California Datsun Engine Overheat Season

[HRH]

Ah hah!   :)  Right back at you Mike.  I think you're right, but it only works until a certain temperature and it depends on the design of the cooling system.  Some are restricted enough without the thermostat that they will cool just fine.  I've run vehicles without thermostats before and they don't reach temperature.  HOWEVER, I've only done that in cooler areas.  Once you get past 100, I'd say certain cooling systems will overheat without some restriction.  I've heard it's more common on large V8 motors, but who's to say.

 

We should do a test!!

[Boaty]

Go take a thermostat out, close the hood, and hold your engine at around 2500rpm for awhile. Unless you're running a god awful amount of radiator, it will slowly over heat. Even mine overheats with a 12" puller, a 10" pusher, and 90% air coverage on an aluminum radiator. The thermostat allows the water to be in the radiator long enough to become cool, while allowing the water inside the engine to be heated to the proper amount, so that the thermostat opens at the designated temperature. Not to say that the temperature will get to a certain steady point, in which the capacity of the cooling system is at peak with a given amount of air flow and heat exchange. But, science will dictate that if the water is flowing too fast to become cool, the uncooled water will increase in temperature because of the engine, where it then flows into the radiator and exchanges less than the heat it obtained, and will trickle down until it never gets cool. Put a thermostat in there, and voila problem solved. Slows the water down when cooler, and flows more when hotter, and it regulates it.

If it were to cool better without one, then all the people in Arizona - where it's over 100F regularly half of the year, would be running without thermostats. It works two ways, one to cool incoming water, and one to heat outgoing water, so that the temperature is controlled instead of random based on cooling capacity.

 

In reference to your conveyor belt theory, yes it'll shed a small amount of heat with a small amount of water, and a greater flow of water would be capable of shedding more heat based on the theory that more hot water = more hot radiator = more heat exchanged with airflow. But it's flawed to think that a large mass of water flowing through a heat exchanger (radiator) will cool equally regardless of flow and temperature.

 

Let's work backwards. Go block your radiator 90% of the way, and blow an equivalent amount of air through a 10% portion of the radiator as would normally flow through the entire unit. You'll find really quick like that they don't put heater cores with jet turbines on them for a reason. Look at a big rig, and note the size of the radiator. Given your theory, they could pump more water through a smaller unit and it would cool to the same capacity. Incorrect. There are 4-6 rows in a big rig radiator, and they are huge for a reason. To contain a large amount of coolant over a longer period of time to exchange a larger amount of heat.

[Boaty]

Oh. AND BECAUSE RACE CAR.

[HRH]

Oooo, I think Boaty just nailed it there!

[datson4life]

so full antifreeze is bad? sorry im tired and too lazy to read it all

so my issue is using only antifreeze and no thermostat?

[HRH]

Yep.  Put the thermostat back in, drain cooling system.  Add 50% water, and 50% antifreeze.  All will be good.

[datson4life]

i will do that right now, and get a new thermostat tomorrow, thanks for all the info fellas, ill let u know how it goes, i wanna be able to go faster on the freeway finally like i use to last year

[datson4life]

ok, finally got the thermostat in, its running a little better, i used a bit of antifreeze and mostly distilled water, i got a 160 degree thermostat

results: on freeway at 65 mph at 3.5k rpm its running at 195 degrees

question: am i on the safe side now?

[MikeRL411]

ok, finally got the thermostat in, its running a little better, i used a bit of antifreeze and mostly distilled water, i got a 160 degree thermostat

results: on freeway at 65 mph at 3.5k rpm its running at 195 degrees

question: am i on the safe side now?

Read entry 56 above!  50/50 antifreeze and water! "A bit" of antifreeze and therest water won't hack it.

[datson4life]

i will buy 50/50 tomorrow   <_<

[DaBlist]

Now that the engineering types have him all confused, just take the hood off to let the heat out and add a pump sprayer to spray water on the radiator like these guys did.

 

 

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[mrbigtanker]

Haha, don't feel bad, I've heard that a million times.  

 

And yes, Boaty, I will agree with electrolysis and deposits.  We sell a NAPAkool conditioner for heavy trucks to skirt that problem.  Of course, diesels have a lot more issues with that than our Datsuns.  And GM has way more issues (had) with deposits and corrosion, hence their brilliant idea for dexcool.  In a GM, I would absolutely use distilled water.  But then, I wouldn't own a GM if my life depended on it.   ;)  Go Ford!

chevy all the way,but hey this is about a overheating issue.

[Komeuppance]

i will buy 50/50 tomorrow   <_<

You don't have to buy premixed 50/50, you can mix it yourself by using full antifreeze and water mixed in a 1:1 ratio. It's cheaper to mix it yourself.

 

Also, make sure your system has no leaks and a good radiator cap.

 

-Robert

[510T]

I am surprised that system pressure has not come up.  Increasing the pressure in your cooling system with a higher-rated rad cap will buy you a few degrees of safety, as long as the system can handle the pressure.  When you increase the pressure, the boiling point goes up.  Overheating happens when you boil your coolant, so if you can raise the boiling point you will be able to safely run at a slightly higher temp.  We are talking a couple degrees, I don't think there is anyone running 100psi cooling systems ;)

 

So switch out the 16psi cap for an 18psi cap and know that your boiling point has risen from 216F to 222F  :)

 

[Dawa]

^the thing is, my man, all of our datsuns are ooooold.

and the majority of us are probably running the stock hoses/or the hoses it came with when we bought it

from the previous owner. putting a higher pressure upon our older systems might not be the best of ideas.

somethings got to give...

some might be able to get away with it, but it might not be recommended unless you have newer/good condition

hoses throughout, perhaps a newer or good condition rad and heater core.

 

thats what i read anyways and it made sense to me :)

 

in newer cars it might be ok

[datson4life]

its running okay and never shot water out or anything, my main concern is hills, im going to san leandro show again on saturday, last time the hill on the way back got the temp up to 210 on a hot day (altamont pass), and i also wanna survive the grapevine to make it to jccs

 

but i did a couple freeway runs yesterday and im satisfied with 195 degrees at 65 mph, i wish i can go faster without the temperature starting to climb

i have cleaned the system, my timing is on the mark, i put a thermostat back in, and it has mainly distilled water, ill do 50/50 today but i dont think that will do much of a difference

[Komeuppance]

Yep, it won't since you're not past 212f, water cools better than glycol anyway.

 

Higher pressure rad cap = blown heater core lol.

 

-Robert

[Boaty]

Yea. 13psi all the way.