96 850 R quick PCV question

Post by **erikv11** » 06 May 2016, 13:06

My opinion on temporary sealing up the base of the PTC is: I would do it.

Post by **Clemens** » 06 May 2016, 13:56

great. Thats what i wantes to hear

beigg · Post by **beigg** » 06 May 2016, 18:56

Remember, anything gooped on to adhere as a temporary fix will eventually need to be cleaned off for the permanent solution.

Happy motoring!

Post by **rspi** » 07 May 2016, 04:55

Do the glove test with the car hot. Also, if you have any breaks in the system, the test can give you a failed negative.

You may also want to do a compression test.

Post by **Clemens** » 07 May 2016, 13:10

Alright. Finally it suchs the glove right in. The 12mm hose mod did the trick. My comptession is 14-14-14-14-13 bar. That is where it should be, although i can't remember having the throttle body plate open or closed.

Anyhow. The hissing sound back from the ptc valve is still there, even after putting quite some liquid sealant on all suspicious arras back there. What i noticed though is it goes away if?i carefully kink the smaller hose running from the intake manifold to the ptc.

Is this maybe just the regular sound of air getti?g?sucked through that tiny hole in the ptc?

Post by **erikv11** » 07 May 2016, 14:52

Ah, well you said there is a leak, not that there is a hissing sound!

Probably didn't need any goop/sealer.

Yes, it is just the sound of air. My V70 does it, my 850 doesn't. But my 850 still has the factory hose, not the modified vacuum line ...

See also https://www.matthewsvolvosite.com/forums ... hp?t=62154

Post by **Clemens** » 08 May 2016, 01:30

So I think the following happened: now that the PCV and ptc work due to the larger hoses I can hear that sucking/hissing Sound from the ptc area. Cuz I never heard that before I´d stick my hand town there to grab for a leak. I could feel a slight airstream in the area of the ptc valve. I then thought this was a massive vacuum leak. Sealed it up. Couldn´t feel the airstream anymore, but still heard that sucking/híssing noise.
Now, after reading your thread I´m happy to know that this is normal with the larger hose. Maybe this has to do something with turbular vs. laminar flow. I can´t remember too much about fluid Dynamics anymore, but I remember there being something related.

erikv11, thanks for all your input.

Just wish I´d have gotten black sealant, the red one looks goofy. Well, time and oil will take care of that eventually...

Post by **abscate** » 05 Jan 2026, 04:11

erikv11 wrote: 06 May 2016, 11:49 If you used some kind of fuel line that's great, you may be just fine.

Yeah, a vac leak there means unmetered air getting in, that is post-MAF. I recently learned that the grommet for the base of the PTC is available separately from Volvo as part number 3507985, they are cheap (only $3 US) so it is a good idea to replace them. I need to get a couple.

Update on his part, now$28

https://www.fcpeuro.com/products/volvo- ... vo-3507985

Post by **Clemens** » 07 Jan 2026, 01:55

And the original one is still working like a charm. Boy, do I wish I hadn't used red RTV sealant or any sealant at all.
Hard to believe this was 10 years ago.
OMG, the R turns 30 in a few weeks. It was 19 when I got it ...
This fall will make it 15 years of 850 ownership for me!