PSHHHHHHH! Sound while driving?

[jcush87]

So The last 2 times I drove my 1996 3.4L 4x4 with 191K miles, I have gotten this loud sound that sounds like some sort of a pressure blow-off.

It happens when I am cruising at about 50mph for a few minutes. The sound seems to come from outside the passenger compartment, but near the passenger side foot well. It sounds like a blast of air that lasts for about 1-2 seconds. It happened 3 times during my 35-40 minute commute.

Wondering if it had to do with the AC, I shut off the AC for about 5 minutes and it did not happen. But there were also 5 minute stretches with the AC on where it did not happen, so that was fairly inconclusive. My AC has been running fine and blowing cold. I have not added refrigerant in probably 2 years which I just did to top it off even though there wasn't any issue.

A bit more history: about 1000 miles ago I had a blown head gasket that I replaced. I also have my ABS light on that happened around the same time. The code indicates a short in the ABS pump. It is probably unrelated, but I figured I should mention it.


Any ideas what could be wrong?

 

[Tinigunner11]

It sounds like you’re hearing the ac compressor clutch turn on to help keep your AC running cold. Start the car and turn the ac on and stand outside of it and listen. You can hear the ac compressor clutch turn on and off. It makes sort of a hissing sound.

 

[zoombyu86]

At first I thought this was a play on you showing off a fancy new turbo setup.

 

[gamefreakgc]

Someone installed a turbo when you were sleeping last night. Surprise!

 

[jcush87]

Yeah, maybe it was a sneak installed turbo with terrible turbo lag because I still haven't felt the power increase!

I plan to drive home with the AC off and see if it happens at all. I guess that might be able to rule that system out.

 

[PetesT4R]

A/C Pressure relief valve?

Do these trucks have an AC pressure relief valve? Honda Civics are famous for this noise when the AC system is over pressure. I did a little research, and it looks like some Toyota’s have them on the back of the compressor.

It seems odd that this would happen after an AC recharge and not be related.

 

[3bears]

the only time I hear a pshhhh sound is when mine is parked and I or someone else yells pshhhh on....fish on......sorry …..haven't been fishing in a few weeks and that's what came to my mind when trying to make the sound you printed

 

[jcush87]

Do these trucks have an AC pressure relief valve? Honda Civics are famous for this noise when the AC system is over pressure. I did a little research, and it looks like some Toyota’s have them on the back of the compressor.

It seems odd that this would happen after an AC recharge and not be related.

Well I haven't had a recharge in about 2 years! Not sure why it would act up now. I'm pretty sure it is AC though, after work I started the car and a different noise happened for about half a second until I shut the AC off.

I turned it back on and it blew cold but I didn't want to chance it so I drove home without it.

I let the AC run for about a minute in my driveway when I got home, it still blew cold. But the compressor didn't shut off, not sure how long the compressor should run before cycling. I thought it was shorter than what I ran it for though.

 

[Collkid]

Blow off valve.

 

[jcush87]

Blow off valve.

Any idea what would be causing it to exceed the pressure and blow?

 

[Collkid]

Any idea what would be causing it to exceed the pressure and blow?

Sorry, that was a bad joke.

Blow Off Valves are used in Turbo setups.

 

[jcush87]

I am leaning towards this sensor being faulty right now, anyone have experience with the AC Pressure Switch? I can do he continuity verification, but I cant really verify what pressure is in the line when continuity is broken without the required gauges.

http://www.teamtoyota4x4.org/archiv...oypdf/02rmsour/2002/024runne/ac/presw/ovi.pdf

 

[Tinigunner11]

Could possibly take a video of the sound?