Bars Stop Leak / Cracked Head Gaskets

Hi. This question is in reference to the first call of this weekend’s episode of Car Talk.

I once had a cracked radiator in a 92 prelude. I used the Bar’s Stop Leak in the radiator and it seemed to seal it just fine. A couple weeks later, the radiator blew! The mechanic at Midas told me that it was my fault because when I used the Bar’s Stop Leak, I changed the pressure inside the radiator and caused the radiator to blow. Is that true or false?

My next question is: During that 1st call to Car Talk this weekend, when a woman had a cracked head gasket, Tom and Ray guessed that the car had 189,000 miles on it. What would have made them guess that? Do head gaskets typically go bad after a certain amount of miles? I thought head gaskets cracked from not having regular coolant changes.

False…well, sort of false. The pressure inside the radiator is controlled by the radiator cap. When the coolant reaches a specified pressure, usually about 15psi, the cap releases fluid into the reservoir. What you probably did was plug up a leak from corrosion such that the pressure was allowed to build to its norm and an area already weak from corrosion blew out.

Head gaskets usually last the life of the engine, except pn certain specific cars like mod-'90s Saturns. They don’t blow out from infrequent coolant changes, they blow out from overheating or bad design or manufacture. Overheating causes dimensional differences in the block and head that can allow insufficient compression of specific areas of the gasket leading to the combustion gasses blowing out a spot on the gasket. Overheating can actually cause the head to warp, doing essentially the same thing. Bad design can allow inconsistant heat expansion between the block and the head causing inconsistant pressure on the critical gasket areas when the engine is at running temp.

In short, anything that causes inconsistant “loading” of the gasket can allow the combustion to blow throgh. Once a breech is formed, erosion makes it get even bigger.

Excellent post! Early Corollas (1970s), the infamous Chevy Vega, and a few others had bad design engines or inferior gaskets.

I once had a leaking rad experience while camping in the woods in Main. The car was a small block V8 Chevelle Malibu. Although I don’t believe in Stop Leak as a good solution, I found a can at a nearby gas station, put it in, enjoyed the resr of our stay, and drove we home 700 miles and had the rad re-cored (those old rads could be rebuilt) at my local garage. My wife and kids thought I was their hero for saving our vacation. While the stuff was in there, the cooling system behaved perfectly, no gaskets blew. Conclusion, in a bind, Stop Leak will be OK if the rest of your cooling system is up to scratch and you don’t have weak head gasket. I would worry somewhat about the radiator cap not releasing the pressure. In that case, leaving the cap off till you get home will work, especially on an older car. On new cars, engine service warning lights may come on.

I once held off a repair on a 3.8l taurus with a slightly leaky head gasket by using Barr’s stop leak. I drove it for several more years and many miles. Eventually it got worse and I junked the car with over 200k miles on it. Durring this time I did not dare to change the antifreeze as it may have disrupted the seal. It turned out to be well worth it as a new Head gasket is $1100.

Thanks doc. And yours was an excellent supplemental post.

I actually had a '72 Vega, bought new. They were really cool, sort of sporty little cars for the first few months until things started heating up, blowing out, and falling off. I dumped mine after the rear wheel came off…even after getting it checked twice under the recall. The retainer C-clip in the carrier assembly in the differential would fall off and the whole wheel and axle would slide right out of the housing. Scary!

Bar?s now makes a new product called ?Headgasket Fix.? It?s very different from the older ?Headgasket Repair.? It comes in a tall cylindrical bottle. It doesn?t require draining the radiator like most products. It?s simple ? pour it in and go.
I used ?fix? on my 1998 BMW 5 series when it began running rough, steaming out the tailpipe and losing coolant. Oftentimes the leaking cylinder piston would stick causing the starter gear to grind and make a horrible noise as if I had a thrown rod. To loosen the stuck piston I put the car in drive and pushed it a few feet. After that I added the Bar?s and drove it around for a while. My car began running better and better the more I drove. After about 100 miles it ran perfectly and was no longer losing coolant. This stuff works great. ? BTW, yes, you just disconnect the upper radiator hose and pour it in.

Scribe-is BMW’s repair still working with the ‘Headgasket Repair’. I have a leaky head gasket on a Saab 9000. The car is not worth repairing per my mechanic. I have tried Bars Stop Leak with some success. The leak diminished (less coolant being added) but right now it’s pretty cool weather in our area so the car does not overheat too much driving around town. On short highway trips the temp gauge goes higher than normal.

My 1994 Toyota 4Runner has an internal/external head gasket leak and my mechanic told me that the engine was trashed. I purchased a bottle of the 20oz Bars Leak Head Gasket Repair and within 5 min of pouring the solution in the radiator, the stream quit coming out of my tailpipe! I drove the truck 20 miles, the compression has returned, no overheating, and no stream from the tailpipe. I do not know how long this fix will last but I will keep everyone updated.