Jas16 wrote ...

this is making me worried. As far as I know in the cars 10 year, 111k history no cooling related items have been changed apart from water pump as part of cambelt service at 100K earlier this year.

I will go through the car's history paperwork again to be sure.

Tjensen wrote ...

Is it age or distance (=heat ?) that kills the plastic? Both are available quite cheap on ebay. I have now (130 000km, 7 years) changed one (in the alterantor area) and have both as new spares.

Jas16 wrote ...

this is making me worried. As far as I know in the cars 10 year, 111k history no cooling related items have been changed apart from water pump as part of cambelt service at 100K earlier this year.

I will go through the car's history paperwork again to be sure.

e3steve wrote ...

If you have any doubt, change it out! It’s not an expensive part, nor is the job itself difficult if one knows the engine well. I can swap them out — the ‘stat housings — in around two hours and without breaking any of the peripherals that are in the way.

The alternative is heartache and, as some have found, can be fatal for the engine!

The coolant inlet (on the front of the engine and above the alternator) tends to just weep; you’ll smell the coolant when the engine is hot. The coolant outlet (‘stat housing — in between the vee) distorts and bursts open at the seam from heat and cooling system pressure. That pressure is greatly reduced to practically zero if the correct OAT coolant is used. It’s the presence of any added water — even deionised — that creates elevated pressure.

Incidentally, while working in the engine’s vee it would be wise and economical to test and replace the glowplugs, as the task of doing so is much easier once that outlet/housing has been removed...

Jas16 wrote ...

thanks all, I wasn't clear in my original post, but is it different as mine is the 2.2hdi version?

vaho wrote ...

On 2.7 HDI you can always install a coolant level sensor. Then you basically do not have to worry and prematurely change these pieces. You can inspect and take action after the level drops and there is a warning.

RodHagen wrote ...

We lost the thermostat housings on two 2.7L HDis (Peug 407s) within 5000kms of 110,000 kms. In both cases the failure was at the "seam". In each case it was clear that the failure was partly due to one of the threaded receptors for the machine screws holding the thermostat in place "letting go" from the plastic in the rear part of the housing. This seems to have reduced the strength of the overall device enough to cause the seam to split, presumably when the thermostat opened or some such. In one case the rear smaller (oil cooler?) hose connector had also partially failed.

I managed to get a few more thousand kms out of one of the housings by sealing with heat resisting epoxy, and adding self tapping screw where possible around the periphery, but it is really much less time consuming to simply replace it. Amazing how quickly you can replace it with a bit of practice following the instructions on this site!

Don't know about on the C6 version of the engine, but its worth noting both the alternator clutch pulley and the accessories serpentine belt went on each car at almost the same time as the thermostat housing failures!

Chatted to a very experienced Peugeot mechanic who said he'd met with very few 2.7 V6 HDi engines on Peugeots or Citroens that hadn't suffered similar failures to the same three components by 120,000kms.