Hi John,

Glad you got it sorted without having to dismantle too much of the system. My bet would be that just the repeated switching from hot to cold while running could have got the heater valve opening more effectively.

Are you in a hard water area? If so, I can see that the vinegar may well have helped also.

Andy

Hi There all Magneteers, and those who contributed to this thread.

Problem solved! I connected a hose to the pipes that carry the water to the heater, and flushed through with mains pressure water,then reversed the flow, repeating this several times. To be honest not a lot of sludge or scale or rust came out.
I then used some radflush and took the car out for a long spin to circulate it through the system, suspecting that the main blockage was in the heater matrix itself. I did then start to get some warmth out of the heater, for the first time in my 11 years ownership.
On my return I drained the radiator again - still no great amount of sludge/scale or rust.
Being a bit reluctant to try anything too caustic in the system, I tried a 50/50 mix of distilled (white) vinegar and water and went for another long run & left the car to cool and for the vinegar to do it's work, about 4 hours.
All of these runs were carried out whilst changing the heater controls to hot & cold alternatively.
I am pleased to report that this all seems to have worked - the car is now very cosy and more fun & comfortable to drive in the cold weather.
A final drain and refill of the correct ratio of water and antifreeze brings the problem to a very satisfactory conclusion.
So a big thank you to Trevor and Andy for your usual wise and excellent advice.
Should anyone wish to try distilled vinegar, please don't beat a path to my door if it goes wrong -you're on your own, but it did work for me - very well!
John Barringer

Hi John

The heater problem is well documented as Andy has laid out , your suggestion of using a strong descaler is OK leave it in the system for at least 12 hours, but you will need to neutralise after use for the reason that Andy has given. Bicarbonate of Soda will correct the pH but a good flushing with a hose is normally sufficient

When I rebuilt my engine the amount of crud filled a large jam jar, and again the problems are normally where the low pressure areas are or where there are restrictions such as the cylinder head .

One final point is to check that the valve is actually opening, the valve is a very poor design and is very restrictive even in good condition.

Kind regards
Trevor

Hi John,

Flushing the matrix with the heater valve in situ will restrict the flow somewhat even if the valve is fully open. Consequently there is more likelihood that the water will channel through the heater element, cleaning only a small proportion of the matrix. I think that filling the heater with Radflush might do some good although I would be a bit cagey about using a stronger descaler. These usually contain formic or acetic acid which may tend to dissolve the copper matrix.

Another point to check before you reconnect the system to the engine is the possibility of restriction or blockage in the side connection on the cylinder head.

Andy

HI all,
I've tried flushing the system out, connecting directly to the pipes that go into and out of the heater box. Water now flows with equal force whichever way round the hoses are connected, and not a great amount of sludge has come out, initially just brownish water, but now it is clear. I'm assuming that the water channels in the heater box are well & truly clogged up and the water flushing through is just bypassing the heater internals.
I am tempted to not dismantle the heater box, I'm getting too old for the gymnastics involved, and wonder whether, once I've got the radiator back in place(I'm painting the radiator top at the moment to complete my "tarting up" of the engine bay) whether I could just try some Holts Radflush, even if I have to repeat the flushing process a couple of times. Or could I try some kettle descaler instead, but applied in the same manner that I would the Radflush. My worry is as to whether the kettle descaler is too strong. Does anybody have any views as to whether there is a lot of difference in the "Viciousness" of the 2 products.

Any ideas?
John Barringer

Hi John,

You may well be correct and the matrix could be choked up. I assume you have tried operating the lower heater control back and forth while attempting to flush. It is this control which operates the heater valve - which could well be the cause of the trouble. It may be corroded and blocked, and/or the control cable could be incorrectly adjusted so that it doesn't open properly.

There are some helpful articles in www.zmagnettetech.info/ but some of them are not correctly indexed. If you simply type "heater" into the search box on the Home page you will get links to these articles. In the first one there is my picture of the correct positions of the water valve and its control cable in each of the 4 control lever settings. You may find this some help in checking whether your system is correctly adjusted.

I think it may be just possible to see this by pulling back the carpeting without removing anything else, although the photos were taken while the parcel tray was removed.

Hope this is of some help

Andy