Hello guys,

I went thru the search and found a few things, but looking for some real world experience with this radiator upgrade on a Z06.

I have a very low mile Z that I’ve been putting a few more miles on, and this south Florida summer heat can be brutal on these poor bottom breathers.

would love to hear from those who did the upgrade with and without the fans from Dewitts.

Are the fans worth the additional expense for a street car or not.

appreciate the feedback.

PS- also any tips in install and getting the air out of the coolant system once you break it open.

Thanks!

 

I went with the full size and spal fans... on a naturally aspirated car you could try just the radiator first and make sure to have your fan settings adjusted and see where that gets you... every car and climate is different so if it doesn't quite get you where you want then add the fans... the fans are great though especially when needed, I have a 3" thick intercooler that basically blocks the whole radiator plus the condenser in between and it doesn't get hot so in my case the fans are more crucial

 

Awesome- thank you!

 

Not that it should necessarily prevent you from buying a DeWitts replacement for your C5, but based on my experience (and others have confirmed the same experience), the DeWitts C5 radiator in later model C5's (after GM moved the ABS system from the back of the car to the front) has clearance issues. Specifically, in my 2004 Z06, the upper radiator hose interferes with the brake lines coming out of the top of the ABS system once I installed the DeWitts.

I fear that someday those brake lines will wear all the way through the upper hose since they are rubbing.

I tried contacting DeWitts a few times on-line about this and no one got back to me. I tried calling a few times and they say I need to talk to someone in particular and connect me to that person's voice mail. I have left a few messages but they never get back to me.

If I were you, I'd talk to them about this interference problem, and if they haven't fixed it yet, I'd go with another brand. That said, I'm actually quite happy with mine (other than this hose rubbing issue) and with just the stock fans the car has always run cool even on very hot days doing 20 minute HPDE sessions.

 

Very good information as I have an 04 Z06. I will call and speak to them about this.

 

2003.5 Z06 here. No issues, fit great with stock fans. Running EOC model with C6 oil lines. Now supercharged and still no issues and cools well. Fans don’t run over something like 30mph so I never saw the point of getting the more powerful fans. Clean out the AC condenser really well when you have it apart.

 

Certainly don't want to hijack here, but I think this is important to the OP. How much clearance do you have between your upper radiator hose and the brake lines? If you managed to get clearance, did you have to do something to achieve it? I have the same EOC model with C6 oil cooler lines, so I'd like to know if there is something I can do to get clearance.

 

I will double check in a few days when I get back home. Feel free to PM me as I’ll probably forget. My radiator is lowered a few inches too with AA supercharger kit. But I had the radiator well before and it was never an issue. I’ll be happy to snap some pics.

 

Here are my pics showing the upper hose interference I have with the brake lines with my DeWitts C5 radiator. Not shown here is that the brake lines pushing the hose up in this area also causes a kink in the hose under the air bridge.

 

If you plan to track your car, especially if you plan to do so in the summer, you NEED this upgrade (or a comparable one).

Fans are optional. I recommend them if you are running a forced induction system - especially a supercharger; the heat soak makes the temperature creep up during idle on a hot summer day; the fancy fans make this a 100% non-issue. I personally like mine, quite useful.

 

Not sure if the EOC changes the radiator, but I’ve read mixed reviews on it, so I wasn’t going to get it with that. Just a standard manual version.

I am torn on the fans as well- I don’t track the car, but South Florida summers are brutal standing still. With 15% off everything is around $892 shipped. Which seems like a decent deal.

I can always add the fans later I guess.

 

I recommend separate oil cooler. Caveat: it will cost significantly more to use a separate unit. Bonus: more isolated systems, better cooling capacity, and far more flexibility in your cooling setup.

I paid I think $1000 or so for my dewitts manual rad with fans, and I think shipping, a couple years ago. Would buy again.

Since I track the car I worked with @ImprovedRacing and RichieRich to come up with an oil cooling system that made me happy. And I can tell ya, it does work well so far! Needs some more modification of some plastic bits to improve airflow, but I dropped like 15 degrees F on the track while doing most of the same track (in the same conditions) in 3rd instead of 4th gear. Happy with this setup and would recommend it to anyone with similar needs.

 

Thank you for reporting this, I never really noticed it on mine that the hose sort of touches one of my brakes lines, but I’m running the standard dewitts no EOC with a LS3/LS7 water pump, so the hose is a bit of a different angle. I wonder if running a different hose would help with the clearance, or possibly adding a thick enough layer of rubber or neoprene padding where the radiator sits were to help with this clearance.
Heres mine by itself and after slightly lifting it up.

 

Imo I love my Dewitts Radiator w/out fans honestly cools to well if you’re not beating on the car though If you live in cold climates. Im running the standard dewitts manual version no EOC with an LS3/LS7 water pump with a 160 thermostat and my cruising coolant temp is 174-178 in the current nor-cal weather.

Upgraded last year in April after getting tired of the Cars performance in the hot summers of california. It was nice seeing my coolant temp rarely ever above 200 during the 100+ ambient temps. I also wanted to go with a separate EOC route but decided not to because I only autocross the car which would of proved to be overkill with the dewitts. Though if I was going to get one I would go with a Setrab Engine Oil Cooler. I believe theirs a couple of guys on the forum running them.

 

These two pictures I believe sum up the problem DeWitts has with their C5 radiator when put into later models with the ABS module in front. Their 'core' is a little shorter than stock, so they had to add a bit to the top and bottom mounts to make it fit. Probably designed on an early C5, there were no brake lines in the way, so they added some height to the top mounting ears. This essentially pushes the upper hose connection point 'down' in the car, which puts the upper hose into contact with the brake lines. A simple redesign would fix it, even just a slight angle up to the upper hose connection would do it.

 

Your coolant temperatures are a bit too low. I would recommend a 180 degree thermostat. There is absolutely no advantage to running below 190-200 ish.

 

Okay some what of a short/long story I originally didn’t plan on running a 160tstat. I ran the stock LS3 tstat but my highway cruising temp would always be above 199 and when stopped would then lower down between 192-199. So I bought a 180 and 174 tstat put them in a pot of water and boiled them to test them, the 174 was fully open around 190. So I decided on that one because my original water pump had the 187 tstat and it was close to it. After installing the 174 tstat my cruising temp was now 192-195 and I couldn’t get it below 192 ever. I made 100% sure all of the air was out of the system. So I bought another 174 tstat tested it and it opened fully slightly after the 174tstat I already had installed. Motorad has some bad quality control. So I then bought two 160 tstats tested them both and went with the one that was fully opened at the hottest point out of the two. Which is the one I have installed now. At first I didn’t like the idea of it running so cool but I rarely take this car out in winter. What I loved about running this tstat is the mere fact that the dewitts works so well in its cooling capacity. During the summer my oil temperature(running amsoil SS 5w30) never once went above 210, it would be between 190-200 cruising/spirited driving. Only when I was stopped for long periods of time it would be between 200-210, but would drop as soon as I was moving. This was in 90-100+F ambient temps. Also the car didn’t heat soak like it did with the original Cooling system. So now regardless of cold or hot ambient temprature it always feels fast.



TL DR I stuck with the 160tstat because my oil temperature now runs cooler then it did before. But cool enough to still evaporate all the moisture in the oil. Which I really like, I know its not good to run this cool, but I rarely drive this car, especially in the winter but when I do I drive it like I stole it.

 

Interesting. So you wanted to find a thermostat that you felt was 'reliable'. I think my problem with your strategy is this: 199F is not an issue. 192, 195F is not an issue. Even if you ran at 220F all the time it wouldn't be an issue.

You are right that as long as your oil gets hot enough to get all the water out it's probably fine... but it takes longer to heat up with your coolant that cold, and that means your "short trip" just became longer.

 

I did find it to be an issue when my car would get above 200F it didn’t pull as hard, it was noticeable. Also when the temp was around 220F my oil temp wasn’t far behind which I didn’t like, and it definitely felt slower above 215F then 200F. Sure I could of left the hotter tstats in place but they only gave it a head start to reach 200F which I didn’t favor.. I honestly don’t plan on running like this long term. Down the road I plan on tracking the car more, by then I will install a separate oil cooler, and install a hotter tstat as I no longer would need to rely on the radiator to keep my oil temps down.

I’m honestly not certain it really affects it much on a short trip, I always wait for the oil temp to be =>75 before I slowly drive away and only get on it above 170F. The only oil temperature difference I noticed on the same 5.9mile trip I would take to work before and after the cooling changes was 8-11Fdegrees.(180-184F v 191-193F) arriving to my work parking lot. But I barely take this car out to work or short trips. Even then I only drive the car around 2000 miles a year now and replace the oil yearly with amsoil. Though I will admit I did run mobil 1 euro 0w40 in the past when I was auto-crossing more with multiple sessions and that oil definitely took forever to warm up with the stock cooling system when it was cool out, can’t imagine now.

 

I realize this topic has been dead for a few months, but I'll throw in my $0.02 since summer is coming.

I'm in Phoenix, AZ.

- I installed the DeWitts manual radiator (no AT cooler) with integral engine oil cooler in my 2004 MM6 coupe.
- I used a non-thermostat adapter block with 10AN adapters
- I ran 5/8 (10AN) cloth braided lines to the radiator
- I kept the stock fans

This setup works well for me. My old commute was 10 minutes and the integral oil would usually get the oil up to ~200 degrees (15 mins would get it to 210). The car runs at 195/220 (coolant/oil respectively) all year long (even in 120 degree summers with the AC on).

I don't see that bigger fans are necessary as they are always off above 35 mph. Again, my temps never get high and my AC always blows cold even sitting still in the summer. But, I can't argue against them either. If my stock fans ever die, I'll probably upgrade because "why not?"

If I were (or ever get into) racing, I'll add an external oil cooler and t-stat in series with the integral oil cooler.