What is the small hose on the thermostat housing on '05 XC70? Topic is solved

kcb203 · Post by **kcb203** » 30 Dec 2017, 11:43

I tore it while removing it during a thermostat replacement. I can't seem to locate if on any parts diagrams. I'm not sure if I need a molded hose or just get some hydraulic hose at the parts store. Given the holiday weekend, I'm hoping to be able to get something at a regular parts store today. Thanks.

kcb203 · Post by **kcb203** » 30 Dec 2017, 14:56

I figured it out--somehow I missed this thread in my search:

viewtopic.php?f=9&t=83461

It's part of the PCV system. I was able to buy generic hose at the parts store and cut to fit.

Post by **abscate** » 30 Dec 2017, 15:24

Present on PCV from 1999-on

Post by **br0dy519** » 17 Dec 2019, 17:49

Apologies to resurrect an old thread, but this hose has me wondering a very important question.

I've noticed some seepage underneath the thermostat, upper rad hose is fine, everything is snug. I've noticed this smaller ID PCV hose is cracking at the hose clamp and lots of gunk around that nipple. Is it possible for that to cause a coolant leak? I'm just not sure if this is only a passage for air or if it is possible for coolant to leak out of there (don't want to check outside in -14c temperatures tonight. lol)

Thanks guys and really happy to be part of this community now.

Post by **oragex** » 18 Dec 2019, 04:09

Very possible and pretty common coolant leak on the turbo engine (non turbo doesn't have this hose on the thermostat housing). Worth looking at the coolant tank as well, underneath it as these may sometimes develop a small crack (disconnect the small sensor before lifting), at the small return hose at the top, also the cap can leak at the small gasket.

Post by **br0dy519** » 18 Dec 2019, 14:45

oragex wrote: ↑18 Dec 2019, 04:09 Very possible and pretty common coolant leak on the turbo engine (non turbo doesn't have this hose on the thermostat housing). Worth looking at the coolant tank as well, underneath it as these may sometimes develop a small crack (disconnect the small sensor before lifting), at the small return hose at the top, also the cap can leak at the small gasket.

Good to know I'm in the right spot. Replaced the overflow tank and that upper smaller ID hose clamp this year, definitely not leaking from there. Also put a new cap on last year too. No signs of any white crud build up near the expansion tank. That smaller nipple on the thermostat definitely shows some white build up.

Just a question do you think that hose is 5/16" ? It looks about that.. or maybe even small as 1/4" . I have some fuel line sitting around do you think that would be sufficient to splice in there... I realize I have to be VERY careful on the PCV side of that hose as it's on a plastic fitting I believe?

Thanks again man your many hours of effort have helped many of us.

Post by **br0dy519** » 23 Apr 2021, 19:51

br0dy519 wrote: ↑18 Dec 2019, 14:45
oragex wrote: ↑18 Dec 2019, 04:09 Very possible and pretty common coolant leak on the turbo engine (non turbo doesn't have this hose on the thermostat housing). Worth looking at the coolant tank as well, underneath it as these may sometimes develop a small crack (disconnect the small sensor before lifting), at the small return hose at the top, also the cap can leak at the small gasket.
Good to know I'm in the right spot. Replaced the overflow tank and that upper smaller ID hose clamp this year, definitely not leaking from there. Also put a new cap on last year too. No signs of any white crud build up near the expansion tank. That smaller nipple on the thermostat definitely shows some white build up.

Just a question do you think that hose is 5/16" ? It looks about that.. or maybe even small as 1/4" . I have some fuel line sitting around do you think that would be sufficient to splice in there... I realize I have to be VERY careful on the PCV side of that hose as it's on a plastic fitting I believe?

Thanks again man your many hours of effort have helped many of us.

Just quickly updating this old thread. The hose is 3/8" if you cut a heater/transmission/fuel line to the correct size you can use a generic and not kink it.

Galway362 · Post by **Galway362** » 06 Aug 2022, 13:49

Does coolant run out of the thermostat through that hose? Mine appears to be clogged

Post by **cn90** » 06 Aug 2022, 21:28

Yes,

Coolant runs through that small hose to warm the PCV system in the winter.
You can replace that small hose with generic hose.
I'd recoomend Gates hose, which you can find at local auto parts stores.

Galway362 · Post by **Galway362** » 07 Aug 2022, 07:16

Should I be able to manually (with a hose) get water to run through the hose? It appears to be blocked.