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R53 2003 MCS Heater Matrix Replacement (5 replies)

ihughes
5 years ago
ihughes 5 years ago

R53 2003 MCS Heater Matrix Replacement

Ian Hughes

ihughes
5 years ago
ihughes 5 years ago

I've been smelling hot coolant inside my mini for quite a while now, but it comes and goes. Last time it went into the workshop for an oil service I asked them to check over the engine for coolant leaks (radiator, thermostat housing etc) as I didn't appear to be loosing any coolant from the header tank.

However, whilst cleaning the car for its Beaulieu outing I noticed a slight stain on the passenger footwell carpet and on feeling around the bottom of the plasic side panel of the central console/heater housing I did discover a trace of coolant.

Not wishing to miss Beaulieu I stuffed a load of kitchen towel into the bottom of the heater housing and topped up the header tank which was down slightly.

Anyhow, I made to and from Beaulieu safely (topped up the header tank again before leaving). Then during the week I used the car for a very short trip to my local town center only to discover a very wet carpet and serious loss of coolant once I got home.

I have subsequently removed the two (easy) torx screws that hold the heater matrix side cover (passenger side footwell) in place but haven't (yet) managed to get the third screw out which is tucked right up under the parcel box and close to the engine bulkhead. This gives you enough movement of the side cover panel to be able to examine the heater flow and return pipes and the bottom corner of the matrix itself. Sure enough, I have a leaking matrix which is steadily dripping from the bottom corner. However, the flow & return pipes are all dry and so are the couplings/clamps that attach the pipes to the matrix.

The replacement of the heater matrix is fairly straightforward (assuming you can get the third screw out of the side cover!) BUT, it is extreamly difficult to actually work on the heater area in general, because you are effectively kneeling down outside the door and resting your weight on your elbows whilst trying to use your hands to undo the clamps etc.

ALSO, if you read up on the job in the Haynes manual it says you have to disconnect the top couplings of the heater flow and return pipes from the engine bulkhead underneath the airbox in the engine compartment. This in fact is NOT necessary and you can apparently change the matrix by simply undoing the bottom couplings on the pipes and matrix.

Given the difficulty of working on the heater area inside the car, and the need to drain and then refill and bleed the cooling system after replacing the matrix I am going to get my local workshop to do it.

One thing I would say is as soon as you detect the smell of hot coolant inside the car I'd definitely check the bottom of the center console side panels for any trace of leaking coolant. Also, the heater matrix failure is quite a common problem on Gen 1 Minis of all types.

ihughes
5 years ago
ihughes 5 years ago

Well, I have now got the heater matrix replaced and everything is watertight again. The workshop originally sourced the replacement matrix from Eurocarparts BUT the one supplied that was supposed to be OEM quality wouldn't fit! So we had to source a replacement direct from BMW.

Also whilst changing engine oil & filter we discovered that one of the power steering pipes was badly corroded and had a slight leak. So, another visit to BMW to source a replacement that should be fitted today.

Martin Charles
5 years ago
Martin Charles 5 years ago

Hi Ian,
Useful write up - thank you. It is a problem that those of us with Gen.1 cars will increasingly find as our cars get older.
Out of interest how much was the genuine matrix from BMW?

Martin Charles
5 years ago
Martin Charles 5 years ago

Thanks for the update Ian, yes I would agree a reasonable bill for all that work including fluids and VAT.

Yes carpet should clean up fine, but might take a few goes at it, I use Turtle Wax upholstery cleaner and I'm very impressed with it having used it for a few years now.

I have a new project I'm working on at the moment as a new daily driver for me, a Mk.4 VW Golf GTI 25th Anniversary edition 1.8T petrol, the interior although sound was filthy and it has come a really well after a couple of treatments.

ihughes
5 years ago
ihughes 5 years ago

Got the car back with all jobs done and all fluids staying where they are supposed to be!

In the end I had the following jobs done:

- Replacement heater matrix with BMW supplied unit (£73.15 plus £13.84 for fitting kit).

- Replace return pipe kit for power steering pump (£89.16).

- Engine Oil & filter changed plus new sump plug.

- Rust treatment & underseal to area of floor in front of drivers side rear wheel arch.

Total bill including labour, consumables & vat = £441.32

I didn't think the total was too bad for everything that was done especially the hassle and difficulty they had in replacing the heater matrix!

I was a bit surprised at the corroded power steering return pipe; it's tucked up behind the pump and not really exposed to road/rain muck etc. Also, I didn't realise the cooling fan for the PS pump was facing straight down on to the road and presumably sucks air in to cool the electric motor. When we lifted the car to check out the work (when I went to collect the car), the fan had a big bit of paper wiping towel caught in the blades which it must have picked up from the workshop floor! This might be something to watch out for esecially if you drive over plastic or paper rubbish laying in the road. Potentially even worse if your car has lowered suspension.

The rust on the floor I was aware of from previous MOT was quite superficial.

Now I've just begun the process of trying to clean the carpet of spilt/leaked antifreeze. This is going quite well using an aerosol carpet cleaner followed by vacuming with my wet/dry vacum cleaner.

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