ZSPEED77 Posted July 11, 2007 Share Posted July 11, 2007 My 350 conversion runs hot on the highway only. I started with a belt driven fan and the JTR radiator. Now I use a Ford fan with a 3-row copper and brass radiator, The only difference between the two setups is the copper and brass cools down quicker when I get off the highway. When I'm on the highway above 50mph the temp shoots up to 200-220 always. It doesn't cool down unless I get off the highway. I've tried driving with my hood propped open and my inspection lids removed with no change. Has anyone else experienced this symptom? 77 280, 350, auto tranny, vette diff. Quote Link to comment Share on other sites More sharing options...
COZY Z COLE Posted July 11, 2007 Share Posted July 11, 2007 When you say Ford are you using the 2-speed Taurus fan with thermal relay control?? LARRY Quote Link to comment Share on other sites More sharing options...
jdarkme Posted July 11, 2007 Share Posted July 11, 2007 Do you have an airdam? I ask because I remember reading that if the airdam is not sealed to the radiator support that it basically dumps all of the air under the car just before it gets to the radiator. Search for threads started by bastaad525, I think he had the same problem. Quote Link to comment Share on other sites More sharing options...
piston Posted July 11, 2007 Share Posted July 11, 2007 either way, i would assume if air is running through the radiator core at highway speeds, it should cool it better compare to off the highway... Quote Link to comment Share on other sites More sharing options...
naviathan Posted July 11, 2007 Share Posted July 11, 2007 Head gasket...Just throwing it out there. Hasn't been mentioned, but it is possible. Just for fun dump a tube of aluma-seal in the radiator when cold, drive for 15-30 minutes, let cool and then see if it stops. Quote Link to comment Share on other sites More sharing options...
ZSPEED77 Posted July 11, 2007 Author Share Posted July 11, 2007 yes I have the high power Ford fan. But not from a Taurus. I have one from a Thunderbird and one from a Mark 8 or whatever that car is. The fan fits the radiator like a glove. It actually looks like it was made for it. I bought two since they were so cheap. I also have an air dam and the original pan that sits in front of the radiator. With the Ford fan I can feel the air being pulled from as far as the bumper. I could never feel the belt fan pull that hard. My friend and I have considered airflow problems out of the engine compartment since my auto tranny fills up the tunnel but there is no easy way to test that. I have thought about a possible headgasket issue. Unfortunately I couldn't tell from a possible loss of water because it would get so hot it would blow out the overflow bottle. I have no driveability problems either. Quote Link to comment Share on other sites More sharing options...
MikeJTR Posted July 11, 2007 Share Posted July 11, 2007 What transmission are you using? What gear ratio are you using? Quote Link to comment Share on other sites More sharing options...
ZSPEED77 Posted July 12, 2007 Author Share Posted July 12, 2007 Turbo 350 tranny 2.87 diff. gear Quote Link to comment Share on other sites More sharing options...
mario_82_ZXT Posted July 12, 2007 Share Posted July 12, 2007 How old are your radiator hoses? Old ones can become soft and collapse when under high flow like on the highway. Also, check your timing. Mario Quote Link to comment Share on other sites More sharing options...
ZSPEED77 Posted July 12, 2007 Author Share Posted July 12, 2007 Everything is new. I've only been driving the car for a couple of months since the conversion. Keep the ideas coming I'm bound to have missed something.. Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted July 13, 2007 Share Posted July 13, 2007 Also make sure the spring is in the lower hose! Quote Link to comment Share on other sites More sharing options...
ZSPEED77 Posted July 13, 2007 Author Share Posted July 13, 2007 Yes, we added a spring in the lower hose. Quote Link to comment Share on other sites More sharing options...
zero Posted July 13, 2007 Share Posted July 13, 2007 Well if it isn't overheating below highway speeds then it isnt the fans or anything. I would check for pressure leaks everywhere. If you have a small hole say in the thermostat housing or in a hose, it'll leak pressure and the coolant will boil over. Other than that, maybe the thermostat isnt opening fully, and it doesn't become an issue till a higher cooling capacity is needed, ie the constant load of highway speeds. Just hope it isnt the headgasket. Quote Link to comment Share on other sites More sharing options...
80LS1T Posted July 13, 2007 Share Posted July 13, 2007 Is the fan wired correctly? Your not spinning it backwards are you? That would cause an overheating concernt at highway speeds because its trying to fight 60mph wind... Guy Quote Link to comment Share on other sites More sharing options...
mobythevan Posted July 13, 2007 Share Posted July 13, 2007 Is the fan wired correctly? Your not spinning it backwards are you? That would cause an overheating concernt at highway speeds because its trying to fight 60mph wind... Good call, my tractor has a pusher from the back like that. If the fan is flowing correctly, then a lot of the problems at highway speed still come down to air flow and ducting. If you do not seal up everything in the front from the air dam/front inlet to the radiator, not enough of the air will make it through the radiator even if the fan is running at highway speeds. It comes down to pressures in front of the rad and behind the rad. A lot of times the engine compartment becomes pressurized at high speeds with no belly pan under the front, but the pressure below the radiator (between front and rad)is lower , so the air goes right under and around the radiator like mentioned above. Of course you can check all the normal things (rad cap, hoses, head gasket, coolant mixture, blockage, thermostat, system pressure, etc etc), but in the end I belive you need that front end sealed up at least between the air inlet from the front end and the radiator. People might get by with less, but why not fix it good like the factory does on newer cars. I like to look at newer cars to see how they seal up everything with foam, duct everything, just to get ideas for these older cars. I hate overheating problems Quote Link to comment Share on other sites More sharing options...
rags Posted July 13, 2007 Share Posted July 13, 2007 Okay I'll jump in. Lets start from scratch. Has the car ever run cool (normal operating temperature) on the highway with the V8? If it did, what changed? If not, what are you using for induction and ignition? What RPM is the engine turning at highway speed? Have you tried the airdam to rad support tray? Not the oem one that goes under the car, but a tray that goes from the top of the airdam to the top of the lower rad support? Just doing this helped my car on the track with it's cooling issues. Joe Quote Link to comment Share on other sites More sharing options...
ZSPEED77 Posted July 13, 2007 Author Share Posted July 13, 2007 The car has always run hot on the highway since the v8 converison. I never had trouble with the inline-6 turbo setup. I even had an NPR intercooler in front of everything with the old setup. Ignition is a crane HI-6, I'm running a q-jet, previously had a holley. My timing is roughly 15 initial, 38 mec, 45 vacuum. I haven't altered any stock body panels yet except I've always had an aftermarket air dam on the front. The stock pan is on between the airdam and radiator but I've never had the pan between the radiator and front crossmember. My friend and I have talked about cutting some holes in the engine compartment to help air leave but we are still undecided where it would be most beneficial. We are leaning towards exhausting the engine compartment in the front wheel wells. Alot of air pressure is present around the firewall. With the electric fan you can actually feel the air blowing out of the hood vents from the driver seat at idle. Also, with the inspection lids removed you feel the same air pressure. Yes, the fan is working in the correct direction. Now that I do have my one leak fixed I'll be able to tell if Im losing water through a headgasket as long as I can keep my overflow from overflowing. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted July 13, 2007 Share Posted July 13, 2007 Nissan added a chin pan on the early 240 to prevent turbulence underneath the car from disrupting flow through the radiator. Adding a chin pan and a good air dam might help. And like said earlier, seal the areas around the side of the radiator to force air through the rad. Quote Link to comment Share on other sites More sharing options...
ZSPEED77 Posted July 14, 2007 Author Share Posted July 14, 2007 I performed a test yesterday evening. If I sit in my car and rev the engine @ about 3000 rpms with the hood open the car heats up just like on the highway. I'm beginning to think it's not an airflow problem and possibly a water flow problem. I installed a high-flow thermostat last night and the temp runs about 10 degrees cooler than it was under the same conditions. I may go ahead and try a higher flow water pump. Quote Link to comment Share on other sites More sharing options...
MikeJTR Posted July 15, 2007 Share Posted July 15, 2007 I performed a test yesterday evening. If I sit in my car and rev the engine @ about 3000 rpms with the hood open the car heats up just like on the highway. I'm beginning to think it's not an airflow problem and possibly a water flow problem. I installed a high-flow thermostat last night and the temp runs about 10 degrees cooler than it was under the same conditions. I may go ahead and try a higher flow water pump. Sometimes, rebuilt water pumps have defective impellers, or it may be designed for reverse rotation (used with most serpentine belts). If you purchase a water pump, it may be a good idea to purchase the pump from a Chevrolet dealer, and make sure it is designed for the correct rotation. Also, it may be a good idea to put a restrictor in the heater hose -- this helps improve coolant flow through the radiator when the thermostat is open. Don't run more than 50% anti-freeze, as this can be too thick to run through the engine. It seems like you have been able to diagnose the problem that is similar to the problem Jason had when he used the JTR radiator, and had cooling problems at freeway speeds. Hopefully, you will come up with a solution and let us know what it is. Quote Link to comment Share on other sites More sharing options...
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