97 850 Hissing and Rough Idle Topic is solved

dairyqueen814 · Post by **dairyqueen814** » 25 Mar 2017, 07:53

Hi guys
Really quick, hopefully simple problem. I've got a constant hissing going on and I'm almost positive its a vacuum leak. The car is wonky when idling and the idle almost chokes out when I'm braking. There is no leak at the tree and I just want to get an opinion before taking off my manifold to poke around. I know the vacuum system is relatively simple on my car and I might just need to clean/replace the PCV as it hasn't been done in 50k miles.
Also maybe unrelated my throttle sticks closed the tiniest amount. I think I just need to spray carb cleaner in the throttle body because I know the flame trap is right there and might have a bit of goop leaking in.

Anyway thanks in advance!

Post by **theWIFES_S70** » 25 Mar 2017, 08:15

The only lines connected to the braking system are the brake booster vacuum hose and the brake booster check valve. Sounds like it could be coming from there. Take some pictures for us and let us take a gander!

dairyqueen814 · Post by **dairyqueen814** » 25 Mar 2017, 08:18

I'll try sometime this week. I know the car backwards and forwards it's just a matter of time spent chasing gremlins that I don't have anymore. Thanks for the direction!

Post by **erikv11** » 25 Mar 2017, 09:47

Big fat brake booster line, easiest way to check it on an NA is to pull the battery. You don't need to pull the manifold just yet, save yourself the hassle if you can. Replace with any thick walled vacuum line, I have used silicone there.

On the throttle plate you are on track. Pull the ducting to the throttle while you are checking the brake booster, spray some carb cleaner on a rag, wipe it out real well.

dairyqueen814 · Post by **dairyqueen814** » 26 Mar 2017, 14:02

Awesome I'll give it a go this week. Will report back either way.

dairyqueen814 · Post by **dairyqueen814** » 30 Mar 2017, 04:53

So yesterday I was hunting down the sound. I checked all my vacuum lines, everything was fine but I couldn't inspect the lines behind the manifold. I have the Snabb intake spacer so I just popped off the manifold to check..... well the manifold came off and as it turns out the Snabb spacer rotted out and was pissing air. Seriously? The part I bought so I wouldn't have to worry about replacing it was ruined. Long story short, after 2 hours of driving around to different Volvo dealerships who thought they had a gasket but didn't.... In a summer car.... getting dirt all over it... But it's fixed now.

Thanks all!
Now I just have to find the clunk in the rear end..