Hello, I have a 1998 Civic LX with a D16Y7 engine. It has 220,000 miles and the only major maintenance that has been performed is an exhaust manifold replacement (due to a crack) which apparently is a common issue with this model. The symptoms I have been having for the past week are as follows:
The temperature gauge starts to climb towards H while the car is sitting in traffic or idling for a lengthy period of time. When the car starts moving again, the temperature gauge retreats to normal operating temperature. The coolant level seems to be slowly leaking as I have added around ½ gallon in the past couple weeks. There is no external leak showing and there is no smoking in the exhaust. Recently, my car has had sputtering issues on cold start-up (usually after sitting overnight). The sputtering only lasts for a couple seconds and then the engine runs perfectly. One of these start-ups presented a check engine code of PO301 and P1399 (random and cylinder 1 misfires).
Any idea as to the cause of these symptoms? Thanks!

 

Overheating only while sitting still is usually because the radiator fan doesn't work. Jump the fan switch (on the thermostat housing) and confirm the fan starts immediately when you turn the key on. Test drive with the switch jumped, fan running all the time, and see if there is still overheating. If that resolved it, the fan switch is bad.

You may have engine damage from overheating. Get the system completely full and start it cold with the radiator cap off. Watch for bubbles in the radiator when you rev it. If you get steady bubbles (or coolant gushing out in a severe case) there is a leak inside the engine, hopefully just the head gasket.

 

i quick way is to see if your oil is getting milky...check your dipstick...if it looks like chocolate milk instead of oil...headgasket.is it steaming out the tailpipe???if its not leaking externally,its going somewhere.