I've seen a growing number of posts from people who install headers on LT1's, and end up with the A/F control system running excessively rich. I've always assumed that these problems are typically caused by exhaust leaks before the O2 sensors, and misfires causing "false lean" conditions, or damaged O2 sensors.

One recent post cited a lot of smoke after the installation of Jet Hot coated headers. While it would be reasonable to assume that it was simply the result of oily hands, I had another thought
(always dangerous). Is there anything used in the formulation or application of the ceramic coatings (e.g. Jet Hot) that might be an O2 sensor contaminant..... silicone comes to mind?

Anyone know the composition of these coatings? Would incomplete curing leave them susceptible to contaminating the exhaust stream?

Just a stab in the dark.....

 

I'm not sure of the composition of Jet Hot's material, but Techline's "equal" is called Cermakrome™. The coating will withstand base metal temps of 2000 degrees. It's unlikely the coating is effecting the sensors. The coating does not effect the egt temps either. All it reduces is underhood temps. Anything is possable however. The coating could have been applied inproperly. ie. oil on the headers, inproper curing procedure. Some exhaust coatings require 1hour @ 500* Some require just room temp. I feel very strongly that something else is the problem.

 

I have no idea if coated headers could contaminate the sensor, but I think the problem is there is less exhaust heat in the collector of a long tube header compared to the original manifold, and the o2's can be damaged by removal (if it is stuck in the manifold) or installation (if it is overtorqued).

 

I 'Think" ( i know, dangerous) Fred is asking about vented gases or by products from the coating it self. As it continues to cure and or burn off the polishing compounds(yes they are tumble polished).

Fred I am not sure but I have not had any issues with mine so far(few years, 9k miles).

It is an interesting idea and I would also like to hear more on it.

 

Yes.... its just a random thought at this point. And yes, I am talking about "gassing" or possibly fine particle dispersion of silicone or phosphorus reacing the sensors.

It just seemed odd when I read several posts in a row where the headers went in and the codes for "slow" O2 sensor response showed up almost immediately on both banks. And since they don't all have the problem, might be related to improper cure.

I agree, damage, contamination with penetrating oil, inadequate operating temperature further from the engine, etc could all contribute to "faulty" sensors, but I'm trying to think outside the box. One of the people with the problem asked Jet Hot the same question, but their answer was along the lines of "in 5 years we've never had a complaint about the headers smoking", so it wasn't too helpful.

I've seen reference to "silicone" in the coating process... possibly used in the dispersants in one process.

 

These two contradicting statements fail the heat transfer common sense test. If less heat is being felt in one place, it is being retained in another.

If outgassing of the coatings is a concern, simply give them the first heat cycle, without the sensors in. Bring them up to full operating temperature for a few minutes, and anything left from the manufacture will likely outgas at that time. Then, return the sensors, and worry no more.

Slow O2 response can also result from the sensor being substantially further down the pipe. I'm speaking generally here, as I'm not sure which headers you speak of.

 

I too have seen the exact link that Fred is talking about, because I saw him post in there. I applaud him reopening a "sister-thread" to this...especially in the advanced tech discussion.

So how many cycles is neccessary to blow out any possible contaminants? Some people say only a few minutes the very first time they are installed. O2 sensors I would assume could definitely be damaged from an incured coating being prematurely heated to running temperatures.

I just talked to a rep from thunder racing and he said it also depends on the brand being compared. He seemed to suggest that not all ceramic coated headers are also coated on the inside. Jet Hots for example are coated inside and out, so I am wondering if there may be a problem from being too general with this comparison? Basic oils from uncoated metal fabrication are different than a coated byproduct?

 

Well guys, my new O2 sensors should be here today (I'm the guy with the thread whose O2's got ruined), and the car is in the air, now I'm just waiting for UPS to come. I'll keep you guys posted and tell you if replacing the O2s does the trick.

 

I installed the new O2s and drove the car for awhile, and it runs like it should! So now we know what the problem was. The car runs very smooth.

-Matt

 

Some ceramic coatings use PTFE (teflon) in their formulations. PTFE will vapourize at around 600 - 700° F. That may be part of the problem. Techline reformulated most of their coatings last year to eliminate PTFE's. You may want to check with Jet-Hot to see if they are using PTFE's in their header coatings.

 

i know this is an old thread but i think it should be a sticky in the exhaust section.

i had this problem when i installed my pacesetter LT

 

Perhaps it's the "if a little bit is good than more is better" problem. Too much silicone or not an appropriate type. For instance; the GE high temp silicone RTV-159 has a very strong Acetic acid scent and is labeled to 500 degrees F, The Permatex high temp silicone 101BR is labeled to 700 degrees F and claims to be "sensor-safe". The Permatex has a much different smell than any other silicone sealant I've ever used ... somewhat like an Amine. I used the Permatex on my installation and since I didn't have the back end of the system installed by dark it got to cure for about 16 hours before I started the engine. I've had no apparent sensor problems.
ooops, just noticed the thread age. But still ...

 

I'll give my contact at Swaintech a call and ask about any outgassing or other compounds used, see what I hear back. FWIW I've had problems with 'header paint' like pacesetter uses, but on high end coatings I've never had a problem.

 

my pacesetters were coated, and as soon as i had problems i called bran herter and he was like, "yup seen that a whole bunch of times"

 

To be honest, pacesetter is the "bargain basement" of the header market, and I've seen quite a few different horror stories of fitment alone. Them using a really cheap coating that would burn off and trash o2's does not suprise me. But higher end coatings like Jet-Hot and such should be beyond those things. They also should have better quality control practices to help get more consistent results.