Morris Minor Owners Club

Stephen has giving you a not totally correct description of the antifreeze issue, principally around Colours and the Glycol types.

As you said

59Elva wrote: ↑Thu Jul 02, 2026 5:36 pm Years ago there was a move away from ethylene towards polypropylene glycol as being more pet friendly.

It's the additives that are the issue, not the base Glycol liquid, either ethylene or polypropylene can be the core coolant.

It's about the technology of the additives.
Inorganic Additive Technology (IAT), Organic(OAT), or Hybrid (HAT) (including sub-versions of... ).
Note that the coolant industry can't even agree on the description, let alone the colours.
Some Companies call it 'Additive Technology' while many call it 'Acid Technology'...

Anything pre- late 1990s requires IAT, because the engines/radiators include metals that can be damaged by the OAT/HAT additives.


See this USA website for an American viewpoint, including Colours.
In your case, Green is almost certainly right for IAT, but the appearance of the green deposits in your photo is a little concerning....
https://gmb.net/blog/inorganic-vs-organic-coolants/

Think I found the problem. I don’t know what the catalyst was that caused the failure. What I’ve found so far seems related to alloy locations. The water pump outlet was solidly plugged. Question is how much more is in the system or of it was limited to the alloy components. Wish I knew what might help dissolve it. Mild acid, vinegar? Caustic, washing soda? Or some kind of organic solvent like methanol? Maybe soap?
Oh well, now I have an excuse to clear and paint the radiator and fan and investigate the crank pulley being out of time.
PS
Geoberni
Thank you for the link, I’ll check it out .

Somebody may of used a sealer like case seal to stop a leak and overdosed being a small engine. Or as suggested earlier some wrong antifreeze type but that usually attacks certain metals, never seen it crystallise. Another possibility is two substances have reacted with each other.
Put samples in dishes and try your various solvents to find the most effective before filling the engine block.

I have never seen such severe crystalline deposits in real life but I have seen it on car restoration TV programmes. It happens in engines where the car has sat for many years filled with coolant. Another possibility is that two incompatible types of coolant were mixed causing some chemical or other to precipitate out. If a car is going to be laid up for many years it is advisable to drain the cooling system including the block to prevent this happening. Unfortunately, it is usually never planned that a car is laid up for years.....

Other thoughts are a previous owner topping up with neat antifreeze and never draining down over many years. IAT antifreeze has a limited life and the cooling system should be periodically completely drained, flushed and replenished. I changed to using deionised water some years ago and this has made a big difference in keeping the coolant clean and rust free.

Stephen

So far the green crystals were confined to the aluminum components. Oddly the metal doesn’t look to be damaged by it. It cleaned up pretty well with a small welder’s wire toothbrush. The radiator looks pretty clean and drains as fast as I can feed it with a garden hose.
So what I have is a 1275 of unknown origin with what looks like an aftermarket alloy pump. I suspect the aluminum thermostat housing isn’t original to what was an air injected head. The studs are too long and no boss to mount the air pump.
The consensus given the mix of iron, brass, aluminum, and a bit of steel is to use IAT, either ethylene or polypropylene coolant?
Thanks all,
Bill B

While the radiator was out of the way I pulled the crank pulley and discovered the source of the timing error. One key, two key ways. The original one is damaged. I assume someone cut the second one to save the harmonic damper. Just by eyeball the second keyway looks off a bit.
I didn’t find crank handle spigot bolt in my spares so no starting this one by hand. I was going to post a pic but keep getting a HTTP Error?

My little traveller coped ok in the heat except when doing a long (2 mile) uphill on a dual carriageway at 55mph.

Started to misfire towards the top but fine as soon as the road flattened out and I could ease off the throttle

I’m thinking vapourisation and I’m making a heat shield just in case

Been fine before and after now it’s a bit cooler.

I now have circulating water!!
Also a bright yellow fan and a new thermostat. Had the distributor out to check the point gap. Put the pulley back to its original position. I clocked it against the good side of the keyway and set the timing to 7* bdc.
Still running rich so I exchanged the dome, piston, needle assembly from an old spare carb. It sounded better. Worn jet maybe ? I had hoped to drive as is for awhile but if I can’t lean it out I might have to go to the twin carb setup which will force me to come up with a different exhaust system. Suppose I could try to separate the intake manifold and make a blank off plate for the existing exhaust manifold.

Haven’t started the truck in a week or so. Been fiddling with the replacement carb and exhaust. I stopped at the auto parts store for some high temperature manifold paint and asked about antifreeze. It’s still a couple months before I need it but this is what they suggested. It’s blue but MAT. What I need with the alloy pump and copper radiator is IAT correct?

59Elva wrote: ↑Wed Sep 09, 2026 12:29 am Haven’t started the truck in a week or so. Been fiddling with the replacement carb and exhaust. I stopped at the auto parts store for some high temperature manifold paint and asked about antifreeze. It’s still a couple months before I need it but this is what they suggested. It’s blue but MAT. What I need with the alloy pump and copper radiator is IAT correct?

Correct, colour is irrelevant because colours change in different markets and there is no international standard for colour coding.

The Industry can't even decide how many types there are .

Some say 3....,
IAT (Inorganic Additive Technology): Traditional green or blue fluid used mostly in older vehicles (pre-2001). It needs replacement every 2 to 3 years.
OAT (Organic Acid Technology): Long-life orange, red, or pink fluid used in many modern cars. It can last up to 5 years or more.
HOAT (Hybrid Organic Acid Technology)

While others break is down even further and include Phosphate-free HOAT, Phosphated HOAT (P-HOAT), and Silicated HOAT (Si-HOAT).

What you need for pre 1980s vehicles is the Inorganic.

Just to illustrate the confusing state of the Coolant Industry, Valvoline are a significant global company.
Their website https://www.valvolineglobal.com/en-eur/ ... r-coolant/ actually says:

NEVER RELY ON COOLANT COLOR-CODING

In the past, color-coding played a fundamental role when it came to the choice of coolants. Namely, coolant colors indicated different product properties, applications, and vehicle compatibility.

Today, this is not so. Coolant colors may vary based on the lubricant manufacturer. Not to mention that the same color can be used for different products. For example, we mentioned that IAT coolants, used in older vehicles, are green. However, Valvoline’s most innovative Si-OAT coolant formula that is used in newer vehicles, HT-12, is also green.

On the other hand, we can also notice that different colors can be used for products in the same category. One such example is our HT-12 Pink and HT-12 Green coolants.