LT5 Cooling and Radiators

[Dynomite]

A lot of guys get caught in traffic on HOT 100 deg F days observing the temperature gauge move toward the cross hatch area (230 deg F +). That seems to be typical of the Cooling System for the LT5 in traffic with AC ON. And those High Engine Coolant temperatures often caused by trash between the AC Condenser, Oil Cooler or Radiator or trash on ALL three. Especially if there is any oil film on the Oil Cooler.

I am installing my third Ron Davis Radiator tomorrow in what was suppose to be my Stock 1990 in CA.....did the same to what was suppose to be my Stock 1990 in SD.

I will take the 1990 for a run when it is 100 deg F ambient today with stock radiator and then another run tomorrow in 100 deg F ambient with the Ron Davis. Including idling as in sitting at a stop light for both (Stock and Ron Davis) with air on and off to see what maximum coolant temperatures are like for both Stock and Ron Davis.

Originally Posted by XfireZ51

With both fans running, my Fluidyne is keeping coolant temps at 90C at idle in 95F weather.

Yesterday took a 1991 with Ron Davis Radiator for a cruise with 95 deg F ambient and Coolant stayed around 194 F cruise (60 mph) and rose to 206 F with Air On Idling. This using the Fan Controls for Digital Read Out of Coolant Temperatures.

This testing with the same identical AC Condenser, Same identical Oil Cooler, Same Identical Coolant Fans and same identical 180 deg Thermostat.

The objective here is to create a baseline of simple testing criteria to determine how ZR1 radiators (1990 and 1991) will function cruising and in traffic (idling). The simple baseline criteria are 100 deg ambient temperatures, 180 deg thermostat, and functioning AC.

If you want to test radiators....this is the time here in central CA
Jun 16
Hot with plenty of sunshine
98°Lo 61°
Jun 17
Blazing sunshine and hot
101°Lo 63° more
Jun 18
Blazing sunshine and hot
101°Lo 62° more
Jun 19
Hot with plenty of sunshine
100°Lo 64° more
Jun 20
Hot with blazing sunshine
103°Lo 66° more

Note:

Engine RPM.

My experience in all ambient temperatures.

A. In sixth gear running 65 mph (less than 2,000 rpm) the Coolant always gets a bit over 200 deg F. On Hot days the coolant will get a bit over 213 deg F. The key is the Water Pump is not pushing enough flow through the fully open thermostat to cool the engine to a Temperature where the Thermostat takes over (180 deg F).

B. If I shift to 5th gear at 65 mph (more than 2,000 rpm) the coolant temperature drops to Thermostat control (180 deg F) on cool days and drops to near 200 deg F on Hot days.

My findings are simply that the stock water pump is a bit low on coolant flow rate at rpms under 2,000 rpm. As you can see there is a big jump in Coolant Pump Flow rate between 1,000 rpm and 2,000 rpm and it is in this area or engine RPM that the Coolant Flow Rate is not sufficient in HOT Climates when the ZR-1 is moving in 6th gear at 65 mph.

The overheating issue when idling at a stop sign on HOT days (100 deg +) is more related to Fan Air Flow.
Tests at 50 deg F ambient.
Going 65 mph in 6th (1500 rpm) coolant temperature 205 deg F.
Going 65 mph in 5th (2200 rpm) coolant temperature 192 deg F.
Idling at 750 rpm coolant temperature 204 deg F.
Engine rpm 2000 rpm (not moving) coolant temperature rose to 213 deg F.

So...….At 65 mph it is the coolant flow. At 0 mph (Not moving with rpm at 2,000) it is the air flow.

If I could get the air flow higher while in traffic the issue would then be the coolant flow again where keeping rpm above 2,000 rpm would solve the High coolant temperatures on hot days in traffic.
The Coolant Pump Flow at 800 rpm is 15 gpm. The Coolant Pump actually gets more efficient as the rpm increases from idle to 2,000 rpm.
As Per Marc Haibeck graph provided to the ZR-1 Net email list by Graham Behan about ten years ago, the Coolant Pump flow rate through the engine (not the radiator or thermostat) is:
15 gpm at 800 rpm
18 gpm at 1,000 rpm,
44 gpm at 2,000 rpm,
65 gpm at 3,000 rpm,
90 gpm at 4.000 rpm,
120 gpm at 5,000 rpm at which time cavitation is starting.

NOTE:

See the following post for a complete update regarding Engine RPM.

Post 7 - Thermostats, Fans, Water Pump, and Radiators

[RussMcB]

Good timing for me. I am shopping for improved cooling.

What is the Ron Davis model number, and how does its price compare to the Dewitts "drop in" model?

I've heard good things about the RD unit, and I've heard (very recently from one of our respected tuner vendors) that they've started using the Dewitts radiator instead because it cools as well and doesn't require modifications (shroud trimming).

I also read (in this post from 2002*), that the Ron Davis generic Chevy NASCAR model can be purchased for much less ($300?), works well, but requires slightly more mods (like maybe a longer hose - maybe splicing in a short straight section of pipe).

http://www.corvetteforum.com/forums/c4-tech-performance/296834-best-radiator-griffin-vs-ron-davis.html#post2867027

[Dynomite]

Originally Posted by RussMcB

Good timing for me. I am shopping for improved cooling.

What is the Ron Davis model number, and how does its price compare to the Dewitts "drop in" model?

I've heard good things about the RD unit, and I've heard (very recently from one of our respected tuner vendors) that they've started using the Dewitts radiator instead because it cools as well and doesn't require modifications (shroud trimming).

I also read (in threads a few years old), that the Ron Davis generic Chevy NASCAR model can be purchased for much less ($300?), works well, but requires slightly more mods (like maybe a longer hose - maybe splicing in a short straight section of pipe).

See Installing a Ron Davis Radiator and Testing

1. Ron Davis Radiator.
I little expensive at a bit over $600 and you have to trim the fan baffles 1/2 inch (the center part that sticks out further) about a 30 minute job. The Ron Davis then fits right in.

Ron Davis Radiator w/o transmission cooling

Coolant temperature stays at a constant 185 deg (70 deg F ambient) with 180 deg thermostat.*
a. 1989-1996 C4 Type V8 All Part No. 1-16CV8996
b. Rated 800 Hp
c. Manual transmission
* Coolant Temperatures will climb a bit to the Fan Off Coolant Temperatures (200 deg F) with AC on (100 deg F ambient) See testing below.



2. Ron Davis Radiator Installation.

First....Drain Coolant from system and remove Air Cleaner, Air Cleaner Housing.
A. Removed Oil Cooler Adapter from Oil Cooler.
B. Removed three 10 mm bolts bottom Fan Housing.
C. Disconnect the two fans electrical.
D. Remove two 10 mm nuts and one 13 mm bolt on Passenger Side.
E. Remove one 10 mm nut and one 13 mm bolt on Drivers Side.
F. Remove two 10 mm horizontal bolts on Drivers side.
G. Remove two 10 mm horizontal bolts on Drivers side holding ??? to Drivers side of Radiator Shroud.
H. Disconnect Temp Sensor bottom of Shroud.
I. Remove five 10 mm bolts top Fan Housing.
J. Remove three 7 mm bolts left and right bottom side of Shroud.
K. Disconnect Vent coolant overflow hose top Passenger Side.
L. Lift Drivers Side Shroud clear of Hood Hindge.
L. Lift Passenger Side Shroud bending the lower tab up and around AC lines.
M. Lift and remove Fans.
N. Disconnect Top Radiator Hose.
O. Remove three 13mm bolts from Thermostat Housing (More Coolant will drain from the system).
P. Loosen short radiator Hose between Thermostat Housing and Radiator (Twist).
Q. Remove Thermostat and remove Thermostat Housing Half that was connected to Radiator.
R. Lift and remove Radiator.
S. Clean Oil Cooler, AC Condenser, and bottom of Radiator Housing.

Disconnect Oil Cooler Adapter .......................................Remove Shroud lifting Drivers Side First


Lift out Stock Radiator followed by Fans........................Trim center parts of Fan Housing 1/2 inch


Install Fans followed by Ron Davis Radiator and Shroud


3. Baseline Stock Radiator Testing at 100 deg F ambient temperature and 180 deg Thermostat (Fans on at 205 deg F and off at 200 deg F).
Testing a 1990 ZR1 with stock radiator (AC Condenser, Oil Cooler, Radiator Clean) at 100 deg F ambient temperature. Using Fan Controls for digital readout of coolant temperatures. Coolant mix is identical for the stock radiator and the Ron Davis Radiator.

Cruising 60 mph in 5th gear (AC Full ON fans at speed 10) coolant temperature 225 deg F
Did not cruise with AC OFF as temperature of coolant is not prohibitive.
Idling (AC Full ON fans at speed 10) coolant temperature 235 deg F
Idling (AC OFF) coolant temperature 230 deg F

4. Ron Davis Radiator Testing at 100 deg F ambient temperature and 180 deg Thermostat (Fans on at 205 deg F and off at 200 deg F).
Testing a 1990 ZR1 with Ron Davis radiator (AC Condenser, Oil Cooler Clean) Using Fan Controls for digital readout of coolant temperatures. Coolant mix will be identical for the stock radiator and the Ron Davis Radiator.

Cruising 60 mph in 5th gear (AC Full ON fans at speed 10) coolant temperature 197 deg F
Idling (AC Full ON fans at speed 10) coolant temperature 213 deg F
Did not cruise with AC OFF as temperature of coolant is not prohibitive.
Idling (AC OFF) coolant temperature 208 deg F

5. Testing of 1991 ZR1 with Ron Davis Radiator and 180 deg Thermostat (Fans on at 205 deg F and off at 200 deg F).
The 1991 ZR1 with Ron Davis Radiator, AC Full On, and 100 deg F ambient temperatures the Coolant temperatures stayed around 197 F cruise in 5th gear (60 mph) and rose to 213 F with AC Full On Idling (208 deg F with AC Off). This using the Fan Controls for Digital Read Out of Coolant Temperatures.

The testing of the 1991 ZR1 was conducted with identical Ron Davis Radiator with the identical AC Condenser, Oil Cooler, Coolant Fans and identical 180 deg Thermostat. The ambient temperature was 100 deg F. The 1991 ZR1 has SW Off Road Exhaust as compared to the 1990 ZR1 with Stock Exhaust.

6. Summary of Ron Davis Radiator Testing using a 1990 and 1991 ZR1 in HOT ambient temperatures cruising and in traffic (idling).

The objective here is to create a baseline of simple testing criteria to determine how ZR1 radiators (1990 and 1991) will function cruising and in traffic (idling). The simple baseline criteria are 100 deg ambient temperatures, 180 deg thermostat, and functioning AC.

Both the 1991 and the 1990 ZR1 Coolant temperatures on a HOT Day (100 deg F ambient) behaved the same with both Coolant Systems settling in at 197 deg F cruising at 60 mph in 5th gear with AC Full On. At a long term idling (more than 15 minutes) the coolant temperatures settled in at 213 deg F with AC Full On. With AC OFF the coolant temperatures dropped to 208 deg F.

[Tyler Townsley]

Any chance of trying a 200 deg oil cooler thermistor instead of the stock 240 unit in your testing? I have not investigated who makes them and their ranges. I added 4 12 v ( 2 per side) computer fans to the wheel wells on mine. It made a difference but I have made a comparison yet. The oiler cooler system does not open with a stock thermistor until 235-240 degrees which kind of makes it useless.

Tyler

[Dynomite]

Originally Posted by Tyler Townsley

Any chance of trying a 200 deg oil cooler thermistor instead of the stock 240 unit in your testing? I have not investigated who makes them and their ranges. I added 4 12 v ( 2 per side) computer fans to the wheel wells on mine. It made a difference but I have made a comparison yet. The oiler cooler system does not open with a stock thermistor until 235-240 degrees which kind of makes it useless.

Tyler

I am installing the Ron Davis tomorrow so would not have time to see what the 200 deg oil cooler thermistor does with the stock radiator. I am of the thinking that air flow is significant contributor to cooling the LT5 and Daryll (Goldcylon) is on to the solution with higher flow rate Spall fans. And yourself with the additional air flow in the engine compartment. I recall Daryll also has an after market aluminum radiator installed. Daryll might post up some cruising and idling coolant temperature information on one of those 100 deg F AZ days....even say a 115 deg F AZ day .....including specifics on the radiator and cooling fans

I do know after market aluminum radiators do make a difference but I think higher air flow would also contribute to a real solution given I get a temperature drop of 10 degrees F just by the moving air flow cruising. Comparing the 1991 with Ron Davis and the 1990 with stock radiator I did find close to a 30-35 deg F difference cruising and idling although the 1991 was tested on a 5 deg F cooler day.

I know it will be 100 deg F tomorrow within a degree so my test tomorrow will be identical regarding ambient temperature and regarding AC Condenser, Oil Cooler, Thermostat and even coolant mix.

If (tomorrow) I get coolant temperatures cruising with AC on in the range of 190 deg F and in the coolant temperatures in the range of say 210 deg F idling I would say After Market Aluminum Radiators are the answer.

[Paul Workman]

Ahem....

'Case you can't do ºC to ºF in your head...



...this might be worth cutting and pasting!

[QB93Z]

I like your approach, Cliff

On a few occasions, I had cooling problems in my high mileage, 1994 Yellow ZR-1 with the original radiator. The problems occurred when I was stuck in stop and go traffic on a hot day. These conditions match the test condition Cliff is describing.

In March 2014, in preparation for our 30-day trip to the Southwest, I tried to clean the radiator of debris by blowing compressed air through from the back (fan side). I decided that the cleaning method was not working very well so I chose to remove the radiator from the car so I could clean it more completely and straighten some fins that I bent trying to use the compressed air.

With the radiator out of the car it was obvious that there was debris stuck in the fins. The best way I found to remove it was to lay the radiator flat on the driveway, lift it about 3 inches and slam it down on the concrete. Each time I did this, I got a debris pattern of fine, grit like fine sand, that matched the circles of the two fans. I repeated the mechanical shock cleaning many times until the grit was mostly gone. I straightened the fins and reinstalled the radiator.

With the cleaned, original, 150,000 mile radiator, the cooling system, is working fine. I had no problems in the Southwest or on any trip since.

I believe that any cooling system analysis needs to address the air flow through the radiator. Based on the conditions of my radiator, I doubt that even an additional fan or higher flow fans would have helped.

Thinking back, based on the time it took to clean the radiator, it might have been better to just install a replacement radiator. At the time, I was interested in seeing if I could "solve the problem". On other ZR-1's, I have installed both the DeWitts and the Ron Davis radiators.

Jim

[RussMcB]

Originally Posted by Tyler Townsley

<snip> ... The oiler cooler system does not open with a stock thermistor until 235-240 degrees which kind of makes it useless.

A thought: One possible benefit of a late opening oil cooler is cooler air to the radiator when the oil temp is below 235-240. If the oil cooler opened sooner, it would heat the air getting to the radiator.

[Dynomite]

I can do that conversion in my head (9/5 +32) and I have a nice APP on my cell phone (C to F) called Measures which also has a well used inches to millimeters conversion......AND....on the cell phone it is right there in my pocket (wrench in left hand and measures in right hand)......and/or Paul's phone number in right hand

If you forget 9/5+32 C to F just remember water boils at 100 deg C and 212 deg F........9/5 of 100 is 180 (20x9) +32 is 212. OK Paul....and that I can do in my head

Now.....doing Calculas in my head is another story (Area under the Power Curve for example) but I can calculate areas of triangles and rectangles in my head

A Stephen Hawking I am NOT.....he does everything in his head which is pretty amazing for sure

Originally Posted by Paul Workman

Ahem....

'Case you can't do ºC to ºF in your head...

...this might be worth cutting and pasting!

Originally Posted by QB93Z

Thinking back, based on the time it took to clean the radiator, it might have been better to just install a replacement radiator. At the time, I was interested in seeing if I could "solve the problem". On other ZR-1's, I have installed both the DeWitts and the Ron Davis radiators.

Jim

Excellent write up there Jim and I think you have hit on the dilemma.....buy new Aluminum after Market or stay with well cleaned stock risking possible radiator leaks in an old radiator later on. I think the Aftermarket Aluminum Radiator may have a bit more cooling capacity with the same air flow.

Also might add that your cleaning procedure is right on and should be applied to AC Condenser as well as the Oil Cooler.

Especially the Oil Cooler sometimes accumulates an Oily Film (from where I am not sure) which contributes greatly to reducing the Air Flow through the Oil Cooler and as a result through the Radiator. A good degreaser sprayed on the Oil Cooler helps clean the Oil Cooler.

And I am sure you have the Radiator Debree Screen to stop larger obstructions such as leaves and that plastic bag that floats up from the pavement

[WARP TEN]

Originally Posted by QB93Z

I like your approach, Cliff

On a few occasions, I had cooling problems in my high mileage, 1994 Yellow ZR-1 with the original radiator. The problems occurred when I was stuck in stop and go traffic on a hot day. These conditions match the test condition Cliff is describing.

In March 2014, in preparation for our 30-day trip to the Southwest, I tried to clean the radiator of debris by blowing compressed air through from the back (fan side). I decided that the cleaning method was not working very well so I chose to remove the radiator from the car so I could clean it more completely and straighten some fins that I bent trying to use the compressed air.

With the radiator out of the car it was obvious that there was debris stuck in the fins. The best way I found to remove it was to lay the radiator flat on the driveway, lift it about 3 inches and slam it down on the concrete. Each time I did this, I got a debris pattern of fine, grit like fine sand, that matched the circles of the two fans. I repeated the mechanical shock cleaning many times until the grit was mostly gone. I straightened the fins and reinstalled the radiator.

With the cleaned, original, 150,000 mile radiator, the cooling system, is working fine. I had no problems in the Southwest or on any trip since.

I believe that any cooling system analysis needs to address the air flow through the radiator. Based on the conditions of my radiator, I doubt that even an additional fan or higher flow fans would have helped.

Thinking back, based on the time it took to clean the radiator, it might have been better to just install a replacement radiator. At the time, I was interested in seeing if I could "solve the problem". On other ZR-1's, I have installed both the DeWitts and the Ron Davis radiators.

Jim

Hi Jim--HIL KING had the same issue at about 40k miles or so. Had the radiator removed and it was about 40% blocked with debris (you probably have a photo or two of it in your archives; I believe they were polaroids). Used a low pressure water hose to clean it. Put a 1/4" mesh debris screen on it (and also on WARP TEN). --Bob