Hissing Sound on 4.9L
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Hissing Sound on 4.9L
Just changed the lifters on my 96 with the 4.9L. Put everything back new pushrod cover gasket, new pcv valve and I reassembled all the valves and intake manifold. When I started it up the lifter tick seemed to go away but a hissing sound replaced it. Any throttle input caused the engine to bog/die. I wanted to break in the lifters but a hissing sound led me to stop running it. I know for a fact that a few vacuum lines got messed up in the process but I figured one or two small plastic vacuum lines wouldn't be the real culprit (regardless I have ordered more vac line). I am going to spray soapy water around intake stuff to check but is there anything else I should do? Engine is running pretty good at idle.
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Would the brake booster line really cause the engine to bog? I will spray intake manifold later today with soapy water and see if it bubbles. Also I noticed the pcv valve appeared to have a bit of smoke coming from it upon initial startup. I suspected residual oil at the top of the valve covers was burning off as it does not smoke anymore but would this pcv valve seal be absolutely essential? I mean essential to the point that the engine bogs? If so I will add some gasket maker around it but I can't see that being the case even if the vac line does go back into the intake.
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From: Houston/Sugar Land
I believe the brake booster has the most or close to the most vac on the engine. Yes the PCV seal is important as is all vac lines. The PCV has a rubber grommet it slides into on the valve cover.. The grommet needs replacing at times if the PCV is loose.. Shake the PCV when you check the grommet and see if it rattles. If so it usually means it is OK. If not replace it, which I would do anyway, if putting on a new grommet. You don't need any gasket maker for the PCV just a good tight grommet. Hope this helps. EDIT: If you have propane you can use it to find leaks when the RPM's increase. Of course no flame only propane.
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From: Mojave, Ca
How is soapy water gunna help you? The intake manifold is under a vacuum, so your soapy water is just gunna get sucked into the cylinders harmlessly through any broken gaskets.
You can use brake cleaner around the intake manifold if you have a large leak. The brake clean will cause the engine to run rough if there is a leak. Take a close look at your PCV valve and brake booster lines for disconnects and cracks.
You can use brake cleaner around the intake manifold if you have a large leak. The brake clean will cause the engine to run rough if there is a leak. Take a close look at your PCV valve and brake booster lines for disconnects and cracks.
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Ah I see. I found a grommet during reassembly and was confused but put it on the pcv positive pressure side instead of the pcv valve. Is it possible to add the grommet with the intake on or will I have to remove it all again?
Edit: Just saw the post about not using soapy water. I feel stupid haha. The weird thing about the pcv is that of the two ports on the valve cover, one of them is a pcv VALVE (going to the intake manifold) and one is a pcv breather (going to the air tube kinda by the MAF). The thing about these two things that makes me question a vacuum leak there is that the pcv breather has never had a fitting on it (while I have owned it) and would thus just release any vacuum pressure that the pcv valve would hope to return to the intake manifold, no? The truck ran fine without the pcv breather hose before, with no real changes made except for removing the pcv valve grommet nothing should change?
I should also mention one of those itty bitty vac lines by some electrical sensors in the rear of the valve cover broke too. It was a red one if that helps. I will send pictures later apologies in advance.
Edit: Just saw the post about not using soapy water. I feel stupid haha. The weird thing about the pcv is that of the two ports on the valve cover, one of them is a pcv VALVE (going to the intake manifold) and one is a pcv breather (going to the air tube kinda by the MAF). The thing about these two things that makes me question a vacuum leak there is that the pcv breather has never had a fitting on it (while I have owned it) and would thus just release any vacuum pressure that the pcv valve would hope to return to the intake manifold, no? The truck ran fine without the pcv breather hose before, with no real changes made except for removing the pcv valve grommet nothing should change?
I should also mention one of those itty bitty vac lines by some electrical sensors in the rear of the valve cover broke too. It was a red one if that helps. I will send pictures later apologies in advance.
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From: Houston/Sugar Land
Should have nothing to do with the intake.
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Well not related to intake perhaps but does anyone know off-hand if the grommet can be changed with the manifold on? The pcv valve is pretty far under the manifold. Regardless the pcv breather being open would release any pcv valve pressure that is supposed to reenter the intake?
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From: Mojave, Ca
The pcv valve sucks a controlled amount of air out of the crankcase into the intake manifold to remove any fumes from the crank case. That air needs to be replaced by fresh air so you have the vent that's plumbed to the snorkel, just past the MAF. This allows the air to be metered by the MAF. If this isn't sealed, you'll get unmetered air into the intake and it'll throw off your fuel/air mixture. It's should be sealed.
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I understand that both SHOULD be connected. However the engine has not made that noise before and the pcv vent going to the snorkel has never been connected. So could the pcv valve still have a vac leak even with another hole in the valve cover where the pcv vent to snorkel would go? As in how could vacuum for the pcv valve be achieved if there is just another hole for the other pcv vent that is not there just a bit further down?
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I understand that both SHOULD be connected. However the engine has not made that noise before and the pcv vent going to the snorkel has never been connected. So could the pcv valve still have a vac leak even with another hole in the valve cover where the pcv vent to snorkel would go? As in how could vacuum for the pcv valve be achieved if there is just another hole for the other pcv vent that is not there just a bit further down?
Tuned
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From: NJ
Red one *could* be the noise, that's the fuel pressure regulator and is under constant manifold vacuum. I've seen them break before, it can cause a rich condition, which is different than what you describe observing, and the noise would be pretty hard to hear since the leak is small.
The missing grommet should be repaired but is not the source of the noise, since the crankcase vent isn't under full manifold vacuum. 1" or 2" of water at most. It wouldn't be audible.
I would use propane or ether around the areas of suspected leakage, which at this point includes everything you touched for the lifter replacement job. You never know what is is until you do the work, but I'd guess the gasket between upper and lower intake manifolds missed a bolt hole, the EGR valve gasket is screwed up somehow, or that the brake booster line has a big crack in it somewhere that isn't visually obvious. You did re-attach the brake booster hose, right?!?
The missing grommet should be repaired but is not the source of the noise, since the crankcase vent isn't under full manifold vacuum. 1" or 2" of water at most. It wouldn't be audible.
I would use propane or ether around the areas of suspected leakage, which at this point includes everything you touched for the lifter replacement job. You never know what is is until you do the work, but I'd guess the gasket between upper and lower intake manifolds missed a bolt hole, the EGR valve gasket is screwed up somehow, or that the brake booster line has a big crack in it somewhere that isn't visually obvious. You did re-attach the brake booster hose, right?!?
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Thank you everyone for all the replies, I am still poking through your links and comments. I did some checking around on the vac lines yesterday with the engine running and just used my fingers to cover the suspected tubes that sounded like they were leaking to no avail. I noticed the sound coming from the back of the valve cover and checked the egr tube which also had no leak. Finally I covered the pcv valve and found two small holes. When I covered the holes with my finger there was no longer a hissing sound (hooray!). I am going to buy a new pcv valve fitting and grommet to ensure a good seal this time as well as add the tube that goes from the snorkel to the pcv breather. That being said, by no means am I done with vacuum lines and am going to order some tubing to replace the cracking plastic lines (I found this link to this tubing in another thread somewhere in a forum from 2009)
Vac line replacement: https://www.mscdirect.com/product/de...rItem=48635932
Vac line replacement: https://www.mscdirect.com/product/de...rItem=48635932
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