1999 S70, ''air escaping" sound upon acceleration

ashlee2319 · Post by **ashlee2319** » 18 Oct 2013, 10:01

I have a 1999 S70. Occasionally, when i am stepping on the pedal, there will be a sound of air escaping. (Would this be considered a ''ping'' noise?) This only happens when I am accelerating.

A few months back, before i had all my codes cleared, the EVAP emission code would come up. And also, Meineke dudes said i had a vacuum leak. I used carb cleaner to possibly pinpoint it, but nothing.

Would this be related to the PCV system? or the Purge Valve?

Any input is appreciated, thanks.

Post by **rspi** » 18 Oct 2013, 10:30

Likely a vacuum leak. It could be anywhere. Most of the vacuum system is the PCV.

ashlee2319 · Post by **ashlee2319** » 18 Oct 2013, 11:06

How would i access those vacuum lines?

850TurboTurtle · Post by **850TurboTurtle** » 18 Oct 2013, 15:50

I had a similar noise on my 850T and it was both cracks in the vacuum line elbows and a hole in my turbo intercooler hose. I replaced both - not sure which was the main culprit, but my power and mileage both increased immensely afterwards.

There are several vac lines running from the vacuum tree on the intake, to sensors mounted on the fan cowling, into the passenger end of the intake manifold, behind the MAF sensor, and back near the turbo. The S70 is probably similar, but I don't have a diagram on that car. Good luck.

ashlee2319 · Post by **ashlee2319** » 21 Oct 2013, 16:37

Thank you for your reply. I have sprayed carb cleaner just about everywhere. And, nothing. Just gonna take it for a smoke test.

ashlee2319 · Post by **ashlee2319** » 23 Nov 2013, 20:42

Quick update:

Took it to a Volvo specific independent shop. Told them about it and that I wanted a smoke test done to find my vacuum leak. They claim that since an 'evap leak' code came up, he didn't want to waste my money doing the test because it would be pointless. He said having an 'evap leak' code wouldn't affect the performance of the car (e.g. noticeable loss of acceleration power due to vacuum leak).

Is this true? Doesn't sound right..

thankswww · Post by **thankswww** » 23 Nov 2013, 21:17

I'd say it's a bit unfounded to say that a leaky evap system wouldn't affect performance. From my experience, leaking air, or changes in fuel pressure can affect performance and gas mileage.

Post by **precopster** » 24 Nov 2013, 01:16

The vacuum system is not the same as the PCV system.

Leaks in the vacuum system directly affects the spray pattern and swirling effect of the fuel being sprayed toward the valves and therefore performance is directly affected.

The PCV system is separate from the intake system though it is connected by means of hoses going directly into the intake to be re-burned again.

The systems remain related because one connects to the other.

When the PCV is blocked it has positive pressure whereas the vacuum system always has vacuum.

Evap codes relate to another system which takes in fuel vapours from the unpressurised fuel tank and from the unused and again unpressurised fuel at the intake manifold as a return system.
It needs to maintain a certain pressure so it can feed these vapours in to a charcoal canister. There are sensors which measure the pressure of the system.

socompsp · Post by **socompsp** » 24 Nov 2013, 01:41

is your s70 n/a or turbo? you could have a boost leak and/or a vac leak as well. i would have indy do the test anyhow. also you yourself can look for any lines in bad shape. they are easy to spot, usually if a line is dry/cracked/flaky and crumbles, it needs attention. to put pressure on your turbo plumbing you would either need to buy or build a test tool. a tut on how to build a boost leak tester can easily be found on google or youtube. the only tricky thing to check for a leak in would be the cbv. in which case if it had failed youd know it cause that hiss would be LOUD.

ashlee2319 · Post by **ashlee2319** » 04 Dec 2013, 12:16

It is a Non-turbo.

and I believe my PCV system is fine, i checked it doing the oil dipstick test.

I have a hunch that there's maybe a torn line on top of the fuel tank. But, i don't have the equipment to lower it myself. Thinking I should still get a smoke test done anyway.