Series three heater matrix blowing cold

grewth · Saturday at 10:24

I've got a dual heater set up on my 1970 88 diesel.
Hot coolant comes from the bypass outlet near the thermostat, flows into a series three heater box/matrix, then from there into the original type flat square heater, and finally back to the rear union on the cylinder head.
Now the flat type heater is getting really nice and hot, and the two speed fan working perfectly.
The single speed (snail blower) on the series three matrix is also running OK, but the heat output is more like tepid, not quite even luke warm.
Hot coolant is obviously flowing in and out, but no hot air is apparent.
The rubber hoses are hot all around.
Can't quite figure this one out.
Matrix core caked in crud ?
I can't really see how, it's fed from a series three type wing vent with grille.

tottot · Saturday at 12:15

The foam rubber seal between box and bulkhead can be an issue. If rotted away heat escapes back into engine bay.

Rangieman123 · Saturday at 12:17

Is the Series 3 heater body getting hot when the engine is up to temp? Have you removed it and given it a flush. They seem to act like a cooling system filter and sludge up.

grewth · Saturday at 12:43

tottot said:
The foam rubber seal between box and bulkhead can be an issue. If rotted away heat escapes back into engine bay.

From memory, I just chopped out a rectangular hole in the NS footwell and sealed the joint with household draft proofing strips, the sticky back ones, plus maybe a touch of silicone sealant.
Doubt if it's failed to any great extent.
Unfortunately, I tack welded a steel grille over the apparture to keep prying fingers out.
Now it's keeping me from inspecting it properly.

tottot · Saturday at 12:47

Any possibility of air lock in the series one? Otherwise box out time I recon.

grewth · Saturday at 13:07

Rangieman123 said:
Is the Series 3 heater body getting hot when the engine is up to temp? Have you removed it and given it a flush. They seem to act like a cooling system filter and sludge up.

Not as hot as I'd like it to be.
And thinking about it, it never has quite lived up to expectations.
I've just remembered that I've got a brand new series three matrix kicking around somewhere, leftover from a previous project.
Just a case of hunting it down before I go any further

Dragonwalker · Saturday at 13:49

grewth said:
I've got a dual heater set up on my 1970 88 diesel.
Hot coolant comes from the bypass outlet near the thermostat, flows into a series three heater box/matrix, then from there into the original type flat square heater, and finally back to the rear union on the cylinder head.
Now the flat type heater is getting really nice and hot, and the two speed fan working perfectly.
The single speed (snail blower) on the series three matrix is also running OK, but the heat output is more like tepid, not quite even luke warm.
Hot coolant is obviously flowing in and out, but no hot air is apparent.
The rubber hoses are hot all around.
Can't quite figure this one out.
Matrix core caked in crud ?
I can't really see how, it's fed from a series three type wing vent with grille.

Maybe crud on the inside restricting flow ? Take it out and back flush it, while it's out tidy up the heat box, tighten the seams and re insulate

Rangieman123 · Saturday at 14:58

I vaguely remember reading years ago that it was possible to fit the better heater matrix from a 90 into a Series 3 heater as an upgrade.

grewth · Saturday at 16:01

Rangieman123 said:
I vaguely remember reading years ago that it was possible to fit the better heater matrix from a 90 into a Series 3 heater as an upgrade.

I thought that you had to make the box bigger.
Maybe not.
Anyway I know that I've got a brand new S3 matrix somewhere (although it's Britpart not OE)
Worth giving it a try I'd have thought before resorting to more radical measures.
Remember that I already have the standard 2A heater which works reasonably well.
Also, IIRC, the 90 type matrix is quite expensive, although everything is relative.
If an expensive heater modification actually lets you see where you're going, and prevents an accident, it's got to be worth every penny.

Tall Ratbag · Saturday at 22:14

As the heater matrices are in series with each other, and the flat heater is getting hot, this suggests that the water flow is OK, and the problem lies on the air side.

grewth · Sunday at 12:00

Tall Ratbag said:
As the heater matrices are in series with each other, and the flat heater is getting hot, this suggests that the water flow is OK, and the problem lies on the air side.

Your logic is faultless.
If I get time this afternoon, I'll be taking the offending matrix out for examination.

Citizen Kane · 2024-11-11T17:05:30+0000

The water flows in the opposite direction, it comes out of the head first so the it could be the flat heater is taking most of the temperature out of the water before it gets the the Series 3 matrix.

Series three heater matrix blowing cold

grewth

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tottot

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Rangieman123

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grewth

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tottot

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grewth

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Dragonwalker

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Rangieman123

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