3 radiators all different and I'm debating which one to use.

Living in the Phoenix area has major advantages in the Fall/Spring (Dec to Mar), great weather in the two Summers (Mar to mid-May and mid-Sept to Dec), but also some challenges during the HOT (mid-May to mid-Sept). It was 112* today and it'll be more than 3 months before it cools off to the Summertime temps again.

So now it's already past time to make sure the Vette will survive. I was hoping to find a couple things to make it better than last HOT and I started with radiators. Here's what I have available for my '08 A6.

1. My OEM used 125K miles, unknown capacity (it's still in the car), core thickness .95"
2. GS OEM used 15K miles, 2 quarts capacity, core thickness 1.30"
3. Either aftermarket or Z06 OEM used 2K miles, 2.3 quarts capacity, core thickness 1.03"

I use a side spray wand to clean the radiator and condenser every year near the start of the HOT and I did that today, but the DIC still read 194 at 70 mph on the freeway and jumped quickly to the 210+ area when on normal streets and less than average traffic. The stat is a 160*, so it's full open by 178* and the fans are set to start at 192 and be on 90% by 203. I'm using a B&M 5 3/4 x 11 flat plate cooler to help the trans with a 4000 stall converter. It's mounted horizontally at the bottom of the condenser to use vertical air flow. The trans fluid flow exits the B&M and then flows through the radiator cooler. I also have a Vararam CAI that tends to block some of the airflow and I'm seriously considering going back to the stock one during the HOT.

With all that info, which radiator would you pick and why?

 

Question for my 08 A6 base engine also...

Do I have an option of putting a bigger radiator in it? Will a bigger radiator just slide in with no problems? I'd be interested in a bigger radiator. It has an A&A supercharger.

 

Your temps are actually normal. What are you thinking it should be? I go through those super hot days here too and I'm at 198 on the highway and just under 220 in heavy traffic. Normal.

 

#3 because it has the most capacity.

 

Heavy rush hour traffic can put me in the 230-240 range quickly and since I monitor temps closely in those situations, I shut down the AC and crank the heater to maximum. If it doesn't cool off much, I'll stop and idle for a bit.
The bigger problem is that the trans temps fall into that same range and high temps quickly shorten trans life.

 

Now those temps are getting out of range. I never see over 220º when its 115º outside here. Turning your ac off may be a bit counterproductive though. The fan runs higher when the ac is on unless you have it tuned different.

 

I vote for one with TIG-welded aluminum end tanks instead of the standard crimped-on plastic tanks. There's DeWitt's, the Z07 unit, and others.

The interface between the plastic tank and the core can spring a leak at the most inopportune times. They seem to become more fragile with age and the stress of installation and removal. If I was being cautious about cooling reliability, I wouldn't consider a used OE radiator for that reason.

 

I have a Z07 unit as well and think that is the best of all worlds, but that wasn't one of the choices!

 

That was my initial thought too, but overnight it got me to wondering why the #2 with the 1.30" core thickness had less capacity than the #3 with the thinner core.

So today's research and additional measurements brought some answers. I've quickly eliminated the #1 radiator, because none of the dimensional data exceeded either the #2 or #3.

I found that the #2 has 39 tubes 23.5" long that are .080 x 1.30 .016 wall. The total interior volume is 63 cubic inches. The #3 has 43 tubes 23.5" long that are .080 x 1.03 .015 wall and a total interior volume of 56 cubic inches. The only conclusion I can reach is that the #3 has a 25 cubic inch smaller internal cooler for the transmission that more than compensates for the smaller volume of the cooling tubes.

So considering the #2 has more volume available for coolant flow (meaning it'll flow slower) through tubes with 16% more external surface area, I'm picking it for my replacement.

Then I questioned why a GS A6 using the same LS3 would have a larger radiator than my base LS3 A6. I'm guessing that the airflow through the larger grille opening is less than through the base grille plus the vertical flow created by the air dam. Any other thoughts about that?

Thanks for the replies and bumping me into doing more in-depth investigation.

 

Tom

Once you reach the 230/240 coolant range the trans temps get into the range whereas they also become a problem.

Here is a thought
A larger more efficient trans cooler with the addition of DEI coolant wrap around the trans lines and the DEI exhaust wrap for the exhaust pipes near the trans too.

 

I'd try the free solution first. I'm a big fan of KISS.

Remove the Vararam and block off the hole in the shroud with something to give the radiator max airflow.

I have feeling your trans cooler is causing this issue (GM tests in your backyard I think and if they were seeing these temps they'd have spec'd a bigger radiator. So I'm afraid just removing the Vararam won't work but since it's free, it's what I'd try first.

Some say removing the rear weatherstrip by the windshield allows the hot air to escape (that might be a c5 thing as I think about it). I've been dubious as I know at speed that's a high pressure area that nascar uses for cold air intake so it might actually be counter productive. But, if it comes off easy like it does the c5, easy enough to test.

You could try running your hood unlatched but careful, at 60 it'll rise up about a foot.....you better be able to see over it (from experience...forgetting to latch the hood properly in the staging lanes)! Knowing you, you could fab up some latch extenders and see if that helps....actually as I type I think someone makes them for the rear hatch, those might be the same.

 

If you remember the Shadow Can Am "GoKart" car, it had overheating issues because the water moved through the radiators to fast, so you may be onto something!

 

Maybe not less but slower. The GS as more of a road track car needs to run for longer periods at high speed without overheating.

 

Since I'm the overly inquisitive kinda guy, I'm planning on making one change at a time and record the differences. It'll be no problem to test stuff at 100* ambient here in Phoenix nearly any day for the next 3-4 months.

First change will be the radiator, then a 25/75 coolant/water mix, followed by replacing the CAI with the stock unit and blocking the hole in the shroud. If those don't get the job done, I'll get an overkill trans cooler plus an inline t-stat and bypass the radiator cooler.

I think part of the problem is the excess heat from the 4000 stall converter that overloads the radiator and the B&M can't handle it by itself.

 

yup

 

Another cheap test you could try is dumping a bottle of Water Wetter in it. I've heard it really does make it run cooler.

 

Tom why not swap air cleaners and rivet something over the hole before you buy a radiator?

Also when is the last time you flushed the fluid real well with one of those reverse flush kits?

 

I already have those radiators. #1 in car, #2 recent gift from friend, #3 purchased last fall, but never installed. But Joe, you know I'm weird that way and will want to keep the Vararam if possible.

I'll flush the system before I do the 25/75 solution.

The hood seal was removed about 5 years ago and I tried the hood latch spacer then too. The spacer might have worked by itself, but made no difference with the hood seal out. It seemed that just a small space was enough when stopped or slow speeds and probably too much at 25+ mph.

BTW, I've read about the Miami artist before and now he's getting more well known.

 

Tom, I always love your scientific methods to mods my friend.

I still wish you'd try just !Vararam. lol

Hoxxoh (the artist) is a really cool guy. I'm glad he's getting some traction. He paints with spray bombs and adjusts the spray for the effect he desires. I told him that Home Depot sells a trigger that would save his index finger, and he said "dude i've got millions and millions of presses on this index finger, it's doing just fine". lol

 

I don't have added heat from an altered auto trans and my temps run around yours. Matter of fact a couple weeks ago my oil temp was in the 205-215 range, coolant a little less in air temp of about 80. I think that's normal for me w. stock thermo and much cooler ambient temps. If you're worried, I'd go aftermarket rad, but really unless those temps go higher, I don't see why you would.

But, if I have to pick, I'd go w. #3. Haven't read other posts, but I'd also do a flush and refill just to make sure everything is right about the fluid if/when you do the rad. change.