Peugeot 308 CC - Leaking again!

[xantia_v6]

After driving the car for another week, i can confirm that all the engine management and drivability issues are fixed.

It took a few days for the Ecu re-learn the characteristics of the wastegate control loop and throttle actuator. Acceleration is now smooth and predictable.

The car has now been put away for the winter.

First snow on the Southern Alps as we wait to fly out.

[CitroJim]

Excellent news Mike

[xantia_v6]

Grumble... Grumble... Grumble...

I was about to report how well the car is running (having covered about 600 km since the last repair), but today it decided that it was too boring to 'just work' and on the first decent run (60 km), after stopping the car briefly, the A/C decided that we did not really need to be cooled. it was about 30 degrees, and with the roof down, life was bearable. After the next stop, we got good cooling for about 2 minutes before it started blowing warm air again.

After getting home, I connected diagbox and after faffing around looking for the A/C parameters (they are in the BSI), came to the conclusion that there is no fault with the A/C but it is being commanded (by the engine ECU) to cut-off the compressor.

The engine ECU had its normal array of intermittent superknock faults (which seem to be best ignored), and a new permanent PO599, thermostat heater control circuit high fault.

Uncle Google tells me that this is a common fault with these engines and requires replacement of the thermostat housing. I have not really understood why the thermostat needs a heater, but apparently it does.

Next step is to try to find a local source for the part, probably from a BMW spares shop or dealer. The replacement operation looks suitably fiddly.

[CitroJim]

I must say this car really does seem to raise some most bizarre faults Mike. What on earth can go wrong with a thermostat housing?

[xantia_v6]

They look like this, and have the thermostat and 3 electrical components integrated...

[CitroJim]

They look like this, and have the thermostat and 3 electrical components integrated...

That's a bit silly So the senders cannot be replaced individually? That's terrible... What a shocking waste...

Good for BMW I guess.. Lots of profit from selling stuff that's not strictly necessary and an environmental nasty in throwing away stuff that with a bit of forethought could have been repaired..

Makes me rather angry and disgusted to be honest...

[RichardW]

DickieG had both these faults with his Daughter's C3 IIRC. The first he fixed by doing a BSI reset! The second required a new stat housing; I think the stat is electrically actuated, and it gives up in the end.

[Zelandeth]

Electrically actuated thermostat...just what...*why?!?*

Wax capsule thermostats have done just fine for the last 50 years and probably then some...

Bet that part ain't cheap either.

[xantia_v6]

There is a waxstat hidden in there.

Here is a quote gleaned from a BMW forum:

I have gleaned more info from a local BMW dealer. The thermostat apparently works in a conventional manner, that is to say it opens and closes with change in water temp. but...

In addition it is electrically controlled by the managment system according to throttle position ie load. When the engine needs to work hard the management systen will open the thermostat even more to supply additional cool water from the radiator.

The management control is done via a heating element, which is the part that fails.

[bobins]

So they've got a heating element to warm up a waxstat to cause the thermostat to open more. Is this progress ???

[Hell Razor5543]

Why not just have a controllable valve that can (when the load is great enough) open to allow for a greater flow? The wax thermostat would still do its' job.

[CitroJim]

What a load of old ....

[xantia_v6]

It is hard to see the benefit of such intensive management of the engine cooling. I read one report where someone substituted a 50 ohm resistor (not thermally connected to the cooling system) to eliminate the fault code, with no observable side effects.

BTW today the behaviour was the same as yesterday, from cold the A/C works normally for the first run (yesterday's 1 hour, today's 10 minutes), then after a hot start the A/C does not work at all.

I have ordered a replacement housing from the UK. At the price, it is unlikely to be genuine, but I have not read any reports of people having trouble with the cheap ones.

[RichardW]

They probably had trouble with the standard set up on test so added the additional cooling. Mind you, the 'test' was probably caning the arse off it in 40C heat up a big hill just after a big long downhill run that had closed off the stat - I would imagine that in all 'normal' use it will be fine with just a standard waxstat.

[xantia_v6]

I can confirm that the work-around by adding an external resistor seems to work. I had a rummage through the junk box and found a 47 Ohm 10 Watt resistor (probably salvaged from on old black and white TV about 40 years ago). I put some flying leads onto it, and connected it in place of the heater on the thermostat, and the A/C is now working reliably again. I will still fit the new thermostat assembly when it arrives, but that could be a couple of weeks away.

For anyone needing this in the future, the heater connector is item 'd' in the diagram below:

fair use of PSA documentation