Question: Help! The engine in my car just crashed. It's a '94 Accord and according to the repair shop the sprocket broke off from my camshaft. They're telling me it will cost about $1,100 to fix and may go as high as $2,000 if other damage is found. The bad parts is they say they won't be able to tell about the additional damage until they do the $1,100 fix first -- does this sound right? I'm not sure if the car is worth putting this kind of money into, as it has close to 200,000 miles on it. The mechanic did his best to explain the repairs but I could sure use some help to understand this so I can make the best decision. He offered to buy it if I didn't want to fix it.
Answer: Wow -- this is an unfortunate situation. It sounds like the bolt holding the camshaft sprocket to the end of the camshaft came loose, or the camshaft began to bind due to overheating or lack of lubrication.
Your cam is a broomstick-diameter shaft containing many egg shaped lobes which press and release each of the engine's valves. This part is located at the top of the engine, in the cylinder head, and is driven by the crankshaft via a cogged rubber belt. Sprockets are toothed discs (roughly the size of a can of cat food) securely attached to the end of each shaft, and mate with the belt. Some engines drive the cam using a chain, and in older engine designs the cam is located closer to the crankshaft, in the engine block. The cam must rotate in exact harmony with the crankshaft for proper engine performance. Should it not, due to a belt, chain, or sprocket failure, the improperly positioned valves of some engines can strike the pistons, bending them. This an expensive calamity as the cylinder head must be removed and several to all valves replaced. Renewing a timing belt when recommended is a prudent decision!
If you roll the dice and renew the camshaft, sprocket, and timing belt, you'll be deeply invested, and have perhaps a 50-50 chance of being good to go, or committed to the unpleasant second stage repair. When the repaired engine is started, bent valves would then be readily apparent, as the engine would run poorly, if at all. Removing the cylinder head first would confirm valve condition -- laying all the cards on the table, but obligate a rational person to do at least a standard valve job due to the many miles on the clock. You'd then be looking at a bill of perhaps $1500 or more. There's always the additional chance of additional issues such as cylinder head warpage, cam journal galling, or corrosion damage.
I checked the private-party used car value of your car with Kelley Blue Book's free and helpful calculator: www.kbb.com Based on the condition and options you supplied, the car is worth about $2,200 in good running condition. Since the repairs may almost equal the value of the car, you'll need to consider your fondness of it, the odds of future additional issues such as the transmission, suspension, air conditioning, and engine peripherals. If the car is in really nice shape, it may be a keeper, otherwise it might be worth considering the purchase offer and start over with a new or lower mileage used car. Only you could know the right path to choose.
