Sudden Hissing near Valve Cover (5.0 V8)

Abram · Mar 26, 2025

Hey everyone, I'm trying to sort something out. This morning I had a number of things all occur at once which were not exhibited yesterday. On starting the vehicle and under acceleration I'm getting some white smoke and water from the exhaust (though it's not billowing). Previously I would only have a very small amount of white smoke on a cold start for about 30 seconds (not a big deal). Additionally when accelerating I'm hearing an almost straining or hissing sound from the engine. I popped the hood and I was hearing a "pulsing hiss" (forgive my lack of understanding) from the valve cover / PCV area. Lastly my brake pedal suddenly makes a very audible "click" when I depress the pedal.

All of these things occurred simultaneously which is making me feel it's linked to something specific. I am not seeing any faults when scanning with the IID and both the Oil and Coolant levels look good (plus no obvious signs of leaking under the vehicle). Is there a value I should check specifically with the IID to try and narrow down what's going on?

I had intended to replace the PCV valves as I have no knowledge of when they were last done (if ever) so I thought it would be a good preventative maintenance item for me to do on my own, but now I'm wondering timing-wise if something happened suddenly in that area?

djkaosone · Mar 26, 2025

It's very common that the pcv valves go bad and have a hole in them. Just get 2x LR133579, cheap ones on Amazon are fine too.

As for your brake issue, you might want to check your brake pedal switch XKB500110. Not sure if that's the cause of your click, but the truck will do funny things with this switch going out. Just take a look around the brake pedal and see if there's anything obstructing it. Here's a good explanation of it.

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powershift · Mar 26, 2025

White smoke is coolant burning. I'd do an oil change to ensure it isn't chocolate milk instead of oil.

Are you seeing the white smoke from your rear-view mirror or do you get out and inspect the exhaust? Hot or cold engine temperature is one thing to note when its happening too. I haven't noticed any white smoke on mine in 1.5 years since I've owned it at any temp.,, but the environment can influence that. Water draining out should only happen when cold and that is the cats converting the dangerous gasses into water. Pretty brilliant and expensive.

16FujiDisco · Mar 27, 2025

Brake pedal click - mine does this as well, and it’s been doing it for as long as I can remember now; no issues.

Like you I noticed it one day and now I can’t ‘un-hear’ it. I assumed it always made that noise and I just didn’t notice it…until I did. Doesn’t bother me, and there are plenty of times it doesn’t register in my brain, but then there are days I hear it every time. Mostly in slower, in town, stop and go situations where you are gently pressing the pedal, vs a brake at speed type of stop.

I figured it was the switch or relay that triggers the illumination of the brakes lights, but I could be wrong.

Jimmy Brooks · Mar 27, 2025

Abram said:
Hey everyone, I'm trying to sort something out. This morning I had a number of things all occur at once which were not exhibited yesterday. On starting the vehicle and under acceleration I'm getting some white smoke and water from the exhaust (though it's not billowing). Previously I would only have a very small amount of white smoke on a cold start for about 30 seconds (not a big deal). Additionally when accelerating I'm hearing an almost straining or hissing sound from the engine. I popped the hood and I was hearing a "pulsing hiss" (forgive my lack of understanding) from the valve cover / PCV area. Lastly my brake pedal suddenly makes a very audible "click" when I depress the pedal.

All of these things occurred simultaneously which is making me feel it's linked to something specific. I am not seeing any faults when scanning with the IID and both the Oil and Coolant levels look good (plus no obvious signs of leaking under the vehicle). Is there a value I should check specifically with the IID to try and narrow down what's going on?

I had intended to replace the PCV valves as I have no knowledge of when they were last done (if ever) so I thought it would be a good preventative maintenance item for me to do on my own, but now I'm wondering timing-wise if something happened suddenly in that area?

Definitely PCV valves. Funny story I had the same issue minus the white smoke. Ironically I had also just done a decarb on the intake valves right before I noticed the hissing so I assumed that I didn't seat the intake right. So I took another 2 hours pulling off the intake, seeing that all the seals were set right, double checked when I put everything back together and the hissing was still there along with a whine when I would turn the car off. I was so frustrated that I threw my glove at the engine bay and it landed right on top of the rearward PCV valve on the breather hole and the whole car started making the whining noise and idling rough as if it had a major vacuum leak thats when I realized it had been the PCV Valves.

Anyway your issue is definitely PVC valves, white smoke is also a key indicator (pulling oil into the intake and burning it in combustion), mine didn't have the white smoke so I never considered PCV valves. As for the clicking with the brake petal, if you hear it only when the car is in park/neutral then its probably the lock in the shifter engaging/disengaging allowing you to go into reverse/drive/park. If its all the time (in drive moving at speed) then I would look into the brake switch like @djkaosone said.

Abram · Mar 27, 2025

Thanks everyone, I was also strongly suspecting the PCV valves as well I just thought it was ironic that I had already ordered them and then to do as preventative work and then to have it suddenly **** out before I even get the parts. I must have felt it coming somehow! I'm not terribly worried about the brakes since the pedal feel is normal and they are activating as expected, I just thought it odd that it was suddenly present, perhaps it's always been there as noted, but if so it was just suddenly much louder.

Re: White Smoke - It was not billowing but it was consistent (though I only observed from outside the vehicle). I checked the oil and coolant levels and both were correct (re-checked this morning too).

EDIT: I went over to the shop I work with for service just in case and we took a look together and replaced the PCV valves, unfortunately that wasn't the problem. The valve cover itself cracked. I've not had the best luck so far with this rig.

Longtrail · Mar 31, 2025

Thanks for making me aware of the brake switch clicking noise, I was blissfully unaware until reading this thread and now I can "happily" report that I also have a loud clicking noise - great!!! :ahhhhh:

Abram · Mar 31, 2025

Longtrail said:
Thanks for making me aware of the brake switch clicking noise, I was blissfully unaware until reading this thread and now I can "happily" report that I also have a loud clicking noise - great!!!

Terribly sorry lol, but… you’re welcome?

Longtrail · Mar 31, 2025

Replacement looks really easy so not a biggie!

Sudden Hissing near Valve Cover (5.0 V8)

Abram

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djkaosone

'11 LR4 HSE LUX 5.0L V8

powershift

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16FujiDisco

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Jimmy Brooks

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Abram

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Longtrail

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Abram

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Longtrail

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