SOLVED: 1998 Tahoe 5.7L - Strange Coolant Leak From Above Oil Filter

[AlekAuto]

Edit: I'm an idiot. It was just a freeze plug. Whoops! I swear I'm normally on top of these things lol

Hey everyone. Crossposting this with a couple other forums.
I usually work on Japanese cars, so I'm hoping someone can help me out here. I inspected a 1998 Tahoe with the 5.7L Vortec engine. On this engine, there's a hole above the oil filter. I'm gonna be honest, I have very little idea what this hole is for, but what I DO know is that there's an enormous amount of coolant leaking from it.
Whenever coolant is poured into the radiator, it takes a moment to settle, and then pours out of this hole. Never in my life have I seen anything like this.
I was upfront with the owner and told them that I was stumped and literally couldn't imagine where that coolant was coming from, and we might wanna find someone who knows GM engines a bit better than I do.
I can't think of anything other than a cracked engine block, but I also didn't wanna give it a death sentence without actually confirming what's happening first. I couldn't fine any lines that ran anywhere that could lead to this hole, and I couldn't imagine how you'd even begin to fix an issue like this. without taking the engine apart I looked at the schematics and couldn't figure out where the coolant could be coming from.
I told the owner that whatever it was, it probably wasn't gonna be a quick fix, and that'd I'd try to do more research to see if I can figure out what's going on without having to take the whole engine apart. Maybe I should finally buy a borescope.

Anyways, if anyone has any idea what the hell is going on here, that'd be much appreciated.

Here's a video of it:

https://www.youtube.com/watch?v=VcLXrk-6CoY
Thanks!

 

[Fless]

I can't tell if it's really originating from where I circled it below, but that's a freeze plug on the engine block. It's there to pop out or leak if the coolant freezes.

Let's ask @Eman85 and @exp500 for comments.

 

[AlekAuto]

I can't tell if it's really originating from where I circled it below, but that's a freeze plug on the engine block. It's there to pop out or leak if the coolant freezes.

View attachment 469877

Let's ask @Eman85 and @exp500 for comments.

That's prolly it, I'm guessing the freeze plug rotted out. Don't I feel stupid for not thinking of that first lol

 

[Eman85]

From the video it looks like the freeze plug, core plug or whatever kind of plug you want to call it is leaking. That one isn't too bad to get to, knock it out, clean the hole really good with a wire brush on a drill. Coat the new plug with Permatex from a tube and knock it in. Might have others close to rotting out so it's your call how deep you want to go. If you go scratching around on others you might poke through them.
If you really want to dive deeper that oil filter adapter is usually the cause of an oil leak and if removed will make it easier to get to the plug. Of course that will lead to whether the lines them selves are leaking as they usually do so you could replace them. The you'll find the joys of aluminum radiators with plastic tanks that crack easily. Once you're done and the system is filled if you pressure test it you'll find the other major source of a coolant leak at the intake gaskets corners. Start on that and you'll find the distributor housings that are plastic and the ears crack off where the cap mounts and the gears wear out causing performance problems.

 

[Fless]

From the video it looks like the freeze plug, core plug or whatever kind of plug you want to call it is leaking. That one isn't too bad to get to, knock it out, clean the hole really good with a wire brush on a drill. Coat the new plug with Permatex from a tube and knock it in. Might have others close to rotting out so it's your call how deep you want to go. If you go scratching around on others you might poke through them.
If you really want to dive deeper that oil filter adapter is usually the cause of an oil leak and if removed will make it easier to get to the plug. Of course that will lead to whether the lines them selves are leaking as they usually do so you could replace them. The you'll find the joys of aluminum radiators with plastic tanks that crack easily. Once you're done and the system is filled if you pressure test it you'll find the other major source of a coolant leak at the intake gaskets corners. Start on that and you'll find the distributor housings that are plastic and the ears crack off where the cap mounts and the gears wear out causing performance problems.

Sounds like a rude game of dominoes!

 

[AlekAuto]

From the video it looks like the freeze plug, core plug or whatever kind of plug you want to call it is leaking. That one isn't too bad to get to, knock it out, clean the hole really good with a wire brush on a drill. Coat the new plug with Permatex from a tube and knock it in. Might have others close to rotting out so it's your call how deep you want to go. If you go scratching around on others you might poke through them.
If you really want to dive deeper that oil filter adapter is usually the cause of an oil leak and if removed will make it easier to get to the plug. Of course that will lead to whether the lines them selves are leaking as they usually do so you could replace them. The you'll find the joys of aluminum radiators with plastic tanks that crack easily. Once you're done and the system is filled if you pressure test it you'll find the other major source of a coolant leak at the intake gaskets corners. Start on that and you'll find the distributor housings that are plastic and the ears crack off where the cap mounts and the gears wear out causing performance problems.

Well, you summed up exactly why I try to stick to Japanese engines.

It was the freeze plug, btw everybody. I fixed it and now it's fine. It was a total pain in the ass to get a hammer in there.

 

[exp500]

Please EDIT Title page, add "SOLVED". Helps when searching. Thanks.

 

[Eman85]

Well, you summed up exactly why I try to stick to Japanese engines.

It was the freeze plug, btw everybody. I fixed it and now it's fine. It was a total pain in the ass to get a hammer in there.

I have a few freeze plug drivers that use a handle so you're not trying to swing a hammer in close, one uses an air hammer.
I laid out the usual scenario when you're working on a 25-30yo truck. These are all common items on this model vehicle. I was never a Japanese or any other foreign vehicle tech, it's just what you know or get used to. When I started a Japanese vehicle was a Datsun and not many of them around back then, a foreign vehicle was a VW Beetle.

 

[homesick]

Well, you summed up exactly why I try to stick to Japanese engines.

It was the freeze plug, btw everybody. I fixed it and now it's fine. It was a total pain in the ass to get a hammer in there.

Meaning that they don't leak? Don't use freeze plugs? Don't need hammers?

joe

 

[AlekAuto]

Meaning that they don't leak? Don't use freeze plugs? Don't need hammers?

joe

I thought it was apparent that I was talking about everything else he said, not this freeze plug situation. I take full responsibility for being frazzled and asking a dumb question on that point lol

 

[AlekAuto]

I have a few freeze plug drivers that use a handle so you're not trying to swing a hammer in close, one uses an air hammer.
I laid out the usual scenario when you're working on a 25-30yo truck. These are all common items on this model vehicle. I was never a Japanese or any other foreign vehicle tech, it's just what you know or get used to. When I started a Japanese vehicle was a Datsun and not many of them around back then, a foreign vehicle was a VW Beetle.

If I'm being serious, you're right about it being what you know or get used to. My truck is about the same age and it has a different crop of issues that I prefer dealing with. It's not really about which is objectively more reliable or easier to work on (although there are some outliers that very much are objectively more difficult to work on), more just about which issues are you more comfortable tackling on a daily basis, and generally speaking, Japanese engines have issues that're in my comfort zone.
Never gonna hear me defend the Nissan VQ's various design flaws (I'd actually say it fits the "objectively harder to work on" criteria), but I have a lot more fun working on that one than the Vortec or the Triton lol

 

[homesick]

I thought it was apparent that I was talking about everything else he said, not this freeze plug situation. I take full responsibility for being frazzled and asking a dumb question on that point lol

It wasn't obvious to me, man; but I'm very literal minded.

joe

 

[Fless]

It wasn't obvious to me, man; but I'm very literal minded.

joe

I had to chuckle a little at your response a few posts back. It reminds me of the responses that Jack Reacher gives in the book series.

 

[homesick]

I had to chuckle a little at your response a few posts back. It reminds me of the responses that Jack Reacher gives in the book series.

It still makes no sense to me, but it's ok.

I've seen both movies. I didn't know about the books, but he sounds like my kind of smart ass.

joe

 

[Fless]

It still makes no sense to me, but it's ok.

I've seen both movies. I didn't know about the books, but he sounds like my kind of smart ass.

joe

Never have seen the movies, but am currently in the middle of the book series. 25+ books.

 

[Joseph Garcia]

If I'm being serious, you're right about it being what you know or get used to. My truck is about the same age and it has a different crop of issues that I prefer dealing with. It's not really about which is objectively more reliable or easier to work on (although there are some outliers that very much are objectively more difficult to work on), more just about which issues are you more comfortable tackling on a daily basis, and generally speaking, Japanese engines have issues that're in my comfort zone.
Never gonna hear me defend the Nissan VQ's various design flaws (I'd actually say it fits the "objectively harder to work on" criteria), but I have a lot more fun working on that one than the Vortec or the Triton lol

I do have to agree that Japanese motors (only experienced with Honda motors) tend to go forever. I've had many Hondas over the past half century, and the only one that ever had a motor issue was a 1975 Civic that I turbocharged without a waste gate, and I melted a piston. CLEARLY my fault, and not the motor's fault. Most of these Japanese motors went well over 100,000 miles, and I NEVER changed anything in these motors, except the oil, oil filter, and air cleaner element. NOTHING else.

Maybe, I've been lucky.