2.5 heater matrix replacement

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White Exec
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Orga / RP numbers: RP7165
1996 2.5TD saloon, Exclusive, Polar White
1992 BX19D Millesime, Sable Phenicien
Location: ex-Ealing, Cheshire, W.Sussex & Surrey. Now living in Sayalonga (Malaga, Spain)

2.5 heater matrix replacement

Post by White Exec » Fri Dec 01, 2017 9:58 am

Having replaced the two tired-looking long coolant heater feed hoses from engine to bulkhead, I still have a slight smell of coolant in the cabin. Checked yesterday on the matrix connector, suspecting the O-rings there, but found the clamp-connector nice and dry, with no signs of leakage.

Must now bite the bullet and replace the matrix itself. Smell is boosted by the blower, so guess the matrix itself has a weep. Carpets and underneath all dry, for the moment.

Have already laid in a spare (Nissens), and read up on the excellent self-help posts about getting old one out and new one in. Another contortionist job, probably for next week.
Chris
1996 XM 2.5TD Exclusive RP7165 Polar White
1992 BX19D Millesime RP5800 Sable
1989 BX19RD Delage Red Deceased; 1998 ZX 1.9D Avantage auto Triton Green Company car 1998..2001; 2001 Xantia 1.8i auto Wicked Red Company car 2001..2003

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raynoon
Could do a 2.1 headgasket
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Re: 2.5 heater matrix replacement

Post by raynoon » Fri Dec 01, 2017 5:40 pm

Best of luck with that task. All these problems that could arise are starting to worry me slightly.
1993 Citroen XM 2.1 turboSD auto
1995 Citroen XM 2.1TD Auto EXCLUSIVE

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White Exec
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Posts: 6642
Joined: Fri Mar 11, 2011 7:38 pm
Orga / RP numbers: RP7165
1996 2.5TD saloon, Exclusive, Polar White
1992 BX19D Millesime, Sable Phenicien
Location: ex-Ealing, Cheshire, W.Sussex & Surrey. Now living in Sayalonga (Malaga, Spain)

Re: 2.5 heater matrix replacement

Post by White Exec » Sat Dec 02, 2017 5:25 pm

I know a few of these have been repaired recently.
Does anyone know the exact size of the two O-rings ? (6467 40 NFP, but no dimensions; same part across all XMs)
Best I can find is Will's recollection of 22x3, and an old Ebay ad which said 16.5 ID.

Looking at the new matrix, there are two circular grooves on each port: inner one (with raised positioning lug), and a larger outer one. Which one does the O-ring sit in?
Chris
1996 XM 2.5TD Exclusive RP7165 Polar White
1992 BX19D Millesime RP5800 Sable
1989 BX19RD Delage Red Deceased; 1998 ZX 1.9D Avantage auto Triton Green Company car 1998..2001; 2001 Xantia 1.8i auto Wicked Red Company car 2001..2003

xmexclusive
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Re: 2.5 heater matrix replacement

Post by xmexclusive » Sat Dec 02, 2017 7:34 pm

Hi Chris

Been trying to select a better size before I attack the car as one of mine is leaking.
I make the original size ID 21.5mm by Dia 1.5mm, that gives 25mm OD fitted as the pipe is 22mm Dia.
Have a recovered matrix and a pair of pipes and have tried a few variations.
The last one was 20 by 3mm which fits the pipe well but the ring is too thick to fit into the matrix holes.
It gives around 27.5mm OD fitted.

Have just ordered up some 21 by 2mm which should give around 25.5mm OD fitted and an extra 0.5mm ring length over the original.
I am hoping that will increase the seal I get.
They should turn up in the week so I will try them and let you know.

PeterN mentioned that he found putting two rings on the pipe made sure of a seal.

The pipes and matrix sockets have half moon locators.
It is important that the pipes are rotated to get these to locate correctly.
Doing so brings the clamp bulge on the pipe parallel with the matrix face so an even clamp force around the o ring.

John.

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White Exec
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Joined: Fri Mar 11, 2011 7:38 pm
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Location: ex-Ealing, Cheshire, W.Sussex & Surrey. Now living in Sayalonga (Malaga, Spain)

Re: 2.5 heater matrix replacement

Post by White Exec » Sat Dec 02, 2017 9:39 pm

Hi John,

Thanks for checking all that out, and so quickly.
Have been verniering up my new matrix, along with a collection of new O-rings and a short length of 22mm Cu pipe.
Agree with your dimensions.
22mm pipe drops into the lower bore, astride the half-moon lug.
Diameter of O-ring recess is 25.5mm.

A 1.50mm O-ring is too loose a fit.
A 2.50mm ring is too chubby.

I didn't have a 2.00mm, but had a couple at 1.80mm.
These are a gentle interference fit in the gap, but have no squash, and also don't look as if they fill the depth of the ring recess enough to be compressed by the plate. I don't have a plate to play with, but I'm assuming it's flat - or does it have a raised ring to press down on the O-ring?

Your guess of a 21x2mm O-ring is probably right for the job.
What I wonder, though, is whether it'll have enough depth.
Is it possible that the OE rings were tubular, not round in cross-section - ie had a bit more length.
Could Peter therefore have been doing the right thing in using two rings on top of each other?

Note also that the (Nissens) O-ring recess is tapered/chamfered. Is this to allow a chubby ring to be crushed in, or to accommodate a metal protrusion on the clamp plate?

At least a tube of Hylomar Blue arrived today, from Scotland.
Chris
1996 XM 2.5TD Exclusive RP7165 Polar White
1992 BX19D Millesime RP5800 Sable
1989 BX19RD Delage Red Deceased; 1998 ZX 1.9D Avantage auto Triton Green Company car 1998..2001; 2001 Xantia 1.8i auto Wicked Red Company car 2001..2003

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Re: 2.5 heater matrix replacement

Post by xmexclusive » Sat Dec 02, 2017 10:48 pm

Hi Chris

There are two types of clamp plate.
The early type is "H" shaped flat plate and clamps each tube only half way round.
I throw any of these in the scrap.
I think clamping only half an "O" ring is asking for trouble.
The later type are a complete figure of "8" clamping the full circle of both "O" rings.
The "8" clamp block is cast with raised pressure rings to load the clamp bulge on the pipes.
It also has six locating projections, pairs either side of each of the pipes and a further pair either side of the clamp bolt.
None of these locating projections are very tall and all if a little miss aligned can catch on the plastic surround of the heater matrix.
Not easy to check all this as you fit the pipes to the matrix but once pushed together correctly everything is captive and aligned.
Not keen on the double O ring solution as the extra 1.5mm holds the locating projections just apart as you try to line everything up.
Hence my search for an O ring that is an extra 0.5mm larger rubber diameter.

The taper you have spotted in the matrix ports closes with the clamp bulge as the assembly is fully tightened.
There is at the end of the taper a further 1.5mm parallel section which is where the O ring sits.
So no great compression of the standard O ring even when everything is lined and bolted up.
I am hoping the extra half a mm will tighten things up just right.
Spent nearly £2.50 inc post on fifty O rings so I hope it works out.

John

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White Exec
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Joined: Fri Mar 11, 2011 7:38 pm
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1992 BX19D Millesime, Sable Phenicien
Location: ex-Ealing, Cheshire, W.Sussex & Surrey. Now living in Sayalonga (Malaga, Spain)

Re: 2.5 heater matrix replacement

Post by White Exec » Sun Dec 03, 2017 8:49 am

Hi John,

Thanks for confirming all that detail.
Reassuring that the pipe ridges engage with the taper and compress the O-ring.
Agree that a 2mm ring should be better. It will elongate a little when sandwiched in its groove, and that will help compression further.
If I can't find any locally, I'll order some from Polymax.
Chris
1996 XM 2.5TD Exclusive RP7165 Polar White
1992 BX19D Millesime RP5800 Sable
1989 BX19RD Delage Red Deceased; 1998 ZX 1.9D Avantage auto Triton Green Company car 1998..2001; 2001 Xantia 1.8i auto Wicked Red Company car 2001..2003

User avatar
White Exec
Citroen God!
Posts: 6642
Joined: Fri Mar 11, 2011 7:38 pm
Orga / RP numbers: RP7165
1996 2.5TD saloon, Exclusive, Polar White
1992 BX19D Millesime, Sable Phenicien
Location: ex-Ealing, Cheshire, W.Sussex & Surrey. Now living in Sayalonga (Malaga, Spain)

Re: 2.5 heater matrix replacement

Post by White Exec » Sun Dec 03, 2017 1:02 pm

Bit of progress this morning: O-ring stockist located in Malaga, so will try to collect some 21x2mm etc tomorrow.
O-rings in Spanish are juntas toricas, I discover.
Chris
1996 XM 2.5TD Exclusive RP7165 Polar White
1992 BX19D Millesime RP5800 Sable
1989 BX19RD Delage Red Deceased; 1998 ZX 1.9D Avantage auto Triton Green Company car 1998..2001; 2001 Xantia 1.8i auto Wicked Red Company car 2001..2003

User avatar
White Exec
Citroen God!
Posts: 6642
Joined: Fri Mar 11, 2011 7:38 pm
Orga / RP numbers: RP7165
1996 2.5TD saloon, Exclusive, Polar White
1992 BX19D Millesime, Sable Phenicien
Location: ex-Ealing, Cheshire, W.Sussex & Surrey. Now living in Sayalonga (Malaga, Spain)

Re: 2.5 heater matrix replacement

Post by White Exec » Mon Dec 04, 2017 1:46 pm

Picked up a few of each of 20x2, 21x2 and 22x2mm from Malaga.
Checked with a short length of 22mm Cu pipe, with a half-moon notch in its end:
21x2 looks a snug enough fit, with just a bit of squash;
22x2 works as well too, minutely tighter fit, but not a lot in it.

Will tackle the job on Thursday. Citroen PRO coolant has a very distinctive smell - just like Fernox c.h. anti-corrosion fluid.
Chris
1996 XM 2.5TD Exclusive RP7165 Polar White
1992 BX19D Millesime RP5800 Sable
1989 BX19RD Delage Red Deceased; 1998 ZX 1.9D Avantage auto Triton Green Company car 1998..2001; 2001 Xantia 1.8i auto Wicked Red Company car 2001..2003

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Re: 2.5 heater matrix replacement

Post by xmexclusive » Tue Dec 05, 2017 12:11 pm

Been trying the 21x2mm rings which arrived this morning.
I think the prize goes to PeterN.
Using an actual pipe, bolt, clamp and heater matrix out on the desk was instructive.
Any ring more of 3mm dia does not allow the pipe to seat.
Did not have 2.5mm dia ring to try but consider an oval or narrow oblong ring would be best fit for a single ring.
Original ring or a single 2mm dia one gives virtually no seal compression before the bolt is fully tight.
The extra 2mm "O" ring seats well and the clamp closes to virtually the same position as with a single "O" ring.
The clamp locking up with uneven or incomplete compression of the single "O" ring may well explain the frequent leakage problems.
It is not unknown for leaks after heater replacement but it can take time to notice unless you have a very good sense of smell.
The coolant finds its way behind the centre console panel into the sponge under the drivers foot well carpet.
It takes a very large amount of coolant loss this way before the carpet shows as wet.
When it does the wetness tends to be mainly behind the rear centre of the carpet plastic foot tray.
Well away from source.

John

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