C4 Grand Picasso 1.6 Hdi, New Thermostat Housing/bleeding System...

[alfsc4gp]

For about a month now my 1.6 HDI VTR+ has had a coolant leak.  I wasn't sure where the water was going but I was topping it up every day and after doing a 30 mile round trip to work and back it was using over a litre per day!  I took the car to my local Citroen dealer and got one of the technicians to look at it...He said it looks like its your thermostat housing, and then he had the cheek to tell me "you won't be able to fix that".  Little did he know that I am a tad mechanically minded...I build Mclaren sports cars for a living!  So I said thanks and I went on my way.  The trouble with the housing in question is its buried away on the side of the engine and you cannot simply replace the thermostat...You have to change the entire housing as the thermostat is moulded into the plastic housing.

The new housing was £76 inc vat from Citroens, but I found one elsewhere for £57. Halfords has them for about 45 quid but it was hard to get to Halfords from my house.

 The procedure went something like the following:

 Remove the air intake pipe and the front air intake box which is 

in front of the battery.  Remove the plastic battery cover and remove the battery followed by the lower plastic battery box, then the metal battery tray (Note: this requires removal of the LF front wheel and wheel arch liner to access one m13 bolt, the rest are under the bonnet).  The flat electrical fusey thingy which clips onto the top of the plastic battery cover can be left alone (leave it connected to its wires) and just move it to one side.  Remove 1xm13 bolt holding a metal bracket which is directly in front of the Thermostat housing and remove the bracket. Disconnect the hoses from the housing...The left hand one at the back of the housing has a special push fitting which I did not know to to remove...Eventually I worked out how...squeezing the white clip down with a pair of molegrips.  Now you can get to the four m6 stainless bolts that hold the housing on.  take the old housing off and replace with the new one, remembering to fit the new blue plastic gasket.

Whist I had easy access to the airbox I noticed that the right hand securing grommet had broken off the lid!  This had allowed the bottom right hand corner of the airbox to rub against the push fit pipe from the back of the Thermostat housing...wearing the box paper thin!  I repaired it by glueing some self amalgamating tape over the hole and I glued a suitable rubber grommet to the lid.  Now the airbox fits properly and it no longer rubs on the pipe...By the way, repair is highly recommended as a replacement airbox is about £118!!!

I put everything back in reverse order, filled it with water and antifreeze and then set about trying to bleed the cooling system.

Believe it or not but I search for hours on the internet for information on how to do this, and could find absolutely nothing!

So here is how I did it...Even after filling the system through the expansion tank, no water was seen coming from the top of the radiator when the top pipe was pulled off...I filled the radiator through the top inlet with a hosepipe...The rest of the coolant was red antifreeze and distilled water. Replaced the hose and undid the bleed cap on the front of the thermostat housing whilst the engine was running...There was only a tiny amount of air that came out and then it ran clear.  When the airbox was off I noticed another bleed cap on the heater pipes at the back of the engine...I reached around the back and undid this one too...I could not actually see the other bleed cap once the airbox was on so it was all done by feel.  That is as far as I could go to bleed it as they seem to be the only two bleed points in the whole coolant system. Even after running the engine for more than ten minutes the radiator was still stone cold but the fan did come on after I put the A/C on inside car and turned the heat right up.  This worried me as surely the radiator should get warm???

After ringing Citroen the next day about this they basically said that it sounds normal as a the rad on a Diesel takes ages to heat up!  I am still worried that I have not bled the system properly...I will just have to assume I have!  Unless you guys know different?

Edited August 20, 2016 by alfsc4gp

[paul.h]

Citroen seem to use a tall funnel that fastens to the coolant expansion tank when filling/bleeding the coolant. This raises the level and puts a bit of pressure to help the air get out. When changing the coolant on our previous C3 1.4 petrol 2003 model, I applied vacuum (with a Mityvac hand pump) to the cylinder head bleed point to pull the air out since it was not coming out on its own, plus I did not have the funnel. Some air still remained and could be heard going round the cabin heater but after some use and a bit more bleeding it was gone. Also squeazing the various hoses helped a bit.

 

If you want a workshop manual, the Citroen service box through ebay is worth having.