: o2 sensor thread repair



cadillacmax
03-03-09, 07:33 PM
while removing the rear o2 sensor on my 96 cadillac eldorado to change it (engine cold) i believe i screwed up the threads as i had to use a breaker bar with a 2 foot cheater on it for about 3 1/2 for 5 turns.. i've tried screwing the new one in at every angle and it just wont take.. the threads have to be repaired. i see a lot of these kits on the internet.. my goal would be to get a tap that i will be able to extend with.. something? and do it in the car.. i just got this engine in and running (and throwing codes) from a HG repair and bottom end rebuilt - but looking at the manifold itself and the position it's in i may be better off taking off the whole thing out again if it's impossible to do in the car.. i definitely dont want to do either of those to mess with the threads i can see with my eyes and touch with my hands.

lessons learned - 1) whoever didn't put anti seize in the previous o2 sensor replacement is on my shitlist
and 2) if your engine is out and you are already spending like 1500 dollars on parts dont cheap on out the o2 sensor on the early obd2 caddys.. it's in a B*TCH of a place to get to. had to use a combination of 2 different sockets when the o2 sensor was in different positions and removing those heater pipes while the engine is in is a project of its own.

anyone have any suggestions to save my back from my cold, cold floor for another bunch of hours?

tateos
03-03-09, 07:54 PM
Ouch - sorry to hear that. You may be able to rock the entire cradle forward for access...or maybe drop the cradle in the back, but only enough for access?

Why did you remove the sensor in the first place? I left mu original in when I did my HG project.

cadillacmax
03-03-09, 09:52 PM
Ouch - sorry to hear that. You may be able to rock the entire cradle forward for access...or maybe drop the cradle in the back, but only enough for access?

Why did you remove the sensor in the first place? I left mu original in when I did my HG project.

i have the powertrain cradle down by the back four bolts about 3 inches because alldata told me to.. though aside from being able to get a hand in there, it didn't get any easier with it down. the car was sitting for months on end and spewed oil from the rear main when it was started so we didn't grab codes before we started the project. there was no compression on two adjacent cylinders and the oil was a nasty murkey kind of greenish shit color like it was run for months without anyone noticing. the previous owner *cough*mybrother*cough* didn't take care of his ride one bit :\
anyways i haven't (aside from the 80 dollar helicoil kits online) been able to find any kind of insert kit for o2 sensors at any of the stores i've been to or even a big enough tap to try and chase the threads and straighten them out without drilling. if anyone knows a good workaround to replacing the entire manifold i'd love to hear it :)

99Classillac
03-03-09, 10:01 PM
You gotta change O2 sensors when they're hot. Like 120 degrees or more. I guess you can put inserts into the stripped holes.

cadillacmax
03-03-09, 11:07 PM
yup.. that's the plan. dunno what the thread pitch is on the o2 sensor currently.. there are only like 3 threads to measure it on and 2 or 3 of the toothed feelers that came in my tap/die set seem to fit :\
helicoil sells an o2 sensor rethreading kit m18x1.4 which is an odd size imo.. gonna keep lookin around and see if i cant find an exact measurement for this car.
oh and i realized i didn't answer the second poster's question.. when the car started (and didn't burn up as i had expected it to) and ran for a few minutes i got a no activity reading from the rear and front sensors and changing the front one out eliminated the code for that one.. was hoping it would do the same here. i wish i would have taken it in for this little side job - cadillac has to deal with this all the time they'd probably just charge like 2 hours for it :o

sassanach
03-11-09, 10:00 AM
m18x1.5 is the standard thread for 02 sensors:)