Still overheating?

I had a track day this weekend and I have some questions about what an ideal coolant temp is.

Relevant parts:
1992 NSX
Koyo Radiator - installed 3 months ago
All coolant hoses replaced in last 2 years
Scorp Coolant Tank w/ aftermarket cap (not for bling purposes but b/c stock one was in bad shape)
Stock Thermostat
CT Headers
Taitec Exhaust
Prospeed RDX Injectors and Tune
Coolant is only 3 months old, car is rarely driven outside track days and weekends.

Ambient temp was 96 degrees F. Running Thill West which is short and technical. Spent most of the track in 2nd gear. Coolant temps (measures at the top radiator hose) were 236+. I ran Thill East a month ago, ambient was approx 82 degrees and I had similar coolant temps (236-240 range).

My question is are these considered high coolant temps for the NSX? If they are, what else can I do to get them lower? I have Water Wetter that I haven't added yet but what's left that I haven't considered?

I was at THunderhill 9/19, have some mods as you, and also experience overheating problems (as expected). Outside temp did reach 95, and the NSX in general will get over 225 degrees. I ended up having to drive home without AC to avoid overheating.

I'd be interested to finding ways to lower coolant temp as well.

Edit: NCRC on 9/18, new Mishimoto radiator by Shad

It must have been 9.18 right? With NCRC? I was there 9.19 and Thill East was a motorcycle day.

I also forgot to mention I have a type r hood and under good ducting.

Interesting we both have the same issue. I did throw the heater on to quickly cool things down when pulling off. With the help of the FB page, I think I might need to rebleed my system, or take a look at my thermostat.

I'd check for air in the system but ultimately I'd look into a better radiator with higher cooling capacity

I always run hot days with the heat on full fan on low...windows down.....old spice on high...

My Koyo stood up to 90+ F days on the track in our thin Denver air with a similar setup to yours. I'd re-bleed the system or invest in a vacuum filler for your coolant. That's what the pros (Kaz and LarryB) use and their customer tracked cars never have air bubble/overheating issues.

How about "water wetter" too

Aftermarket coolant tanks do not have the air separation that the OEM tank does. If you are getting air in the system it may be worth investigating further?

Thanks for all the feedback everyone. Here's my plan of action:

Rebleed cooling system
Swap in OEM coolant tank
If these 2 don't fix it then I'll check out the thermostat.

Doc, I've run with the heater on full blast before as well, it works but I feel like I shouldn't even need to get to that point. Hopefully all it needs it a good bleed.

Thanks everyone, I'll update once I get a chance to try all of the above. It'll be a few weeks until I have the time to do it.

You might want to change your water / coolant ratio to something like 75 water / 25 coolant. Water is a better heat conductor. What Honda sells is a 50 / 50 blend. Just make sure you use distilled water and the correct ratios. Or while rebleeding, you may just want to refill with distilled water to increase your water ratio.

Also make sure your front bumper to radiator duct is in good condition and sealing properly.

Interesting, the coolant is sold already at a 50/50 blend? Nevermind, I just looked at it looks like it's premixed at a 50/50 ratio. So I would just add some more water to dilute it more? So in CA we don't need to maintain the recommended 50% minimum of coolant? Are the corrosion concerns brought up in the manual not applicable in warmer climates?

Front bumper duct is nice and tight, but thanks for the recommendation.

I also ordered Mugen thermostat since I'll be checking it out anyway.

From what I've read it's helpful to tilt the rear of the car up when bleeding as well, anyone done this and found it helpful?

Yep lift the bum up in the air it helps a lot when refilling the coolant otherwise getting air in the system is greatly increased

First things that come to my mind would be,
- rebleed the system (front and back)
- Check type of coolant this can have a big effect

In the shop I specifically use a -20 coolant instead of the common -36 since the higher the antifreeze the lower the cooling performance. (using metric coolant types)
I often also see the red G12 coolant in cars that do not need it (including NSX) it can even create chemical reaction with the internals.


Some interesting facts from Honda:

Thanks Scammy and Adnan, great advice. I'll be tackling this is a few weeks, feeling good that I have all the bases covered.

Defiantly a different ratio / type of coolant.

We are required to run distilled water (or a non glycol based coolant) in race group (I use water wetter as well) and we race in 100+ degree weather. Car sits around 195-200 degree's in that heat with a MASiV radiator, and was about 210-215 consistently with my Koyo radiator.

As mentioned above, air pockets, coolant type and ratio and you should be fine.

How and where in the engine are you measuring coolant temp?

ScienceofSpeed said:

How and where in the engine are you measuring coolant temp?

Click to expand...

This question was probably not directed at me but after a leaking coolant expansion was replaced i'm now hovering at ~172F while hwy driving with some partial stop and go driving in 90-95F ambient. This is with the MASiV radiator and a Type R vented hood, and reading from the OEM sensor. I plan to bleed the coolant again to make sure. I think the leaky coolant tank allowed air to get into the system as the car cooled down.

Hopefully OP can get to an acceptable temp by just bleeding the system and using a quality mix of coolant/H2O/waterwetter. 200F +/- 15 deg isn't horrible but i'd rather run on the cooler side of this.

ScienceofSpeed said:

How and where in the engine are you measuring coolant temp?

Click to expand...

I'm measuring at the top radiator hose, which I believe is the inlet?

- - - Updated - - -

At highway speeds in similar temps I'm at about 190-195, so I have some work to do here.

RYU said:

This question was probably not directed at me but after a leaking coolant expansion was replaced i'm now hovering at ~172F while hwy driving with some partial stop and go driving in 90-95F ambient. This is with the MASiV radiator and a Type R vented hood, and reading from the OEM sensor. I plan to bleed the coolant again to make sure. I think the leaky coolant tank allowed air to get into the system as the car cooled down.

Hopefully OP can get to an acceptable temp by just bleeding the system and using a quality mix of coolant/H2O/waterwetter. 200F +/- 15 deg isn't horrible but i'd rather run on the cooler side of this.

Click to expand...

+1 to something not quite right. It took a 40 minute session at Road Atlanta in July before I found what I think is the "natural" cooling limit of my stock-ish '92. (stock ECU, stock motor, just a tailpipe, stock rad, Dali cylindrical coolant tank). Good bleeding is A) difficult and B) essential on these cars.

That said, going slowly (sub interstate speeds) at high RPM will maximize heat generation with the revs, but with less flow through the radiator due to lower speed won't dissipate it as quickly.

R13 said:

Good bleeding is A) difficult and B) essential on these cars.

Click to expand...

Definitely worth the money to get the vacuum filler if you track your car. Ensures no air whatsoever.

I bought this one because it looks like the one Kaz uses LOL. Worked perfectly on the NSX and also on the GT-R and RDX

http://www.amazon.com/gp/product/B0081N522E?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00

Honcho said:

Definitely worth the money to get the vacuum filler if you track your car. Ensures no air whatsoever.

I bought this one because it looks like the one Kaz uses LOL. Worked perfectly on the NSX and also on the GT-R and RDX

http://www.amazon.com/gp/product/B0081N522E?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00

Click to expand...

That is a very cool tool. I've been looking at it for a bit but can't quite figure out how it works. Looks like it needs to be hooked up to a compressor? Do you fill the coolant first and then attach this device to suck out the air in the system? OR do you use this device to fill the coolant.

RYU said:

That is a very cool tool. I've been looking at it for a bit but can't quite figure out how it works. Looks like it needs to be hooked up to a compressor? Do you fill the coolant first and then attach this device to suck out the air in the system? OR do you use this device to fill the coolant.

Click to expand...

Regan, it is pretty simple. First, drain coolant. Then, attach unit to the rad cap (or coolant bottle in the NSX's case) and use shop air to draw a vacuum in the system (this eliminates all the air). Fill a 5 gallon bucket with Honda Type II coolant and dunk the fill hose in there. Attach the fill hose to the unit and open the valve. Vacuum will draw the coolant into the system and you just wait until the level gets to the fill line on the bottle. Then, just close the valve and remove the unit. Kaz takes it a step further and does the factory bleed sequence after filling, but I don't think Larry does. The cool side benefit to the tool is that it also let's you know if there is a leak in the system, since it won't hold vacuum with a leak. When I did it on the NSX, I just left the vacuum for 5 minutes and checked the gauge before filling- it shouldn't move.

ah, gotcha.

i was *hoping* there was a device that just sucked out the air after the fluid has already been filled. that didn't seem possible but I understand now how this works. If you build vacuum first then I get that. This also a good way to check for leaks by definition.

I am definitely getting this. Thanks!

Honcho said:

Regan, it is pretty simple. First, drain coolant. Then, attach unit to the rad cap (or coolant bottle in the NSX's case) and use shop air to draw a vacuum in the system (this eliminates all the air). Fill a 5 gallon bucket with Honda Type II coolant and dunk the fill hose in there. Attach the fill hose to the unit and open the valve. Vacuum will draw the coolant into the system and you just wait until the level gets to the fill line on the bottle. Then, just close the valve and remove the unit. Kaz takes it a step further and does the factory bleed sequence after filling, but I don't think Larry does. The cool side benefit to the tool is that it also let's you know if there is a leak in the system, since it won't hold vacuum with a leak. When I did it on the NSX, I just left the vacuum for 5 minutes and checked the gauge before filling- it shouldn't move.

Click to expand...