Intake manifold gasket leak?

[95escahoe]

I had a pretty good oil leak from the valve covers and the valley cover gasket, so I replaced the intake gaskets and knock sensors while I was in there. I had a slight stumble at idle, which has gone away since the reseal. However, I cleaned the throttle body and IAC actuator so that may have been the problem. I didn’t have any stumble at speed.

I would recommend changing the knock sensors as well as the knock sensor harness while you’re in there. The rear knock sensor in this engine was completely submerged under water and pretty rusted. The rubber plugs in the factory harness had shrunk and turned hard like plastic, allowing water in.

Good luck with yours and let us know how it turns out.

I did pretty much the same, intake & valve cover gaskets, knock sensors & harness, I had pretty much the same idle issue, great at speed and at idle it ran a lil rough, I already cleaned the TB & MAF and did new plugs and wires but none of that solved it, the intake gaskets were pretty shot all hard and nasty and someone took out one of the knock sensors at one point and cracked the cover that pops in, gonna pick it up in a few and hopefully it's all good now


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[Newkon]

The metal Fel-Pro gaskets work well and have a wider sealing surface than the factory gaskets. They’re reasonably priced too.

https://www.amazon.com/Fel-Pro-MS98016T-Intake-Manifold-Gasket/dp/B0027XYKZO

I recently put them on the 5.3L in my ’02 Silverado that has 215k miles. No more leaks.

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What did you use to clean that? Gunk and just plug the intake holes from any overspray? Looks really good. I recently did my valve cover gaskets and considering doing my intake manifold gasket. I don't need to do the intake manifold but i figured I might as well. I just bought the truck.

 

[95escahoe]

Update: driven it for a few days truck runs mint so glad it was an easy not too expensive fix


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[eohat]

What did you use to clean that? Gunk and just plug the intake holes from any overspray? Looks really good. I recently did my valve cover gaskets and considering doing my intake manifold gasket. I don't need to do the intake manifold but i figured I might as well. I just bought the truck.

You can use a soft plastic scraper to carefully move dirt away from the intake ports. Then spray B12 Chemtool on some shop towels and clean enough area around each port to apply 2” wide 3M Painters Tape. After that you can spray the heads and valley cover directly with B12 as the painters tape doesn’t seem to be affected much by the cleaner. You’ll want to wear quality rubber gloves to protect your hands. Black RTV is for sealing the knock sensors and blue thread locker is for the intake manifold bolts. If you want to replace the foam pad insulators under the intake manifold you can pick them up at your local GM dealer for about $15/pair, GM #17113563.

 

[Newkon]

did you spray b12 directly onto the lifters as well? I recently did my valve cover gaskets but was afraid to use any sprays on the lifters because I didn't want any issues. Thanks for the info!

Also, were the knock sensors in pretty bad shape? Or did you just want to change them while you were down there. And does the foam pad insulator just sit between the intake manifold and the plate underneath it?

 

[eohat]

did you spray b12 directly onto the lifters as well? I recently did my valve cover gaskets but was afraid to use any sprays on the lifters because I didn't want any issues. Thanks for the info!

Also, were the knock sensors in pretty bad shape? Or did you just want to change them while you were down there. And does the foam pad insulator just sit between the intake manifold and the plate underneath it?

I just used B12 to clean the outside of the engine, I didn’t spray anything inside. The valve covers and valley cover were in place when I was cleaning the engine. I sprayed B12 on a shop towel to clean the valve cover rails and valley cover rail. I wouldn’t recommend spraying B12 on lifters, rockers or anything inside the motor.

The knock sensors were pretty rusted but still functioning. I had to remove them to replace the valley cover gaskets so it made sense to replace them while I was there.

There are two foam insulators under the intake manifold; here’s a pic of the front one.

 

[95escahoe]

I just used B12 to clean the outside of the engine, I didn’t spray anything inside. The valve covers and valley cover were in place when I was cleaning the engine. I sprayed B12 on a shop towel to clean the valve cover rails and valley cover rail. I wouldn’t recommend spraying B12 on lifters, rockers or anything inside the motor.

The knock sensors were pretty rusted but still functioning. I had to remove them to replace the valley cover gaskets so it made sense to replace them while I was there.

There are two foam insulators under the intake manifold; here’s a pic of the front one.

View attachment 70794

What is the purpose of the foam insulator?


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[Tonyrodz]

What is the purpose of the foam insulator?


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I was just thinking that. Maybe to act as a silencer of some sort?

 

[95escahoe]

I was just thinking that. Maybe to act as a silencer of some sort?

Maybe can't think of another reason


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[quest51210]

Maybe can't think of another reason


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to prevent future coolant leaks onto knock sensors I believe