Cooling Down a L98, Is it Possible?
10-16-2017, 02:24 PM
#1
Racer
Thread Starter
Cooling Down a L98, Is it Possible?
I know this has been hashed and rehashed many times, but I could not find a definitive answer. I, like many of you, think the L98 runs too hot for comfort. Is there any way to actually bring this engine to 180f max? I am thinking a bigger, 3 row radiator, and lower tstat should be enough to keep the operating temps lower. Is this logical, or am I missing something?
As a side note, I want to express how important it is for C4 owners to make sure you clean your radiator are of debris. I ignored this instruction for awhile, did it this weekend and was blown away by the amount or garbage and debris in there. Car still climbed to 230 easy in traffic, then fan brings temp to around 210. I would like it to never get to 230, if possible.
As a side note, I want to express how important it is for C4 owners to make sure you clean your radiator are of debris. I ignored this instruction for awhile, did it this weekend and was blown away by the amount or garbage and debris in there. Car still climbed to 230 easy in traffic, then fan brings temp to around 210. I would like it to never get to 230, if possible.
10-16-2017, 02:43 PM
#2
Team Owner
The L98 and the later LT1 engines are designed to run hot. This was done to help with lowering emissions. Operating temps at around 190-210 are perfectly normal. The fans are set to turn on at 230+ degrees and the fans run constantly once the A/C is turned on.
If the original radiator is still in the car, it could be that years of the coolant passing thru the tubes have reduced the thickness of the tubes and heat transfer is not as good as when the radiator was new. Replacing the radiator with a OEM design will help to drop observed coolant temps.
Make sure that the lower airdams are in place and in good condition. They are designed to direct incoming air up into the A/C condensor and radiator.
If the original radiator is still in the car, it could be that years of the coolant passing thru the tubes have reduced the thickness of the tubes and heat transfer is not as good as when the radiator was new. Replacing the radiator with a OEM design will help to drop observed coolant temps.
Make sure that the lower airdams are in place and in good condition. They are designed to direct incoming air up into the A/C condensor and radiator.
10-16-2017, 02:58 PM
#3
Drifting
Member Since: Mar 2017
Location: Nashville TN
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2017 C4 of Year Finalist
200 degree temps are perfectly normal-when I would worry is if the fan isn't keeping up. 230 is a little hot, but cleaning out the radiator and the area in front of it should both help.
I took the radiator out of the car entirely, then filled it with vinegar for about 45 minutes, then flushed and backflushed the radiator. I also took some time to unbend most of the bent fins on the radiator. After doing all of that, it was like a new cooling system! The whole thing barely hit 200 in the summer heat.
You can also modify your cooling fans to run when you flip a switch. I'm not 100% sure I recommend it (it's bad for the fans to just leave them always running) but it's super easy, you just ground the relay for the cooling fan through a switch. That plus a 160 degree tstat will keep you very cool even during summer heat. If you break 200 even with the AC on I'd be surprised.
I took the radiator out of the car entirely, then filled it with vinegar for about 45 minutes, then flushed and backflushed the radiator. I also took some time to unbend most of the bent fins on the radiator. After doing all of that, it was like a new cooling system! The whole thing barely hit 200 in the summer heat.
You can also modify your cooling fans to run when you flip a switch. I'm not 100% sure I recommend it (it's bad for the fans to just leave them always running) but it's super easy, you just ground the relay for the cooling fan through a switch. That plus a 160 degree tstat will keep you very cool even during summer heat. If you break 200 even with the AC on I'd be surprised.
10-16-2017, 06:11 PM
#5
Team Owner
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C7 of the Year - Unmodified Finalist 2021
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I have done it all, and the DeWitts makes the real difference.
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rrt898 (10-19-2017)
10-16-2017, 06:22 PM
#6
Le Mans Master
I know this has been hashed and rehashed many times, but I could not find a definitive answer. I, like many of you, think the L98 runs too hot for comfort. Is there any way to actually bring this engine to 180f max? I am thinking a bigger, 3 row radiator, and lower tstat should be enough to keep the operating temps lower. Is this logical, or am I missing something?
As a side note, I want to express how important it is for C4 owners to make sure you clean your radiator are of debris. I ignored this instruction for awhile, did it this weekend and was blown away by the amount or garbage and debris in there. Car still climbed to 230 easy in traffic, then fan brings temp to around 210. I would like it to never get to 230, if possible.
As a side note, I want to express how important it is for C4 owners to make sure you clean your radiator are of debris. I ignored this instruction for awhile, did it this weekend and was blown away by the amount or garbage and debris in there. Car still climbed to 230 easy in traffic, then fan brings temp to around 210. I would like it to never get to 230, if possible.
10-16-2017, 06:40 PM
#7
Team Owner
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St. Jude Donor '05
^^^blow the fins out from that backside they plugged up
i put a hypertech chip 160 stat so the fans came on cooler big difference but in traffic it will still get to 200ish.
The dewitts/dual fan combo rocks, put a 160 in too youll love it.
i put a hypertech chip 160 stat so the fans came on cooler big difference but in traffic it will still get to 200ish.
The dewitts/dual fan combo rocks, put a 160 in too youll love it.
10-16-2017, 06:44 PM
#8
Team Owner
Pro Mechanic
Under ALL conditions? That is going to take a bad assed radiator, some stout fans and programmable fan control. $1000.00 should get you the hardware necessary to get that job done.
"Never get to 230" is easy, and WAY different (50* different) than what you said above. Good cooling system maintenance and a fan reprogram or manual fan control would accomplish "never get to 230". .
"Never get to 230" is easy, and WAY different (50* different) than what you said above. Good cooling system maintenance and a fan reprogram or manual fan control would accomplish "never get to 230". .
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Ahnenerbe (10-17-2017)
10-16-2017, 07:47 PM
#9
Le Mans Master
My car runs at 178 to 182 degrees all year long as long as the car is moving at least 30 mph.( My engine has never seen 200 degrees) I have a Dewitts radiator, a Dewitt's high speed fan , a 180 degree stat , a Stewart high flow water pump, and have my fan programmed to come on at 196 degrees , and go off at 180 degrees...This combination is the best I have found and the only time my car goes above 182 degrees is when I have an extended stay at a stop light... Even when the temps go up at a light , they go down to 180 degrees again in less then a minute after I start moving...Like mentioned above, the Dewitt's radiator is what makes the big difference, I'm also running a 383 stroker in my 89 which runs a little hotter then a stock 350.. The larger and more efficent Dewitt's radiator also stops the temps from rising as quickly when the car is stopped...
I tried using a 160 degree stat, and my car would run at 160 degrees in cold/cool weather with the Dewitt's radiator, this is way to cold for a engine to run. The 180 is perfect with this combination.. ..WW
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I tried using a 160 degree stat, and my car would run at 160 degrees in cold/cool weather with the Dewitt's radiator, this is way to cold for a engine to run. The 180 is perfect with this combination.. ..WW
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Last edited by WW7; 10-16-2017 at 08:11 PM.
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Ahnenerbe (10-17-2017)
10-16-2017, 08:34 PM
#10
Drifting
Member Since: Mar 2017
Location: Nashville TN
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2017 C4 of Year Finalist
My car runs at 178 to 182 degrees all year long as long as the car is moving at least 30 mph.( My engine has never seen 200 degrees) I have a Dewitts radiator, a Dewitt's high speed fan , a 180 degree stat , a Stewart high flow water pump, and have my fan programmed to come on at 196 degrees , and go off at 180 degrees...This combination is the best I have found and the only time my car goes above 182 degrees is when I have an extended stay at a stop light... Even when the temps go up at a light , they go down to 180 degrees again in less then a minute after I start moving...Like mentioned above, the Dewitt's radiator is what makes the big difference, I'm also running a 383 stroker in my 89 which runs a little hotter then a stock 350.. The larger and more efficent Dewitt's radiator also stops the temps from rising as quickly when the car is stopped...
I tried using a 160 degree stat, and my car would run at 160 degrees in cold/cool weather with the Dewitt's radiator, this is way to cold for a engine to run. The 180 is perfect with this combination.. ..WW
.
.
.
.
I tried using a 160 degree stat, and my car would run at 160 degrees in cold/cool weather with the Dewitt's radiator, this is way to cold for a engine to run. The 180 is perfect with this combination.. ..WW
.
.
.
.
Get the 180 tstat. Once you get everything cleaned up, a 160 will keep the engine running too cool. And, in hot weather, opening the tstat that early doesn't really keep it any cooler than a 180 will.
10-17-2017, 01:12 PM
#11
Racer
Thread Starter
Good advice my friends. To be clear, for anyone reading this in the future, the question was how to make the L98 run cooler. I have already done the basics, clean and clear dam area, new rad, new water pump, and new 180 tsat. Vette runs at 180-190 while driving, in traffic quickly gets to 230, then fan kicks on. This is perfectly normal and how engine was designed.
As a couple of you have stated, putting in a dewitt fan, and tweaking fans is the way to go to lower temps. I am going to try this as it makes sense, plus a bigger rad=lower temps. In my perfect world, I wouldn't need a fan, but I know, especially in stop and go, that would spell disaster. So it appears the final answer to this ongoing question is to install this combo, it's the only way to get this engine cooler.
As a couple of you have stated, putting in a dewitt fan, and tweaking fans is the way to go to lower temps. I am going to try this as it makes sense, plus a bigger rad=lower temps. In my perfect world, I wouldn't need a fan, but I know, especially in stop and go, that would spell disaster. So it appears the final answer to this ongoing question is to install this combo, it's the only way to get this engine cooler.
Last edited by Ahnenerbe; 10-17-2017 at 05:20 PM.
10-17-2017, 01:54 PM
#12
Good advice my friends. To be clear, for anyone reading this in the future, the question was how to make the L98 run cooler. I have already done the basics, clean and clear dam area, new rad, new water pump, and new 180 tsat. Vette runs at 180-190 while driving, in traffic quickly gets to 230, then fan kicks on. This is perfectly normal and how engine was designed.
As a couple of you have stated, putting in a dewitt rad, and tweaking fans is the way to go to lower temps. I am going to try this as it makes sense, bigger rad=lower temps. In my perfect world, I wouldn't need a fan, but I know, especially in stop and go, that would spell disaster. So it appears the final answer to this ongoing question is to install this combo, it's the only way to get this engine cooler.
As a couple of you have stated, putting in a dewitt rad, and tweaking fans is the way to go to lower temps. I am going to try this as it makes sense, bigger rad=lower temps. In my perfect world, I wouldn't need a fan, but I know, especially in stop and go, that would spell disaster. So it appears the final answer to this ongoing question is to install this combo, it's the only way to get this engine cooler.
10-17-2017, 03:06 PM
#13
Le Mans Master
You can try lowering your stock fan on/off temps first , if that doesn't work the Dewitts fan puts out 2360 cfm while the stock fan only puts out around 1700 cfm.. This high speed fan would help get the temps down lower and get them down faster..WW
Last edited by WW7; 10-17-2017 at 06:25 PM.
10-17-2017, 09:41 PM
#14
Melting Slicks
My '87 rarely gets over 200F even in traffic. I put a 160F thermostat in. I also switched the aux fan switch in the head to 180F. Then a rewired the fans so the main is switched from the 180F head switch, and the aux from the ECM output. The A/C will turn both fans on. No wiring harness' were harmed :-)
My 350 marine engine runs at 140F all day long so I'm not too worried about performance impacts. Everything is cooler including the cabin and hood (no clear coat peeling).
My 350 marine engine runs at 140F all day long so I'm not too worried about performance impacts. Everything is cooler including the cabin and hood (no clear coat peeling).
10-17-2017, 10:38 PM
#16
Melting Slicks
(1) get a quality high flow pump with a machined or cast impeller with curved impeller vanes, NOT a $49.95 unit with a stamped sheet metal impeller with straight "water wheel" vanes.
(2) close off, or at least obstruct the water pump bypass circuit, the third hole on the pump mounting flange.
(3) put a valve in the supply hose to the heater core and keep it closed during hot weather.
(4) if your quality (don't cheap out here) thermostat doesn't already have a hole or two in the disc, drill a couple of 1/8 th inch holes.
the idea behind number (2) and (3) is to prevent hot water from being short circuited back to the suction side of the pump without first going to the radiator, and number (2) promotes even cooling of both cylinder banks.
(2) close off, or at least obstruct the water pump bypass circuit, the third hole on the pump mounting flange.
(3) put a valve in the supply hose to the heater core and keep it closed during hot weather.
(4) if your quality (don't cheap out here) thermostat doesn't already have a hole or two in the disc, drill a couple of 1/8 th inch holes.
the idea behind number (2) and (3) is to prevent hot water from being short circuited back to the suction side of the pump without first going to the radiator, and number (2) promotes even cooling of both cylinder banks.
Last edited by mtwoolford; 10-17-2017 at 10:39 PM.
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Ahnenerbe (10-18-2017)
10-18-2017, 11:59 AM
#17
Melting Slicks
Install a wire screen/mesh above the air dam to keep out larger debris in the future. These cars suck up all kinds of junk from the road and it's not possible to keep the radiator perfectly clean all the time. That's why I didn't go nuts trying to remove every pebble and twig. Good enough is good enough and my temperatures are very consistent after doing the basics. Sounds like you are on the road to success 
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Ahnenerbe (10-18-2017)
10-19-2017, 12:40 PM
#18
Safety Car
Other tricks to stay cool
Hello Everybody,
I installed a new Derale PWM fan controller on one of my Corvettes. This particular car has had issues with running hotter than normal (240* plus). I am running a higher than normal compression ratio which means more heat. The car has a aluminum radiator with a nice fan shroud but having two fans running at 100% started to make me crazy.
The Derale kit I bought from Summit is the following: Derale PWM Adjustable Fan Controller Kit #16795
This device can control one or two separate fans and will start the fans at 60% of their rated speed instead of the standard 100% upon startup. This controller can constantly "adjust" the fan speed to maintain the desired temperature that you select. The controller uses "Pulse Width Modulation" to control the fan speed. It also has a maximum load of 65 amps for the fans which is more than my two SPAL fans draw together.
When I turn on the car and flip "On" the A/C switch both the fans start running at 60% of their rated speed. If the engine is running hotter it will continue to ramp up the fans all the way to 100% of their rating. If the engine doesn't need the extra cooling air then the fans will automatically slow down to whatever level that you want to keep the car's temperature at.
These fans take their power directly from the battery and can run after shutdown to cool the car off more completely. The temperature reading HAS to be taken by a sensor mounted at the output of the radiator. This means you can't wire the sending unit into the water pump or intake manifold as your battery will be drained by the fans cooling down the block instead of the coolant.
Overall the system is easy to install and works like a charm on my Corvette. I have two SPAL fans mounted on a shroud behind a "Be Cool" radiator. When those two fans come on at 100% it gets way to noisy for me. I have tried three different fan controllers and this seems to be the best so far. Once again I can hear the engines sounds as opposed to having to listen to the roar from my cooling system.
This fan control system seems like a good option for those using aftermarket cooling fans. It was just shy of $160 for the controller and the installation took less than an hour on my Corvette.
The only thing I wish I could add is a switch that tells the car that it is going over 30 mph at which you don't really get much benefit from the fans.
I hope you all find ways of protecting your engine while keeping your Corvette Cool!
I installed a new Derale PWM fan controller on one of my Corvettes. This particular car has had issues with running hotter than normal (240* plus). I am running a higher than normal compression ratio which means more heat. The car has a aluminum radiator with a nice fan shroud but having two fans running at 100% started to make me crazy.
The Derale kit I bought from Summit is the following: Derale PWM Adjustable Fan Controller Kit #16795
This device can control one or two separate fans and will start the fans at 60% of their rated speed instead of the standard 100% upon startup. This controller can constantly "adjust" the fan speed to maintain the desired temperature that you select. The controller uses "Pulse Width Modulation" to control the fan speed. It also has a maximum load of 65 amps for the fans which is more than my two SPAL fans draw together.
When I turn on the car and flip "On" the A/C switch both the fans start running at 60% of their rated speed. If the engine is running hotter it will continue to ramp up the fans all the way to 100% of their rating. If the engine doesn't need the extra cooling air then the fans will automatically slow down to whatever level that you want to keep the car's temperature at.
These fans take their power directly from the battery and can run after shutdown to cool the car off more completely. The temperature reading HAS to be taken by a sensor mounted at the output of the radiator. This means you can't wire the sending unit into the water pump or intake manifold as your battery will be drained by the fans cooling down the block instead of the coolant.
Overall the system is easy to install and works like a charm on my Corvette. I have two SPAL fans mounted on a shroud behind a "Be Cool" radiator. When those two fans come on at 100% it gets way to noisy for me. I have tried three different fan controllers and this seems to be the best so far. Once again I can hear the engines sounds as opposed to having to listen to the roar from my cooling system.
This fan control system seems like a good option for those using aftermarket cooling fans. It was just shy of $160 for the controller and the installation took less than an hour on my Corvette.
The only thing I wish I could add is a switch that tells the car that it is going over 30 mph at which you don't really get much benefit from the fans.
I hope you all find ways of protecting your engine while keeping your Corvette Cool!
10-19-2017, 12:54 PM
#19
Melting Slicks
For example, in the situation where I'm stuck in traffic and the engine temperature is spiking, the placement of the sensor won't tell it anything about the engine temperature... it will only see the radiator output which may be perfectly fine. In that case, I am guessing the system would depend on the stock fan settings triggered at 228F? Doesn't that defeat the purpose of enhancing the cooling system?
Just looking to understand what is going on here... thanks.
10-19-2017, 10:22 PM
#20
Racer
The best improvement I've had was removing the stamped steel rockers and going with full stainless steel roller rockers. Everything that I had read about reducing friction which reduces heat turned out to be true.