Hello! I have an '04 G35 Coupe 6MT (sorry for posting over here, but for the purposes of this question it's a 350Z), and I'm at Mid-America Motorplex this weekend with NASA. I'm having an overheating issue today and am hoping for some ideas. The engine is mostly stock, it's around 85 degrees today, I've added a fairly large oil cooler and am running 30% coolant/70% H2O, along with waterwetter. When I push the car hard, the water and oil temps creep up until I have to back off and let it cool (which it quickly does but is very frustrating). Any ideas what I could do to keep the engine a little cooler? Thanks in advance!!!



-6MT4me

 

A stock car would not have that problem.

 

Please post some numbers. Also, are you F/I or N/A? How many miles does the vehicle have?

 

As said above, we need some actual numbers to go by. Do you have an aftermarket water temp gauge?

 

All very good questions. I have an oil temp gauge and it's running around 270. The water temp gauge is stock, but I'm 2 "ticks" from the top of the range when I let off (way way too warm...). The oil cooler is a Setrab model, around 8"x12", 2" thick.

The radiator is stock. The engine is honestly mostly stock (350Z intake, 5/16" plenum spacer, and a mandrel-bent Y-pipe in the exhaust). Otherwise all mods are to the suspension... No FI, no nitrous, nothing special power-wise. Also, no blown head gaskets (engine pulls strong and no oil the in coolant or vice-versa), the gas mileage is fine on the street and no codes are being thrown by the ECU. Just getting too hot.

Any advice would be much appreciated!

--6MT4me

 

owner's manual states a 50/50 water/coolant mix is recomended. Water heats up and also cools down quicker than coolant, and the fact that you have 70% water could be the cause of rapid heading.... I would go back to the original factory spec then work from there. gl

 

I appreciate the suggestion, but I'm not sure I follow... Water is a better cooling agent than antifreeze-- antifreeze raises the boiling point and lowers the freezing point, and is a great rust inhibitor/water pump lubricant. Otherwise it wouldn't be in there. Some race groups require 100% water, but this being a street cat I went to 70% water. Water can transfer heat from the engine to the radiator and from the radiator to the air better than coolant can.

The vehicle has 34K miles.

 

Water is a better heat transfer medium than coolant, so you are on the right track with your mixture.

As you get faster and faster on the track, your car is going to run hotter. More grip, earlier application of power, all means that you are putting more thermal load on your engine. You should consider running a free flowing exhaust system, and running test pipes vs. cats for the track. Freeing up backpressure will reduce thermal loads as well.

First suggestion is to upgrade your rad to the large Koyo. This will probably cure the overheat issue you have on a stock engine. While you are at it, you might try switching to Evans NPG+ waterless coolant, which has a 375F boiling point, and is friendlier to your engine, even if its running hotter than ideal.

Oh, and make sure you cooling system is well purged of air.

I have a VERY fast NA track customer, and he has no issues with temps, even in 100F track days. We are running a Koyo rad, Seitrab(Stillen oil cooler), and the rear coolant bypass modifcation. That's about it. His track coolant temps are about 210-220F maximum on the super hot days, and He pushes the car harder than I have ever seen!

Hope that helps.

 

Is that Mid America Motorplex south of Omaha Ne . ? To bad Im layed up , I would come watch . I broke my ankle a couple weeks ago .

 

Great suggestions Sharif! I hate to add the Koyo radiator from a weight standpoint, but you're right that may be the only option left at this point. I tried just 15% coolant previously, but found out that on the street when stuck in traffic w/ A/C it would boil the coolant and this get air in the system. Not good... Maybe my crank underdrive pulley is contributing to the problem when at idle. Any idea what oil temps your client runs? I have a cooler around 3x the size of the Stillen and I'm still running 270F (around 160-180F on the street). Does the NPG coolant actually cool any better, or just raise the boiling temp?

What is the rear coolant bypass modification? Sounds interesting!

Yep, I'm going to be at MAM again tomorrow in Pacific Junction, IA.

--6MT4me

 

What time ? I may come down any way . What color is your G35

 

Pretty much all day, probably 8AM-2PM... Dark blue car.

 

If I come down I'll drive mine down . 03 DG .

 

He also sees about 260-280F oil temps which I realize is on the hotter side of ideal. We run Motul 15/50W 300V oil, which is as about good as it gets on built high endurance engines. Make sure you are running fresh oil prior to the track event, and change it immediately after the event.

I imagine you are running hot, becuase you are running fast....right?

The koyo rad weighs maybe 2-3 lbs more than stock...well worth it. It's 100% aluminum, so it very svelt. But seriously, the rad is the ticket for you, IMHO.

 

Have you checked you thermostat and fans, but being new I doubt those are bad. As Sharif said make sure you have no air in your system, this can wreak havoc on your coolant temps. I would also look into a 3 row Koyo.

 

I would also suggest the koyo and maybe a bigger oil cooler or different fluid.

 

6MT4me, how was temp at track today? Welcome to my350z and please visit Autocross/Road forum sometimes. I like to thank you for tips on Tokico cable-adjusters that you sent me couple years ago.

I probably wont have skills and/or need to keep engine above 5.5K too long, but damn, I am just about to copy your setup (70/30 plus water wetter with setrab oil cooler), and than, only after Vortech is installed, if needed add 36mm Kojo radiator.

Suggestions here on this board are adding a lower oil pan spacer for an additional quart of oil capacity and aftermarket pan with finned case, and also 1.3bar radiator cap.

Some are suggesting vented hood or even removing all the seal in the back of the OEM hood or adding washers to the hood hinge to lift the back of it little more; and also removal of the rear weather stripping (near the windshield). Question is how much downforce is affected with these hood changes.

Please keep us posted of any solution to the overheating issue that you might find.

Sharif, is this link rear coolant bypass mod that you mentioned above or actually the thermostat inside block oil adapter for the setrab oil cooler?

How much is EGT lower with true dual 2.5” exhaust vs OEM exhaust?

Thanks

 

6MT4me, I race too, I live in Miami, and temperatures over here are abnormal! The radiator in my opinion won’t be of much help unless you change your thermostat, and the reason is that the water on your engine would not go to your radiator until the thermostat opens up. With a bigger radiator will cool down the water faster, and you will see the difference only if the thermostat is open as I explained before. I agree with other members that an open exhaust will help to reduce heat temperatures on the engine bay, other thing that you may want to add is a thermal wrap, this will increase the temperature inside the exhaust pipes (hot air will travel faster) and isolate a little bit the temperature.

 

Hi Dovla,

Yes, that link is for the rear cylinder coolant bypass modification that I mentioned earlier. You can install this with the engine inside the car, but its a fair amount of work.

I havent logged EGT's on an NA car to compare bone stock exhaust, with a true dual setup, so I can't comment. But reduced backpressure will result in a happier/cooler running engine.

 

I'm not sure the Koyo is a drop in fit for a G35 (remember folks, there are a few differences between the Z and the G)

For the original poster: Something is wrong if your G is running that hot. My G is JWT FI'ed, and while it does run warm on the track (water temps about 205, and oil about 250-260) it is certainly not running that hot. Not sure why you would be running that hot. I would guess maybe you have an air bubble or two in your system?