Head Gasket Replacement

A casual night on the town turned into a steaming mess after my radiator cap blew off. My 1991 Honda Civic Si was overheating. By the time I stopped at the gas station the water cooling system was completely empty. In a hurry, I filled the radiator before letting the engine cool. I should have waited, but created a commotion at the gas station when steam started pouring out of the hood. Water flowed through the cooling system, which surrounds the piston cylinders. The head and block contracted, stressing the head gasket, causing it to fail. The gasket keeps the cylinders sealed at the head and block interface from air and water. I drove out onto the street and steam started coming out of the exhaust pipe. The car did not have enough power without the head gasket sealing the cylinders, so I stopped and called a tow truck. An unfortunate problem became an interesting two-week long project during the summer before I came to MIT.

A professional head gasket replacement costs over a thousand dollars. The Owners Manual is an incredible resource to have when doing any repair. My car's distributor also stopped working intermittently before the overheating incident. I did not know what the problem was when my car would not start, but I found an LED light underneath the dashboard that displays codes when the onboard computer detects electrical problems. Using the Owners Manual, I decoded the the LED message, which designated that there was a problem with the distributor. I replaced it with a $150 used one, and it has worked for a few years now.

Replacing the head gasket required disassembling the timing belt, intake manifold, and engine head. First, I unplugged the distributor and sensors electrical connections. I labeled and unplugged the hoses, some of which were hard to get to.

The manual called for taking apart the valve assembly to remove the camshaft and timing belt, but I managed to slip it off with the camshaft still fastened to the engine head. This might be impossible with newer or bigger belts, but avoiding it saved me hours of re-assembly (installing and calibrating valves is a laborious task). I would refrain from using excessive force using a lever or something, for fear of bending the camshaft. I was able to do it with my hands.

The head bolts were very corroded, making it very hard to remove. One broke while I was loosening it. After I took the head off, I found that it broke about an inch recessed into the block. This was a huge problem because I could not grip it to unscrew it. The project should have taken about four or five days, but I spent the next week trying to remove the screw.



What you see is the engine block with the 10 engine head bolts (one of which broke!). You can see the water cooling ducts surrounding the piston cylinders. When the engine overheated, the block that you see contracted at a different rate than the engine head, causing the gasket to deform and fail. This let water rush into the cylinders, creating steam and severely limiting pressure.

First, I tried using E-Z Outs of various sizes. This requires drilling a hole in the broken/stripped bolt, then using the E-Z Out which is essentially a screw with reverse threads. When the E-Z Out catches in the counter-clockwise direction, it torque's the screw loose (hopefully). I broke three of these things just because I was applying so much torque to them with a large wrench.

After the E-Z Outs failed, I accepted the fact that the broken bolt was stuck. Instead of getting it out, I drilled out the hole with an oversized drill bit and used these amazing gagets called HeliCoils. To insert them, I tapped the newly drilled hole with a tap larger than the original (specified by the helicoil), and threaded in these spring-like parts. They make the thread smaller, and impressively held when I tightened the engine head back on. These were truly a life-saver!

I put everything back together and the car still runs to this day. It burns a lot of oil, but hey, it moves. Working on the engine gave me great, hands-on experience and understanding of how engines are laid out and how they work. Despite the mal-use, Honda engines are incredibly robust and are so easy to fix.



The old head gasket left behind a material residue that was burned onto the block and head. This picture shows me scraping it off with a screw driver (there maybe better tools out there but this worked fine).