How Hot Is To Hot

[GTSBoy]

I don't know what coolant you guys use but the one i buy has got glycol in it. Which is twice as resistant to boiling than water... Therefore adding more concentrate (glycol) reduces the chance of boiling. Seeing as your car is reaching 95-100 degrees you want more glycol. If you run premix coolant chances are your engine won't get damaged but if you are planning on running it hard then yes add more glycol. You don't want your coolant to boil!!

Kind of on the right track but majority wrong.

Ability to move heat: Glycol has a 15% increase in circulated heat flow than water. Which is handy for when your coolant decides to pass right next to your exhaust manifold and turbo.

Heat capacity: Both water a glycol see the same results up until and beyond 122 degrees. Therefore pointless in 95-100 degree ranges

- Boiling point of water 99.98 degrees

- Boiling point of glycol 197.3 degrees

Without doing any calculations a 50/50 mix of the two will give you a boiling point of around 110 degrees. Which is great for you!

You are so far wrong that you don't even know why you are wrong.

Water has a specific heat capacity of 4.184 J/g.K

Ethylene glycol has a specific heat capacity of 2.76 J/g.K at typical coolant temperature.

Therefore without any further use of brain cells required, each gram or water circulating has the ability to absorb and carry away 4.184/2.76 = 51% more heat for every degree of temperature rise than glycol does.

Water is the best coolant, BAR NONE.

Glycol is added primarily as anti-freeze. It does have a higher boiling point than water, and it does raise the boiling point of the coolant when mixed with water, BUT, you need to consider another point, which is that radiator caps generally are set to permit the pressure of the cooling system to rise quite a long way above atmospheric pressure. And surprise, surprise, surprise, pressure increases the boiling point of liquids too. In fact, you can run water only in a cooling system at well above 100°C and it WILL NOT BOIL. Sure, you might be prone to a bit of localised boiling on hot spots in the head, and this is where the glycol will help.

And it is at this point that you might want to mention your professional qualifications to talk about heat transfer design work. If you choose to, I bet I can trump you. Not trying to bitch slap you here, by the way. Just trying to make sure the correct info is on the forum wherever possible.

Edited February 1, 2014 by GTSBoy

[discopotato03]

And the rad cap is designed to raise the cooling system pressure above atmospheric which raises waters boiling point anyway .

It isn't the water temp that does the damage its the gas pockets which form if it boils in the jackets . Where there isn't coolant there isn't cooling and the localised difference in temperature is good at cracking and warping heads and breaking them free of their head gaskets .

[89CAL]

From memory its the implosion of the air bubbles that causes the issue. This is going back a bit but I think the air in the bubble gets superheated around the cylinder walls then when it implodes and has an immediate temperature drop its not good at all. But anyway, seen as I cant remember 2nd year tafe from a few years ago I wont say that what I have said is fact

But as GTSBoy has said, running high glycol concentrations is pointless. My last post was slightly ill informed on the glycol side but this was only because ive never needed to research it as I have never had any cooling issues, either with water or premixed coolant which is all ive ever used. I work on heavy mining equipment which runs premixed PGXL coolant in sometimes 50ish degree ambient air temps and no breeze and they rarely have problems unless its caused by something else (e.g radiator blockage)

I replaced my viscous fan hub today because it was getting up around 90 degrees when you came to a standstill and without even plugging it in to a laptop I know its made a difference. Dont remember my fan ever making so much noise driving around. So OP keep in mind that if your temps seem normal at speed and higher when parked, you most likely have an airflow issue

[Ben C34]

was waiting for GTSBoys response. Was not disappointed.

[MatthewT85]

may or may not help but are you finding the level in the overflow bottle decreasing?

my brothers sr20det 180 was having huge heating issues where it was hitting mid 90s on a small 15 min drive home, the level in the overflow was decreasing a bit as well

he tried so many things thermostat, new water temp sensor, new water pump as that was leaking...

tuner recommended removing ac and license plate for air flow and also putting back shroud.

when i drove it to him(tuner) 100ish km away the temps hit 100 and i had to stop.

on the drive back after tune it hit 85 once. i was thinking there was still air in the system(thats why overflow was emptying. Cause it was a lot better

we got it back took the ac out, bled the system and this time i had a funnel in the neck of the rad and as the water rose i squeezed the upper pipe and air came bubbling out, did this about 10 times air was still coming out...

we then stopped drove it and it hit 90C

after that was back to 81-82 and since no heating issues, even at powercruise didnt rise

so i put it down to flow as well as air in the system, also overflow level dropped once and has been at full since...

so just saying air in the system and also air flow can make a huge difference

i could be wrong but these things have fixed his heating issue so.... could help others

[GTRPSI]

Agree, raisng the boiling point is only usefull if your overheating, if your overheating solve your overheating issue, not just adding antiboil to cope with the problem.

All cars ive had, when making the coolant mix more concentrated ive noticed as the concentate is larger the base running temp is higher with the same thermostate in the car.

[Leeroy94]

Im a Design Engineer, Hydrology. I didn't really put that much thought into it, just went off the top of my head.. But I'm sure the more information he gets the better. Just trying to give the bloke some ideas that don't cost him hundreds of dollars. Not a competition.

To JordansR32: Take my advice if you want, It worked for me. But I wouldn't be driving around without adding more concentrate if your car is reaching those temps. Its not a long term fix.. But it will give you time to figure out what it is and possibly save up for what is needed to fix the problem.

[KiwiRS4T]

I recently replaced my radiator with a brand new stocker. My car never overheats even on a hot day at the track. I had a stock front bar but I cut some of it away and moved the number plate out of the airstream. A lot of people seem to have problems when they replace their radiators with aftermarket alloy ones. Maybe some are very poor at their job?

[JordansR32]

Thanks for all the replys guys gone into great deal in some of the answers will try what Matthew said, could possibly just air still stuck in the system, and maybe it's worth buying a brand new stock radiator, but will start will cheapest option first haha

[JordansR32]

Thanks for all the replys guys gone into great deal in some of the answers will try what Matthew said, could possibly just air still stuck in the system, and maybe it's worth buying a brand new stock radiator, but will start will cheapest option first haha

[MatthewT85]

yeah definately try putting a funnel in there so it makes it the highest point possible

also my brother and i have an ASI rad from ebay so not all of them are bad

do you have an aftermarket bar or anything that can block airflow? AC or intercooler with bugs and crap in it?

[boostn0199]

jack the front of the car really high when bleeding makes it so much quicker and easier.

[abr33]

Pure demineralised water and redline water wetter?

On my 25, I have a cheap 50mm radiator, here where the temperature has been literally 46 degrees, I run a gktech fan, 2 thermos on radiator, one on oil cooler and water has never gone over 90 on the road yet. Even with aircon flat out.

I run 50/50 castrol coolant and water wetter. Will try just water and wetter next.

Not sure if its been said but how healthy is your water pump?

[JordansR32]

Yea I'm sure the radiator is fine, I know some can be bad. Yea I usually bleed it on a hill facing up but I'll try jacking the front up

Yea its a brand new genuine water pump, only been on for about 6k

[GTSBoy]

Pure demineralised water and redline water wetter?

That would be good, apart from the problem of corrosion. You simply cannot expect an RB to not turn into a sludgy mess if you don't have a good mix of corrosion inhibitors in with the coolant.

[niZmO_Man]

was waiting for GTSBoys response. Was not disappointed.

+1

[Leeroy94]

Jacking the car up works great or if you have a steep driveway that works fine too.

Just in case someone is unsure of how to bleed a cooling system here is a basic guide:

- Jack the front of the car up or park on a steep hill as suggested earlier.

- Make sure the radiator hose and heater hose clamps are tightened securely.

- Set the heater control lever to hot position but leave the fan off.

- Release the radiator cap and bleed valve bolt (pictured below).

- Fill the radiator gradually (filling speed: slower than 2L per min) to the top of the spout with coolant.

- Fill the radiator until the coolant in the reserve tank reaches the MAX level line indicated.

- After closing the radiator cap and bleed valve bolt, start the engine and allow it to idle.

- The engine will continue to idle until the thermostat opens. (Touch the radiator flow hose and make sure hot water is flowing).

- If a large volume of air remains the water temperature gauge needle will move past the middle as the engine temperature rises abnormally. If this occurs, stop the engine wait until it cools and add water to the radiator repeatedly as described above.

- After the thermostat opens, race the engine for 10 seconds at 2500rpm two or three times.

- Check that the water temperature does not rise excessively.

- Stop the engine and allow it to cool, Release the radiator cap and check the fluid level. If the fluid level lowers, return to step 4 and repeat the process.

Edited February 2, 2014 by Leeroy94

[denisonnd]

I wonder if R32 engine bay is smaller then R33's.

I have S2 RB25DET in S15 Silvia. I have aftermarket radiator, no heat wrap or anything like that. Water temp stays at 88C-90C most of the time.

I haven't bled the system yet. But I think it also has something to do with engine bay. R31 guys seem to ger lower temps then R32 with similar set ups I believe.

My plan is to bleed the system, get exhaust wrap and change thermortat (in case it doesn't fully open).

Would you expect higher water temps out of RB25 in a S Chassis? What do you guys think?

[jay-rod]

Over 120 = Ur prob boiling the water

Over 110 = Not so good

Under 110 = Ok
Under 100 = Great

Under 90 = Awesome, prob not pushing the car

Under 80 = You just start the car?

Under 70 = Dont push the car!

My opinion

[JordansR32]

So went for a drive last night, gave a good thrashing and stock gauge didn't move past halfway but aftermarket temp gauge read 98, while skidding it and about 80ish crusing, so don't think thats considering. Made sure coolant was bled again properly.

Not the biggest fan of putting the temp sender in the top coolant hose I think its not the best way to do it, has anyone done anything different? What about tapping into the factory sender wire that the stock dash gauge works off? Or is that just a silly idea?