C5 II runnig hot (overheating) when towing

[Romzi]

I don't think it's a coincidence the car's overheating and there's a reported fault with a coolant bypass valve.
I tried to google what this bypass valve does and read one explanation that it's to bypass the thermostat when the engine is under heavy load.

Can anyone confirm that?

[white exec]

Romzi,
Can you post your VIN number, so we can confirm exact engine, production date and cooling arrangement?
Thanks.

[Romzi]

Tnx.
VIN is VF7**************[VIN obfuscated, can be read by forum staff]
You're probably looking for this:

[MikeT]

Apparently they modified the housing to do away with the two solenoid valves (the other is a "degassing" valve).

"A" : Previous assembly.
"B" : New assembly.
The following parts have been discontinued :
(1) Venting electrovalve
(2) Degas pipes
(3) Bypass solenoid valve
(4) Coolant outlet housing (piloted thermostat)
The connectors of the following components are disconnected :
Bypass solenoid valve (at "a")
Coolant outlet housing (piloted thermostat) (at "b")
Venting electrovalve (at "c")
Replacement parts available :
(5) Coolant outlet housing
(6) Degassing pipe
3 plastic tie wraps
3 connector protectors
N.B. : The plastic tie-wraps and the connector protectors are fitted on the engine electrical harness connectors.
3. Additional operations
The elimination of these 2 solenoid valves results in the appearance of the following 2 fault codes which do not give rise to any customer complaints :
P1579 : Cooling circuit degas solenoid valve
P1597 : Cooling circuit by-pass electrovalve
If the 2 solenoid valves are absent : Ignore the presence of fault codes P1579 and P1597.

[white exec]

That looks to be the answer, or certainly a very sensible mod/update.
The EV was ditched for a reason.
Let us know how you get on, Romzi.

[Romzi]

I just checked under the hood. I have the older type with 2 solenoids.
So if i understand it right: the best option is to convert to newer (and simpler) design?
The only thing i don't understand is how the f..... cooling is working at all?

[GiveMeABreak]

So your build date was 2 October 2004 (10190) and that mod was made to vehicles produced from 27 February 2005 (10338). So if you still have those parts the fault could still be relevant, unless you've had the modification in which case it's a ghost.

It's great when things are simple like this...

[white exec]

Looks like you'll simply need to replace the complete water outlet tank with the later type...

You'll need the studs, #9 and #10.
Does that housing come complete with its thermostat?

[Romzi]

Replaced the thermostat. Not very nice job.
So far so good, I will know more when I'll be towing again.

[EDC5]

Good to hear.

It seems strange that Citroen removed the two solenoid valves instead of working the issues out and solving the problem. I assume there were practical reasons for fitting these valves in the first place!

It sounds similar to the coolant level sensors that were present on early 407 and mk2 C5's. They caused issues and were removed completely from later builds rather than being re-engineered to solve said problem.

[white exec]

I wonder whether someone, somewhere in the organisation simply decided that as many mechanical devices as possible should be replaced with electrical/ECU servo units, and so . . .
Just glad they didn't get as far as digital timing belts!

Let us know how things go, Romzi.

[GiveMeABreak]

^ Something tells me Chris is a die hard Hammer & Tongs chap!

Now, where are those suspension calculation curve diagrams I was looking for.....

[white exec]

The ultimate insult! No, I'm all for electronic control (I do run an XM, after all), but willy-nilly electrification of hydropneumatic and fluid flow functions doesn't always seem justified. Take, for example, the electric motor driven suspension pump on C5, which clogs then combusts itself. How many 6+2 engine-driven pumps did this?

If it was broke, then it deserved fixing, of course.
But just to shave 0.05% off the fuel consumption figure, p-l-e-a-s-e !

[GiveMeABreak]

I know - but everything on our cars now has to be recycled into loin cloths at some point, for when we run out of natural resources. Just look at how much plastic there is under the engine nowadays - and what little metal there is is destined to rot very quickly it seems.

[EDC5]

I wonder whether someone, somewhere in the organisation simply decided that as many mechanical devices as possible should be replaced with electrical/ECU servo units, and

I think you've got a point here, PSA cars have always had loads of electronics on them when other manufacturers still did things in an analogue or mechanical way.

Still, I'd like to see their justification for fitting the degassing and coolant bypass valve as I'm sure some engineer must have been very proud of his innovations.

Take, for example, the electric motor driven suspension pump on C5, which clogs then combusts itself. How many 6+2 engine-driven pumps did this?

If it was broke, then it deserved fixing, of course.
But just to shave 0.05% off the fuel consumption figure, p-l-e-a-s-e !

I'm not definitely sure but I think spilling of LDS on to the suspension motor is what precipitates the problem; the gunk in mine when I cleaned it was definitely oily.

What I don't understand is that on the X7 there are two electro-hydraulic pumps directly on top of each other. One for the steering and one for the suspension, surely it would be better to have one engine driven pump for both... it's just neater in my view.