1999 5.7 350 vortec P0304 cylinder 4 misfire

[socal k1500]

The amount of residue on your radiator is alarming for sure

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.

I’ve never flushed this system and I doubt the original owners did. According to the Facebook group everyone says dexcool looks like that when mixed with universal coolant which I’ve down for sure.

The gunk didn’t feel oily too me.

 

[SableSlayer]

I’ve never flushed this system and I doubt the original owners did. According to the Facebook group everyone says dexcool looks like that when mixed with universal coolant which I’ve down for sure.

The gunk didn’t feel oily too me.

Okay I hope they're right!

 

[socal k1500]

Okay I hope they're right!

After a week and half I heard back from the shop. They did a lot so I’ll just throw a quick list here

Vaccum test - good
Smoke test - good
Compression test cylinder 4 - good
Fuel pressure test - good
Checked the injectors - good


They did a leak down test and according to them the pressure loss was insignificant but they did hear / see bubbles in the radiator but only once. Wasn’t a consistent thing.

They also noted it looked like there was condensation on the under side of the oil cap and the radiator was low on coolant but no over heating or anything.

They did every diagnostic they could think of and their best guess is to pull the heads and have them sent out to check because they think it could be a cracked head. But the guy was honest that they aren’t sure.

He also threw out that if I do that and they replace heads or have them machined and valve job it would be like 3800$

I threw out there the intake manifold gasket multiple times but kept saying they really don’t think that’s it. So I’m out 370$ for the time spent running all the tests and back at square one when I could have just checked the intake gaskets myself I guess. I gotta figure out what I wanna do next it’s really hard to find time with my work and my one year old to dig into stuff like this on my truck.

 

[SableSlayer]

After a week and half I heard back from the shop. They did a lot so I’ll just throw a quick list here

Vaccum test - good
Smoke test - good
Compression test cylinder 4 - good
Fuel pressure test - good
Checked the injectors - good


They did a leak down test and according to them the pressure loss was insignificant but they did hear / see bubbles in the radiator but only once. Wasn’t a consistent thing.

They also noted it looked like there was condensation on the under side of the oil cap and the radiator was low on coolant but no over heating or anything.

They did every diagnostic they could think of and their best guess is to pull the heads and have them sent out to check because they think it could be a cracked head. But the guy was honest that they aren’t sure.

He also threw out that if I do that and they replace heads or have them machined and valve job it would be like 3800$

I threw out there the intake manifold gasket multiple times but kept saying they really don’t think that’s it. So I’m out 370$ for the time spent running all the tests and back at square one when I could have just checked the intake gaskets myself I guess. I gotta figure out what I wanna do next it’s really hard to find time with my work and my one year old to dig into stuff like this on my truck.

How mechanically inclined are you? Those intake gaskets take aren't bad to change yourself and there's a few videos showing it. I totally get them not thinking that was it cause I did all those same tests multiple times and they checked out. The little bit of bubbles in the radiator really make me think intake gasket.

 

[socal k1500]

How mechanically inclined are you? Those intake gaskets take aren't bad to change yourself and there's a few videos showing it. I totally get them not thinking that was it cause I did all those same tests multiple times and they checked out. The little bit of bubbles in the radiator really make me think intake gasket.

I decided to man up and I’m looking at doing the heads and intake gasket at all once. Going to save my money for some new complete heads and all the gaskets

 

[Orpedcrow]

You must be registered for see images attach

I bet the intake gasket on #4 looks like mine did.

 

[socal k1500]

You must be registered for see images attach

I bet the intake gasket on #4 looks like mine did.

I’m wondering if I just go for it and do the intake manifold gaskets and wait on the heads since they are so expensive.

 

[Orpedcrow]

I’m wondering if I just go for it and do the intake manifold gaskets and wait on the heads since they are so expensive.

$3800 for two head replacements seems high to me.

I just paid $2200 for my engine rebuild, that included replacement rebuilt heads.

Of course that was with me doing all the labor of removing and reinstalling the engine.

The lower gaskets isn’t that bad of a job if you’re a little mechanically inclined. Just be clean and thorough. Stay organized, take pictures, don’t drop anything into the ports or the valley. Take account of your 10mm sockets before you fire it up the first time

 

[Orpedcrow]

You must be registered for see images attach

You must be registered for see images attach

These permadry gaskets are good. Metal with some kind of vulcanized rubber or something.

These (regular factory replacements) are garbage. They are plastic and the rubber seal just falls out of them.

You must be registered for see images attach

 

[socal k1500]

Video 1 overall

Video 2 above oil filter

I took some videos I thought maybe I’d find an obvious coolant or oil leak but man I see oil leaking everywhere it looks like

i know you guys are sick of me dancing around the obvious of just pulling the intake manifold off. I promise im just as eager as soon as i do ill post pictures. Im really hoping its just the gasket and non a valve issue