Mystery Mist

[addo]

How are you fitting the seals?

Normally you seat them in the matrix bores with rubber grease or petroleum jelly, lightly grease the incoming pipes and then it's just like riding a bike... I'm wondering if you're fitting the seals to the alloy pipes first, and they're not then conforming properly in the matrix head.

[407iain]

My new 407 mists up a bit. I'm currently putting it down to the leather interior and the weather. One day it can seem fine, then as soon as we get either a sudden rise or fall in the temperature it mists up!, I've checked the old 406 favourite leaky lights, al the carpets and nothing. If it still does it in a few months time in the warmer, hopefully drier weather it will be going back a long with a moan.

Sent from my lt901 using Tapatalk

[evilally]

Hi Addo, spent another couple of hours this afternoon and did as you suggested, o rings seated in the matrix first with a little silicon grease. This is how it looked:



....the very second the engine was running there was a waterfall in the foot well. I haven't a clue what I'm doing wrong

[spider]

That's odd

As although there's two matrix's and two pipes sets depending on build, the seals are the same for them: 646240 , assume these are the seals you were supplied with ?

The pipes not twisted or damaged at their ends no ?

[evilally]

This is an "AVA" pattern part which is equivalent to the part number I got off of Servicebox (there were 2 listed but I checked the build code). The O rings supplied were too small, which I didn't think anything of at the time, I just got a new set from the dealer. However the fittings look identical to the Valeo one that I took off. I did attempt to refit the Valeo to see if it was an issue with the pattern part matrix, but I got the same problem Pipes not damaged and look fine.

Either it's a crap design or I'm not very clever, or a combination of both Another day tomorrow with no heating

[spider]

I wish I could think of something else to help, there's not really anything else there just those o-rings as far as I remember. A distorted pipe would be obvious hopefully and you've double checked that. Hmm.

[ACTIVE8]

The sign as you know is the click click from behind the glovebox. In theory the dash comes out for it but everyone just used to snap a piece of plastic off to get at it to 'fix' once you'd pulled the glovebox out.

Shame they went from the lever/cable to the button recirc on / off as the early cable ones (only models without AC) never failed.

Recirc motors are reasonably common, I'd jam it open so its always fresh and unplug it or remove it personally.

If only it was this easy to this job on an Xantia!

Cables long life, and better.

Motors/servos in effect it's like radio control, although with a wire link, and no radio connection.

Obviously it helps with the dash design, as wiring can be routed in a way that a cable cannot, but the demise of the use of cables causes different problems.

[spider]

Any luck so far ?

[evilally]

Hi Andy, got so fed up with it I abandoned it for the week. Will get back to it over the weekend and report back. I notice the same matrix and fittings are used in some kinds of Landrovers. The Landrover boys seem to have this issue a lot, to the extent that some have replaced it with a matrix with conventional rubber hoses.

[spider]

Ah OK.

The only other idea is another set of pipes from a donor, there is not really a lot else it could be.

I think the LR has its own series (no pun intended) of demisting issues, I recall the 'round' type heater was the one to replace or vice-versa and bad coolant in the later models would zap the matrix too. Either that or vibration.

[evilally]

A small step closer, I currently have 3 matrices on the go, I'll break this down:

I originally ordered a Nissens matrix from a seller on ebay. What turned up was an AVA brand matrix. The seller says logos and brand names are "for reference only" At any rate, it's complete junk, arrived damaged and was supplied with the wrong O rings. It has half as many fins as the Valeo, and the heater output is definitely impaired as a result. The first issue was I couldn't get it to seal at the pipe unions, even with new OE O rings. I have figured this out however. It turns out, the pipe unions are a little deeper on this pattern part. What was happening was that the O ring sat too far forward, and wasn't sitting above the little locating cut-outs on the pipe, hence the leak. I solved this by fitting the old O ring first, then the new one on top. This spaced the new one forward suitably to make a seal. However with me taking it in and out and lot and generally man handling it, I've cracked the plastic, so it's a write off.

Second one up is a Nissens one I ordered elsewhere. This is far better quality and has more fins (although not as many as the OE). However can you spot the problem:



....the pipe connectors on the Nissens sit at the wrong angle, and as such it is impossible for the pipes to engage properly. I'll be returning this item for a refund.

For the time being I have refitted the old Valeo. I have used the double O ring method which I think is a good idea. On the Valeo, the second O ring sits slightly proud of the housing and is compressed into place when tightened up. This will likely make a better seal. The core seems fine and the leak seems to be where the plastic is bonded to the metal. I am considering putting it in to a local radiator place for reconditioning, as pattern parts seem hopeless.

[evilally]

I thought I'd update this, in case it helps someone else Googling in the years to come.

I finally sourced a Valeo replacement from AEP direct. It came special order from Valeo for £55 delivered. Slightly more expensive than your average pattern part, but trust me, it's worth every penny. It's sealed up no problem (I fitted 2 O rings per pipe just to be cautious).

The AVA pattern part has half as many fins and heater output is impaired. The first step on the pipe connectors is too deep meaning the O ring does not sit above the cutout on the pipe and the whole things leaks like mad. Likely it would seal if you fit 2 O rings, the first acting as a spacer, but me man handling it in and out cracked the plastic (it was of inferior quality to the Valeo), so I couldn't prove this. Ended up in the bin, waste of £33.

The Nissens was much better quality than the AVA, but still did not have the fin density of the Valeo. A design problem seems to be that the pipe connectors are not at the correct angle, engaging the alloy pipes with them is impossible, at least on the 406 at any rate. Seller accepted this as a fault and refunded me.

So moral of the story is, just pay the extra £20 and get the Valeo