Could a coolant leak cause O2 sensor fail?

[jimbo747]

Background: 1993 Loyale EA82 SPFI. About three months ago, after an "at home" engine reseal, I had a leaking manifold gasket. During the repair I got some coolant into the cylinders, which I cleared by removing the spark plugs and cranking the engine. Replaced the plugs, started the engine (started and ran fine, just blew some white smoke for about three minutes until the residual coolant cleared. Then 1 week later, I get a code 32. Replaced the sensor and life was good until three weeks ago.

 

Yep, another manifold gasket leak. Replaced them again, (used copper rtv this time). Started and ran great. 1 week later, I'm getting code 32 again. The funny thing is, I only get it when driving to work on the highway for about 5 miles. At the end of the day, I start the car, the code clears in abotu a mile, and stays off until I'm on the highway again for 5 miles. I saw in another thread someone mention the same phenomina.

 

So, could a dousing in coolant cause the O2 sensor to fail? If not, any suggestions as to what to look for? I'm willing and ready to replace the sensor again, but would like to know why they keep failing.

[idosubaru]

i've done this numerous times as well and never had that problem. so i'm going to guess it's not the coolant.

 

what about the two manifold gasket leaks, i'd be more concerned about that. how did that happen, are you just it was just the gasket both times?

 

could just be coincidence that it happened around the gasket time or maybe the wiring is hosed, so moving the intake/wiring harness somehow moves and contributes to a short int he O2 sensor wiring? just a random guess.

 

the one O2 sensor issue I had ended up being the O2 sensor wire (it's a one wire style on yours) was warn down to bare metal and would ocassionally ground out if it touched metal. i think it was where it passed through the engine cross member, but it was like 10 years ago.

[naru]

Yes

[Log1call]

I don't think coolant is rated as O2 sensor safe but i don't think it causes sensor failure either, not in my experiance. The problem that causes coolant loss can cause O2 sensor readings to be out and therby cause a O2 code however.

 

Anything that can cause a missfire or a lean or a rich mixture can set that O2 code, it doesn't mean the sensor is faulty, just that the reading it was feeding into the ecu was out of acceptable range.

 

Since it only does it on the highway I'd suspect it was just a missfire that was going unnoticed.

[naru]

http://www.lambdasensor.com/main/mfaults.htm

[4x4_Welder]

Yes, it contaminates the sensor and prevents it from actually sensing the exhaust, same as bad oil consumption. You might be able to burn it off over time, but while it's not reading it'll be running rich, and the sensor will get sooted up.

[jimbo747]

Thanks all. The link to the lamda website was especially helpful.

 

I'm really baffled by teh two manifold gasket failures -- sense they occured on the same cylinder head both times. I chanded the bolts and triple check the torque settings. We'll see what happens.

 

I'll also run the length of the single wire to make sure that it's not frayed somewhere along the length. But like I said, the really weird thing is that fact that it only comes onl after driving 70 MPH exactly 5 miles. Afer I stop for the day, then restart, the light goes off within one mile, and stays off until I get back on the highway and drive 70 MPH exaclty 5 miles. If I drive surface streets or stay below 70, the light stays off..

[Log1call]

That site was perhaps a little biased... they were selling sensors! Their description was that the anti-freeze would eat away the sensor, they didn't say it would interfere with it's operation exactly.

I still think that antifreeze will not set a O2 code or cause your ecu to missbehave. I'm a mechanic and have done dozens of head gaskets and never had to change a O2 sensor afterwards.

Anything that can make the motor missfire, or run a bit too lean or rich, can set that trouble code. Since it only happens at highway speed I would doubt it is an air leak. Have you checked your air and fuel filters?

[erik litchy]

the manifold gaskets wont fail if you use the gasket shellac on them. same happened to me.