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Discussion Starter · #1 ·
My car overheats terribly in traffic everytime. I have a four row radiator, 160 degree mr. gasket therm., 16 inch flex fan w/shroud, highflow waterpump,catchcan,10ilb cap. and a good mixture of water/coolant. I have a crummy stock electric guage out of a firebird, it starts at 100 the middle is at210 and redzone is 260. It runs in the middle of 100-210 which i figure is about 165 all day perfectly, but as soon as I sit in traffic it starts to rise, after a bit it gets up to about 220-230 at the worst!!! But is seems to run Okay(not great though) I had a 16inch electric fan pushing from the front of the radiator, but the motor went dead so i took it off. Is this guage likely faulty or do I have a problem! any Ideas??
 

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First, a 10# cap is too low. Go with a 15-16. A flex fan isn't too good either. Since your car is acting up in traffic, not on the road, you have an air flow problem. Try a clutch fan with a shroud, properly spaced, and I think you'll find your problem resolved.

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Rick Dorion
69 RS Conv,355,M20,4.10's
 

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Some flex fans like flex-a-lite green blade are like a four blade fan in flow with no extra air flow.
they do make higher and lower flow flex fans, just a thought.
Don't put a high pressure cap on an old radiator or it will spring a leak.
Make sure your core fins are clear of bugs.
David

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[This message has been edited by davidpozzi (edited 07-27-2001).]
 

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<BLOCKQUOTE>quote:</font><HR>Originally posted by rs1968ss:
What exactly does a clutch fan do? Mine runs hot as well and I have just a straight fan. I also put an electric pusher on the front and it seems to help but it still runs too hot for my tastes. Should I switch it to a clutch setup?
<HR></BLOCKQUOTE>

Thermal clutch fans adjust how fast the fan turns based on temp. If it's hot it tightens up and spins faster with engine rpm. When it's cooler it lossens and the fan speed slows. A non-thermal loosens up with rpm and tightens at idle..

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...Dennis
'69 RS Convertible w/SS trim
'96 Z28SS #1679 of 2410
"The Club"
 

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If your car is a late model check for the condition of the front underneath plastic cover. Some newer models have them to avoid the situation where the hot air from the engine compartment flows from under the car to the front of the radiator or grill and enters again thru the radiator. This situation makes the cooling system less efective when the car is standing still.

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[This message has been edited by ORENCH (edited 07-27-2001).]
 

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Discussion Starter · #8 ·
all these ideas? but which one? Why wiuld I have a airflow problem? the air pulls through just fine. Also wouldn't a 180 stat run hotter? Why a clutch fan v. flex fan, flex fans are supposed to pull a lot at low rpm, they just flatten out at high rpm. also what does anyone think about my guage? I've also heard sraight water makes it run cooler.
 

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Cody -

All good suggestions - take one at a time - I agree it is an airflow problem -

Take a heavy piece of paper (card stock) and set it in front of the radiator (2-3 inches) at idle and see if it will get sucked up against the radiator. It should get sucked against it and held. That will give you an idea of airflow. also you say you have a shroud - make sure the fan aligns in the shroud - I prefer 2/3rds to 1/2 of the fan blade in the shroud.

I personally do not care for flex fan - I'm a traditionalist - like clutch and hard fan - but if you are sucking good air - and YOU like it - stick with it (careful - they are known to blow apart at high rpms)

You mention good water / antifreeze mix - should be 50-50 OR LESS antifreeze - water does grab the heat better. If you run straight water it would help -> but this is not addressing the root cause of the problem.

Is the engine modified? If so - stock exhaust manifold or headers? (air restriction makes engine run hotter)

You mention high flow water pump -> why do you have one? it could be moving water too fast to properly cool.

How old is the radiator? could be getting blocked and not flowing well.

Gauge could be a problem - but I would check airflow first...

Steve
 

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I ran into a similiar problem right after installing my new pulleys. They slowed the belts down and I ran into a problem with fan speed at idle, in traffic. The cheap solution was to put the car into nuetral when sitting-that made the rpms come up and helped water circulation as well.

Then I put on an electric fan from a junkyard ($20). That fixed it completely....almost.....now I need a better alternator!!

Does it ever end?!
 

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Cody,

Start with the basics!! If you have any question at all about the guage, replace it!! That is what you are using to base everything else with. If you still over heat at idle and your cooling system is in good shape (radiator, 15lb cap, hoses, waterpump, 180deg t-stat and a 50/50 fluid mix) check your timing!! Low inital timing can cause the engine to make more heat....

I also don't like flex fans, as stated they come apart and do much damage. They also flatten at rpm and form a dam blocking air flow. If your fan is only 16" it may be too small for the shroud. I think 18" is the correct size but measure your shroud to be sure!!

If your car is overheating at idle, timing and air flow are the 2 biggest causes. That is why folks have suggested it! The t-stat opens and closes to control water flow but once the temp gets past the t-stat rating it will just stay open.

Don't let this overwhelm you!! You need to assess the problem and then dig in!!




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...Dennis
'69 RS Convertible w/SS trim
'96 Z28SS #1679 of 2410
"The Club"
 

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I read this once in some sort of hot rod magazine. I have never tried it so I don't know if it works. This is a method to figure out if you have an airflow problem or not. Start the car and let it idle in your driveway or garage (open the door if in the garage) garage would be better, less wind. Take your 20" box fan (the ones you can get at Wal-Mart for around $20) and put it on something so that it points directly into the grill of the car at the radiator. Get it as close as possible to the grill for maximum airflow. According to what I read, if you don't see a 10 or 20 degree drop in engine temperature, you have an airflow problem. Like I said before, I haven't ever tried this so I don't know if it works. I doubt your guage is at fault. Since the guage goes up when at a stand still, the engine is obviously getting hotter. I think that this points to an airflow problem. You might want to buy a cheap water temperature guage to check it against the one you have now. Good Luck.
 

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Discussion Starter · #13 ·
Thanks a lot for all the advice! I'm going to try the cardboard idea. and check my timing, my fan is about a little over half way in the shroud, I saw a guy with a broken flex fan it flew up and put a big dent in his hood and cracked the paint, maybe I will get a clutch?Oh yeah I have a ten pound cap that came with the catch can, Is this the right one i think its lower so it can siphon fluid in and out of the can.
 

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First, shoot the thermostat housing with an I.R. gun and check that reading against your gauge so you know what your actual temperature is. Then put a 15# (stock spec) cap on it. Then ditch the flex fan and use the stock shroud, clutch, and fixed fan, and make sure the radiator is sealed to the radiator support and the shroud is sealed to the radiator so all the incoming air is forced through the radiator, not allowed to spill around it. If you still have the same problem, it's your radiator. All the other stuff is band-aids; get the basics right and the system will work, just like it did when the car was new. Changing the "system" always causes problems - that's what created the market for the "band-aids".

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JohnZ
'69 Z28 Fathom Green

[This message has been edited by JohnZ (edited 07-27-2001).]
 

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Cody,

I live in Houston, run the factory AC and drive my 69 daily in traffic. I used to have the same problem you have - last summer. The car would always overheat in traffic. I have a clutch fan, 160deg thermostat, underdrive pulleys, 15# cap, etc. Two things are different this summer. First, I have the total timing on my machine set so that I have 12 in crank, 12 on vacume at idle, and 24 mechanical advance at 3000rpm. This combo really seemed to cool down my underhood temps. I also installed an overflow tank on the radiator. I built this out of a windshield washer bottle that I placed in the right fender behind the battery. This combination keeps the temp gauge steady with no boiling over and the temps here have been over 100 most afternoons when I get stuck in traffic. My engine and I both remain cool.
 

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Discussion Starter · #16 ·
what about my ten pound cap? too little it came with my catch can, will a 15 pound work with the can?
 

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Discussion Starter · #17 ·
Also whats the hottest safest temp. to be running, before their is damage? Was running at 220 doing damage?
 

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Doesn't matter what cap you have on the catch can - the one on the radiator is what controls cooling system pressure; the only connection to the catch can is the nipple below the radiator cap seal, which only opens when the pressurized boiling point is exceeded (265 degrees with 50-50 antifreeze and a 15# cap).

Occasional running at 220 won't hurt your motor, although it pains you to see it on your temp gauge; most modern cars run at 200-210 all the time for improved combustion efficiency and reduced emissions. Put the basics to work as I outlined earlier and you shouldn't see 220 again.

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JohnZ
'69 Z28 Fathom Green
 

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Discussion Starter · #19 ·
Johnz thanks for the advice. I checked my air flow coming from the front of the radiator, first while idling i put a piece of paper in front of the radiator and it stuck to it really good, then i tried a piece of thick cardboard and that stuck to it also not really good, but it stuck, so i figure my air flow must be alright, there are however spaces on the side of the radiator where air can sneak by but since my test worked i'm thinking it might be okay. Also i was wrong i just checked my cap it is a 13ilb cap. My questions are, do i still need a 15ilb? do i really need a clutch fan, and how bad do you think these holes at both ends of the radiator are affecting?
 

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JohnZ - You mentioned sealing the radiator to the radiator support. Are you talking about a real seal or just getting it close up against the support?

I just installed the BB radiator in my '69 and there's a gap between the support and the core - the tanks touch the support of course. There is also a "flanged" area on the support that extends toward the core but doesn't touch it??


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Scott
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