This problem goes back to before the resto, in the early 90's. Back then I thought it was the radiator. She runs at 170-180 cruising. Sitting in traffic at 80 degrees or above the temp will creep up even without the A/C on. Just to see how far it would go I've let it get as far as 210. I can cool it down by putting it in neutral and bringing the RPM's to 2,000. I can't run the A/C while stopped or the temp rises quickly. After she gets 190+ she starts to vapor lock and loses power and will stall if I'm not careful. The history that I think applies....My bottom end has around 65,000. Since the resto the car has around 9,000 miles. I did the following during the restoration. New cam, lifters, timing chain and gears. New roller rockers. New Holley 750 DP with 1/2 plywood spacer. New 4 core radiator from Poston. New Heavy Duty Fan Clutch. Heads were rebuilt. Headers Jet Hot coated. Perfect original fan shroud. Perfect original 7 blade steel fan. Water pump modified for high volume. I tried water wetter. New 160 degree thermostat(bench tested). The fan blows lots of air. In fact it roars even when its cold out. I'm getting low on ideas here. I think, not sure, that the stock 70 lark could be run with or without the a/c on a 90 degree day and sit in traffic without overheating. What the problem be? I wonder about the exhaust crossover passages and the non-stock headers and cam. Could there be exhaust going through the intake and heating the water that wouldn't be there in the stock engine? Somehow this engine is making a ton of heat. Any ideas?
I've got a 3 core in mine and I've tried the water wetter and some of the 40 Below stuff (2 cans) and it seemed to help a little.Mainly I notice the difference in the cooler months but I also live back in Des Moines now.When I lived around Dallas it seemed to get hot no matter what I did.210 deg.isn't too bad though.If it doesn't go higher than that I wouldn't worry too much.You might try an electric fan.That will also free up around 15 HP for you also.The newer cars run around 220 anyway for emissions purposes.
sounds like a thermo. i'd change it out. but before that do you have the little tester bubble ball thing that tells you how good your anti freeze is good to? i tested mine and its -20. you should test yours. you may have to much water and its causing it to heat up. when i do my system i flush everything out, fill the block with water, add 1 1/2 gallons of anti freeze, start the motor and let the cycle and then top off with water. I'd say its a bad thermo.
hot ... you have to remember that any cam ...and new carb ...and headers..and any other mods mean more fuel ..better breathing means more flow and more power means more heat . I would take that old fan off and put an electric on ...we use one from a 2000 camaro and it fits like a charm ...works great too !! That way you can put a low 165 thermo and then use the fan thermo to start whenever you want ...mine takes the temp down from 190 to 165 in about 2 mins.....while standing still and running. Mark
Yes I again say double check the thermastat. Also have you checked the radiator itself? Make sure that air is making it through all of it, As I had said on another post people hose off the bugs on the front and think its clean all the way through! Take a trouble light out when its dark and look at it from the other side. If those fins are coated with years of road dirt they dont work to good. I sprayed mine with a load of Simple Green cleaner then hosed it threw til it stopped bubbling! Its clean now! My temp gauge says I am running about 190 - 200 all the time in the summer with the A/C on it had gone as high as 230 in traffic with A/C on, before the cleaning. Remember 2 things. First off when moving slow or stopped with the A/C on your fan is pulling HOT air that is passing through that HOT A/C unit in front of your radiator. Another thing do you have a good size overflow for back up juice? And last but often over looked when adding fresh antifreeze Dont use tap water used distiled! PS:Antifreeze is not what keeps your car from boiling it is the PSI of your cap. When you put water under pressure you raise its boiling point. That is why people get BLASTED when they take there cap off! Running at 230 and a couple of pounds of pressure all is well. Take the cap off and you are now 18 degrees past boil. If you get your car to boil out with a good 13 to 15 LB cap you are pushing the temp scale! PPS:Hope this comes out ok I am typing without my glasses on! Mark
thermostat is too cold...... high flow & 160 thermo doesn't allow the thermostat to close enough to regulate your flow, allowing hot antifreeze to cool off in your radiator. which is why you're fine on the freeway and not in traffic. Switch to a 180 or 190...
If you are ok on the freeway and not in traffic, it's simply either an airflow or water flow issue. At higher speeds, air is literally forced through the grill, through the A/C condenser and then through the radiator. At low or no speed, the only thing getting air through all of that is your fan pulling through. Just because it makes lot's of noise doesn't necessarily mean it's pulling a lot of air through. Do you have anything added between the A/C condenser and the grill? Maybe a transcooler or oil cooler? Are there bugs, dirt, etc. stuck in the fins of all of this stuff? Clean it out, then clean it again. Is there enough water/coolant flowing through the radiator? How about flushing and descaling both the radiator and block? Your ignition timing and a lean mixture can make the thing run hotter too. My 70 GS350 used to run great, cool and liked a striped ape when it was tuned correctly. Once the points and the rubbing block wore down, it retarded the timing and it ran hotter and hotter. Sounds like a bit of research yet to go but you can get to the bottom of it if you stay after it. Now, my Firebird is just the opposite. The faster I drive (70 - 90), the hotter it runs. Cools down at idle. Four row Be Cool Aluminum radiator, clean coolant, no rust or scale, all timing advance works as it is supposed to, factory carb that doesn't seem to run lean. I don't drive it much but it is way frustrating to me when I do. I'm lost with this one. Oh, and no vacuum leaks I can find either.
ou: i just remembered that i didnt see anyone ask if you have a fan shroud. Do you have one? i tried my car with out one once and it would always boil over.
The only purpose of Anti Freeze is to prevent freeze up in cold temps, and to provide corrosion protection. A/F actually does not transfer heat as well as plain water. Running 100% water will give the best cooling. You can do this with water wetter. Water wetter or RMI-25 will give you the needed corrosion protection. Running more than 70% A/F can actually make the engine overheat. I had a neighbor who used 100% A/F, and couldn't figure out why the engine overheated constantly.
I have the opposite problem. My 350 heats up on the freeway and then cools down when I slow down?????????????? I ahve anew 4 core radiator, 160 stat(checked and works), new water pump. What gives? It will run all day in traffic at 170-190 and then I will hit the highway and if I drive for 8 miles or more the temp will start climbing to 210 and then I get into traffic and it will come back down. Tim
Have you confirmed that your temp gauge is accurate? I wouldn't expect vapor lock at an engine temperature of 190 degrees if everything else was working properly. A bad thermostat will not cause overheating only at idle. "Anti freeze" also acts as an anti-boil in additon to being a lubricant and anti-corrosion aid. Yes, it does not transfer heat as readily as water. No, that shouldn't make a STINKING BIT of difference if the rest of the system is OK. I usually run 70% antifreeze because my vehicles park outside in the winter, and it can easily get -40 or even colder here. I do not change the ratio in the summer and I don't take out the 205 thermostat in my work truck, either. I NEVER have an overheating problem even at 90--100 degrees outside temperature, even when towing the boat. There is NO SUCH THING as "coolant flows through the radiator too fast to cool off". That is a myth that REFUSES TO DIE even though it violates common sense and the laws of thermodynamics. Drive down the highway, stick your hand out the window on a -40 degree day and see if you're moving too fast for the air to cool you off. My69GS350 has lots of good advice. Another thing in additon to dirty/plugged radiator and condenser fins: Air fins can become so corroded because of time and/or road salt that they won't connect properly to the water tubes of the radiator. They will superficially "look" good, and they may be clean. Still, they are non-functional and no better than dead weight in terms of aiding heat transfer. GS464 also has good advice. Keep in mind that at LOW speed or IDLE, overheating is "usually" a result of too little AIR flow--the fan isn't working properly. At high speed, overheating is "usually" a result of too little WATER flow--the water pump isn't pumping enough, or the radiator water tubes are plugged with scale. There can be other issues, or combinations of issues of course. Still, the rule-of-thumb is low speed = air flow problem, high speed = water flow problem. My advice: You said you have a new fan clutch. I'm hoping you have the thermal kind--most of 'em have a spiral spring on the front, a few have a leaf spring. Start the engine cold, let it fast idle. Pop the hood, let it continue to warm up on fast idle. Listen to the fan at fast idle. It will be loud, and you'll THINK it's throwing a lot of air. Somewhere around 190 degrees engine temp, the fan SHOULD have a SUDDEN AND DRAMATIC increase in noise and air flow. You'll think a tornado hit town, Dorothy and Toto will fly past your garage, and then you'll know that your thermostatic fan clutch actually works. If you don't hear that SUDDEN AND DRAMATIC change of noise, the fan clutch is junk and you need a different one. DO NOT buy a non-thermal clutch, they are low-dollar junk for people who don't want to spend any money. Do you have your vacuum advance connected to ported vacuum? Perhaps you could switch it to manifold vacuum so the timing is more advanced at idle. Too little timing advance can increase the heat burden on the cooling system.
Dorothy and Toto will fly past your garage!?! Man I thought I was doing good when I found "Birds,trees and 2x4's" sucked into the front of my radiator! "Volume and Flow", both for coolent and air is the simple key. And as I have found in my 48 short years, just because it's new does not mean it works! Mark
Similar problem in mine last year. Sorted it out when I found an air-lock in the engine top end. Nothing but hot air was getting to the sender. Working like a champ now.
Thanks for everyone's advice, keep it coming. :beer Freak6264: The new 180 thermostat I installed 9K miles ago did the same thing as the 160 does now stopped in the heat. My cruising temp did drop with the 160. MY69GS350: The thermostat is new and I bench tested it. Not that. The radiator is also new and clean. Overflow tank is original and I always use tap water. Cap is also new and stock rating. 16 psi I think. mhgs: I tried an electric fan I had that I used to run on my NASCAR late model stock car. The engine heated up much faster and would have overheated quickly if I didn't shut it down. The airflow could not compare to the stock fan and HD thermal fan clutch I have. Maybe the 2000 camaro fan flows better than my stock stuff but I'd have to see it to believe it. Larry: I run 100% antifreeze in my vehicles for the last 15 years (successfully) with the exception of the Buick because of this problem. I do this because I feel the water and its oxygen is what corrodes the parts. My theory is no oxygen, no oxidation. Yes, I've read the opposite theory and I proved it wrong in a test. IMHO, If the cooling system is marginal, yes I'm sure you would see a difference between 100% and 50%. If not, you won't see a difference in temps. Shurkey: I have checked the accuracy of my gauge, it's good. I have a NEW heavy duty thermal fan clutch. Summit part #FLX-5655 cost me $74.90. I have never heard my Buick fan make a sudden or dramatic change of noise. I also doubt the clutch I have is junk. It pulls a lot of air. Evidently not enough for whatever problem I have. I have heard this on other vehicles. Vacuum advance is ported. I run 11 degrees initial. It won't start if I try to run any more and I think it pinged when I ran it non-ported but I'll have to try that again. I don't remember for sure. I agree, 190 is too cool to have vapor lock. This is one reason I wonder about the exhaust passages in the intake. GS464: I have a trans cooler but its mounted around five inches in front of the condenser. The condenser is new and clean. I did check the water flow through the radiator visually and it flows great.
Make sure the bypass hose that goes from the water pump and the water neck is in place and not kinked or blocked. I beleave it gets the air out of the pump. On my race car I was having cooling trouble when I took the hose off.Should your clutch fan free wheel cold and lock up when hot? It should cycle on and off when idleing. It does on my van. If it dont cycle that may be the problem. Hope this helps . Dan
100% Anti Freeze ou: They tell you right on the back of the container not to run more than 70%. 100% anti freeze made my neighbors 90's Camry overheat in the summer with the A/C on. He was ready to go for a new radiator until I talked with him. Dropping it back to 50% put his temperature back to normal. The instructions on the back of the water wetter bottle tell you that further temperature reductions are possible with lower %'s of anti freeze. If you are concerned with corrosion, change the coolant every year or two. The additives in anti freeze wear out, and the PH will actually go acidic if left in too long. This will happen reguardless of the concentration of anti freeze to water. As far as no oxygen, no oxidation, I think you are mistaken. The only oxygen in water is the oxygen that is dissolved in it. Oxygen can dissolve in anti freeze also. Still, if 100% anti freeze works for you, and you have no problems, that's great :TU: Schurkey, the pressure cap is responsible for raising the boiling point of the coolant. Yes, the anti freeze raises it somewhat also, but with the proper cap, you can run water + water wetter with no problem whatsoever, racers do it all the time.
Radiators: New replacement ones available today have less tube count and fin density than OEM Harrisons, unless you special order a re-core with high-efficiency or big-tube high-efficiency core. Example: OEM Harrison 3-row core had 40 total rows, 3 tubes per row, 120 total tubes, each tube is 1/2" in depth. A new standard replacement 4-row has 29 total rows, 4 tubes per row, 116 total tubes, each tube is 1/2" in depth and lower fin density. A big-tube high-efficiency 3-row has 45 rows, 3 per row, 135 total tubes, each tube is 5/8". Electric Fans: most powerful single fan available anywhere is the 97-98 Lincoln Mk VIII, 4500+ cfm, needs 35+ amps continous, 100+ amps on startup.
I agree whole heartedly with Larry, drain your coolant and put in a 50/50 (or atleast a 70/30) mixture. I've known a few people who have accidently put in 100 percent Anti-Freeze thinking they bought a Dilluted bottle, and they've all had over heating issues. Anti-Freeze doesn't transfer heat nearly as well as water does, so the engine's heat doesn't get absorbed into the coolant as well as it would if there was water. The heat that does, won't transfer to the air blowing through the Radiator as well as it would either.
antifreeze.. yes I do agree with most all here....antifreeze is exactly what it's name says and thats it .... water by far is the better conductor of heat and for all of us that live in the temperate climates we are nothing but wasting our money other than the anticorrosive properties..and then you can buy in a can the anti corrosives for alot less. my son for the longest time had heating problems and not necessarily boilong over , but an older radiator cap is no where near it's rating and as we all know as you increase pressure you increase the boiling point. Wouldn't put it past a $5 cap that thats the problem. Mark
