Its a 235 Chevy, about 15k on a rebuild. Radiator recored 7 years ago. 160 degree thermostat. Its got straight water in it. And its got an electric pusher fan thats always on. It runs right in the middle of the gauge around town and idling. But on teh freeway it gets up to about 75% hot. What would cause this? I put a new thermostat in it today, and made sure it was topped off, but there must be something else. Why would it only run hot on the freeway?
Here are 2 ideas to check.....You might have some air in the system that has not been pushed out. Or, it could be a clogged water passage.
I'm thinking that the pusher fan is blocking the air flow through the radiator that is needed at the freeway speed. Also, maybe it is not pushing enough of the air that is needed for the water that is now moving faster through the engine and radiator. Just a guess here but I have had similar symptoms on other cars and when I went to a puller fan with a shroud, the cooling problems lessened. Michael
check your timing and make certain your carb is jetted correctly. Too much timing and/or not enough fuel could be causing your heat
Turn off the fan, been there done that, in fact on my custom shrouds for electric puller fans I punch and flare some holes so it wont do that on the highway.
I was always told and have had it happen to me, if it runs cool in town and hot on the freeway its a blocked radiator. might do to get the radiator checked. if its been on the road for 15k then I'm guessing you have not had this problem before on highway driving?
Actually, timing that is too retarded will cause this concern, you are correct on the lean condition.
sometimes high speed overheating is caused by water flow issues. Water pump, coolant blockage or collapsed hose. Check the lower hose, some are designed with a inner spring to keep it from collapsing at high speeds.
Why no antifreeze? That will raise the boiling point of water. I have also used Water Wetter to help dissipate heat and also raises the boiling point. As said before check all the things mentioned before.
Too much timing should make it ping; you would hear that. If you weren't getting the timing to advance, it could be causing it to heat. Neal
are you really sure its over heating? could it just be a malfunction of the Gauge? is it boiling when you stop and check it out? put in a aux temp gauge (known to be good) and check it out..I would start there first
if your running a pusher fan on the engine side wouldnt that make it not work well at 60 plus mph. can you flip it to make it a puller, or just get a puller type fan... nice setup. you should never really run without a good mix 50/50 antifreeze especially to keep corrosion down. good luck
thermostat too low?, not letting the water cool off in the radiator long enough before it goes back through the engine, try a higher temp thermostat see if it helps slow the water down. just a thought. and x2 on the adding some coolant to the mix
its a 235. did you change the water pump pulley? If you put the wrong pulley it can make the pump spin faster than it was designed to operate, too fast to pump the water, or so i've heard
Thanks for the input guys. This problem has only started in the last few months, so something has changed...
Another thing that hapened too. After I filled the radiator, I let the car warm up with the radiator cap off. When the thermostat opened, water GUSHED from the radiator. Probably a couple gallons in just a few seconds. Is that normal?
Do not run plain water - antifreeze (use 50%) acts as a lubricant for the waterpump as well as lowering the boiling point. You are asking for an early demise of the waterpump.
Are the hoses reinforced with a spring? If not, they could have become soft over time/use and are collapsing at higher RPMs slowing down/cutting off water flow. Also block off the top, side and bottom of the grill area as to force air to and thru the radiator core instead of letting it escape around it. -Bigchief.
No No NO NO! Do not use anti freeze in the car unless you live in a cold climate! What will help is a conditioner/coolant people THEY ARE DIFFERENT THINGS! Antifreeze will not help to cool your car. Period. I don't believe it is a thermostat issue, once open at operating temp the flow will not change unless it is closing again. These are only to stop water from flowing so the motor will warm up quicker. In warm climates they are useless and NO it will not effect the flow rate enough to be a liability on the cooling capacity. There are a few things I would like to know, A, has this just started to happen? Its been ok on the highway before? B, When re-built did you use a new water pump or the old/second hand one? C, Whats the motor in? Did you change the grille at all? D, What is the CFM rating of the fan? E, What is the swept area? F, How does air escape from under the hood? A, If it is just starting to happen it could be a few things. Maybe at higher speeds the radiator hoses are collapsing and stopping flow, is there any way to run without a hood so you can see? New hoses could be in order. As FlatOz said it could be a blocked core. B, I ask about the water pump because if its old the impeller may have rusted away quite a bit and still look Ok. With the lower rpm and the fan it may be ok cruising but at speed it may be unable to circulate enough water. As 66ragtop pointed out, if you changed the pulley was it the same size? You could be turning the pump too slowly now. (Are you seeing a pattern regarding water flow?) C, Is the motor worked or stock? Usually a worked motor requires better cooling. If you changed the shape/size of the grille opening it could be that you do not get enough volume of air through the radiator, have you got a large grille insert? D, The Cubic Foot rating of the fan may not be enough to push a sufficient amount of air through the radiator. You can fix that by either upgrading the fan or simply putting an on/off switch in the system so you can turn it off on the highway. It could be effectively acting as a shield and restricting the flow of air, with it turned off and 'windmilling' it will let through more air. E, Swept area, the larger the area swept by the fan the more efficient it will be. If it is too small, even with a high CFM rating you just wont be pushing enough air. F, It could also be trapped air under the hood that is stopping fresh cooler air from flowing through the radiator. A quick fix is to space the back of the hood so that it sits up an inch or so to let air out, louvers in the hood would be better. Hope some of this helps? Doc.
I would drain the system completly, fill it with white vinegar and run it about a week. Drain and flush the system. You'll be surprise what will come out. Cheapest radiator cleaner going.
Kicking water out after a drain and refill when the stat opens is usually the sign of a air bubble in the engine/head. You are getting a local hot spot and when the water hits it it boils making steam which blows it out the radiator when the cap is off. Good idea is to drill a 1/8th" vent hole in the flat part of the stat to bleed the air on fill. If you have been running plain water for a long time sorry to say you now got a bunch of rust etc. in your cooling system.
PS, missed the pushing water bit out, must have popped up while I was typing (Im slow....) Yeah, that would be trapped air in the motor.
Thats a BLOODY good point! Didnt think of that and it could account for the air in the motor. Checked the oil? It could have burnt the gasket between the cylinder and the water jacket, my old 351 Clevo did that, man that was a bitch to track down! Doc.
A. Just started to happen B. New water pump, 15k miles C. Its a 235 and yes the grille was stock and currently is under construction. In fact I first noticed the problem when I changed the grille. I didn't think it could be the problem though as the new grille is much more open. D. I dont know the CFM, but it has been enough for the last several years. E. Again not sure, but it covers quite a bit of the radiator. F. Air must escape out the bottom of the car. Just like stock.
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