1999 5.7 350 vortec P0304 cylinder 4 misfire

[socal k1500]

Well, you should see the indication...AFTER you've blown enough smoke to fill the crankcase.

For the record, Vortecs aren't the only engines to fail those silicone-beaded intake gaskets.

This old gasket set was under a ZZ4 intake manifold--the original 6-bolts-on-each-side design from '55 to '85-ish.

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If my intake manifold gasket was bad wouldn’t it be leaking coolant?

 

[Schurkey]

If my intake manifold gasket was bad wouldn’t it be leaking coolant?

Depends on whether the leak is around the water ports, or the fuel/air ports.

Mine (TBI) didn't leak a drop of coolant--but the fuel/air ports were a mess.

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[socal k1500]

Depends on whether the leak is around the water ports, or the fuel/air ports.

Mine (TBI) didn't leak a drop of coolant--but the fuel/air ports were a mess.

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Hey I just want to say thank you for your time and patience helping me out, I really appreciate this forum and guys like you who help idiots like me out lol.

I’m taking it to my shop who did the injectors on Monday, is there anything I should tell them to look for it to confirm it’s the intake manifold gasket ? I know we discussed a smoke test so that’s a given

 

[Schurkey]

Far as I'm concerned, if this is a Vortec, and you don't know the history of those gaskets...just tell them to replace the gaskets.

Another guy I have come to trust on this forum really likes the thick-paper gaskets. I thought the silicone-bead over a hard-plastic or metal carrier gaskets had improved since the trucks were designed...but apparently not enough.

 

[socal k1500]

Far as I'm concerned, if this is a Vortec, and you don't know the history of those gaskets...just tell them to replace the gaskets.

Another guy I have come to trust on this forum really likes the thick-paper gaskets. I thought the silicone-bead over a hard-plastic or metal carrier gaskets had improved since the trucks were designed...but apparently not enough.

Looking at another thread on here reminded me that ive had some liquid leaking out onto my intake minfold right where it meets the plenum, especially near the distributor i thought it was oil but now im thinking it is coolant which would be a dead giveaway. i will take pictures and report back

 

[SableSlayer]

Looking at another thread on here reminded me that ive had some liquid leaking out onto my intake minfold right where it meets the plenum, especially near the distributor i thought it was oil but now im thinking it is coolant which would be a dead giveaway. i will take pictures and report back

Hey sorry it takes me a while to get as. I haven't figured out how to get notifications of replies yet.

Technically you could get both oil or coolant leaking from the bad gaskets. My bad gaskets looked like they were leaking coolant internally but not externally.
If the shop has any questions just have them read thru this message thread entirely. It really may be a good idea for them to really cause it's hard to find current day mechanics that actually know anything about these motors. Most of the mechanics that worked on them a lot around me are all retired now

 

[SableSlayer]

Same hill same exact misfire, I’m taking it to the shop Monday, I’ll let them know about the lower intake gaskets

Looking at these fuel trims I'm like 90 percent positive you need the intake gaskets replaced

 

[socal k1500]

Looking at these fuel trims I'm like 90 percent positive you need the intake gaskets replaced

Picture one is oil in the valleys under the dizzy there used to be more oil but I cleaned it up at some point

Picture two is dried coolant on top of the manifold where the hose goes in on the front of engine.

Picture three and for probably isn’t related but I need to flush my coolant bad it’s nasty.

 

[socal k1500]

Looking at these fuel trims I'm like 90 percent positive you need the intake gaskets replaced

Flushed my system this all came out

 

[SableSlayer]

The amount of residue on your radiator is alarming for sure

Flushed my system this all came out

Is that rust? The stuff on your radiator cap looks like oil. I hope you don't have a bad head gasket. The stuff on your intake is probably coming from your intake gasket.