Coolant leak help

[Artermis]

Hi all, need help identifying coolant leak on my wife's new 1.6HDi.

It's losing coolant so I've just found out. Underside passenger side is wet and I can see pooling on the rear of the gearbox, below the air intake piping where the box meets the block. so looks like it must be leaking round there. The union's on the bulkhead to the heater matrix look dry.

Can anyone tell me what else might be down there that could spring a leak. Annoyingly I can see where it ends up but I don't know enough to determine where it might be coming from.

Any insight greatly appreciated. Ben

[gazza82]

Thermostat is that end. Not 100% sure what else on 1.6 diesel.

[Artermis]

Cheers Gazza. Starting to regret buying the wife this Peugeot! Damn thing is really starting to put up a fight and we've only owned it four days?

It keeps throwing antipollution and airbag faults at the minute too. Annoyingly despite a thorough two test drives none of this was evident and has only started to occur since we got it home. Drove home absolutely perfectly and has been a git ever since.

Had to take the day off work today to get it sorted and send wife to work in my car. Wife's work don't allow leave in December.

In a throw back to my teenage years I'll just have to start ripping bits off her till I find the wet bit! Still if there is a silver lining it's that it's not the water pump.

[Artermis]

So I think as Gazza pointed out this related to the thermostat.

There is a lot of coolant plumbing in that area, unsurprisingly if the stat lives there, there is also a rigid section of pipe that mounts to the bottom of the stat that runs from the bottom radiator hose around the back of the engine black as a return feed.

I could see that a pool had formed on the back of the gearbox and that from underneath the back of the box and drive shaft was wet with coolant spray and there was some evidence of steam.

The difficultly was working out exactly where this originated from.

Having inspected the pipe unions on the thermostat and the rigid hose below, there was no evidence that these were damaged or leaking, so I concluded it had to be the stat itself.

If you have a look at the attached I was concerned about a slot gap in the bottom left above my blue gloved thumb that runs internally to externally. Obviously seal is removed in the pic but i got the impression that this could be a weakness that forced coolant passed the seal. It almost looks too perfect to be by accident but still.... Also notice that there is some pink calcification around the bolt holes in the extreme edges of the pic. These were evident on the outside on the bolts too, so I figured coolant must be getting out and leaking into the bolt holes too.

I ordered a new stat (£39) and replaced it, just to be sure. There is no evidence of the slot gap in the new unit that you see in the old one - so that must be something!

I ran it up and bled the system as best as I could. How you're supposed to access the rear bleed screw without removing any induction plumbing and the airbox I've no idea.

I ran to the point that the stat opened and made sure I opened up the heater matrix too and it swallowed a good gulp of coolant so hopefully it's 99% there. Will have to keep an eye on it for the next few days. I expect the level to drop a bit more as any last pockets of air work through but fingers crossed it isn't leaking anymore!