So I was changing all of my radiator hoses today and started off with the easiest one being the upper radiator hose connecting the coolant tank to the thermostat. I pulled the hose off and noticed a small lump in it near the tank side of the hose. I cut the hose open to find a little metal pellet.

I checked the new hose and it does not have it. I looks through the forum (quickly though) and could not find anything relating to this.

Anyone have any idea what this is for?
I have had no cooling issues or any problems what so ever with the cooling system.

Should I put it in the new hose?

 

You need this and you car will overheat without it. It's a restrict or and i don't quite understand why it works the way it does but we installed a new engine and hoses and did not reuse these (there is more than one) and the engine almost immediately overheated when it was started. We installed the restrictors and all was/is good with that engine.

 

Sounds good.
I will put her back in.

Weird I wonder why it has to be there?
I was reading around trying to figure out what it was and ran across this..

"The thermostat should be removed and the bypass plugged for racing applications, but NEVER for street use. Do not use "flow restrictors" in the cooling system, free flow is best."

It was at

Rotary Tech Tips: Water Cooling

 

I don't quite understand it either as there is not much info about it out there. I only knew they were there and that he had installed new silicone hoses so when it overheated I immediately thought of them and asked him if he reused them and his response was, "restrictors? what restrictors?",

So I grabbed his old lines and showed him and we then installed them in the new lines, restarted the car, and all was good.

 

Here is the part fyi : ORIFICE, HEATER HOSE. HEATER. 2012 Mazda RX-8 # F10061E09

 

Free flow is certainly not best. A radiator cannot instantaneously cool water. Without a flow restrictor water moves too fast through the radiator and cannot be cooled. Both the engine and water pump are adding energy into the cooling system.

Even in full race applications, water restrictors are installed where a thermostat would normally go. often a washer or flat piece with several holes or something depending on application.

 

Water flows too fast, no good.

it's there for this reason

 

Does anyone now how many restrictors are in the coolant system hoses? I only found 2, one small restrictor at the coolant reservoir and larger one coming from heater core return to the thermostat housing. Are there more than 2? I have over heat problems with coolant system!

 

Is my thermostat toast or even worse water pump, if I did not use restrictors from old hoses?