BXProject

[Vanny]

Well as part of the effort to get the car back on the road, Jay and i took the opportunity to dismantle not just 1 but three knackered heater taps. After some head scratching and brute force, this is what we found;

This is Mickeys knackered heater tap;



Evidently someone had been at it with the K-seal and totally filled the coolant with 'sand' for a bit of a laugh. Once we eventually dismantled the one on my car, we found much the same. Indeed the car had two pots of K-seal when it was a diesel in a vague hope to cure the blown head. Clearly all that happened is that the K-seal 'powder' collected in the heater matrix and tap.

A sort of before and after;



The sand quite literally gets everywhere;



The full dissection with all the parts out;



For the most part, it looks rather like the tap can be readily stripped down and rebuilt. It turns out the sliders are actually ceramic (presumably to stop expansion in the hot), and these are probably the hardest bits to replace.

So a word of warning, DON'T use K-Seal/Rad Weld or similar without at least by passing the cabin heater circuit. And don't force that dial on the dash, if it's stuck its stuck for a reason, and if you snap the lug off the ceramic slider, your stuffed!

[Philhod]

The sand was an old trick. you used to put fine sand and soda in, before there were flushing agents. Get it hot, allow to cool a bit, then remove top and btm hoses. leave a running hosepipe in the top oriface for 1/2 an hour and take the rad off and flush it separately. Clean as a vicars laundry

[docchevron132]

since taps aint been available for ages, thi is the only way now.. I assume the slider has an O ring seal or such?
Cant say I've ever bothered to strip one out!

[Vanny]

Slider has no seal as such, inlet and outlet ports have seals as does the seal between valve case halves.

[Vanny]

Re not using the rad weld, I did it out of desperation. I drove 11 miles with a burst coolant pipe, while towing another car, mostly up hill. In fact the car only stopped because the battery ran out having been on max fans with a dodgy alternator. She did manage another 1000 miles on the rad weld though.

As a useful tip, the brass tubes are peened over at both ends to hold the body together. You need to pull these apart which takes a scary amount of force. You would be well advised to drill holes through the flanges around the case join so that you can bolt the two halves together after rebuild. I suspect alot of swear will ensue if you drop the damn thing mid way to refitting!

[jayw]

I suspect alot of swear will ensue if you drop the damn thing mid way to refitting!

I concur!

[docchevron132]

Slider has no seal as such, inlet and outlet ports have seals as does the seal between valve case halves.

interesting! Must get me some seals then, there's 4 here that are leaking like cunts..

[mat_the_cat]

Bugger. Have just noticed that my tap is leaking today. Fortunately I have a spare, but I'd rather have found out before I refilled with fresh coolant. How much of a ballache is it to take the tap off; does it need all bits removed as in this picture?

[Vanny]

All the bits in that picture come out in one piece. They mate onto the heat core. Normally the leak is between the heater core and the tap if the tap hasn't been done any un due force. In my case the joint between the pipes and the tap block was leaking so needed a full strip down. It was leaking due to it having previously been forced against particulate build up, the 'lever' to push the slider up and down actually leavers the tap and the pipe sections APART and forces the leak.

So the obvious question, have you forced it?

They really shouldn't leak unless they are damaged mechanically by the user. If it is the Hcore/tap union that is leaking then you can potentially separate them, clean and reseal all in situ (well without removing them entirely from the car)

[mat_the_cat]

Have I forced it? No, but…..
Yesterday I had the heater front panel off to solve an earthing problem - now sorted. When I put the knobs back on I thought the temp. knob seemed a little stiffer than I remembered, but didn't think anything of it. I wouldn't have described it as excessively stiff, , just MAYBE not quite as easy as I thought. Now I'm wondering if it's more than coincidence.

Looks like the leak is between the tap and the matrix pipes - unless from where the tap lever comes out the top of the tap. Are you saying that if it's just a leak from between tap and matrix, those 2 round seals can be taken out, cleaned and it all screwed back together without having to actually replace them with new? Think I've found the part no. for them, 95610724 so may try and buy some anyway.

If it is the tap itself that's leaking, then I could pinch the tap off the spares car but that might be just making work for myself. I just can't see why a seal would suddenly start leaking though.

EDIT - It looks like the tap to matrix seals actually sit directly between the ceramic sliders and matrix moulding. I did move the heater knob backwards and forwards several times yesterday, to see if it freed off so they would have seen more movement than they had for the previous few months. Maybe there was a bit of crap present and it's damaged one of them?

After a spot of phoning around it appears as though the O ring style seals are NLA. So I have 3 options - reinstate the seals (after cleaning & silicone grease) that are currently leaking, whip the seals out of the spare car, and hope that they're better, or try and match up with a similar sized round section O ring. I've got a boxed set, which proudly claims to have "a selection of common sizes to suit most applications". In the several years I've had it, the O rings have been exactly the wrong size for everything I've ever needed one for.

Do they normally not need replacing when you change the heater matrix then?

[Vanny]

they should be replaced when changing the matrix. The tap to matrix seals sit in the moulded housing and do NOT touch the ceramic slider.

There not a standard metric size (i bought a box of metric rubbers, non fitted), but i think the master Jay just reassembled with a healthy smear of silicon.

[jayw]

I did indeed give all surfaces a light smear of silicone (avoiding the moving parts) and let it go off lightly assembled then bolted it all up. Et Voila!

But vanny's right, all the O rings in his generous set were too big or the smaller ones once stretched were too thin.

I think that as the housing is quite flexible plastic and only bolted at the corners, when the crap get forced behind the sliders it allows the longer sides of the tap to bulge breaking the seal. Hence i drilled a hole theough either side of the long flanges and bolted the tap together with small bolts.

Everyone should be careful with forcing it when the knob goes tight as the lug on the top of the ceramic slider is quite delicate and easily broken. So, if your knob is floppy by the tap appears to physically work at the plunger on top it's probably the lug that's broken off.

[Philhod]

Any of the hydraulic pipe companies will have a match. The guys I mean make up replacement units for all sorts of applications and have sorted awkward fittings for me in the past.

[mat_the_cat]

Well, the guy who's selling a shedload of NOS bits over on BXC has a set, for £3.50 delivered. Better than the £11 plus VAT that Citroen wanted even if they could still get them. Normally I'd agree with you Phil, but the nearest half decent engineering merchants (and they're pretty farming specific so mainly bigger stuff) is still a 60 mile round trip!

That said, it was weeping a bit after I set off from work, but then I dried it, and checked the 4 through bolts were tight. I basically just cracked them all clockwise, and no more drips. I struggle to believe that I've sorted it, but will check later tonight

[mat_the_cat]

Nope, a drip has appeared, but not actually fallen in the 4 hours since I parked up. I reckon the leak is so small it just evaporates when the coolant is warm.

I think that as the housing is quite flexible plastic and only bolted at the corners, when the crap get forced behind the sliders it allows the longer sides of the tap to bulge breaking the seal.

As mine is leaking from the tap to matrix seals (it appears) are you saying that flexing of the tap body can disturb these seals too? Or just the large seal between the two halves of the tap body? I did replace one of the braided hoses under the bonnet the week previously, so some force will have been applied to the end of the tap behind the block. Maybe that's just flexed things and broken the seal.

I tend to use silicone grease for O rings and the like, rather than a sealant. I suppose that could also be used for the moving parts.

Everyone should be careful with forcing it when the knob goes tight

Good advice, and that is something I always follow.

[Philhod]

The ones I mean are mainly Hydraulics specialists Mat. With not living in a foreign land I have 2 on my doorstep here.
You don't need to buy guesswork kits they even sell singles for a few pence. It probably costs more for all the paper that comes with it.

[mat_the_cat]

Yeah, I know the ones. Was a good one in Gloucester only a few minutes walk away - generally if you just went in for one O ring they'd give it to you, wasn't worth the time bothering with that cumbersome paperwork business...

[jayw]

These seals are completely different to anything used in the hydraulics business, more like elastic bands than any seals i've ever seen.

[Philhod]

They carry everything you ever saw Jay. I even got a replacement for the inside the tube where the splined bits go together in the BX 4X4 g/box It looks like an ordinary O ring about 2" dia but the section is less than 1/16 dia where it would be around an 1/8.usually.

[mat_the_cat]

Bit of an update to this - I recieved the new tap to matrix seal yesterday and set about changing them. Part way though I had a nagging doubt that it was actually leaking from the tap itself (I previously thought it was simply running downhill and collecting in the seam, but it was difficult to tell which way was downhill!)

When I loosened the 4 long bolts the two halves of the tap could move relative to each other enough for a gush of coolant to come out into my hair, so I thought I'd best replace the whole tap. Took 7 hours in all, including removing the replacement tap and spending ages trying to remember where I'd put my entire collection of 7mm sockets. My mood was not improved when I fitted the 'new' tap and realised one of the linkages was not jammed up in the wrong direction into the bulkhead soundproofing. Conclusion - it wouldn't be a bad job apart from the control cables, and the fact it was raining.

I feel your pain Vanny, having to do it all over again!