted

 

Most (but not all) FC's have the radiator neck connected to the overflow bottle, not the filler neck. Check there before doing anything.

 

Dunno how it in down in NZ, but all Zenki / S4 FC's in the U.S. have a sprung thermostat cap on the filler neck on the thermostat cover.

For turbos, the overflow line goes from the filler neck to the front to the overflow located in the front nose, right before the radiator.


-Ted

 

my car is an '86 gxl and already has a hose that i think goes from the radiator to the overflow tank, but the one from the thermostat housing isn't routed to anywhere and the system seems to be making too much pressure. with the tube blocked off, coolant is leaking out from under the 13lb. cap that is currently on the thermostat housing.

so, how many lines should be routed to the overflow tank? any pics of a properly routed system would be appreciated.

 

anyone?

 

You probably had the early S4 design, that's been changed to the later cars, that's why you now have the rad cap on the radiator itself controlling your pressures & overflow quantities. You need a "flat cap" at the thermostat housing now (although a rad cap should work also, I've been driving around forever with a normal rad cap in both places with no problems)...Check the sealing gasket of the cap on the t-stat housing, it might be torn/ missing, causing your "leakage"...

 

Not to hijack threads, but my 88se also has the two caps, problem is though the housing one is leaking. My question is can I just block it off or do I need to have a cap?

 

Again, take a look at the gasket inside the cap...After we twist these things on & off a million times they tend to start degrading to the point they allow pressurized coolant to pass...New caps are only like $16- not a big deal...

If it's the housing flange itself that's screwed, then you've got slightly bigger problems...

 

its not really the flange, its the plastic thing that the cap screws on to

 

You need the FLAT CAP that is shown in this link. http://www.mazdatrix.com/b8.htm Put the flat cap on the filler neck. Then you won't need a hose b/t there and the overflow tank since you already have one from the radiator to the overflow tank.

 

I've seen pics on this forum of the pressure relief (not thermostat) cap on the S4 radiator, and that's what it shows in the FSM. What gives?

 

My US spec S4 TII has a flat cap above the thermostat and a sprung rad cap where the hose to the overflow bottle connects. My plastic thermostat housing neck broke so I replaced it with one that had a connector for the overflow neck. I blocked off the connector so that it would work for my application. I would suggest that the previous owner of Busted-7's car might have done the same.

Essentially all cars need to have an overflow hose from ONE spot where there is a cap with a spring.