There is a hissing noise after the engine has warmed up?

DIGGITYDUG

MEMBER
2009 FORD ESCAPE
3.0L
6 CYL
2WD
AUTOMATIC
190,000 MILES

I have a hissing noise when the car is warmed up, it is not there unless I drive the vehicle for a bit. I tried disconnecting the connector and hose to the purge valve when the car was started and warmed up to see if there was any suction or vacuum but there is none. I tried spraying wd-40 around the hoses but the idle did not change. II know it is somewhere in that area but I cannot find out where, for the life of me. I do have some low idle at rare times, the low idle occurs is when I go for a long drive shut the car off then restart it, the evap small leak detected code came up. I cleared the code and it never came back but I still hear that hissing noise when the vehicle is warm. Would be appreciated if someone could point me in the right direction of where the common leaks occur. Also, can a purge valve still be faulty even if there is no suction?

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,758 POSTS

Hi,

As far as common leaks, there really isn't one hose I could point to. However, WD 4 may not be the best to locate a leak. Carb cleaner is usually more reactive when it is drawn into a leak. (actually, starting fluid causes the RPM change the quickest, but it is very volatile and dangerous to use for this).

Take a look at this link:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

You mentioned there was no vacuum to the purge valve. Are you able to follow that hose to see if it is broken or disconnected? Additionally, the idea that you sometimes have a small EVAP leak could be related. These are very difficult to locate at times.

If possible, have the EVAP smoke tested to see if there are any leaks present. Basically, smoke is injected into the EVAP system at a very low pressure. Smoke will leak out where the leak is located.

Also, try moving the hoses around to see if anything changes the sound. I've even seen people use a spray bottle with water in it to mist hoses to see if the sound changes.

Let me know. Also, keep in mind it may not be a hose. Check around the intake manifold as well.

Take care and let me know what you find.

Joe