leaking coolant from thermostat bleeding screw

[saskak]

Hi All,

Noticed that the coolant is at the min mark. I managed to trace the leak to the "Radiator drain plug" or bleeding screw cap. This is a black cap, like a bike tyre cap on top of the coolant thermostat. See pdf (PARTNER VP (M59) - M59F 1 13E40B - DURITE HOSE COOLING.pdf), item N: 3. The screw is positioned on the very top of the thermostat housing (PARTNER VP (M59) - M59F 1 13E86B - OUTLET TANK SWITCH PROBE.pdf)
It is slowly dripping, I tried to screw it, but it does not want to move and it seems that is leaking where the cap/screw connects to the hose. I also tried to push it, but it does not really want to move at all, maybe should have tried with more force.

Has anyone seen something like this? I could not find this screw anywhere and most thermostat housings are sold without the screw, so not too sure what to do with this one. If I remove it completely without draining the coolant, I suspect quite a bit of coolant will leak.
Car is Peugeot Partner 1.6HDi (9HXC engine; 92bhp; 2007; M59), a badge difference to the berlingo. I know that the gasket leaks on these with age, but it is not the gasket this time.

Any help is more than appreciated.

Cheers,
saskak


  PARTNER VP (M59) - M59F 1 13E40B - DURITE HOSE COOLING.pdf (Size: 143.98 KB / Downloads: 27)

  PARTNER VP (M59) - M59F 1 13E86B - OUTLET TANK SWITCH PROBE.pdf (Size: 50.83 KB / Downloads: 12)

[cancunia]

Is there another similar air bleed screw where the heater hoses go through the bulkhead? If so, there are some posts on here about replacing them with normal dust caps.

[saskak]

Is there another similar air bleed screw where the heater hoses go through the bulkhead? If so, there are some posts on here about replacing them with normal dust caps.

I suspect it is the same air bleed screw that goes through the bulkhead. The thing is that it does not drip from the cap itself, but somewhat past that. It has a rubber o-ring, so it could be that it has gotten slightly loose or the o-ring has failed. I think it is the same as the one in the photo.    

I will probably unscrew the cap, capture the coolant and take it off for inspection.

Cheers,
saskak

[cancunia]

Maybe some silicon instant gasket would help when you're putting it back?

[saskak]

Maybe some silicon instant gasket would help when you're putting it back?

Good idea, I will see what I can do tomorrow.

[saskak]

Yes, it was slightly leaking from the "radiator drain plug" or the thermostat housing bleeding screw.
Took it out, but there is nothing wrong with it, the rubber o-ring is like brand new. Cleaned it a bit, refitted it, topped up the coolant, bled it slightly, put a small rubber o-ring at the end of the cap. Drove for quite a while and it is not leaking at all. Weird, I will monitor to see if it will restart leaking from the screw.