bullfrogslayer

I've got a 99 4-runner, 4wd, with a 5vz-fe motor. While freeway driving between 70 & 80 mph I get a blow-off sound ("pish"), similar to turbo blow-off, every 30 seconds or so. Any ideas?

wyoming9

iTrader: (1)

Can`t really say I am not allowed to drive that fast!!

Are you losing any coolant ??

A leak in the heater core might do that as the vehicle flexes

Auto or Manual Transmission??

bullfrogslayer

Manual transmission. I recently replaced the heater core about 50k miles ago, though I guess it's possible I botched that job. The blow-off doesn't only occur at those speeds but it only occurs when under load and at 30 second intervals at those speeds. It happens at shorter intervals at lower speeds. I tried revving the engine at the same rpms but the blow-off doesn't happen unless under load.

TheDurk

Try a new rad cap.

vasinvictor

iTrader: (3)

Maybe the turbo fairy came and visited you. I have nothing helpful to add

bullfrogslayer

Whaaaat? There's a turbo fairy?

bullfrogslayer

So I live in SoCal and my a/c is pretty much always on. But I turned it off for once and found that I only get the blow-off sound when the a/c is on. After I figured this out, I turned it on a few times and found it made the sound every time at the moment I turned on the a/c. So it looks like it could be the a/c compressor or condenser. Anyone else had this issue with their a/c? It's still blowing cold.

akwheeler

check the tension on your a/c belt. it's probably slipping a little when the compressor clutch engages.

vasinvictor

iTrader: (3)

Yeah it normally will not make that noise. There is no pressure anywhere that's "blowing off", so you are probably hearing slipping belt. The tensioner takes a 14mm on the front bolt, just loosen it, then a 14mm on the bottom tensioning bolt. Might have to remove skidplate to get to it.