The Viper Generation 2 motor RUNS HOT by design. A fact I did not know until much later, and failed to pick up on. The water pump flows at a linear rate, pumping 13 gallons per minute (gpm) at idle to 114 gpm at 5,600 rpm. It generates 30,000 British Thermal Unit (btu) maximum.
By design, it's thermostat opens between 195 F and 205 F! For nearly all of us, that is 15 to 25 degrees HOTTER than past experience tells us what is OK!! Again, the thermostat DOES NOT FULLY OPEN until 212 F to 219 F!!! YIKES!!. I present a range, as the factory Viper Crate motor book is slightly different than the factory service technicians trouble shooting books. Further, the service manual says that 250 F is OK under "extreme conditions"!!!!!! Probably racing. YOW!!!!!!!!
The crate motor book lists a thermostat that starts to open at 180 F. It fully opens around 195 F. In all probability the engine will still run in the 200's.
Which would have been great had I read the book more carefully. I would have been able to change it more easily. Changing a "stat" on the Gen 2 motor requires removing the entire fuel/air manifold, lines etc. Roughly a 4 hour job on a Viper. On my car accessibility is definitely a problem. Due to more stuff to remove, I probably would need closer to 8 hours.
The Gen 2 Viper radiator sits lower than the engine, which requires an extra pressure tank and lines. It has a 2 speed electric fan providing low and high speeds, which cycles according to engine temperature low to high and reverse when cooling. It also has a shroud than has flap doors which open allowing more air flow as speed increases.
Radiator caps increase the pressure inside the radiator. That increased pressure keeps the coolant from boiling. Water boils at 212 F. Most antifreeze boils around 238 F. A radiator cap increases the boiling point by 3 degrees F for each psi increase. Therefore, if a cap is rated 16 pounds per square inch (psi) the boiling point inside the radiator/engine is 212 F + 48 F or 260 F. Most cars use a 16 psi cap.
I saw an article in HOT ROD MAGAZINE about a company in Michigan that made custom radiators. I started calling and investigating my needs for a radiator almost as soon as the motor mounts were done and the motor and transmission were initially fitted in. Remember this build took the better part of 17 years to complete. Being ever the optimist, beginning in 2011, I contacted all the usual custom build vendors, Summit Racing, Griffin, Be Cool, Champion, etc.etc. I made an assumption, WRONGLY, that they all knew cooling systems and what was required for a good design. Even today they seek minimum information about the engine, how it will be run etc. Generally, they ask opening size, engine horsepower and ask for a sketch of the core support.
They all were somewhat helpful, and depending on when I contacted them, had poor to very good web sites for designing a radiator. I finally settled on MARK 7 Custom Radiator in Michigan. The company featured in the magazine article. As it turns out, that was A MAJOR MISTAKE!
MARK 7 was a specialty machine shop fabricating custom and regular car parts for the industry. In addition, it WAS a custom radiator builder.
After much discussion, I provided them a full sized pattern of the radiator core support, core support opening measurements, Viper engine coolant flow rates from idle to wide open throttle. As listed, they are 13 gpm to 114 gpm. I also provided them with maximum BTU (British Thermal Units) per hour with a maximum of 30,000 BTU. We exchanged a lot of communications about opening size, radiator position in front of the core support or behind the support, clearances from the motor to the core support, water pump inlet location, fan thickness and potential clearance issues and more.
The first issue was the water pump inlet pipe/tube. As manufactured it projected upward and though the opening in the radiator core support. I removed the pump, cut off the inlet tube, shortened it and turned it, utilizing an already existing bend, 90 degrees, and had it welded into its new position. Space issue solved I thought! Adding an oil cooler and lines created space problems directly under the pulley tensioner on the lower left as seen in the picture below..
It was a poor design! The radiator outlet is 2", the hose 2" and the pipe angle IDs reduce to 1 1/2"inch then 2" inch, then 1 1/2" then 2" inch hose. It leaked due to the angles and welds requiring two (2) hose clamps per end..
The next issue was the amount of space from the nose of the water pump pulley to the radiator. A three (3) inch thick radiator would be within a fraction of an inch. Also in play were the inner wheel well/fender supports and battery tray. A larger radiator would require hacking them up to make a radiator fit if installed in the normal position on the back side of the core support leaving NO ROOM for any type of fan! They also are structural members for the core support and outer fenders.
There is a hood support and hood opening latch attached to the front of the radiator core support for vertical and horizontal strength as well as attaching a cross nose body piece. There was approximately two (2) inches of space from the face of the support to the back side of the hood support. I needed at a minimum 3" inches of space for a radiator and if mounted in front of the core support it had to be lower than the hood latch/support assemble making any radiator lower than the core support opening. The final design had the radiator in front of the core support and behind the hood latch assembly and using a low profile, heavy duty, 1,900 cfm flat blade, electric puller, 16 inch fan.. Attached directly to the back side of the radiator with no shroud. It came with a relay, temperature sensor and fuse.
The back side of the radiator and core support.
Note how the 16" inch electric puller fan is installed. While the design worked, I found out later there should have been some kind of shroud creating a "tunnel" for the fan to pull air through the entire opening. Nothing was ever said about shrouds during the design process! I also learned later that ideally a fan should be a minimum 1 1/2" inches from the back side of the radiator.
Beginning with the first trip to the gas station nearly every each trip was was an adventure in MURPHY's LAW. It ran ok and temperature was ok to the station, approximately four (4) miles. As soon as I pulled away the car was at 230 F! Stopped IMMEDIATELY and started checking. The fuse had blown. Two fuses later I called the fan manufacturer. Due to the economic downturn and auto bankruptcies they had closed ALL their American offices and tech support. A few days later I did get a call. Their written instructions failed to say they were for a light duty fan! My fan needed a higher rated fuse. Mark 7 supplied the fan and should have known or said something.
I was not getting a good temperature reading at the Auto Meter gauge. I had jumper-ed into the Viper head temperature sensor and Viper harness. More calls. The Viper sensor registers a different voltage. The corrugated hose you see in the above picture was scrapped. In its place went a new hose, Auto Meter pipe with sensor fitting, sensor and ground. That meant I was not reading the engine temperature, only the coolant temperature. The PCM reads and monitors the engine but there is no after market fixes for that. I have since found out you can monitor engine temperature and other functions by plugging a scan tool into the OBD port and selecting the desired function
On its way to its first official cruise-in the weather was hot, humid a slight threat of rain and about 88 degrees, roughly ten (10) miles. There was a little "splatter" or spray on the windshield. The indicated temperature was between 210 and 220 F. (Remember no hood). Checked everything and found some coolant around the overflow and the radiator. No problems going home. Called Mark 7 and told them about the noisy fan, fuse and spray. After a lot of himing and hawing they said pry off the billet cap cover and check the radiator cap. It was shipped with a 13 psi cap! Remember I said most cars come with a 16 psi cap? Vipers require a 17 psi cap! I got a 17 psi cap and put it on.
Episodes like this continued on and off all summer. After a lot of research and talking to a local restoration shop I fabricated a fan shroud removed the fan and reinstalled everything. It helped a little. I added an adjustable temperature fan control switch. That helped a little.
Further research said move the fan off the radiator and back as far as possible. I removed everything and re-fabricated the shroud allowing me to pull it back a full 1 1/2" inches off the radiator. That helped a bit. Kept researching, found a diesel truck 16" inch, low profile, 3,000 cfm (cubic feet per minute) curved blade (quieter than flat, more efficient) fan with a two (2) year warranty, circuit breaker and wiring for a VERY reasonable price. Tried it in close to the radiator first, then flipped the shroud and pulled it back. That helped keep it near 210 F unless caught traffic. At steady cruise 2,000 rpm to 2.5 k rpm temperature stayed at 210 F.
Seeing shrouds at the various cruise-ins I noticed that they virtually seal the radiator creating a tunnel. My shroud would have to be remade from scratch. I found some 1/8" thick rubber, measured cut and fit it, made some brackets, yanked it out again, and attached it all to the shroud. There still are few small gaps but for all intents there is an air flow tunnel the fan is pulling through. It may be my imagination but I think there was improvement. I wasn't getting spray on the windshield but I was still seeing the coolant level drop a bit after each cruise.
Thinking of the Viper fan/shroud set-up I pulled the fan and shroud again! This time I cut in six (6) 3" x 2" inch vents and made flapper doors from heavy duty truck inner tube. A hair dryer test showed they would open while driving and close when stopped. That helped.
I made it through winter and again hit the cruise-in shows. First hot day 10 mile drive, with the hood now on, droplets showed on the windshield. Definitely coolant! I started wrapping various possible locations with white cloth trying to find the source. Nothing! Then in late June 2018 a mid week show & cruise 92 degrees humid, 18 mile drive Car was happy at 210 F or a needle width less, until we hit stop and go rush hour. Immediately started climbing 220 F+. Got rolling then stopped at traffic light. Temp went up and then down then back up then down some. Droplets on the windshield! Pulled into the cruise grounds and started setting up, chairs etc, opened the hood and set up the display sign. Did not see anything. First two guys who stopped, viewed the car and said the radiator was leaking and bubbling.
Sure enough, three inches from the left tank and about 5 inches down there was fluid and bubbles. We got the car home ok, but I could see additional fluid in the cooling fins and down the front of the radiator. I went straight to the MARK 7 web site. The Machine Shop was there but for radiators it said go to Rad AIR or whoever. I called the next morning and the woman who answered took a message. She said the radiator business was gone; shutdown, out of business!!! but she would pass along my message to the owner. After a day or two I called several more times and left messages.
He NEVER RETURNED THE CALL!!! The radiator is JUNK in 746 miles!!!!!!!!!!!!!!!!!!!!!!!!!!
IN MY OPINION, The radiator was defective from the start. Poor design, 1" 1/2" air gap inside allowing boiling, wrong cap and probably defective from the start; leaking about 2 inches below the air gap. I guess that's what happens when you get sick, plans are delayed, stuff can't be done and things don't go as planned or you run into trouble trying to get things done.
No comments:
Post a Comment