C4 GP II 2014 BlueHDI 150 thermostat issue

[LVII]

First post here, be kind .

I need some help with my C4 Grand Picasso 2014 with a BlueHDI 150 engine.

I got some thermostat related codes (stuck bypass motor) and replaced the thermostat with a new one. I flushed the system and after refilling bled air from the thermostat housing bleed screw and the heater core bleed screw and followed the bleed procedures listed in the members section.

After this the engine warmed up very slowly, and started to drop in temperature when coasting. The drop during coasting was significant (80C -> 60C). Tried bleeding air out but no change. Figured out this was a stuck-open thermostat, as i did not buy a genuine OEM part.

Fired the parts cannon again and bought a new thermostat thinking i'll return the first faulty one - but got pretty much identical results after changing another thermostat, refilling and bleeding. Very slow warming up (my drive to work is about 35 km ~22 miles, and at ambient temp of 5C the engine warms up only to 60-70C during the trip. Seems like a stuck open thermostat again, but that is highly unlikely? I checked the first 'new' thermostat now that it's off the car and it definitely is not stuck open, althouhg the 'bypass' channel is flowing qiute a lot at the position the car has left it prior to disassembly.

What am I missing? Does the ECU need to be coded somehow? It the ECU commanding the bypass motor open all the time or something similar?

Any ideas would be greatly appreciated!

[LVII]

Looks like I might have misunderstood the bleeding / degassing instructions for my specific engine type. As far as I understand i have the DW10DF engine, and therefore need a Diagbox to do the degassing and to adjust the positioning of the bleed valve - so I need to go shopping for Diagbox or Lexia and the VCI adapters/cables...

[Mihael_M]

I did not change the thermostat, but only the antifreeze. After the change, I vented the air on the venting valve. I let it reach operating temperature and then the antifreeze level decreased so when the engine cooled I added a little more. Nothing special needs to be done. But regarding the thermostat, I know that some people had similar problems after replacement. It would be better to find an original rather than an aftermarket thermostat. Your model does not need any adjustment with diagbox.

[LVII]

Thanks for the reply! According to this viewtopic.php?p=820223#p820223 post on the mebers section by Marc it still seems that the DW10FD engine needs the diagbox for this prodecure? The car is EURO6 rated so the diagbox requirement should apply?

I think its quite unlikely for two new thermostats, although not OEM, should behave the exact same way? There must be something i've omitted here.

The engine cooling during coasting is quite a lot, here in this screenshot from Torque there is about 20 seconds of coasting during which the ECT drops nearly 10 deg C even though the coolant isn't anywhere close the thermostat opening temperature of 98 deg C.

I should get the VCI hardware sometime during next week. Lets see if that makes any difference.

[LVII]

Well, turns out i got two bad "non-OEM" thermostats. Got the 'official' PSA thermostat and installed it, bled the system via the bleeding screws and the diagbox procedure, after which the engine heats up beautifully and reaches normal temps of 95..100C in highway driving.

Lesson learned: stay clear of the cheap parts and go for the official oem parts.

Now let's just hope i can get a full refund on the faulty thermostats...

[bazels]

I have the same problem, but diagbox show that ECU commands thermostat to keep partly open at least 30%. Will OEM part change ECU behaviour to keep close until warm up?

[LVII]

I havent now looked at the ECU command to the thermostat for ages but i remember that it hovered around 20-30%. I can hook up with the diagbox over the weekend and check this for you.