Barrs stop leak ??

[Waldoe]

I bought a 70 gmc about a month ago, as far as the motor and tranny goes, runs great, no water in the oil, no tranny fluid in the water. Shortly after I got it I noticed the overflow tank was dark looking, so when i looked in it,it was very dirty. The truck had been driven about 3000 miles in 5 years supposedly. Took the tank off, cleaned it out real good, put it back on. couple weeks later I noticed a small radiator leak after it runs for a while. Truck runs great, did not get hot. I also had new fan belts and wanted to replace the hoses anyway. When I went to take out the radiator the water that came out looked dark brown. At the top of the radiator,where the fill cap is, water is green like antifreeze. The thermostat was also stuck open. I could see where the radiator had been repaired several times before. I decided to have the radiator rodded out and "rebuilt". Decided to change out the water pump also, flushed out the block backwards, and the heater core. It was full of dark brown water. At first I thought it was oil. Put it all back together, filled with straight water, The overflow tank is brown again, looks like wet clay in the bottom of tank. water is brown again in radiator. I pulled out some of the "clay" and put it in a container. I am still filling and emptying the radiator. Hopefully is is some type of stop leak that someone has put in there. I have put stop leak in my radiator about 40 years ago, but would never do it again after seeing this.I can see how it would work if this is what it is, but I would rather fix the problem. In the pics, notice how the water is brown, then after it sits, the water turns green like antifreeze, and the "clay" like stuff settles to the bottom, looks like mud, when dried it looks like dirt. Look at the blob of stuff on the side of the container. After I saw it dried, I put it in a clear glass. Opinions??

[swamp rat]

Humm, I'd have the system pressure tested over night to see if it holds pressure. I have not used Bars stop leak so uncertian of the color, it almost reminds me of a build up of rust from running straight water for too many years. I would say the seller probably flushed the system just prior to you buying it if you checked the coolant then.

[Waldoe]

It is not rust in my opinion. Looks like dark mud

[NTIMID8R]

I have heard of people using CLR or muratic acid in the radiator to clean the block out. Don't know anyone personally that has done this and I would imagine after using either, you would need to replace ALL hoses, water pump and thermostat again. Do not take this as my advice, just something I've heard throughout the years. Do your research before doing this.

[truckster]

It does look like stop-leak to me. I think that stuff is evil.

[Gromit]

Agree with Truckster - no stop leak.. ever.

When I took chemistry 101; the Prof showed us how pure H20 is not conductive! Surprising; since you can imagine if you are sitting in the bathtub and someone suddenly bursts open the bathroom door tosses a plugged in toaster into your tub with you - you might be justifiably worried...

Or if you are standing under a power line in a rainstorm and the 10,000 volt power line suddenly comes down in the puddles at your feet...

But apparently you need only worry about this if there are minerals in the bathtub water.. if it is pure distilled water you would be okay (though I won't be volunteering to test this); hopefully experts on this site will soon weigh in to correct me.

Anyway; I say all this to recommend that you fill your system with distilled water; about 5 gallons should be close - maybe six - you can buy that for about $6 - The galvanic corrosion is the thing to look out for and to try and prevent; in my opinion.

Then change that distilled out maybe once or twice more given what you are seeing..

Personally I don't like the risk of mixing the tranny coolant with the engine block coolant - I keep those two cooling systems separate (which has its own disadvantages, I admit)... So in other words a remote tranny cooler that is separate from the engine block cooler / radiator).

It sounds as if you are going above and beyond already to try and do the right thing; so all I can really offer is my own opinion and props for doing right so far!

[leddzepp]

I've used bars leaks on many vehicles in the past. It does what it says and works great IMO. If you are afraid to use it your choices are:

1. Remove radiator and have it soldered/repaired (if possible)
2. Buy a new radiator

[toolboxchev]

Flush every five days until it stop clouding out quickly. Then run a good radiator flush like permatex.

Dont used that standard retail crap, its nothing but sodium citrate water. It does nothing but create more red oxide in your system.

Do a search here you will find more stuff like oxalic acid and sodium carbonate. I also fitted my system so I could use pressurized air to break everything lose in the system.

Running below normal operating temps now with a 160 thermostat.

[Waldoe]

Thanks for all the replies, and thoughts. One other thing I forgot to mention was that it had a 160 thermostat in it. I could not figure out why. No biggie I thought. I put a 180 in it in hopes of going from 10 mpg to 11. So far it did not work. Ha

[custom10nut]

Don't ever use any of the "stop leak" stuff. It may be a temporary fix, but it creates so much more work, it's not worth "the fix". "Stop leak" will gum up anything that's supposed to slide, most notably, your thermostat, and possibly your small coolant passages, when it settles the first time. Evil stuff

[FirstOwner69]

When I bought my 69 new, there was a substance much as you describe present in the cooling system. Several years later, I tried everything I could think of to remove the goo all to no avail. I always wondered if GM added stop leak at the factory. I never had a leak in 118,713 miles.

Today, GM sells some stop leak tablets comprised of some sort of organic material that they require be added when changing coolant in the aluminum Northstar engines. Several months after I'd installed my 350 GM crate engine in my truck, it began to leak coolant from the bell housing area. I assume it was probably a rear freeze plug. I called GM Performance Parts. Since it was such a hastle to replace the freeze plug and since the engine was not warrantied (I'd had it too long prior to installation and had installed it myself) they said to try the tablets. So far, so good.

[swamp rat]

If your looking for a way to clean the system, my diesel mechanics instructor told us to use dishwashing detergent because its non sudzing, disolve the crystals before adding it to fresh water and run it for a while to get it nice and hot and let it do its work, a short drive somewhere and back ect. Dump it and flush it out a few times with fresh water then drain it and use distilled and antifreeze or just buy the 50/50 pre mix. I have don this on 3 different vehicles and never had a problem.

[Wrenchbender Ret]

If you mix Dex-cool with regular a-freeze it will make a gooy brown mess. Even the so called "mix with any kind". I have used Bars-Leaks for many years & never had a problem. The faulty therm. might have caused it. the engine never warmed up enough to dissolve it. Chrysler had a big problem back in the 70's with brown goo in the cooling system. You could clean & flush the system & put in new A-freeze & 2 weeks later it was all gummed up again. They blamed it on the water pump sucking air.

[Waldoe]

Interesting. Thanks