69 z28 302 running hot on hwy
 

Hi, i just took my 69 z out for a ride tonight, was gonna hit up a cruise that was about 60 miles from town, ive never really got the z out to stretch her legs but has always been great around town. Soon as i hit the hwy the temp climbed to 205 degrees at around 60 mph, the faster i went the higher the temp. Everything is original and stock on the car. Any ideas? the engine has been rebuilt, with all stock oem parts. Thanks

Matt

Re: 69 z28 302 running hot on hwy
 

sure it was a true 205 degrees? Did it smell, boil over, lose some power etc? NO water pump leaks, lose fan belt, bad clutch fan? Hows the radiator situation? Try some of that water wetter solution. 180 is OK in my book.

Re: 69 z28 302 running hot on hwy
 

ive got a aftermarket mechanical gauge, since my factory one was reading hot, my aftermarket gauge was showing all of 205, no boiling over, exept for the a few drips of coolant from overflow. I want to see 180... Imo its running to hot

Re: 69 z28 302 running hot on hwy
 

The fan clutch sounds like a likely culprit. Once the engine is hot, turn it off and if the fan still spins, it's the clutch.

Re: 69 z28 302 running hot on hwy
 

process of elimination I guess Matt. Could be the fan clutch but if it was running cool around town it would probably have acted up there also. Hows your rad. cap?

Re: 69 z28 302 running hot on hwy
 

how warm out side is when this happened

Re: 69 z28 302 running hot on hwy
 

ive tried 2 rc15 caps and one aftermarket... no change, tried a diff thermostat, i even pulled the engine to replace with an offroad cam, and fix an oil leak, i pulled the heads off and put new headgaskets in it at that time, i didnt like the way the factory shim gaskets fit.

Re: 69 z28 302 running hot on hwy
 

its maybe 70-80 degrees outside, the engine was still very warm from the trip, i backed it out in the driveway, let it idle till it got just shy of 200 degrees, shut it off and i can move the fan pretty easily, it was pulling some air through pretty good when it was idling, bad fan??
Thanks!!

Matt

Re: 69 z28 302 running hot on hwy
 

mine moves fairly easy also. maybe try a flex fan if you have one. Off the road cam may make it run a little hotter also. 4.10 gears? Any lead in your gas? Radiator flowing correctly?

Re: 69 z28 302 running hot on hwy
 

91 octane, no lead. 3,73 gears. Radiator flows nice. I'm stumped!!