Show Me Your Crack. (1 Viewer)

[NeverGiveUpYota]

Yup, read into folks all you want. I love a good innuendo.

I want to see manifold cracks before and after repair.
Talk to me about vac readings prior to finding the cracks.
I searched here on mud and came up short. I gather that it's not an easy subject to talk openly about.

I'll be the first to show my crack. I am not jumping balls deep (not a guy but not fair you guys get all the fun w/ words) and pulling my intake yet.
It's miniscule. I'm gonna try the smoke trick (@Spike Strip) w/ a cigar and get my timing set correct as I've been loosely going by ear/feel. And going to check compression as well once the two tools arrive in the mail.

So here's mine:

 

[Output Shaft]

My crack has been filled.
But I didn't even notice it until the machine shop pointed it out to me. It was doubtful that my hairline crack created a significant vacuum leak, but they welded it up anyway.... Since once there is a crack, even faint, it will continue to grow.

This crack happened after I disconnected the EGR system and I feel pretty confident that removing the EGR caused the crack. Manifold was fine for 25 years until the EGR got disconnected. Two years later (or a lot sooner) it cracked.

The EGR inlet pipe normally extends into the intake manifold, creating a super heated "pipe" above the manifold bottom that the fuel flows down on to.... vaporizing it immediately.. or at least heating it significantly.

Without the internal EGR pipe heated any longer, cold fuel will dump straight down onto the blazing hot aluminum intake bottom. That shock & abrupt difference in temperature (I believe) is what causes the crack.
The Heat Control Valve in the ex manifold though is the main culprit. It heats up the bottom of the intake too hot.

That's my theory today anyway.

 

[NeverGiveUpYota]

I like that theory. More on that later. Kiddo woke and I need to tend to him. Thank you tho for your input!

 

[HemiAlex]

I've got a good one. Let me find the pics...

 

[NeverGiveUpYota]

This makes so much sense.

This crack happened after I disconnected the EGR system and I feel pretty confident that removing the EGR caused the crack. Manifold was fine for 25 years until the EGR got disconnected. Two years later (or a lot sooner) it cracked.

The EGR inlet pipe normally extends into the intake manifold, creating a super heated "pipe" above the manifold bottom that the fuel flows down on to.... vaporizing it immediately.. or at least heating it significantly.

Without the internal EGR pipe heated any longer, cold fuel will dump straight down onto the blazing hot aluminum intake bottom. That shock & abrupt difference in temperature (I believe) is what causes the crack.

 

[NeverGiveUpYota]

@Output Shaft can you link a diagram of the heat control valve?

 

[NeverGiveUpYota]

I've got a good one. Let me find the pics...

Cool. I found on your thread a mention of a crack but no pix. I appreciate seeing it now.
You had yours welded too right?

 

[Output Shaft]

This is the drawing in the FSM but it's not accurate.
If the flapper valve sticks in the Hot position, hello cracked intake.

 

[HemiAlex]

Before and after.

I had a very strange idle and power was down for many reasons.

Best use of $25 and a 12 pack ever.

 

[CaptClose]

I'm keeping a close eye on this thread. @davelovesfjs can you post a picture of your manifold crack here please?

 

[NeverGiveUpYota]

This is the drawing in the FSM but it's not accurate.
If the flapper valve sticks in the Hot position, hello cracked intake.

View attachment 1397615

Gotcha. Thanks. I need to check mine out. The spinner thing is def very very rusty on mine.

 

[NeverGiveUpYota]

Before and after.

I had a very strange idle and power was down for many reasons.

Best use of $25 and a 12 pack ever.

View attachment 1397623

View attachment 1397627

$25 to fix that?

 

[HemiAlex]

$25 to fix that?

My friend is a machinist and he knows a few welders.

He also fixed my cracked cylinder head.

He said a lot of old inline 6's break in the same place. No issues 6,000 miles later with either repair. I trust him, he has fixed more than a few over the last 40 years like this.

 

[Thornton Melon]

Here's mine. Quite large. I didn't get the after shot but it looks a lot like Output Shafts.
$20 to weld it up. I wish I would have tried harder to find a machine shop willing to plane the mating surface but after getting laughed out of two shops I doubled gasketed and used way to much copper silicone.
Runs great though.

 

[davelovesfjs]

@CaptClose You can't see my crack! It's covered in JB Weld now... at least the one I knew about. There's still a leak, albeit this seems to make starting the truck much easier. No more 20 minute startup sessions... This is the best photo I have on me at the moment. I'll have to take another one tomorrow.

 

[NeverGiveUpYota]

Here's mine. Quite large. I didn't get the after shot but it looks a lot like Output Shafts.
$20 to weld it up. I wish I would have tried harder to find a machine shop willing to plane the mating surface but after getting laughed out of two shops I doubled gasketed and used way to much copper silicone.
Runs great though.

View attachment 1397927

Wow, that's a clear crack. Had you removed your egr?
And $20 again huh? So it's that cheap to get a weld done. I'm gonna call a guy nearby and see what he says.
And for a machinist... I guess I'll just need to google that because I really have no idea.

 

[Thornton Melon]

Wow, that's a clear crack. Had you removed your egr?
And $20 again huh? So it's that cheap to get a weld done. I'm gonna call a guy nearby and see what he says.
And for a machinist... I guess I'll just need to google that because I really have no idea.

Egr was still in place. It has since been removed. The cracked looked bigger in person. It was pretty raised up.
Call over to the machine shops. They gotta have a larger contraption that can handle the size of the manifold joined together. I think the places I went just had smaller surfacing types of machines---you can tell by the verbiage I use that I know a lot about machine shops.

 

[jpsfj60]

Holy crap! I hope I don't see this when I pull my head off for a rebuild!

 

[Rube]

Might as well share mine. I have a replacement intake that isn’t cracked that I’m planninh to install
I’m its place. Debating whether or not to do the heat riser block off plate. Amy other source than man-a-fre for intake egr plates to keep the pcv hookup?

 

[NeverGiveUpYota]

Oh damn that’s a nasty one. JimC has block off plates as well. I hear they are more stought than MAF. Think long and hard on the heat riser delete depending on how cold it gets where you are.