Hey guys, My 1989 300zx 2+2 start overheating after driving 20 minutes on the highway going around 70 mph, and doesn't overheat on city streets unless im going 55-60(really pushing it). There seems to be no leaks before and after my car over heats. coolant level is always full.

-no white smoke coming out of exhaust, oil level is good, and car runs great.
-no water pump leaks
-replaced water pump

I got a pressure test done, and coolant started to spray from a bypass hose under the intake, behind the upper part of the timing belt housing ithink
heres a pick


But could that really be a problem?? it wasnt leaking before even when the car was extremely hot. Can some one help me on this one?

Do i need to bleed out my systems?(how do you bleed out a z31? no weep hole?)

could it be that i need a new radiator?

 

Hey guys, my 1989 300zx 2+2 start oveheating after 25 mins on the highway going around 70 mph, and doesn't overheat on city streets unless im going 55-60(really pushing it) and after 25 mins. There seems to be no leaks before and after my car over heats. coolant level is always full.

-no white smoke coming out of exhaust, oil level is good, and car runs great.
-no water pump leaks
-replaced thermostat

I got a pressure test done today, and coolant started to spray from a bypass hose under the intake, behind the upper part of the timing belt housing ithink.
Heres a pick (not my car) the hose is under that gold metal cylinder thing

Cost 200 bucks to replace that hose. i looked at it my self and the hose looks fine. its just not tight enough and all the way in by 1/8 of an inch. i cant really get to it cuz a lot of stuff is in the way.

But could that really be a problem?? it WASNT LEAKING BEFORE AND STILL IS NOT LEAKING after dring car for a long time even when the car was extremely hot.no coolant loss what so ever Can some one help me on this one?

Do i need to bleed out my systems?(how do you bleed out a z31? no weep hole?)

could it be that i need a new radiator?

 

Well. I had similar issues. Would drive fine in town but if it ran for longer than 30 minutes, then the car would overheat. After replacing every single hose in the car, we found that the radiator had been filled with stop leak somewhere and clogged. Get your radiator checked for proper flow. Something may be gummed up in there.

 

yeah, skygunner58203. you were right. even the slightest leak can cause overheating. Replaced radiator and bypass hose my self (saved some money).

No more overheating