Frozen Piston Rings – Dave’s Garage

A little over a year my Chrysler minivan burned an exhaust valve. While diagnosing the problem, I did a compression check. All the cylinders had roughly 175 psi of compression, except cylinder six which had zero.

After replacing the burned valve, I checked the compression again, and found this cylinder only had about 70 psi. The engine had an uneven idle and a bit of a skip under acceleration. I decided to leave it for a while and see what happened.

I checked the compression again last weekend, and it was still only 70 psi. Remembering that there was no appreciable wear on the cylinder walls, I realized that the cause of the low compression was either broken rings, or frozen rings.

I knew the fix for broken rings would involve a tear down of the engine. Knowing that Marvel Mystery Oil is the “go to” fix for a frozen engine, I decided to try something that may fix frozen rings that would not involve tearing the engine down. I poured a mixture of 50% Marvel Mystery Oil and 50% Acetone through the spark plug hole, and left it overnight. The next morning I turned the engine over a few times to expel the fluid, then I checked the compression. To my relief, the compression was up to 150 psi. This is still lower than the other cylinders, but more than double what it was. The rough idle and skip are gone. I will drive the van for a few weeks and check the compression again.

This fix is much cheaper, faster and easier than removing the head, dropping the oil pan and removing the piston to mechanically free up the rings.

A 50/50 mix of ATF and Acetone is still my go to concoction for freeing up frozen hardware. The fluid is much thinner than conven-tional penetrating oil. I am still amazed at how well this works, and I almost feel like I am somehow cheating. It works so much better than anything else I’ve used, and it is much, much cheaper too.

Because Acetone is a solvent, this concoction needs to be kept in a sealed metal container. I have a metal oil can with a screw on cap on the end of the flexible tube.


Please email all inquiries to: Dave
or snail mail
32 Turkey Hill Road
Richmond VT 05477

Leave a Reply

Your email address will not be published.