Vacuum Leak?

[schott1984]

Hi there. I had my hood open with the car running the other day. I noticed this occasional PSSSST sound coming from somewhere. It's not constant hissing. Just PSSSST......PSSSSSSSSSSSST...PST. Every once in a while. I took a picture of the area I think it's coming from. Is this a leak, or is it just something that normally happens? Thank you.

[menappi]

I don't really know what that is but I know your engine needs air to run, and is constantly sucking air in, so it doesn't seem to weird. Feel around to see if you can feel a leak. Try this, get some carb cleaner and put one of those long wd40 type straw things on it and spray it around that area. If the idle goes up then you got a leak (pretty sure, this works on hondas).

[jzz30]

dont use wd-40. its a little messy. you can use carb clean but propane would be best. the engine will run funny if it sucks in the propane or carb clean. or you can simply feel around and see where its hissing from and repair it accordingly.

[68pishta]

That is most likely a heater control valve. The random hissing makes sense as the TCU (climate control) is giving this pot random signals to open intermittantly to try an control the inside cabin temp. any vacuum pot that has 1 port can be tested by a mighty-vac vacuum puller tool. This $30 tool has proven itself to be worth its weight in gold to me diagnosing engine faults. Suck a vacuum and watch the gauge. If it doesnt hold a vacuum the pot is bad. My Mazda truck has 9 of these under the hood and 7 were bad when I brought it out of the barn!