I know use of the stuff is controversial, looks like an easy way out, etc.

OTOH, the radiator in my '89 Chev G20 (3/4 ton van) with 305 has a tiny, tiny leak. It will go down, I'm guessing 4 fluid ounces in a day of long driving. After a few weeks of use, if unattended, will start to get badly low.

I had a devil of a time finding the leak, could never see signs of fluid leaking. The other night I started it up and let it idle for about 30 minutes. I came back out after 15 and saw a tiny puddle under the radiator. I swept that water away - it dried up and no more was added to it.

I did the same the next night, after topping the radiator again, and after 5 or 10 minutes saw fluid in the same spot. I got under and could see a small trickle coming down the side of the radiator. After it warms up, the leaking stops (!?). Probably why I couldn't find it before.

My thought is to bypass the heater core during use of the stuff as years ago with an old Dodge I think I largely plugged up the core with two applications of the stuff. I was a few hundred miles from home and it did get me home but w/o almost no heat.

My coolant mix is heavy on water at this point. One idea is to put in the Bars Leaks, run it long enough for it to do its thing, then draining most of it and putting in fresh anti-freeze and water. I think the bulk of the work is done initially - the little pellet thingies melt and go where they will but not sure I want to risk plugging my heater core (hard to replace on these rigs I've read) after I hook it back up.

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1986 300SDL, 362K
1984 300D, 138K

This is up to you .In days gone bye it was the bees knees .But to day with sophisticated engines ,this product can do more harm than good . Can ,and will, block up heater core and more small holes in the system . Cut it at the bud, and replace the radiator, in the long run it will be quicker and last longer.

I've used that stuff and other similar stuff successfully in the past. I'd follow your plan. I can't see any harm it would do.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

If I wasn't in sort of a bind I wouldn't consider it. There is an illness in the family, and I need to pick up some stuff in that town (WA). I just replaced my front rotors and brakes, changed auto tranny fluid and filter, putting in a new O2 sensor and TPS today or tomorrow. Would be nice to put off the radiator thing a bit longer. I recently drove it about 400 miles over a week or so, and while the coolant did get a bit low, it was not dangerously so, so it seems that the leak is very tiny. My welder neighbor, a really good mechanic, thinks that the Bars approach would be good enough. But I am torn between the two schools of thought illustrated above.

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1986 300SDL, 362K
1984 300D, 138K

In the old days, Jaguar recommended Bars Leak be added with every flush and fill. If you've ever changed hoses on a Jag, you'd know why: 20 or more hoses, secured with pathetic Cheney clips. Point is, it's safe to just leave it in there. If there are no leaks, it just continues to circulate.

The one problem would be if your radiator is heavily clogged, in which case Bars Leak will ensure that you will need anew radiator.

Remove the thermostat also if you are going to try it. Whichever brand you use make sure it is the sodium silicate formula.

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“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

If its that small of a leak and its been this way for a while, why not just drive it while adding water as needed and just wait until youre not pressed for time?

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

I had good luck in the past, the couple times in my life that I've used it, with the stuff that looks like hamster food pellets suspended in liquid. I don't remember the name though, it was available at any old auto parts store.

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-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

FWIW shipping by way of a company named Ontrac is about 1/4 of what UPS or any other motor freight charges. Might be worth a phone call to them...

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Toyota is a leader only because their drivers block everyone behind them. Oh what a feeling.

These products work on the chemical reaction they have upon exposure to air.

No air, no sealing.

And they can't seal large areas because they don't have the ability to fill in an area, only to harden up when they make contact with the atmosphere.

If your radiator is full of gunk in the bottom then this will just be more gunk. But if you get enough gunk down there the water cannot circulate. This is a big problem on radiators that have the tank on both ends and not top and bottom. With a 'both ends' radiator it takes only a little gunk to starve off your bottom hose.

I have know people who used this in radiators with both metal and plastic tanks and it has worked like it should. One guy who didn't want to replace a $300 radiator just kept a few bottles in his car and would toss in one every time the plastic tank would start cracking.

I finally pulled one for him at a wrecking yard and installed it.

He still carries bottles of Bars Leak with him. Just in case.

I gather that the sodium silicate varieties are for fixing head gasket leaks. Still looking on that. Good call on removing the thermostat. Wouldn't hurt to put a new one in. I just changed the tranny fluid and filter and whoa, good thing, it was dirty.

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1986 300SDL, 362K
1984 300D, 138K

Pulling a radiator on this rig is a chore. On my Bimmer, it's a piece of cake. I'm getting lazy in my old age.

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1986 300SDL, 362K
1984 300D, 138K

Maybe I'm kidding myself but I'm planning to use the stuff for a while, a few hours of driving perhaps and then flushing the system and putting in fresh coolant. Would take off the big hose on the bottom when it's hot which I'm thinking would drain most of the excess gunk.

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1986 300SDL, 362K
1984 300D, 138K

If you have a collection at the bottom of the radiator, you wouldn't get much by removing the bottom hose. Reason is that a lot of it will be on the hot side and in the tubes. I don't understand why you want to drain it afterwards. Bars Leak will either work or not. If it doesn't work, you will need to replace the radiator now. If it does work, you will need to replace the radiator at your convenience. The Bars Leak can remain in the cooling system indefinitely. It won't clog your heater core, thermostat or radiator unless they are already nearly clogged.

that product made me real angry a while back. Have a look at my dilemma

http://www.peachparts.com/shopforum/tech-help/367814-black-mud-coolant.html

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)