97 Tahoe 5.7 V8 Gross Dirt / Mud / Residue in coolant

[1997TahoeFix]

I know many people don't like StopLeak as a solution for coolant leaks, but I had a difficult-to-locate leak and in laziness and desperation, I used the product. It seemed to work great at first, the coolant stopped disappearing. I figured the leak was plugged. The engine ran great for a month or so.

But now the engine is overheating and emits a hissing noise, as if somewhere coolant is leaking. When checking the coolant, the system is filled with this disgusting gunk:



It's also in the other tank:



Is this residue all from the stop leak product? Or is it years of rust gunk and grime?

Also, moving forward. Obviously I need to flush this entire coolant system in an attempt to clean it out.

My oil does not appear to have coolant in it so I'm hoping this is not a blown head gasket.

My thoughts are I need to do a coolant flush, then a pressure test to find the leak. How would you go about solving the problem of this gross gunk/overheating? Thanks guys.

 

[bigfootchiro]

I know many people don't like StopLeak as a solution for coolant leaks, but I had a difficult-to-locate leak and in laziness and desperation, I used the product. It seemed to work great at first, the coolant stopped disappearing. I figured the leak was plugged. The engine ran great for a month or so.

But now the engine is overheating and emits a hissing noise, as if somewhere coolant is leaking. When checking the coolant, the system is filled with this disgusting gunk:

View attachment 272319

It's also in the other tank:

View attachment 272320

Is this residue all from the stop leak product? Or is it years of rust gunk and grime?

Also, moving forward. Obviously I need to flush this entire coolant system in an attempt to clean it out.

My oil does not appear to have coolant in it so I'm hoping this is not a blown head gasket.

My thoughts are I need to do a coolant flush, then a pressure test to find the leak. How would you go about solving the problem of this gross gunk/overheating? Thanks guys.

Looks like the same color as the stop leak. Did you follow the directions properly on the bottle? I've only used that stuff once in my life, but would never do it again. It's a bandaid to a much bigger problem. I would start by flushing the system, pressure testing it, check each cylinder pressure, look for coolant leaks, etc.

 

[1997TahoeFix]

Looks like the same color as the stop leak. Did you follow the directions properly on the bottle? I've only used that stuff once in my life, but would never do it again. It's a bandaid to a much bigger problem. I would start by flushing the system, pressure testing it, check each cylinder pressure, look for coolant leaks, etc.

Good thought but no, I followed the instructions to the letter. I'm convinced there was something wrong with my vehicle's coolant system which caused this weird reaction with the StopLeak. lt's supposed to flow throughout and coat all the surfaces evenly until it "finds the leak" and plugs it. But magically it allows regular liquid coolant to pass by freely. Instead it all clumped together and ****** everything up.

It either mixed with rust, foul water, something other than the regular recommended GM dexcool coolant I've been putting in it.

Anyone ever seen stop leak spontaneously turn into cruddy beach sand?

 

[haks310]

Man, don't know what caused that but try running this stuff through your system:
https://www.amazon.com/Thermocure-Coolant-Remover-Removes-Cooling/dp/B00R74I5UY?ref_=ast_sto_dp

Ran it in my system for a long while after I replaced the OE radiator on my '95 this past summer/fall. Will run it again in two years after I flush the regular ol' green coolant out.

 

[drakon543]

as above stated stopleak is a bandaid however there are multiple different mixtures for a coolant stop leak. there's a few that will do exactly what your seeing. especially if it was the copper colored paste/pellet style. it coats and seals what it can but the excess is just left to constantly flow through your system. not to be a downer but you dont have to have coolant in the oil for it to be a head gasket. when the system is filled start the engine and let it start to warm up with the radiator cap off. if it doesn't stop bubbling it could be a head gasket. to test further and to pin point the leak about mentioned tests are required.

 

[bigfootchiro]

as above stated stopleak is a bandaid however there are multiple different mixtures for a coolant stop leak. there's a few that will do exactly what your seeing. especially if it was the copper colored paste/pellet style. it coats and seals what it can but the excess is just left to constantly flow through your system. not to be a downer but you dont have to have coolant in the oil for it to be a head gasket. when the system is filled start the engine and let it start to warm up with the radiator cap off. if it doesn't stop bubbling it could be a head gasket. to test further and to pin point the leak about mentioned tests are required.

Exactly how I figured out my head gasket issue. Saw bubbling

 

[1997TahoeFix]

Thanks guys.

I suspect there are a few products on the marketplace who are marketed to DIY vehicle owners like myself, but in fact their real target demographic are shady amateur mechanics who hastily patch leaks and overcharge customers, or worse yet, use these bandaid products to flip broken cars to unsuspecting buyers.

All right, I'm going to flush all this crud out until it runs clear. Then refill with distilled water plus dexcool. Then try to find the leak. For real this time. Pray for my gaskets.

**** LeakStop.

 

[bigfootchiro]

Thanks guys.

I suspect there are a few products on the marketplace who are marketed to DIY vehicle owners like myself, but in fact their real target demographic are shady amateur mechanics who hastily patch leaks and overcharge customers, or worse yet, use these bandaid products to flip broken cars to unsuspecting buyers.

All right, I'm going to flush all this crud out until it runs clear. Then refill with distilled water plus dexcool. Then try to find the leak. For real this time. Pray for my gaskets.

**** LeakStop.

DexCool has been known to eat the intake gasket seals. I flushed everything out and use Zerex G-05

 

[drakon543]

Thanks guys.

I suspect there are a few products on the marketplace who are marketed to DIY vehicle owners like myself, but in fact their real target demographic are shady amateur mechanics who hastily patch leaks and overcharge customers, or worse yet, use these bandaid products to flip broken cars to unsuspecting buyers.

All right, I'm going to flush all this crud out until it runs clear. Then refill with distilled water plus dexcool. Then try to find the leak. For real this time. Pray for my gaskets.

**** LeakStop.

nah don't get me wrong ill tell you its a bandaid until the day i die but the stuff has its purposes. 7pmish and a freezeplug pops a pinhole and your 10 miles from home but there's an autozone about a half mile back. or yout at a rough point in your life and your only car blows a head gasket. 2 cans of bars stop leak and a can of black pepper through a stretch of 6 months got me to my next set of wheels. oddly specific because thats my 2 stop leak saves the day stories. arguably tho black pepper lasted 3 months the bars only lasted about month and a half so maybe more dollar general black pepper saves the day??

 

[1997TahoeFix]

DexCool has been known to eat the intake gasket seals. I flushed everything out and use Zerex G-05

Dexcool was the official recommended coolant in the car's original owner's manual and the Haynes Repair Guide. It's also currently sold at auto parts stores with a giant GM logo, with years and models listed directly on the bottle, boasting itself as the official recommended coolant for my make/model vehicle.

With that much official endorsement, you'd think I could confidently use it without googling around but now I've heard from multiple people that it can cause problems, at least in high mileage vehicles. Whoops! It's frustrating when strangers on internet forums are more helpful than the official literature provided by GM.