Stop Leak Additives
 

I know that many people here frown on using additives to stop coolant leaks. But I have a slow coolant leak from a recently replaced head gasket or intake manifold gasket, and I don't have the time or ambition to start tearing the engine apart again. So I was thinking of seeing whether a leak stopper might do the trick.

After searching, some people swear by Bars Leaks, some by Wynn's, and others by some other brand. So I was wondering if anyone here has had any good or bad experiences with these.

The potential problem seems to be plugging the heater core and/or radiator. So I was thinking I could use a valve to close the heater core off. and since I have an extra radiator, I could put that in temporarily, and replace it after flushing the system.

I know it's not the ideal solution, but some people out there seem to have gotten really good, long term results plugging head gasket and other leaks with some of these products.

Advice on using these products would be appreciated
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At our shop, we see a LOT of small block Chevrolet engines leak at the intake manifold. It seems to happen when Dex cool antifreeze is left in for more than 5 years without being flushed. It also could be that GM changed the gaskets about the same time they started using Dex cool, I don't know. However, we flush the systems, new antifreeze (any brand) and add Bars leak. When the leak stops, don't flush the system until it is due again. If the heater core plugs up, it had problems already and the stop leak only made it worse. In that case, reverse flush the heater core only. DON'T add more if the leak does not stop. One dose only between services.
Paul

Bars Leak is like a miracle in a bottle. On my 190D with a failing head gasket and cracked head, I was consuming about a quart an hour of coolant. I put in a bottle of Bars Leak, and within 10 seconds the coolant consumption stopped completely. It was amazing. I drove that way for over a month, it was cold weather that did me in when I drained some of the water and added antifreeze but not before my cooling system got kinda slushy and cracked my heater core... when that happened I drained it again to replace the heater core and the leak came back. That's when I bit the bullet and pulled the head.

Last week my girlfriend's Toyota blew its head gasket. BAD smoke, running on 2 or 3 cylinders. I had to drive it 10 miles to my shop. I put in a bottle of Bars Leak... within one mile the smoke stopped completely. Within 5 miles the engine was running like nothing was wrong.

Highly recommended!

Thanks for all the advice. I've been doing some research, and Bars Leaks seems to have been a mainstay for a lot of people for a long time. Some others that have also gotten good reviews are Thermaweld, Thermaseal, Steel Seal, K and W Block Seal and K-seal, none of which have particles that could conceivably clog passages. Some people have said that the active ingredient in many of these is sodium silicate, which you can buy for peanuts from any chemical company.

I'm not sure a block sealer will work if my leak is from the intake manifold gasket, though, as the temperature there may not be high enough to cause the chemical reaction these product need. The Thermaseal people says it will seal intake manifold leaks, though

The only thing i'm still worried about is whether these products will damage the mechanism in the AC servo, as I'm not really sure how that works, and it seems to have a lot of moving parts that could get sealed along with the leak????

So, any additional advice would be greatly appreciated.