Matrix

[stuffedpike20]

I think my heater matrix needs replacing.
There are new 'made in China' heater matrixes available online, and some of them claim to fit classic minis AND morris minors. I always thought that the mini matrix was bigger than the minor matrix.
Has any one fitted one of these?

Thanks
John

[svenedin]

I've not fitted one of those. I got mine from ESM and no issues with it fitting (later rectangular heater).

Stephen

[geoberni]

I always thought that the mini matrix was bigger than the minor matrix.

There were 2 different rectangular heaters used on the Minor, 2.8Kw and 3.8Kw, so clearly they used a different matrix to get the different output.
The 3.8Kw (as an option) was from March '64, on vehicle 1060095.

[stuffedpike20]

Thanks both. My car is a 1098.

TBH I am not sure where the leak is. I went for a short drive today and checked the car a few hours later, and could see that a few inches of water had gone from the radiator.
Radiator and hoses are good, and there is no water obviously leaking down onto the parcel shelf from the heater. Matrix seems the logical place though.

[svenedin]

I always thought that the mini matrix was bigger than the minor matrix.

There were 2 different rectangular heaters used on the Minor, 2.8Kw and 3.8Kw, so clearly they used a different matrix to get the different output.
The 3.8Kw (as an option) was from March '64, on vehicle 1060095.

Yes but the 3.8Kw is a very different beast to the 2.8Kw.

The 2.8Kw is the standard rectangular heater. The 3.8Kw is a special heater for export cars to cold climates. It is very different having a separate blower unit in the engine bay so that there is more room in the heater unit in the cabin to have a larger matrix. I have never seen one of these super-heaters.

Stephen


The high output 3.8Kw heater with separate blower

Screenshot 2026-04-16 at 17.22.51.png (590.64 KiB) Viewed 10213 times

[svenedin]

Thanks both. My car is a 1098.

TBH I am not sure where the leak is. I went for a short drive today and checked the car a few hours later, and could see that a few inches of water had gone from the radiator.
Radiator and hoses are good, and there is no water obviously leaking down onto the parcel shelf from the heater. Matrix seems the logical place though.

I would think you would have a soggy parcel shelf or wet carpets if the matrix is leaking? If you top the radiator right up it is normal for the level to drop via the overflow when the engine gets hot. It "finds its own level" which is for coolant to be just above the core in the radiator. Obviously if it drops more than that then there is problem. Modern cars have an expansion tank so that the expelled coolant travels back to the radiator when it cools down.

Stephen

[geoberni]

Yes but the 3.8Kw is a very different beast to the 2.8Kw.

Stephen

Thanks for the greater info, clearly a late model heater is far outside my personal experience, Basil's isn't even Factory fit.

[stuffedpike20]

Thanks both. My car is a 1098.

TBH I am not sure where the leak is. I went for a short drive today and checked the car a few hours later, and could see that a few inches of water had gone from the radiator.
Radiator and hoses are good, and there is no water obviously leaking down onto the parcel shelf from the heater. Matrix seems the logical place though.

I would think you would have a soggy parcel shelf or wet carpets if the matrix is leaking? If you top the radiator right up it is normal for the level to drop via the overflow when the engine gets hot. It "finds its own level" which is for coolant to be just above the core in the radiator. Obviously if it drops more than that then there is problem. Modern cars have an expansion tank so that the expelled coolant travels back to the radiator when it cools down.

Stephen

The radiator has been at a constant level for months, but today the level had gone down just below the core after a short drive.

I will do a compression test tomorrow to see if there is a head gasket problem, but the car is starting and pulling as normal.
Heater matrixes seem to last a loot longer than radiators IMHO. I don't think I have ever had to replace one.

[svenedin]

Thanks both. My car is a 1098.

TBH I am not sure where the leak is. I went for a short drive today and checked the car a few hours later, and could see that a few inches of water had gone from the radiator.
Radiator and hoses are good, and there is no water obviously leaking down onto the parcel shelf from the heater. Matrix seems the logical place though.

I would think you would have a soggy parcel shelf or wet carpets if the matrix is leaking? If you top the radiator right up it is normal for the level to drop via the overflow when the engine gets hot. It "finds its own level" which is for coolant to be just above the core in the radiator. Obviously if it drops more than that then there is problem. Modern cars have an expansion tank so that the expelled coolant travels back to the radiator when it cools down.

Stephen

The radiator has been at a constant level for months, but today the level had gone down just below the core after a short drive.

I will do a compression test tomorrow to see if there is a head gasket problem, but the car is starting and pulling as normal.
Heater matrixes seem to last a loot longer than radiators IMHO. I don't think I have ever had to replace one.

Yes, the heater matrix lasts for a very long time. I have replaced mine once in 37 years and that was only about 3 years ago so it lasted over 50 years.

I had a hard to find leak. To find it I had to put a special florescent dye in the coolant. You could put some cardboard under the car and look for drips.

A classic place for a leak is the bypass hose between head and block. Another common place is heater tap.

Good luck with your hunt!

Stephen

[stuffedpike20]

Thank you Stephen.
The last time I re-newed the bypass hose. I covered it with red rubber grease. I find that modern 'rubber' items last longer if you coat them with rubber grease.

[svenedin]

Thank you Stephen.
The last time I re-newed the bypass hose. I covered it with red rubber grease. I find that modern 'rubber' items last longer if you coat them with rubber grease.

I used a silicone bypass hose, lubricated with silicone grease. It is a very solid hose but I think it would be difficult to fit with the head in place. I changed the hose when the head was off. It may look like a concertina hose but the reality is, it doesn't really concertina at all. You could just use heater hose if you wanted as it is the same inside diameter.


https://www.morrisminorspares.com/cooli ... ps-p829657


Stephen

[stuffedpike20]

I think I have 'false memory syndrome'. I am sure I read somewhere that classic mini matrixes were bigger than minor matrixes....and that fitting a mini one was an upgrade that improved the minor heater.

[svenedin]

I think I have 'false memory syndrome'. I am sure I read somewhere that classic mini matrixes were bigger than minor matrixes....and that fitting a mini one was an upgrade that improved the minor heater.

I recall that Charles Ware used to offer an upgraded heater matrix. The matrix wasn’t physically bigger because a bigger matrix won’t fit in the heater box. It had larger diameter inlet and outlet pipes which they claimed gave higher flow and hence higher heat output. Perhaps someone has an old Charles Ware catalogue and can confirm this? I don't think the "upgraded" heater matrix made that much of a difference and it was recommended to fit a hotter thermostat at the same time which may account for most (or all) of the improvement in output.

Stephen

[stuffedpike20]

Thanks Stephen.
I tried a hotter thermostat once, and the engine did not like it.

As time goes on, I have come to realise that the designers of the minor got things just about right first time....and upgrades are often not necessary, or an improvement.

[svenedin]

Thanks Stephen.
I tried a hotter thermostat once, and the engine did not like it.

As time goes on, I have come to realise that the designers of the minor got things just about right first time....and upgrades are often not necessary, or an improvement.

It was a different era. Nowadays people seem to expect to drive in winter in their shirtsleeves in a climate controlled cabin. Back then, people would drive in their long overcoats, wearing gloves and probably a hat as well. I certainly drove my Minor wearing a long Crombie type overcoat. In my teens they were de rigueur although mine wasn't a genuine Crombie as they were far too expensive. I would often wear my skiing gloves too but then again this was Scotland in Winter in a convertible with all the unwanted drafts.

Stephen

[stuffedpike20]

Thanks to your earlier post, I have just been out to look at my car, and there is a bit of coolant round the base of the heater valve. So this may be the problem rather than the matrix.
It is a late type valve. I know how dodgy these valves are, so always leave it open all year round to avoid leaks. It has lasted donkeys years...and replacing it now, if it is the problem, will be eeasier than replacing the matrix.

[myoldjalopy]

Thanks Stephen.
I tried a hotter thermostat once, and the engine did not like it.

As time goes on, I have come to realise that the designers of the minor got things just about right first time....and upgrades are often not necessary, or an improvement.

It was a different era. Nowadays people seem to expect to drive in winter in their shirtsleeves in a climate controlled cabin. Back then, people would drive in their long overcoats, wearing gloves and probably a hat as well. I certainly drove my Minor wearing a long Crombie type overcoat. In my teens they were de rigueur although mine wasn't a genuine Crombie as they were far too expensive. I would often wear my skiing gloves too but then again this was Scotland in Winter in a convertible with all the unwanted drafts.

Stephen

My first Minor (a SII 2-door saloon) didn't even have a heater! One day I spotted an abandoned Minor in a field and gave the farmer £5, allowing me to remove the heater which I then put in my (previously) cold car