Burnt Valve

[jbprivate]

I bought a '93 SC2 about 3 years ago, Speedometer was stuck at 86k then, so I don't know the true miles nor any history on this car.

I had trouble with over-heating soon after I bought the car. At first it was the fan clutch, so I straight wired the fan. Then the radiator was bad, so I replaced it (several times because I bought from discount auto parts). The temperature gauge has never worked. i tried replacing the sensor but no luck. The car did overheat several times during all this.

About 2 years has passed and it's been a good daily work car. Then it started idling extremely rough. Diagnosis is burnt valve.

So I've taken the engine apart and removed the cylinder head. Big hole in a valve on #3 cylinder.

My question: is the burnt valve the result from the car overheating several times 2 years ago, or is this the result of something else that I need to repair before putting car back together?

Also, what kind of "you might as well do this while you have the engine apart" things should I do?

Thank you

[sierrap615]

the over heatingwould be my guess of the cause of the burned valve. to high or to low of back pressure may also be at fault. or bad valve timing, but thats a long shot. maybe a EGR...

dod you replace the one wire or two wire sensor?

i would replace the timing chain and all components, and the oil pump as well. sometime, i think in 96, saturn added a small hole on the oil pump cover to oil the chain better. also replace the two wire ECT sensor with the new brass replacement. also replace the water pump just incase. while you are at the saturn dealership for parts, buy a new PCV valve, it costs a few bucks more then the universal ones, but its well worth it. clean the intake, throttle body, and EGR of carbon buildup too.

if you have the lower end apart, replace seals, bearings, and piston rings, check measurements, hone cylinders.

[jbprivate]

Even though it hasn't overheated in about 2 years?

I only replaced 1 sensor, it was the only 1 I knew about at that time, after taking engine apart I discovered the 2nd.

I can't afford dealership parts, but all are good suggestions.

I don't have lower end apart, I stopped as soon as I got cylinder head off

Thanks

[jbprivate]

Does this 2nd sensor control the fan? Maybe I don't need the fan straight wired to battery

[sierrap615]

the one wire sensor control the dash gauge, the two wire sensor is feed to the PCM, it controls fan, air/fuel ratio, idle, and a few others. the two wire sensor is a known bad saturn part, if the tip is plastic/resin coated chances are its cracked, the new brass replacement is stronger. the one wire sensor doesn't really matter, it is only for the gauge. a bad two-wire ECT will cause the computer to think the engine is always cold, so the engine will always run rich and hot.

a new thermostat can't hurt ether.

the timing chain kit ($200), PCV valve ($5), ECT sensor($10-18), and oil pump/cover should only be replaced with OEM replacement parts. i have reasons for all.

the water pump, thermostat, and gaskets can be replaced by wherever you want.

also inspect the O2 sensor

be warned, if the valve was burnt, i doubt the cat. converter is in tip top shape. even more so if its 12 years old and have been running rich due to a bad ECT.

does your state have emission testing?

if you go to the service desk at the saturn dealership with the VIN, they should be able print out a service history, that is, if the last owner whent to the dealership.

don't forget the headbolts need replaced as well.