Ok heres the story...Had a MD 5/16th spacer and Injen CAI installed...a month later Im in stop and go traffic for 1.5 hours...Finally get going on the HWY about 65mph and I overheat. The car shuts down and service light comes on. Damn thing is HOT. I pull over and notice there is no steam on top or leak from below. I grap the top radiator hose and can tell there is no coolant in it. Basically the car is empty. I noticed some coolant on the hood back by the windshield in the center. Upon looking around back there I see a small hose is off. Looks like it goes just under the plenum...I called my mechanic who did the install. He said look for another hose as well, under the plenum by the throttle body..And he is on his way to help...So Im thinking how was this related to my recent install...I found the hose that should be connected under the plenum by the TB. It had a brass 90 on it and one end had ELECTRICAL TAPE ON IT!!!!! Now Im pissed...when he showed up I said what the F is this doing on my car...He said it was the bypass and one of his guys must have done it. My question is what is the bypass for, and does anyone know what they could have possibly been trying to achieve? I dont understand why the 90 would be on there. He took it off and connected the hose where is was supposed to go, filled the radiator and I was running. The next morning after cool down I toppped the system off and went to his shop to have the service light turned off. Still no answer to 1) why would the hoses have come off. 2) why was there a bypass. What were we bypassing? Im hoping there was no engine damage due to the extreme overheat. Right now all seems ok. Thoughts...Opinions??

 

Assuming you got the MD spacer and isothermal kit, correct? The Isothermal kit includes a gasket, a heater plate and the TB heater bypass valve.

There are two hoses that connect to the neck of the plenum up where the throttle body attaches. Hot water runs through the neck heating it to warm the TB. The isothermal kit provides a copper heater plate that heats the TB without heating the neck of the plenum, that helps to keep the plenum temperatures down. The heater is really only necessary at temps below 50ºF so a small bypass valve is supplied. You cut the feed hose and install the valve then you can open/close the valve to allow the heater function to work or not. The valve has barbed connections and metal spring-type hose clamps to keep the hose on since it is subjected to the cooling system pressures.

The only way the hose would have come off is if it wasn't installed with the clamps or if the hose wasn't on the tube/nipple properly and the clamp didn't have anything to "bite" on.

The 350Z has built-in overtemperature protection that will shut down the engine if the temperature gets too high. Chances are you did no damage.

You need to find a qualified mechanic to review the Motordyne installation instructions then inspect the current install to make sure it is proper and correct. Also, if the radiator is not properly refilled and all air bled out, you'll continue to have overheating problems as a result of air in the system.

 

You nailed it!! Thank you so much for that info. The bypass had a barbed end on both sides. One fit the hose properly. The other had electrical tape on it. Thats why it came off. Thanks for helping me understand. Also feel better knowing that the engine did shut down properly and it appears no damage was done. I warmed the engine up the next morning and filled the radiator again so my level should be good now...Thanks again for for help!!!!