My brother used StopLeak… should I be worried?

[Jonathan Stiver]

Hey everyone, so I’ve been traveling away from home for a month or two and let my younger brother drive my Mercedes C220 while I was away. It has a very tiny coolant leak I have not found yet but am 97% sure it’s not internal, i suspect the radiator but anyways it requires topping off every 1000 miles or so.

Well my brother decided he couldn’t be bothered with this and put an entire bottle of StopLeak in w/o asking me. This was at least 2 wks / 500 miles ago. With all the wonderful effects of StopLeak ive heard of/seen I’m stressing about it and of course will thoroughly flush and fill with specified coolant when I get home this week but my question is… Might the damage already be done???

Interestingly enough, he says the car runs ~5*C cooler, has more pressure on the upper radiator hose, and hasn’t lost any coolant since he did this. I’ve seen some success with StopLeak on classic cars with radiator leaks but that’s about it. I guess I’m hopeful the best case is the leak is fixed and I’m able to evacuate 99% of the gunk out

Topic

[Bill]

Some brands of stop leak are worse than others. As long as it’s not floating on top of the coolant and there are no other issues I wouldn’t worry about it.

[college man]

Not a fan of a mechanic in the can.

[Jonathan Stiver]

This is what it looks like now. No, it’s not just the lighting or camera, the coolant really is pretty much black….. 🙁

[george gonzalez]

I’ve had good luck with the stop-leak products to stop heater-core and radiator leaks, during the wintertime, when it would have been inconvenient for me to replace them.

What does not seem to work, and what has no scientific smidgen of a chance of working, are the expensive cylinder pressure to cooling system stop-leak products. Don’t spend $39.95 on those.

I would not stress out about this, just rinse the engine with water once or twice until the water comes out clean, then refill with proper coolant. The stop-leak gunk may partially flush out, and if you’re lucky it has insinuated itself into the leak and now you’re in pretty good shape. Some of the gunk, depending on it’s consistency, may have deposited out on the inside radiator passages and heater core passages, but then again if he used that silvery powder stuff, maybe not.

[Jonathan Stiver]

Thanks, that’s what I’m thinking too. I think that’s how these products are intended to be used even if the manufacturer doesn’t necessarily say that. The good news is he says at this point the consistency seems good not gunked up but I told him not to drive it anymore till I flush it. I guess I was thinking about switching to HOAT coolant anyways so maybe no harm done.

[Kevin Criswell]

[quote=”grg8888″ post=82364]I’ve had good luck with the stop-leak products to stop heater-core and radiator leaks, during the wintertime, when it would have been inconvenient for me to replace them.

What does not seem to work, and what has no scientific smidgen of a chance of working, are the expensive cylinder pressure to cooling system stop-leak products. Don’t spend $39.95 on those.

I would not stress out about this, just rinse the engine with water once or twice until the water comes out clean, then refill with proper coolant. The stop-leak gunk may partially flush out, and if you’re lucky it has insinuated itself into the leak and now you’re in pretty good shape. Some of the gunk, depending on it’s consistency, may have deposited out on the inside radiator passages and heater core passages, but then again if he used that silvery powder stuff, maybe not.[/quote]

+1

That’s how I would do it.

And I agree 100% I HATE the headgasket in a bottle/can, tricks people into thinking they can save hundreds of dollars and in the same span end up ruining their motors.

[Jonathan Stiver]

Just wanted to follow up now that I’m back home and had a chance to work on the vehicle. I obsessively flushed the system and ran a cleaning solution in it for a few hours before filling with specified coolant. And the results, so far, are excellent. The car still runs cooler than it did before and holds more cooling system pressure. The old coolant looked a little discolored but the StopLeak looked like it was mostly dissolved.

So didn’t think I would say this, but $4 StopLeak worked, and worked well. I guess the real question is how long it stays like this, and if I end up having engine problems down the road. I’ll report back in 4 years when I rebuild my engine at 300k mi 😉

[college man]

Glad its working out. Thanks for the update and keep us posted
if things change.

[EricTheCarGuy]

Collegeman posted my videos on this topic which basically covers my opinions on the topic. The take away is basically this. If you use stop leak products, it’s imperative that you follow the directions to the letter. If not, then it’s likely going to cause some of the issues you mentioned, and Merc’s are not cheap to fix in my experience. By the sound of things, you’re fine for now but keep an eye out for issues.

Keep us posted and good luck.

[Jonathan Stiver]

Thanks Eric & collegeman. Like I said, I would have never used StopLeak but it seems to have worked out. I just noticed a bunch of black powder separated out and rose to the top of the jug of the StopLeak’d coolant I drained out. I think eventually it would cause problems in the smaller passages and water pump. But I guess I’d have to say all in all I would recommend someone try StopLeak if the alternative is a $300 Mercedes radiator. I would just flush it out ASAP like I did.

[Author]

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