Coolant - thoughts please

At present I’m using Penrite Classic Car Coolant with their Demineralised Water. I have been warned off glycol based coolants in non-pressurised systems. What is the reason for this?

Is this what other people are using in their pushrod motors or have you found something more suitable?


I live in a soft water area so no problems with calcium deposits so I just use tap water with antifreeze to give winter protection and corrosion protection.

If I lived in a hard water area then I would collect rain water instead of drawing from the tap.


Hello Peter,

Your ‘soft water’ is no doubt excellent for producing wonderful single malt! It would be a tad expensive to run the car on that! I wonder what the heat transference would be like on it?

We have soft water in Melbourne which is wonderful compared to most places in Australia. Nevertheless, I chose to use the demineralised water just to make sure all was well. I have an electric fan fitted in the MKV which helps when the car is caught in traffic. I was just wondering if another type of coolant could be used to assist with heat transferance?


Admittedly I don’t live in Australia but my car has survived on tap water and anitfreeze since 1993 and I have no problems of overheating. The range on the gauge is the same as it has always been.

If you find your cooling system is marginal then some people use waterless coolant.


I’ve not heard of advice to avoid glycol coolant in non-pressurized automotive systems. A consideration for many engines is corrosion inhibition, see antifreeze topic at Wikipedia.

Ethylene or propylene glycol added to water reduces the heat capacity per cc, raises the boiling point, and reduces the freezing point.

Corrosion inhibitors are added according to metals present, for example aluminum, iron, steel …

I’ve been using hard Southern California water plus least expensive ethylene glycol in 50/50 mix for about 20 years in my Mark V with same radiator and engine over that period. No deleterious effects and no overheating problems with no added cooling aids. Car was my daily driver for first decade. We don’t get below freezing in my neighborhood and only over 100 deg F a few days a year.

FEIW, Ive almost * exclusively used tap water and standard antifreeze, in everything, from a '35 Auburn, a '35 Rolls, to all the Jags we had, to all my DDs, and sll my customer’s cars, for over 50 years.

Never had an issue.

For those don’t need AF, there are corrosion inhibitors, but they cost a fair amount, and AF usually comes with all that stuff in it, already.

I’m also in the tap water/antifreeze mix camp. I don’t use the “waterless” coolants like Evans because of the lower heat transfer capability. But - to add a perspective on cooling of Pushrod Jaguar engines, we drove our SS100 about 500 miles two summers ago before I dismantled it for restoration. It got hot but not boiling in traffic a couple of times. But these engines are way more forgiving of poor maintenance than the later twin cam engines. Imagine my surprise when I found this upon dismantling the engine.
WARNING. - These photos are for Mature Audiences Only…

It must be the local tap water: even in horribly-neglected engines, I never saw crud that bad.

OO! Yuk! What is it?


Not unless their tap water was from the ocean…

If that really is the result after only 500 miles, there has to be something else causing that much chemistry.

It took a lot longer than 500 miles. The previous owner/family had it for 60 years in Holland and drove it in various rallies at least until 2015. Lori and I started driving it here in Michigan when we acquired it in 2018 - I figured I would learn what was broken or worn before stripping it apart. I knew it had a 1950 pushrod engine that I would replace with the correct 1938 M code engine ( that Ed N found for me). My running repairs were mostly fuel system and some electrical.
I actually use reverse osmosis filtered water and antifreeze in our Jaguars. The SS100 cooling system really did seem OK. I’m a mech engineer with reasonable amount of experience with old sports cars. I did get a lot of calcium deposits out of the radiator. This gelatinous green sludge is most likely from some kind of flush and sealer.
But what fun! Dave

Quite possible. Also, particularly if mixed with hard water, it looks like silicates coming out of the antifreeze solution. Coupled with the amount of corrosion, it had to be over an extended time, I’d say a decade or more.

Corrosion in unrestored XK cylinder heads in the ports around the steel head gasket is a commonly seen problem, which seems to be associated with running straight water in their early years, thus without the corrosion protectors found in most anti-freeze brands. But with modern anti-freeze in a 50/50 solution we don’t hear of corrosion anymore. Here is my XK120 thermostat housing after about 25 years since I cleaned it last, and though there is some corrosion around the outside where the rain and car washing water gets in, or perhaps in the hose connection joint where there is virtually no circulation, the inside is clean.

I use Prestone brand anti-freeze 50/50 with Lake Michigan water in all my cars including the SS and Mark V, and have not had any radiator problems in many years.
For Dave’s car, I wonder what sort of water they have in Holland. Could they have used salt water?

Your second picture is how Tweety’s cooling system surfaces looked: he sat, idle, rarely started from 1983 till 2002, no coolant change, and it looked…fine.

Ditto for Margaret’s cooling jackets. Tap water, antifreeze. Boom, done.

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On the advice of a auto museum curator, I drained the cooling system on my MK V, flushed it twice to make sure the antifreeze was rinsed out then filled it with Evaporust which I bought at Home Depot for $85- 5 gallon pail. I drove the car everyday for two months and then drained it, flushed it twice and put antifreeze back in. The solution went in green and came out black but the inside of the engine and radiator was like new. It lowered my temperature by 20 degrees.
To answer the question above, I use a 50/50 mix of distilled water and glycol.
I have no connection to Evaporust or it’s maker…I just really like the stuff!

Hi Wayne,

That sounds great. Did the car run hotter with the Evaporust in it and how long did you drive it every day for the two weeks?

Is this the product?

It’s available here in 5 litre containers for $95.00 AUD which sounds expensive considering the car needs 25 litres ($475.00! :scream:). It’s much better value in the USA. :cry:


I’ve just found this one in Australia which would seem a more suitable application and made for the purpose. It’s not much cheaper at $395.00 AUD.

Have others used the product before?

Kind regards,


On the forum there are several discussions on using EvapoRust. It isn’t an acid, so it doesn’t hurt aluminum, copper, water pumps or seals. I used it for two months which was probably longer then necessary but when done, I put it in my 1930 Cadillac and used it there for the rest of the summer. It wasn’t as strong as when first used but still worked. I now use it to soak rusty parts in and tho it’s about lost all it effectiveness, if left long enough, it will clean the parts.
I ran the cars using it full strength. It acts like water and I didn’t get in a situation where it would boil over but I noticed a drop in engine temp every day. It is able to clean the engine where rodding wouldn’t get to, it dissolves corrosion anywhere it can get wet even the tubes in the radiator. I did find it expensive when bought by the gallon but I search the net for larger quantities and found that Home Depot would order 5 gallons as would Tractor Supply. Search around the net and see if it’s available reasonably priced any where.

Please read the SDS and MSDS on the Evaporust website.
Contains up to 83% water and 16% chelating agent, examples of a chelating agent are EDTA and Citric acid, both of these chemicals are used in food production.
Gives a good idea of what this stuff is.

A homemade brew worjs toi: from Practical Machinist.

“It’s roughly 50 water/30 vinegar/20 Hydrogen Peroxide/and enough salt to dissolve. You will need to refresh the hydrogen peroxide occasionally as oxygen will come out of solution.”