Pros: Stopped my leak within 10 minutes and hasn't leaked since.
Cons: None, it worked great.
Last Easter the low coolant light came on in our car, a 1997 Pontiac Grand Am with the 3.1 liter V6 engine. I thought it was odd, but filled the coolant up and drove the 40 miles back home... but it was out of coolant again by time we got there. I assumed it was a blown head gasket or something equally time-consuming or expensive, so we took it to a couple of mechanics to look at. It turns out that the leak was coming from two places; the intake manifold gasket and the timing chain cover gasket. We parked the car for a few months while we decided whether to fix it or look for another one.
Well, this year we decided to go ahead and fix the intake manifold gasket. They said that was the more important leak, and that the timing chain cover leak wouldn't effect anything other than cause us to have to dump more coolant in it constantly. Well, that was annoying enough that I figured I would try a random bottle of terrible stop-leak stuff from the auto parts store. I've never had any luck with this type of product in the past, but the car is kind of old and wasn't really worth putting more money into, so I figured a bottle of $16 stuff would be worth a shot.
This K-Seal multi purpose, one step, permanent coolant leak repair is supposed to mix with all types of antifreeze, so it doesn't require draining or flushing of the coolant system. It claims to permanently repair most leaks in head gaskets, radiators, heater cores, freeze plugs, water pump casings, cylinder heads and engine blocks. This 8 fluid ounce bottle that we picked up is effective on engines up to 10 cylinders.
The directions say to shake it vigorously for 30 seconds and then dump it in the radiator or overflow reservoir. After the engine reaches operating temperature, the leak will stop within 1-3 minutes, and then you just leave the K-Seal in for future sealing. It also says it may take a little longer if it's dumped into the overflow instead of directly into the radiator. Well, there is no place to dump it directly into the radiator in the Grand Am, you can only fill up the coolant through the overflow, so that's where we dumped it.
We shook it for a couple of minutes and dumped it in, topped off the reservoir with antifreeze and then started the car. We let it idle in the driveway for 5 minutes or so, and when I looked under the car I could still see a thin stream of water pouring onto the ground. We hopped in the car and took it for about a 5 mile drive around near the house, and when we got back? Not even a drip. Topped the coolant back off, which was maybe a pint low by this point, and it's been fine ever since. We've driven the car a few hundred miles since then and it hasn't leaked a drop.
The label cautions not to induce vomiting if you swallowed this harmful substance. Just stick your finger in the bottle when you open it, it actually burns a little, so if you're somehow swallowing this stuff you've got bigger problems than a coolant system leak.
K-Seal is safe to use on all types of water cooled engines. The FAQ on Solv-Tec's website says that K-Seal works by "...filling the crack with ceramic microfibers that cure to make a permanent repair." When you look at the fluid, it looks similar to a pile of large glitter floating around in a bottle of vegetable oil. The FAQ also says that it does not work on hoses, and that it needs to be exposed to atmosphere to work effectively (and thus it may not work well on a leak such as coolant leaking into the oil).
Well, what more can I say? It seems to have done the trick for my leak so I'm a satisfied customer. Even though I'm not one to recommend such products usually, I would recommend K-Seal because it did what it advertised and my vehicle suffered no ill effects.