QWKDTSN Posted January 10, 2004 Share Posted January 10, 2004 My Z likes to run hot on the freeway, and pretty much any time it's in 5th gear. Remind me of anything I forget: 180deg. thermostat with a small hole drilled. Griffin aluminum radiator 2-speed Taurus fan Radiator sealed off on both sides with duct tape Mild motor (300hp? we'll see) 50%water...45%antifreeze...5% water wetter My Autometer temp sender is by the thermostat. While moving it will usually show 180 deg. on the Autometer gauge. Sitting at a light it will indicate 210 and sit there all day. While on the freeway, however, it pulls up toward indicated 230-250... VERY scary! My hood is not vented so I may be trapping hot air/heat under the hood, or something, but it seems like having a vented hood should not be "required"... Removing the battery/master cylinder doors to vent hot air makes no difference. I am taking my car for a full dyno tune middle of next week and we'll see what happens after that... But until then.... Does anyone have any ideas? It overheats only in 5th gear, it seems.... It can be running hot and I can slow down a bit and drop it into 4th and it will clear right up. That doesn't make any sense I have a T5 with, I believe, a .63 overdrive. It is overdriven pretty far so I think it is .63 though I have no way of knowing. Quote Link to comment Share on other sites More sharing options...
daveshybridz Posted January 10, 2004 Share Posted January 10, 2004 you got that belly pan thats under the car there, that covers the bottom part of the car. its sheet metal , has nice round holes in it? dam i dont know what its called , but anyway that was my problem too Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted January 10, 2004 Share Posted January 10, 2004 The baffle that goes underneath the car between frame rails I believe is called a chin pan. It helps smooth out turbulence underneath the car to help air flow through the radiator. MSA carries them, but I couldn't find it listed on line so you may have to call them. But your car seems to be running hotter at idle that it probably should. Two other things to check. First make sure all of the air is out of the cooling system. Many guys have put the front end of the car on ramps to get the radiator cap above the highest point on the engine. Run the engine to burb the air out. Also make sure your lower radiator hose isn't collapsing with the engine at speed. Make sure there is a spring inside the hose. To see if a hood vent makes a difference, run with the hood unlatched (but on the safety catch). Quote Link to comment Share on other sites More sharing options...
labrat Posted January 18, 2004 Share Posted January 18, 2004 I had the exact same problem in my 81 280ZX/ sbc swap. Turns out the upper radiator hose is higher than the filler lid in the radiator, and I had a huge air pocket in the cooling system. Under serious rpms, the air pocket moves to the radiator, but while idling stays mostly in the hose. It idled fine all day long at ~210 degrees, but highway would leave her smokin... In line filler cap in upper rad hose solved the problem. Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted January 18, 2004 Share Posted January 18, 2004 There are a lot of posts on this board about issues like this. Try searching for more suggestions and solutions. As far as the engine itself, make sure you are not running too lean, and make sure your timing isnt off. Most likely it is the classic issue of too much turbulence impeding the ability for air to flow throught the radiator. Idling at 210 is not really that bad, especially if it just sits there and does not get hotter. Quote Link to comment Share on other sites More sharing options...
quicker240 Posted January 19, 2004 Share Posted January 19, 2004 I had a similar problem one time I am ashamed to say.I wired the electric fan backwards.It blew air out through the radiator instead of pulling air in.was fine at idle,but got hot pretty quickly on the highway.Sometimes the simplest things...... Quote Link to comment Share on other sites More sharing options...
COZY Z COLE Posted January 20, 2004 Share Posted January 20, 2004 Here is my 2 cents worth on overheating problems. In addition to the other replies and older posts, I had a heating problem with my 350 sbc/ HOLLEY blower. My fix was to change to a Edelbrock Victor series aluminum water pump. It has a 3/4" ball/roller bearing that withstands higher torsional loads at high rpm, larger cast-iron impeller that produces max. flow rates for greater pressure and volume, and its pump produces more coolant flow at a higher velocity. I think when you downshift to 4 the higher RPM is increasing your coolant flow therefore lowering your temp. I run at 192 degrees on the freeway and 210 at lights or long stops. The engine performs great at these temps. I had a smaller water pump before and can identify with your freeway figures. I hope this can add some info to a running hot problem. LARRY Quote Link to comment Share on other sites More sharing options...
danc Posted January 20, 2004 Share Posted January 20, 2004 Nion: Had a similar problem with my 83 SBC ZX. Ride around town all day at 100 degrees or whatever outside and it ran around 190-200. It would 210-220 on the highway and then go up to 240-250 at the exit ramp. Good news is it cooler down pretty quick. I changed the radiator hoses with the reinforced ones and jacked the front end up as high as I could when I refilled it. Not sure which one fixed it, but the problem is gone.. Hopefully you can fix it pretty quickly because Mr. heat is not a good thing.. Dan Quote Link to comment Share on other sites More sharing options...
QWKDTSN Posted January 21, 2004 Author Share Posted January 21, 2004 I'm going to do another flush and refill, making sure I have the right proportions of everything... I'm going to be sure to get all the air out again, and see what happens... I have a rigid lower hose and a good pump. I have a bunch of theories bouncing around so it's just a matter of crossing them off one by one. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.