Heater check.

[Arthurdaily]

Good evening everybody, a quick question about heaters. My standard 71 saloon has a standard heater fitted, now I believe I'm right in thinking that the heater pipe from the rear of the head comes through the tap, into the pipe and then into the TOP of the heater matrix, is that right, then from the bottom hose into the engine bay and into the metal pipe that returns it to the bottom of the radiator lower pipe - does that all sound right?

Anyway, I pulled what I believe is the return pipe off and the water is hot after its been running - BUT the heater is not actually pushing out much heat - almost nothing. Does it need flushing you think? If so which pipe do I pump water through - the inlet or outlet pipe?

Thank you in advance!

[beero]

Might need flushing. Flush both ways will give the best result. Maybe the tap and hoses are furred up reducing flow.

[bmcecosse]

Makes no odds which way the water flows......

[IslipMinor]

I would check the heater valve on the back of the cylinder head, is that opening correctly?

The BMC/BL Workshop Manual says that, for the later fresh air heater, the lower heater connection is the feed from the heater tap, and the upper the return to the radiator bottom hose (via a copper tube). Does it really matter? Maybe not, but why not do it as the manufacturer suggests? It is also easier as the holes in the bulkhead are in the same vertical orientation.

[Arthurdaily]

Brilliant thanks, however I have discovered the problem - most of the time I have been checking it at idle only, and at idle there is little water flow, when I rev it a little the water starts flowing. Is this a sign that the water pump is on the way out or is no real flow through the heater pipes normal at idle?

[bmcecosse]

Normal.

[Arthurdaily]

Now I couldn't have guessed that as a teacher ha ha - that does mean that in traffic in winter there is never going to be much heat through the heater? Any modification to allow constant heat?

[Trickydicky]

My 948cc engine struggles to even read 60 degrees on the temp gauge this time of year, this is due to the adequate cooling design of the car and the air temp. I have not tried it but I would have thought blanking off a portion each side of the radiator to decrease the cooling area is the only way of making the heater warmer.
I believe thats why, when the car was in production they produced radiator blinds as a add on.

[lambrettalad]

Iv'e used cardboard as a blind with no problems in the winter

[liammonty]

Check your thermostat and replace it if it's no good or too low a temperature. I've used all my Minors in sub-zero temperatures (in the rare occasions we get them!) and I've never had a problem with either the engine warming up or the heater putting out plenty of warm air (provided the heater valve isn't restricted and the heater matrix and pipes are clear- worth giving a flush). This is in cars equipped with all the different heater types- round, and the more modern square fresh air one. The issue for me is always keeping the heat in the car- too many draughty windows and doors! Try an 88 degree thermostat for the winter. You shouldn't need to blank the rad if all is working as it should- if the engine water doesn't heat up, the thermostat shouldn't be letting water around the rad if it's working!.

BTW, like IslipMinor said, the water inlet to the heater on the cars with the later fresh air heater goes in to the bottom, the return comes out of the top. Seems counter-intuitive, but that's the way they were. Like BMC said, I can't see it makes much difference.

[bmcecosse]

If you want the very best heater - block the bypass pipe on the water pump and fit an 88 or 92 degree thermostat.. Then in 'summer' - change the stat to a 72 and drill 2 X 1/8" holes in the rim to allow some water to circulate if you decide to close the heater valve....although it is better kept open all year round.

[lambrettalad]

moggies are over cooled,I'm thinkng of fitting an electric fan,has anyone ideas on this ?

[bmcecosse]

Doubtful return on the money - in winter you can take the fan off - just don't get stuck in a long traffic jam without switching off....

[lambrettalad]

BMC Your probably right ,i'm thinking of doing some long journeys ,e.g. lands end in the main summer months.not sure about the midges in Scotland

Using pre loved parts

[bmcecosse]

Oh yes - you can be sure of the midges....