O2 sensor and RTV...

[HallenTi]

Several months ago, I corrected my large oil leak (common from what I understand) on the L98 engine in my 1990. So far, it has not leaked since.

My problem (or I think it is my problem anyway) is that the RTV included in the kit didn't say "sensor safe".

After the successful repair, I decided that some of my drivability problem could be from the O2 sensor, and since I had never changed it, I bought a Bosch unit from NAPA for about $21. After I put it in, the drivability problems were instantly gone and I was very happy... for a while. No other changes were made at that time other than the O2 sensor, so I am thinking that the RTV in the kit may have fouled up the new O2 sensor. But, since the RTV was used just on the front and back of the manifold, and a little bit to seal he edges of the paper gasket where it meets the RTV at the end, I am not positive of this... anyone have any thoughts? Will the RTV "eventually" stop giving off the fumes that cause the sensor problem? Could the sensor getting "fouled" be a coincidence and there be another problem instead (I sure don't wan to redo the job to find out it makes no difference)? The plugs (recently changed) look just fine - not rich or oily, etc.

While I don't want to redo the job again (this time, using RTV that I know is "sensor safe"), if this is likely to be the problem, I will do it to restore the drivability. Thanks, Tim

 

[jmccloud]

O2 Sensor

Oxygen sensors usually go bad from age or bad gasoline; like methanol, too much injector cleaner or especially any lead (or 'sted o lead') content. It's difficult to see how intake manifold sealant would affect the exhaust sensor. Or, was your large oil leak elsewhere?

 

[KOPBET]

Fumes from the wrong kind of RTV will be sucked in from the crankcase and will contaminate the oxygen sensor. Don't know how long it will take to stop producing fumes; perhaps a long time. If it were me I'd just remove the bad RTV, re-do the repair with sensor safe RTV, replace the sensor and forget about it.

Anti-freeze will kill them also. Not losing any are you?

 

[HallenTi]

The oil leak was the typical leak at the point where the manifold meets the engine block across the back of the L98 engine. The original RTV had gone south and the leak was pretty bad. The repair fixed that completely, for which I was grateful!

I had known about the "sensor-safe" RTV before I did the repair, and just assumed that the small tube in the kit was OK to use, since the kit was recently purchased. It could be that in this location (across the front and back of the manifold to block joints), the type of RTV doesn't really matter and I am needlessly concerned, since it isn't in the intake air path (however, the fumes could easily be sucked up in the PCV system I suppose which would get them to the O2 sensor). The best-bet is to redo the repair as you suggested, and I expect that this time around, it will take less time as well.

I don't appear to be losing antifreeze, so don't think that is my current problem, but will keep an eye on it and see for sure. Thanks for the tip! Tim