The Americans are right (Heater Core Replacement)

I recall reading somewhere that the Americans believe the only way to fix a leaking heater core is to replace it. Well, I did try some selants and although the results appeared marginally psoitive to begin with, I think that was more wishful thinking than actual success.

Replacing the heater core is not something anyone would really wish to do, but when there is no choice...

Anyway, it's not half as bad as I had imagined, and attached here is the write-up in graphical detail.

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Thank you for all the comments, guys!

It was quite a long job, but compared to many other things, it's quite straight forward and nothing about it is difficult. Just be sure to keep track of all the fasteners and where they go. I had one spare screw at the end, which i eventually figured out where it went (under the ash tray). But actually, the dashboard is held in place by only about half a dozen fasteners, so it's not complicated and the wiring, although it appears messy, is just a case of cutting a few cable ties for access and then replacing them afterwards.

One thing that is good, is that the dash fits quite precisely and there is little chance to refit it incorrectly or to end up with mis-alignments or rattles. It will slide back just as easily as it came off.

If anyone would like to have the "HD" version (5.8MB), please PM me your email.

Zitat von reinhard;92836

...Removing the dash for this swap is not strictly necessary in a LHD car ........

Yes, I think on LHD cars the tubular brace does not interfere with the removal of the IHKA lid and heater core, and so the swap can be performed through keyhole surgery from the centre console opening. Though I think I'd prefer to have more room to work and see what I'm doing.

Zitat von reinhard;92836

...It also gives a one-time opportunity to take care of all those little things that have happened throughout the life span of the car if only to collect the stuff that somehow gets lost....

Yes, I'd previously found a MontBlanc pen !

I also took the opportunity to install a Nokia CK200 kit and upgrade the steering wheel to 3-spoke version, replace a few illumination bulbs, and generally give the interior a good clean and tidy-up.


Now that I've done it on my 840, it's been good practise for my Csi, which also has the same issue and then, next, my friend's 840.

Zitat von dennis320;92856

... Some of the flap motor mounting parts on my A/C sytem was broken strangely and we fixed them. But fixing doesn't work for one of them as we tried 3 times with different adhesives. The broken base part is upper left motor assembly on your pdf doc on page 33 item 19. That part holding the flap motors needs to be replaced and I want to be sure which part is that exactly?

I believe it is number 3 but I just wanted to be sure before take the board out ones more before I get the part. Can you identfy if its still open of if you remember?

It's sometimes difficult to interpret the diagrams from the parts catalogue. However, the motor that you indicated is mounted to the main casing, not the removable lid. The closest part that resembles that in the diagram is No.3, as it has the 4-section vent-opening above it, which links up to the dash board vents.

Updated Version

Attached below is an updated version of the document, which has a few minor items added and some additional clarifications to certain steps.

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Zitat von ukzero;92866

Excellent write up - Mr Haynes beware!

I had the "sickly smell when warm" when my car was still under warranty - the previous owner had paid dearly for this!
I took it to BMW who pressure tested the system and because I was "concerned" left it attached for most of a day. As no pressure drop at all and no sign of moisture they declared it as not leaking and would do no more.

Six years on I still get the smell when the heater comes on, especially first time of the cooler season, but still never have misting, damp patches and the smell has got no worse.

Any leak must be tiny and has not worsened, so I recon a leak sealant may be worth a go in this case. If not - I at least have a step by step guide ready

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I think that even a miniscule leak is sufficient to cause the smell. On my 840, I eventually had all the other symptoms as well (windscreen misting up, traces of coolant from the lower passenger air vent. etc), but the leak was still quite small and the cooling system would hold its pressure. Unfortuantely, during the replacement, I was in a hurry and I did not run the engine with the heater cover off to identify the leak precisely. However, it was apparent that the matrix was covered with a bluish (antifreeze) tinge in the top left quarter, even though there was no real apparent "hole" as such.

The new core does not smell at all, so there was definately a leak from the old one
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I had previously tried Bars leak sealant and although it initially seemed to reduce the smell, particulrly if the heater was being used regularly, in the end it didn't work. I think that the ground root-ginger particles in this sealer are not fine enough for the tiny leaks that tend to develop in the heater core. The other sealers like K-Seal contain copper particles with glass fibres (silica), and are more likely to work for the heater, but they are also more likely to clog-up other parts of the cooling system and leave your cooling system with copper coloured fluid.

If you've managed to remove the radio or the MID from the dash or even replace the steering wheel, then, removing the dash is of the same order of difficulty- it just takes a bit longer, that's all.

I too was daunted by previous posts on the subject and that's why I wanted to try all the alternatives first, but the job is no-where near as difficult as it may seem from looking at the pictures of all the wiring and internal parts of the dashboard. Most of those things just stay where they are.

With all the spare parts and tools ready, the whole job can be completed in one day.... and probably half that time with practise.