overheating - one last time
#1
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overheating - one last time
I know that the topic has been beaten to death, and I've read all of the archives and suggestions about overheating. Most of which lead to 'get a new radiator'. And yes, I have a overheating question, but I'm more interested in the why.
Most posts that I've read have someone's car overheating at idle or slow speeds and disappearing at higher speeds. I actually have the opposite. The car runs fine at idle and okay driving around town. When I'm on the highway and doing 60-70, it will get hot after about 20 minutes at that speed. This is in temperatures around 85-90 outside. If I'm driving around town doing 35-40 the temperature will oscillate around 180 +/- 10 degrees. On the highway it will go up to 210-220 and will continue to peg unless I back off. Its at this time that the cockpit starts to really heat up as well.
What I'm guessing, and I stress the point guessing, is that the radiator may not have the efficiency to deal with the engine heat that is generated at that speed/power combination. Also, I have a pretty much stock 61 with a 283/230 and no special mods. Have a 160 degree thermo and have replaced that which caused earlier problems.
Thoughts? :confused:
Thanks,
Mark
Most posts that I've read have someone's car overheating at idle or slow speeds and disappearing at higher speeds. I actually have the opposite. The car runs fine at idle and okay driving around town. When I'm on the highway and doing 60-70, it will get hot after about 20 minutes at that speed. This is in temperatures around 85-90 outside. If I'm driving around town doing 35-40 the temperature will oscillate around 180 +/- 10 degrees. On the highway it will go up to 210-220 and will continue to peg unless I back off. Its at this time that the cockpit starts to really heat up as well.
What I'm guessing, and I stress the point guessing, is that the radiator may not have the efficiency to deal with the engine heat that is generated at that speed/power combination. Also, I have a pretty much stock 61 with a 283/230 and no special mods. Have a 160 degree thermo and have replaced that which caused earlier problems.
Thoughts? :confused:
Thanks,
Mark
#2
Re: overheating - one last time (mgriffis)
Low speed/idle over heating is a broad spectrum encompassing everything from the radiator to the timing and advance. (Duke will add some more).
I would suspect the radiator or the water pump in your case. As I read the thread I was thinking of a faulty temp-sending unit, but if you said you could feel the car getting hotter inside then it may be somewhat on target. You should check it with an Infrared Thermometer. (IT). You could borrow one or find someone to check it for you. Like Duke mentioned above 40 MPH the fan should not even play a significant role in cooling. When I lived in Alaska in the far north, Aleyaska Pipe Line used to take all their fans off for winter opps. This insured at idle and low speeds the radiator would not freeze (antifreeze will freeze/gel) and the heater would blow hot air.
And they left their trucks run 24/7. And at cruise speeds they would get the air movement over the radiator.
Back to the topic, your problem seems like flow or the Heat Transfer ability of your radiator. Unless you have documentation or proof of how old and how the radiator was maintained assume it needs to be addressed. The water pumps can rot/corrode, the impeller in particular. This will hinder flow in a big way.
Every vehicle I have owned, when the radiator is getting plugged and flow is poor, the vehicle starts to run warm at highway speeds. I could verify this by turning the heater on full bore and watch the temp gage go down.
PS: I have read good things about Tom Dewitts Radiators. I have never bought one or even seen one, but when it is time a factory correct replacement is going in and I will pursue Tom's service.
Mark
I would suspect the radiator or the water pump in your case. As I read the thread I was thinking of a faulty temp-sending unit, but if you said you could feel the car getting hotter inside then it may be somewhat on target. You should check it with an Infrared Thermometer. (IT). You could borrow one or find someone to check it for you. Like Duke mentioned above 40 MPH the fan should not even play a significant role in cooling. When I lived in Alaska in the far north, Aleyaska Pipe Line used to take all their fans off for winter opps. This insured at idle and low speeds the radiator would not freeze (antifreeze will freeze/gel) and the heater would blow hot air.
And they left their trucks run 24/7. And at cruise speeds they would get the air movement over the radiator.
Back to the topic, your problem seems like flow or the Heat Transfer ability of your radiator. Unless you have documentation or proof of how old and how the radiator was maintained assume it needs to be addressed. The water pumps can rot/corrode, the impeller in particular. This will hinder flow in a big way.
Every vehicle I have owned, when the radiator is getting plugged and flow is poor, the vehicle starts to run warm at highway speeds. I could verify this by turning the heater on full bore and watch the temp gage go down.
PS: I have read good things about Tom Dewitts Radiators. I have never bought one or even seen one, but when it is time a factory correct replacement is going in and I will pursue Tom's service.
Mark
#3
Re: overheating - one last time (ghostrider20)
If your cooling system is in good condition, check your engine for a lean burn condition. A vacuum leak or lean carburetor jetting can cause the engine to run hot. Your idle circuit may be correctly jetted but your main jetting may be too lean. You may be able to try a richer jetting to see if it makes a difference in your highway running temp.
#4
Team Owner
Re: overheating - one last time (mgriffis)
I also live in Texas. My 65 factory air Coupe, has been getting hot. It had been getting up to about 230 degrees. I saw a picture of a big block 67 that had the license plate mounted under the left headlight. I removed the front license plate, and now it only gets up to the 230 area sitting in traffic. As soon as I start moving, the gague starts to drop down. I don't know if removing the front license plate would help your problem, but it might be worth looking into.
#5
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Re: overheating - one last time (mgriffis)
Thanks for the advice. Would have never thought the license plate would be high enough to block the intake. Interesting thought.
I'm pretty sure that its my radiator, but I will probably check the engine as well just to make sure that everything is in sync there.
BTW, what is the major difference in the radiators offered on the market? I have read about the obvious difference aluminum rads make, but what accounts for the prices differences between a dewitts, griffin and say a be cool? There is as much as a $300-400 difference between these models and I can't find anything that points out the performance differences and what would be right for what type of car/driving.
Thanks again...
I'm pretty sure that its my radiator, but I will probably check the engine as well just to make sure that everything is in sync there.
BTW, what is the major difference in the radiators offered on the market? I have read about the obvious difference aluminum rads make, but what accounts for the prices differences between a dewitts, griffin and say a be cool? There is as much as a $300-400 difference between these models and I can't find anything that points out the performance differences and what would be right for what type of car/driving.
Thanks again...
#6
Burning Brakes
Re: overheating - one last time (mgriffis)
I had a similar situation w/ a 67 327/350 air coupe I previously owned. Around town it ran ~ 180 - 195, but on the highway it always creeped up over 200 degrees and on hot days would approach 220 + degrees. I purchased a new C/B radiator and immediatley solved the problem.
I have no overheating problems whatsoever with my 67 BB. Even in 95F weather, either idling in traffic or blasting on the highway, it never exceeds 195F. I run the factory C/B radiator and engine driven clutch fan. Here is what I have done to keep cooling in check:
Stewart Stage 1 water pump
160F Robertshaw thermostat w/ 3 holes drilled along circumference
straight water as coolant -- with 2 bottles of Prestone rad anti corrosion
A/C radiator seal kit and flap
remove front license plate
When the cooler weather comes in the fall I drain sufficient collant to add 1 gallon of antifreeze. I change my coolant annually. I'm not sure what radiator & shroud seals are available for C1 Corvettes, but they do help.
Good luck,
Mark
I have no overheating problems whatsoever with my 67 BB. Even in 95F weather, either idling in traffic or blasting on the highway, it never exceeds 195F. I run the factory C/B radiator and engine driven clutch fan. Here is what I have done to keep cooling in check:
Stewart Stage 1 water pump
160F Robertshaw thermostat w/ 3 holes drilled along circumference
straight water as coolant -- with 2 bottles of Prestone rad anti corrosion
A/C radiator seal kit and flap
remove front license plate
When the cooler weather comes in the fall I drain sufficient collant to add 1 gallon of antifreeze. I change my coolant annually. I'm not sure what radiator & shroud seals are available for C1 Corvettes, but they do help.
Good luck,
Mark
#7
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Re: overheating - one last time (ML67)
Generally, highway overheating (with OK performance around town) is a result of a) Not enough radiator or b) A blown head gasket. "Not enough radiator" is usually a result of scale and corrosion buildup in an older radiator, which significantly reduces its heat transfer capability. If you don't know the radiator's history or age, that's probably it.
#8
Former Vendor
Re: overheating - one last time (mgriffis)
You won't find a $300-400 difference in aluminum radiators. Mine, Griffins, and Be-cool are all in the same range. What is $300 cheaper is the copper replacement models which are rated at (3200 btu) . These are not something you want to do. They tested 30% below the factory rad specs. While the $295 price is very attractive, they just don't cut it in 90 degree traffic. Did ya ever notice how many copper rads are for sale with the line "only been in car for six months". That's because that's how long it took to figure out it wasn't working. I sell the correct sb aluminum radiator (4600 btu) for $695 and a five year warranty. I also offer the Griffin replacement (4100 btu) for $495 and two year warranty. The be-cool is the same as the griffin but I don't offer that one. Hope that explains the differences. td
#9
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Re: overheating - one last time (mgriffis)
I have a '61 275hp Fuelie. I have the exact same problem you are having. I suspected the rad. I have the stock style Harrison aluminum radiator. I removed it had it flow tested and flowed fine. I checked the timing, a/f mix seems to be ok. Robertshaw high flow thermostat. I don't know the condition of the water pump and it has been on for about 10years. I was told it could be a high pressure building up in the engine compartment, due to the air not sufficiently passing through the radiator and exiting the engine compartment properly. The faster you go, the more pressure builds, keeping hot air in the compartment, almost blocking cool air flow through the radiator. But if that is the case all these type of cars should be running hot. I am still trying to fiqure it out. If you do pleeeease let me know, and I will do the same. :confused:
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Re: overheating - one last time (agd61)
A "flow test" doesn't mean much , except to tell you the radiator isn't clogged. A radiator's job is to transfer heat from the coolant to the air through its tubes and fins (or plates and fins), and if it has an internal buildup of scale and corrosion that can reduce its heat transfer capability up to 50% (due to the scale/corrosion acting as an insulator), a "flow test" won't tell you squat about that. 99% of all cooling problems are radiator or airflow related, and if nothing major has occurred to suddenly reduce airflow, chances are it's the radiator. If you don't know the history and age of your radiator, you may need one; aluminum radiators are non-repairable, and can die an early death from corrosion and scale if the anti-freeze coolant isn't changed regularly to maintain the effectiveness of the corrosion inhibitor package.
#11
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Re: overheating - one last time (Tom DeWitt)
Tom DeWitt - what is the btu rate for a BB brass radiator?
I just returned through NV and UT. The rad would upchuck coolant and white foam with each shutdown across the 100+ desert states. When I got to WY, everything returned to normal - even with only water in the radiator. I am considering another recore. My outlets have been rotated to make hose attachment easier, and I hate to consider a replacement if it means going back to struggling with the hoses or having a new radiator modified. :crazy:
I just returned through NV and UT. The rad would upchuck coolant and white foam with each shutdown across the 100+ desert states. When I got to WY, everything returned to normal - even with only water in the radiator. I am considering another recore. My outlets have been rotated to make hose attachment easier, and I hate to consider a replacement if it means going back to struggling with the hoses or having a new radiator modified. :crazy:
#12
Pro
Re: overheating - one last time (mgriffis)
No one has mentioned the lower radiator hose, so I will. It happened to me once, the car was fine around town and overheated at sustained highway speeds. Lower radiator hose collapsed under the suction from the pump.
#13
Former Vendor
Re: overheating - one last time (magicv8)
Magicv8, I never had the BB radiator tested, just the small block models. The testing labs get big bucks for doing this, about $4000 a radiator. But based on the data we got from the small block testing, all I can say is an aluminum radiator, equal in size, will be about 25-30% better. I have a personal problem with the 66-67 BB radiator in that it is really no bigger that a small block aluminum 3155316. This radiator measures 22.5" wide and is ALL radiator because it has no loss in end tanks. The BB copper radiator has a 22.5" core, but is bigger in size because it has end tanks. I also find it very interesting GM changed the copper radiators to 27.5" cores from 69-82. Kind of supports my theory that the 3008566 was just a little undersized. That said, If you still want to recore yours and want the original look we can help with the core.
[Modified by Tom DeWitt, 8:36 PM 8/15/2002]
[Modified by Tom DeWitt, 8:38 PM 8/15/2002]
[Modified by Tom DeWitt, 8:36 PM 8/15/2002]
[Modified by Tom DeWitt, 8:38 PM 8/15/2002]
#14
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Re: overheating - one last time (Tom DeWitt)
It isn't the originality - because the non original inlet and 8-10 degree rotated outlet are why I want to keep my end tanks. My end tanks make connecting to an SB at the top easier (check my web page Details link) and the lower hose slips on easily after the outlet is rotated away from the shroud. Can the aluminum rad do that AND handle an A-C exchanger in front of it?
#15
Former Vendor
Re: overheating - one last time (magicv8)
The only thing I could do with the connections is to custom build one that would match what you have now. I don't know why you need this but it can be done. The aluminum two row would give you about 25% more cooling than the copper four row. Less is better!
If you really want cool, and don't care about factory stuff check out this fan/rad combo. We make a radiator that's exactly like the stock copper one but add one more inch in length to allow for the dual electric fans. Now you have no shroud or mechanical fan to get in your way.
If you really want cool, and don't care about factory stuff check out this fan/rad combo. We make a radiator that's exactly like the stock copper one but add one more inch in length to allow for the dual electric fans. Now you have no shroud or mechanical fan to get in your way.
#16
Re: overheating - one last time (Tom DeWitt)
I had the same highway heat up problem at anything over 60mph for more than 20 minutes....the radiator was the original one 37 years young (NCRS Top Flight car). Anyway, bought a DeWitt repro with all the correct markings and labels. Got in a good test of it yesterday going and returning from a show about 60 miles away. At 85 degrees out and humid, I was able to run 70mph with the temp guage staying at or just over the 180 level. By the way, I also had removed the front license plate holder all together to improve flow thru (as was done on the BB's) and installed a rubber seal molding on the top end of the radiator surround (original on later midyears I think). Oh...and the new bolton knockoffs and radials made 70-80mph a pleasure too.
:seeya
:seeya
#17
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Re: overheating - one last time (gilbybarr)
Gilby - My plate has been lowered beneath the chrome cross bar, even with the bottom of the air dam. The BB+auto+A-C bracket would put the plate where my auxiliary headlamps are.
TDewitt - what's the cost of the rad with the twin fans included, and the cost of just an aluminum replacement - both with the lower outlet rotated 8-10degrees clockwise and the upper inlet straight or curved upward 45 degrees instead of a 90 degree kink toward center in it?
[Modified by magicv8, 5:29 PM 8/23/2002]
TDewitt - what's the cost of the rad with the twin fans included, and the cost of just an aluminum replacement - both with the lower outlet rotated 8-10degrees clockwise and the upper inlet straight or curved upward 45 degrees instead of a 90 degree kink toward center in it?
[Modified by magicv8, 5:29 PM 8/23/2002]
#18
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Re: overheating - one last time (gilbybarr)
Tom
I'm interested in a radiator/fan combo for a 65. Completing a frame off resto and do not want any cooling problems. The car is a 385 FB and will have ac. Man 6spd [no auto].
Let me know details if you will.
I'm interested in a radiator/fan combo for a 65. Completing a frame off resto and do not want any cooling problems. The car is a 385 FB and will have ac. Man 6spd [no auto].
Let me know details if you will.
#19
Re: overheating - one last time (mgriffis)
Here I go again, most of the members don`t believe me but replace the 160 with a 180 and it should at least solve the glaring thermostat problem if you have an early model. My 62 360hp car has never overheated and it spent several years with me at the University of Miami when it was new. Now thats hot. It came home with me after finishing Law School and I get the same question up here from new owners of old Vettes wherever I go. "How hot does it run?" I tell them 175 to 180 at any speed or any outside temperture and they all look amazed. I don`t know whether or not they follow my advice, but out of sight out of mind. I know mine is correct and with a 4.56 axle its turning 4,000 RPM at 70 miles an hour and it frequently sees over 100 MPH street racing pump jockeys and gets there in a hurry. A picture of the car is on my site at http://nitroalley.net if your interested. :cheers: Wally
I know that the topic has been beaten to death, and I've read all of the archives and suggestions about overheating. Most of which lead to 'get a new radiator'. And yes, I have a overheating question, but I'm more interested in the why.
Most posts that I've read have someone's car overheating at idle or slow speeds and disappearing at higher speeds. I actually have the opposite. The car runs fine at idle and okay driving around town. When I'm on the highway and doing 60-70, it will get hot after about 20 minutes at that speed. This is in temperatures around 85-90 outside. If I'm driving around town doing 35-40 the temperature will oscillate around 180 +/- 10 degrees. On the highway it will go up to 210-220 and will continue to peg unless I back off. Its at this time that the cockpit starts to really heat up as well.
What I'm guessing, and I stress the point guessing, is that the radiator may not have the efficiency to deal with the engine heat that is generated at that speed/power combination. Also, I have a pretty much stock 61 with a 283/230 and no special mods. Have a 160 degree thermo and have replaced that which caused earlier problems.
Thoughts? :confused:
Thanks,
Mark
Most posts that I've read have someone's car overheating at idle or slow speeds and disappearing at higher speeds. I actually have the opposite. The car runs fine at idle and okay driving around town. When I'm on the highway and doing 60-70, it will get hot after about 20 minutes at that speed. This is in temperatures around 85-90 outside. If I'm driving around town doing 35-40 the temperature will oscillate around 180 +/- 10 degrees. On the highway it will go up to 210-220 and will continue to peg unless I back off. Its at this time that the cockpit starts to really heat up as well.
What I'm guessing, and I stress the point guessing, is that the radiator may not have the efficiency to deal with the engine heat that is generated at that speed/power combination. Also, I have a pretty much stock 61 with a 283/230 and no special mods. Have a 160 degree thermo and have replaced that which caused earlier problems.
Thoughts? :confused:
Thanks,
Mark
#20
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Re: overheating - one last time (wallyknoch)
:crazy:
.....still haven't seen an explanation why a prefectly functioning brass radiator (say, a recored original) will NOT be adequate for a sb vette, assuming adequate airflow over the fins...
...tom, i would be interested in your opinion of the article in chevy high performance about two issues ago where they essentially said the benefits of an aluminum radiator are over rated - in fact, they state that the heat trasfer capability of aluminum is relatively poor, compared to other alloys.....again, they state "opinions" without any data to back it up but it seems to me that there's always a rush to judgement that, all other things being equal, an aluminum radiator is superior to any other....you know, in fact, the afco catalog clearly states that the reason you go to an aluminum radiator is to save weight (i guess racing speeds ensure airflow)...but somehow, this stuff is not making sense - resident cynic that i am
.....still haven't seen an explanation why a prefectly functioning brass radiator (say, a recored original) will NOT be adequate for a sb vette, assuming adequate airflow over the fins...
...tom, i would be interested in your opinion of the article in chevy high performance about two issues ago where they essentially said the benefits of an aluminum radiator are over rated - in fact, they state that the heat trasfer capability of aluminum is relatively poor, compared to other alloys.....again, they state "opinions" without any data to back it up but it seems to me that there's always a rush to judgement that, all other things being equal, an aluminum radiator is superior to any other....you know, in fact, the afco catalog clearly states that the reason you go to an aluminum radiator is to save weight (i guess racing speeds ensure airflow)...but somehow, this stuff is not making sense - resident cynic that i am