Pryo Bushing Needs Retightening Again

[JPope]

Brass bushing for Pryo constantly needs retightening. The only apparent movement is between the brass bushing and the cast iron manifold. Have read about others having this problem. Did a a search in this forum for only results so far, and found a method called staking (striking manifold ?? or brass bushing?? with a sharp point to create a burr to minimize movement of bushing, yet still allow removal if necessary). Was wondering if others have had success with this method, any points to consider when doing, or have other methods worked, if so what are they?

 

[Philip]

Myself I would change out that brass fitting. With the temps of our exhaust up to 1200 degrees. It is very close to the melt temps for brass.



I do not know the brand of your pyro. My Auto Meter came with a steel fitting for the probe.

 

[Bob Wagner]

try stainless steel and anti-seize compound, works like a charm

 

[illflem]

2nd Bob's advice

 

[LSMITH]

Stainless is the best way, but you can stake it until you decide what to do. Take a small sharp cold chisel or a sharp centerpunch and lay it on the manifold right next to the bushing and give it a smack. You are looking to roll a small amount of iron over into the brass threads. It won't take much to hold it, so go easy. Basically put a burr into the threads for them to grab on when it tries to back out. Two or three small stakes are better than one big one too. If you decide to pull it out at some point it will unscrew unless you got way out of hand with the staking and you can take the stakes off with a knife or a small file in a couple seconds.

 

[JohnE]

I deal with Cummins C series (8. 3 l) Compressed Natural Gas (CNG) engines. The new models have a back pressure sensor plumbed into the turbo elbow next to the O² sensor (pyro). The brass fitting always loosen the first time we run the engines. Tighten it and they loosen on the next running. Cummins finally started changing out the brass fitting with stainless steel.



I have a 1/8" brass fitting for the pyro probe on my personal truck. It turns out the fitting was just long enough to seat the hex against the instake manifold without the threads protruding on the inside. I snugged t against the manifold and no loosening problems yet.

 

[JPope]

Thanks for the replies, experience, information.

For the record it is an "Isspro R658SHT-PL thermocouple short adjstbl w/plug ht. ", for a EV series guage. Instructions for the guage show a 3/19/02 Rev. D date, and it was installed a week after that, wonder if revision E shows how to secure the adjustable feature, though presumably they meant the probe thru the bushing!

Was installed with anti-sieze as was previously recommended here, but guess I did not need that in this case!!!

Will be staking until a SS bushing is located.

 

[snowracer69]

well....

JPope, you beat me to the question. I've been having the same problem with my thermocouple too. I have an Autometer Z-series and used a 1/4"x1/8" brass adapter on mine, as was recommended on here. It worked great, but keeps coming loose. I thought about throwing a few gallons of Loc-Tite on it, but then realized 1200* would melt that like it was it's job! So, to stainless I will go. Hopefully this isn't a special order item from Napa or Autozone.



BTW, you guys said 1200* F is about the melting point of brass... . um, what will 1400*F do to it?