C5 X7 2010 HDI heating problem. Another one.

[N1k4_99]

Hi, I took a look at these similar topics:
https://www.frenchcarforum.co.uk/forum/ ... hp?t=72851 (Does not have a Webasto)
https://www.frenchcarforum.co.uk/forum/ ... hp?t=70137 (Pipes that goes to/from matrix get hot)
The problem (and the solution) could be the same, however - I decided to make another topic, as there are some differences...

The car:
Citroen C5 X7, 2010., 2.0HDI, (automatic - although I doubt that is relevant) with Webasto (the remote has a Citroen logo, so I assume that it is not additionally installed).
Dual zone A/C system.

The problem:
The cabin heating is not working. At all.

The history:
I bought the car in July this year (2022). As the weather got colder, I noticed that the heating is mildly warm, even if the cabin temp is set to max.
In the beginning, I was able to get the relatively warm air inflow by revving the car in neutral to 3-3500 rpm for 15-20 sec. As soon as I let the revs go down - the air flow was back to slightly warmish.
Also - I was able to get the warm air inflow when I start the Webasto. 15-20 second after starting it - the air inflow would be almost hot. As soon as I turn it off - the air inflow temp was back to almost cold.
However - at some point - after experimenting with webasto and turning it off - The air inflow temperature was measurably higher (like 3/5 of hot). The temp was set to max.
When the mornings got colder - I started the Webasto again, but the temperature was not rising at all. Even this 3/5 temp can not be reached anymore.
For a few days - no matter if I set the temp to Min or Max (Both Driver's and Passenger's) - the air inflow temp does not change at all. Not even warmish.

Additional info:
Coolant level is normal.
I would exclude the thermostat problem, as the car gets warm in time, and the coolant temp indicator stays at 6 or 7 lines, even if I get on a highway and drive 120-130 km/h.
The hoses that lead to the radiator and back to the engine are both very warm, almost can't keep my hand on them.
The hoses that go into the cabin to the matrix are noticeably colder. The right one (looking at the cabin) is relatively warm, the left one (that has a bleeding cap on it) is a bit colder than the right one.

If I hadn't managed to get the temp by firing the Webasto, and if I hadn't had the so-so warm (mentioned subjective "3/5") air inflow for a short period, I would suspect the Matrix, but this short improvement confuses me.

Unlike "ExOduS442xb" - I have a Webasto, and this is a main reason why I made another topic, as the problems/solution might be different.
Unlike "mihkel" who has Webasto - my hoses that go into matrix are mild warm.

Could Webasto somehow "block" the flow of the coolant towards the Matrics?

Is Webasto connected "Inline" or "Parallel" with cabin matrix?

And not less important: Is it possible to replace a cabin matrix (if needed) without disassembling half of the car (yes - I am aware that this is a French car - but I can hope - can't I?)

Cheers,
Nika

p.s. - I suppose it will come down to Mark's reply in this other topic: "It's possible you have a blocked heater matrix or a faulty air mixing distribution motor / flap. Having said that, the flaps and motors on the C5 X7 (MK III) are far more reliable than the MK I or MK II, so I would be looking to get the coolant system checked, possibly flushed out and changed." - but I just want to exclude the Webasto from the equation...
p.s.s. - Thank you Mark for your activity on this forum. I was looking for some info from time to time, and every third post was yours. Respect.

[mihkel]

Hey! "Great" to see that we have more of these problems. Hope we'll get to the root of the problems quicker.

I'll leave you two schemes of 2.0 HDI coolant hoses. From here it seems that the aux heater is connected in series so all the heating coolant flows through it.

[N1k4_99]

Hi Mihkel,
thanks for the answer.
If I read the schema correct, my type has hose "9", and the model without webasto has hose "11"?
I red your post also - so I took my side panel and tried to feel the temperature of the pipes that goes into matrix.
One is hot that i was burned myself, and the other one was slightly warmer then my hand.
So I am quite convinced that blocket matrix is my problem...

I will try to wash it with a underpressure water.

Can anyone confirm that it is possible to replace the matrix fairly easy, without dissasembling half of the car?

Cheers

[Ross_K]

Hi Nika, for replacing the matrix Mihkel posted a link to a Russian site in his topic.

It seems to be missing some pictures, but the steps are described

According to this post the replacement of the heater matrix is quite straight forward:
https://www.drive2.ru/l/537905828393387441/

Google translate does wonders when English sites do not have any information on the job at hand

[N1k4_99]

Hi Ross,

thank you for the tip.
And thanks to Mihel for finding this Russian topic.
In the meantime, I managed to find the Video tutorial as well...



I have to remove my side panel again to take another look - why did he disassemble half of the car, when he is cutting the metal plate anyway.
There must be some catch.
In my wild dreams, the cutting makes enough room to take out the matrix, so the removing of the side panel would be enough...

Cheers,
Nika

[Ross_K]

Thanks for sharing that video. Nice solution!

I guess he had to remove the lower console around the gear shifter because the support bracket isn't fully accessible by removing just the side panel? It looks like one piece which requires the radio etc to be removed first. it probably doesn't add that much time to the job

[Ross_K]

I like how the Peugeot 508 uses a two-piece bracket in the same place

The Citroen engineers like to do things the hard way

[N1k4_99]

... A quick update: I tried to flush the cooling system. I bought a "Bardahl" dedicated fluid for this purpose.

Steps that I did:
- drained the Antifreeze;
- disconnected two hoses from the matrix;
- connected the hose with the tap water to the inlet pipe, and washed it out. Repeated the procedure with the Outlet pipe and again... The water was so dirty in the begining, that I thaught that alone will be enough. After a minute, when the water was clear enough - I connected tap water to two matrix hoses, to flush the rest of the system. Also the Expansion tank;
- Filled the Washing fluid with tap water, and drove the car for a couple of kilometers manually in second gear at 3000 rpm;
- Very soon the heating was available in the cabin, not hot but warm enough after those freezing days;
- I drained the fluid, washed it with tap water, and put the antifreeze in.

And - the cabin heating was not working. As before.

Then I drove in manual mode at 3000 rpm again - and the heating started.
If I keep it at 1500+ revs, the heating is available (not hot, but available).
As soon as the rpms drop bellow 1500 rpm, very soon the heating is not available...
(All of this tested yesterday on my way home and this morning on my way to work)

I start to suspect that I had 2 problems (and the first one was at least partially solved). The second one is related to the fluid flow. At low revs, the flow through the matrix is low.
(It looks like I could make a poem about this...
When the rews are low,
I have a problem with the flow,
as it's trought the matrix slow...)
Sigh.
Reasons?
Water pump?
The temperature indicator does not show anything abnormal. Even in the summer, there were no more than 6-7 strips when the car is warm. I do have a subjective feeling that it is getting warm rather slow, but I am mostly driving downhill on my way to work. And my mechanic (and a good friend of mine) tells me that 2.0HDI does take some time to get to an operating temperature...

I was flushing the cooling system yesterday after work, so I didn't have time to remove the side panel again to check the temperature of in/outlet matrix pipes - I will do it today. Quite curious what will I find out, as last time the inlet was hot, and the outlet was hardly warmer than my hand... As the garbage was exorcised from the matrix, I expect the outlet pipe to be at similar temperature as inlet. And that leaves the open question - what will the inlet temperature be at low revs (idle) when the car is warm...?

p.s. - last preview before the "Submit": "... A quick update:"... And people say that I am not much of a talker...

[mihkel]

It's not that uncommon for water pumps to fail on some cars - impeller losing its blades or just not spinning anymore (loose on the shaft).

I would start by getting temperature readings from the hoses. You can see some reference numbers from my thread on two cars viewtopic.php?t=70137 IR temperature gun won't show any good numbers on the aluminium pipes to the heater core so you should measure the rubber ones going to the cabin. I'm seeing that 5-10*C drop across the heater core would me maximum. Anything more and it still might be clogged. The engine temperature for the HDI should be 83*C and that's 7 strips on the cluster.

I opened up my heater radiator and I could see some residue in it which I think won't be flushed out.

[N1k4_99]

Thanks Mihkel,
I'll experiment a littlebit during weekend...
Cheers,
N