Thread: Coolants for older engines

Originally Posted by landrover dave

................... Why would you want a coolant that raises the boiling point to arount 125C!..............................

It's not the coolant that raises the boiling point to 125 degrees C its the pressurisation of the cooling system. At normal atmospheric pressure water boils at 100 degrees C. As pressure increases so does the boiling point.

In my old series LR with its 4 lb system this was increased to 107 degrees C. In my Defender with its 15 lb radiator cap the boiling point is increased to 120 degrees C.

This is why it's a bad idea to remove a radiator cap from a hot engine. Instant decrease in pressure causes 100 degrees + water to instantly turn to steam.

Wouldn't go to the snow on a free ticket so don't need anti freeze and don't trust OAT coolant not to stuff a perfectly good older engine, regardless of manufacturers claims that their coolant is compatible. Google Dexron coolant for the reasons why. Though I would trust OAT coolant in a system specifically designed for it.

A clean cooling system that's flushed annually and filled with clean water with a good corrosion inhibitor has always worked for me. I have used RMI 25 cooling system treatment for many years and it works for me.

Never quite worked out why people want to put anti freeze in their cooling systems when they are in a country where (in most places) it never freezes.

Deano

You are correct in saying pressurising raises the boiling point, but ethylene glycol has a higher boiling point than water! A i6lb cooling system boils at around 112C at sea level, add glycol and that temp raises to about 122C! Glycol has a higher boiling point than water.

As far as I can see the only benefit of running a glycol mixture is that if system pressurisation was to fail a higher than 100 degrees C boiling point in the coolant would be retained. This could be beneficial in the case of cooling system damage when running with the radiator cap loose. But apart from this no real benefit that I can see.

Modern vehicles run cooling systems at reasonably high pressures (greater than 20 psi) which gives a boiling point of around 126 degrees C or greater, my old Defender at 15 psi gives me 120 degrees C. Why do I need a glycol solution ? (apart from the reason above).

It may be that a glycol solution has greater thermal efficiency in that it can move heat more efficiently, I don't know. But then the rest of the system would need to be dimensioned for this as well.

But really, what is too hot ? At what temp is engine damage / component failure likely to occur ? It doesn't strike me as a very good idea to be driving with an engine temp of 120 degrees C +. If it gets to 100 degrees C I reckon it's way too hot.


Deano

Originally Posted by landrover dave

What I posted about coolants was learnt from a radiator specialist! Why would you want a coolant that raises the boiling point to arount 125C! By the time your motor overheats the damage is done! I have never heard of a motor that has local hotspots, thats what design engineers are employed for!
Take your radiator to a reputable radiator repairer and get them to dismantle and clean it. Then ask them how blocked it is! The only way to remove the crystalized glycol is to poke a rod down each tube!
Not all coolant manufacturers make coolant without glycol, they are of course going to tell you their product is good!
And my teacher at tradeschool taught me that

I've been running ethylene glycol based coolant for years without any problems, same in the UK where it's obviously more important during the winter months. Never had cooling problems (apart from the odd split hose) in 30 plus years of motoring and never had a radiator rodded. Just relied on regular coolant changes.

The comment about hotspots was from a coolant manufacturers website, not sure which one as I've visited so many recently. The statement was that if the original manufacturer specified ethylene glycol coolant then it was possibly because of localised hot spots in the engine.

My biggest concern is the different advice from different coolant manufacturers. I get the impression that the latest OAT coolants may be OK but I;ll stay with traditional anti-corrosion packs.


Colin

Wow guys, Now I am totally confused. It really is not that simple. I still dont know if the Tectaloy Extra Cool Gold RED is ok for my Discovery 1 300tdi. I will call Tectaloy tomorrow and see what they say. Thank you all for your time and effort and I really appreciate all of your advice. It seems the answer is not so simple and straight forward as one would hope. Maybe I will drain the coolant in the morning and fill with lime cordial. hahahahahahahahahahahahaha thanks guys - Gerry (wedgetail37)

as i understand it the glycol is an anti freeze agent

if your not in an area where you water is likely to freeze you just use an anti corrosion agent with demineralised water (eg rmi25 or similar)

the glycol impedes the waters ability to adsorb heat at it's natural rate so some people add redline water wetter to compensate.

if you add water wetter your temop gauge can show a hotter temp but overall your system and therefore your engine will run cooler if it is past the thermostats opening temperature

any 300tdi system was designed to run with a glycol based coolant

yet to find a valid reason for using something other than what it was designed to support.

A few points perhaps should be made relative to the above discussion.

1. All Series engines (except V8 and Isuzu!) were designed and specified to use water as a coolant with no additives except when operated in freezing conditions, when a glycol based antifreeze was specified. Soft or rainwater was recommended.

2. Glycol has a lower heat capacity (specific heat) than water, hence heat transfer capacity is less for antifreeze coolants than water. In a sense this is compensated for by a higher boiling point, but this does not increase the rate of coolant circulation, so uneven heat distribution in the engine may be exacerbated by the lower heat capacity, and in any case the advantage of the higher boiling point is not relevant until the engine is already well above the intended operating temperature.

3. Glycol is much better than water at finding leaks, hence the traditional view that you only use it when necessary for antifreeze protection.

4. Some engines, in fact possibly most current engines, were designed to use high glycol content coolant, but this does not mean that this is an advantage in engines that were designed to use water. All modern engines require corrosion inhibitors because of the wide use of easily corroded alloy bits in the cooling system - which were not used in Series engines except for the V8 (and the isuzu).

John

Quote "All modern engines require corrosion inhibitors because of the wide use of easily corroded alloy bits in the cooling system - which were not used in Series engines except for the V8 (and the isuzu)." end quote.

John, the 1600cc engines had alloy thermostat housing and water pump.
These corrode easily and can be a bugger to remove.

Keith