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  1. #1
    Member ProEMTPFF's Avatar
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    Default Thermostat/fan question?

    What temp is the OEM thermostat set at for a '86 L98? I live in Florida and I've been thinking of going to a 160 Deg. stat because of the heat down here. My car in traffic runs around 130+ Deg and the car starts running like crap. I think a 160 down here will work perfect for me BUT I have seen some people in here talk about switching the fan on sooner? Should I do this also and how do I switch the fan? I also think I might do the coolant bypass. This car is running WAY to hot here. Please give me your opinions and suggestions. I know this subject has been beat to death with people in colder climates but I can't find any responces from Florida. Thank you in advance.

  2. #2
    Vettefan87's Avatar
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    To answer your question I believe it is 195 with the fan kicking on at around 230. I run a 160 degree stat, and I have a Hypertech Thermo master chip that turns the fan on at 175 degrees. You can manually run a switch and just switch the fan on and off if you want, or you can fork over some money and buy a chip that turns it on itself. You will notice improvements in cruising temps by doing the 160 degree stat, but when you sit in traffic the temp will soar.

  3. #3
    Member c4cruiser's Avatar
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    87 Gold Z52 Coupe 02 EB Z51 Supercharged Coupe

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    You should first do a complete inspection of your cooling system. The biggest problem with cooling is the trapping of dirt and debris in the front of the radiator and the A/C condensor. Vettes take all the cooling air in from underneath the car and there can be a bunch of junk up there that is clogging the flow of air.

    You can direct a stream of water from behind the radiator and flush out a lot of stuff. A shop vac can remove a lot of stuff before you use the hose. You could find that this will help cooling a bunch and it a noc-cost job.

    When was the last time you had the coolant replaced? You should do a flush and refill every 2-3 years and use a good ethleyne glycol (green) coolant and distilled water in a 50-50 mix. Old radiator hoses will go soft and they can collapse which cuts the flow of coolant into or out of the radiator.

    Radiators will wear out over time. The coolant tubes in the core will get thin and lose their ability to effectively transfer heat. Thermostats do wear out and if it is not opening all the way, coolant flow becomes restricted.

    I'm not a big fan of mods or add-ons for solving cooling issues. The correct equipment in good condition works fine. GM did lots of testing in extremely hot conditions and what they put into the car works. The fan operation is designed to keep coolant temps at a point where emissions are reduced. A thermostat that opens at lower temps simply allows full flow of coolant at that lower opening temp. Once the stat is open, it really has no effect in stop and go driving where airflow is reduced or extremely hot ambient air temps.

    If the fan relay is working and the ECM is receiving the proper signal from the temp sensor so it can ground the relay and start the fan, the system is working as designed. If you have either the Z51 or Z52 package, you will have a secondary cooling fan (in front of the A/C condensor) and that fan should start at around 230 or if you turn the A/C on. The standard fan should start around 228 and turn off at around 205 or so. Once the car is moving at higher speeds, the fan does not do much of anything to reduce coolant temps.
    So check the entire cooling system before you add a lower temp stat, computer chip or fan override switch.

  4. #4
    Member ProEMTPFF's Avatar
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    Default

    Also, what about some of those anti-freeze and/or radiator additives out there that claim to keep the car cooler? Anyone try these? Do they work? I HAVE to cool this car down some. BTW, the fan switch, 160 stat and new gasket is on order. I hope these help. I have the Z51, the radiator is clean and I'm no fan of GM OEM parts. I do need to flush the radiator enen though the car has ONLY 9100 miles on her BUT the fluid is 19 years old.

    Fan Switch: http://www.madvet.com/shop?frame=3.944

  5. #5
    Vettefan87's Avatar
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    Yes immediatly do a flush of the antifreeze that stuff eats away at the head gaskets and what not, which I know to much about . You could lean the mixture out a little instead of going 50/50, go like 70/30. The 70 being water since it cools better then coolant.

  6. #6
    Member G Winter's Avatar
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    vettefan, I am not so sure you are right about mixing less coolant , the antifreeze aids in cooling ,, ever try to run air conditioning without antifreeze. Car get warm real quick . Have to do a little research on that one to be sure.
    Some of the additives to help cool do work according to the dirt track racers around here, not sure what brand they use.


  7. #7
    Moderator vetteboy86's Avatar
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    The only reason the additives work is because they are basically water with some additives. Therefore increasing the water content in your cooling system. The reason we use coolant around here is because water freezes at around 32 degrees F. So we use coolant to stop the freezing process. Has anyone left a straight mixture of water in the block over the winter. Not good.

    Craig

  8. #8
    Member ProEMTPFF's Avatar
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    I've heard that a product called "water wetter" by Redline and "Purple Ice" by Royal Purple works wonders. Also the Amsoil brand anti-freeze is awsome. BTW, water does cool much better than antifreeze. Most race engines just run water in them. I might try the Amsoil with the 70/30 mix and add some water wetter or Purple ice. Both suggest doing this. I live in Central Florida and my car stays in my garage in winter unless I'm driving it so I don't think the 70/30 will hurt me at all. Also, using a Propylene Glycol Antifreeze like the Amsoil brand with one of the additives in a 70/30 mix rather than "normal" antifreeze will help reduce heat while keeping the water from freezing.

  9. #9
    Member WhalePirot's Avatar
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    Water has the best heat transfer characteristics, therefore is the best coolant. However, in addition to the known freezing issues, antifreeze contains anti-corrosion agents and some lubricants for your water pump.

    Many of us feel that 160 is too cold. I run a Robert Shaw 180 with fine result. More important are the maintenance issues mentioned, like fresh coolant and leave/debris removal.

  10. #10
    Member c4cruiser's Avatar
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    Running pure water as a coolant will allow the system to transfer heat better. But without the additives for anti-corrosiion and the like, you can quickly build up rust and corrosion in the system. Ever notice how fast a rust film appears on the brake rotors after you wash your car?? Also, water freezes at 32 degrees. If you drive your car during cool temps and the air passing thru the metal radiator tubs cools those tubes to 32 or below, the water in therew can freeze. Think wind chill factor!

    A reduced ratio of coolant to water only raises the freezing protection level of the coolant. A 50-50 mix of coolant and water provides a -37 degree freezing protection level, while also providing the best level of anti-corrosion protection.

    Watter Wetter and other additives are supposed to reduce coolant temps, but my experience with it is that I have really only seen a 5-7 degree drop while in heavy traffic with no real effect at freeway cruise speeds. I had read that these additives have a sort of "shelf life" in that after a period of time, they lose their effectiveness.

    ProEMTPFF- One reason that race engines run pure water is that if there is a major coolant spill like a crash would cause, the water will not cause the track surface to remain slippery. Anti-freeze on the track will be about the same as oil on the surface. It's a safety issue rather than cooling. I have never really heard much about Amsoil antifreeze but I do know there is lots of discussion about their products compared to other lubricants and in all honesty, I have not heard a lot of positive comments. Not sure what a "propoylene glycol solution is. Is this something you have experience with as a customer or as a dealer?

  11. #11
    Member ProEMTPFF's Avatar
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    I've used the Amsoil antifreeze/coolent with propoylene glycol in my 2-stroke race bike, my Kawasaki ZX10 and in my ATV's......all had over heating issues and the coolent helped. I'm not a Amsoil dealer just have been a customer from time to time.

  12. #12
    Member c4cruiser's Avatar
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    Been following the same question you posted on teh CF. There's lots of good advice both here and there

    I wouldn't worry too much about the temps you see unless they are consistently above 230 and hold there even with the fan running. As I mentioned, a clean cooling system both inside and outside is the key to effective cooling in C4's.

    If the cooling system has not been maintained over the years, it's very possible that some of the tubes in the radiator core could be blocked or just have reduced flow. You may have to consider pulling the radiator and having it rodded out by a reputable radiator shop.

    When I was returning from the 50th Anniversary celebration at Bowling Green in 2003, we headed thru Las Vegas over that 4th of July weekend. I was driving my 92 and had done a coolant flush and refilled with 50/50 Prestone green coolant and distilled water. I had also replaced the upper and lower radiator hoses.

    We encountered air temps in the 105-110 degree range about 100 miles east of Vegas and going Hoover Dam and even saw 112 in town! The car never got above 230 even at city traffic speeds. It still has the original 195 degree stat and the original radiator.

  13. #13
    Vettefan87's Avatar
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    Quote Originally Posted by WhalePirot
    Water has the best heat transfer characteristics, therefore is the best coolant. However, in addition to the known freezing issues, antifreeze contains anti-corrosion agents and some lubricants for your water pump.
    That is why I suggested running perhaps a 70/30 mix, try to get the best of both worlds.

  14. #14
    Member ProEMTPFF's Avatar
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    I installed the "Low Temperature Electric Cooling Fan Switch" from Mid America and left the stock 195 Deg thermostat in. I took the car for a spin "hard run" and the temp gauge stayed in the 186-206 range. Nice improvement! Then the next day around the same time, temp and humidity installed the Hypertech 160 Deg thermostat. Again, I went for a spin, ran the car the same miles and even harder than the day before. The result was a temp gauge staying between 175-182. I'd go to say thats a marked improvement over the entire stock "OEM" setup. Also, the car feels more responsive. Ohhhh, I also did the intake coolent bypass when I changed the fan switch. I say the General doesn't know......jack crap about fine tuning these cars from the factory.....thats my opinion anyway.

  15. #15
    Member WhalePirot's Avatar
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    Default Be glad it is so easy to grab more power!

    Quote Originally Posted by ProEMTPFF
    I say the General doesn't know......jack crap about fine tuning these cars from the factory.
    They must set the car up to run and be reliable in any climate; on varying fuels with various maintenance. We only have to do it for one. The coolant bypass is designed to prevent icing, which I have experienced, on a different car. It was strange and I was lucky to diagnose it, because there was no evidence to observe after the car sat for a short time(melted).
    One thing I learned after doing all the mods to my car, is respect for the engineers who built it. The performance, AND reliability, including proper cooling etc., etc., that I tampered with and lost, at least temporarily..

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