Car overheating with 25% coolant slightly?

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FCD

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Mallorca, Balearic Islands, Spain
So my old Capri recomends a 50/50 Ethylene Glycol antifreeze-Water mix as per the owner's manual.

The other day returning from a loong 1600 Km road trip i noticed my temp gauge was climbing more than usual, almost to the max, so i pulled over and carefully opened the rad cap, more than a bit of coolant escaped from the radiator, i continued to the nearest gas station and put in some cheap distilled water in it, after that it no longer overheated and it seems to be fine, i was doing 80-100 Mph for about 100 Km ( 60 Miles ), outside temps was around 35C ( 95F ).

I am currently using green ethylene glycol coolant, pre mixed 75% water and 25% ethylene glycol, it was changed last year.

Should i go up to a 50% coolant or go lower than 25%? Where i live we never see temps below 0C ( 32F ), the hottest summer days it might be 40C ( 104 F ).
 
Why not use the recommended 50/50 mix ?

Not only does it work at the temperature range you describe but it lubricates your water pump for greater longevity and it prevents corrosion throughout your coolant system. Corrosion causes various problems and it impedes heat transfer.
 
Coolant mixture is a balancing act. Water has twice the cooling power of antifreeze, but antifreeze raises the boiling temperature and prevents nucleant boiling. You don't want boiling to occur because of cavitation, plus steam has only 1/14 the cooling power of water.
 
It is not normal for the temperature gauge to "climb" at all. It should stay at the same temperature throughout different driving conditions.

Assuming the system is full, overheating on the highway is likely the fault of the radiator. The water passages could be clogged, or the air side fins are falling off or clogged with bugs and debris.
 
Originally Posted By: Kestas
Coolant mixture is a balancing act. Water has twice the cooling power of antifreeze, but antifreeze raises the boiling temperature and prevents nucleant boiling. You don't want boiling to occur because of cavitation, plus steam has only 1/14 the cooling power of water.


You sure do talk fancy.
grin.gif


The balancing act was figured out a long time ago by engineers and that is why a 50/50 mix is recommended by every vehicle manufacturer. The balancing act takes into considerstion more than just temperature since coolant has several responsibilities in an engine.

There are environments where a 60/40 coolant/water mix can be of greater beneifit but those are extreme environments.

As for how your post relates to the OP in Spain. Can you think of any possible reason to run less than a 50/50 coolant ratio?

 
Originally Posted By: FordCapriDriver
... i noticed my temp gauge was climbing more than usual, almost to the max,


I think you should return to a 50/50 mix, right after replacing your radiator.
 
Could the issue be a rad that's full of debris or bugs? MN gets a lot of insect hatches that plug things up. I usually install a piece of door screen over the front to keep the fins from filling up and the screen is easily removed and cleaned. Or the impellers on the pump are worn as the pump had been in service for many years.
 
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I am not replacing the rad, it's been refurbed with a new 3 row core about 3 years ago, and it was pressure tested about 5 months ago and it's perfect.
The front of the rad is not blocked, maybe a couple flies on it but not more.

At the moment it's fine, today i was at the yearly technical inspection where you are required to keep the engine running, it was idling in the sun for a good 25-30 minutes and the temp gauge did not seem to climb any more than it usually does, maybe it was simply a random occasion where it got a bit too hot, i did do a good 600 Km that day which is way more than the trips i usually do with it.

If it does it again i'll start looking into it more and will probably switch to either a 40/60 or 50/50 mix.
 
You can lead a horse to water
grin.gif


Good luck and be thankful you live somewhere that allows speeds of 90-100 mph.
 
Originally Posted By: ArcticDriver
You can lead a horse to water
grin.gif


Good luck and be thankful you live somewhere that allows speeds of 90-100 mph.

The speed limit is 75 Mph, but usually you won't get a fine unless you go waaay above the speed limit, i did about 80-85 most of the trip, you don't get a fine for that, 100 Hp only in some downhill sections of the highway i was on.
 
Originally Posted By: WobblyElvis
I would guess the engine was low on coolant to begin with. If so, why?


This seems the most likely explanation, since after topping off the OP found things to be fine.
The OP was looking at an actual increase in observed temperature.
Since we know that water removes heat more effectively than antifreeze, the 25% antifreeze mix cannot have been a factor.
Where did the lost fluid go?
It would probably be advisable for the OP to keep an eye on coolant level and look for leaks.
We all know what the worst case scenario is, so the OP should probably also pull the dipstick and check down the oil fill hole regularly enough to rule this possibility out, or to embrace the horror.
 
Originally Posted By: fdcg27
Originally Posted By: WobblyElvis
I would guess the engine was low on coolant to begin with. If so, why?


This seems the most likely explanation, since after topping off the OP found things to be fine.
The OP was looking at an actual increase in observed temperature.
Since we know that water removes heat more effectively than antifreeze, the 25% antifreeze mix cannot have been a factor.
Where did the lost fluid go?
It would probably be advisable for the OP to keep an eye on coolant level and look for leaks.
We all know what the worst case scenario is, so the OP should probably also pull the dipstick and check down the oil fill hole regularly enough to rule this possibility out, or to embrace the horror.


The oil looks perfectly fine, i'm 99% sure it does not have a blown head gasket, as i said today i was out and about again in the heat for about 2 hours, including half an hour of idling in the sun and it was fine.

I'll see what it does over the next weeks and if nothing out of the usual happens i won't worry about it.
 
There should have been quite a bit of pressure (at least 10 psi) opening the radiator when hot. If not you are low on coolant and have a leak.
 
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