Silicon sealant and lambda sensors
Discussion
HI
After fitting Megasquirt to my car and ditching the bosch flapply afm from the intake I have modified my airbox so it has a nice round pipe all the way to the throttle body.
I have used silicon sealant on part of the airbox but on reading the Megasquirt site it states that the fumes from the sealant can kill the wideband sensor.
This seems unlikely to me as I doubt there would be much left of the fumes by the time combustion has taken place, any opinions?
After fitting Megasquirt to my car and ditching the bosch flapply afm from the intake I have modified my airbox so it has a nice round pipe all the way to the throttle body.
I have used silicon sealant on part of the airbox but on reading the Megasquirt site it states that the fumes from the sealant can kill the wideband sensor.
This seems unlikely to me as I doubt there would be much left of the fumes by the time combustion has taken place, any opinions?
Edited by james0 on Tuesday 25th August 16:33
Silicone sealant that releases acetic acid as it cures can harm catalytic converters - obviously only if the gas can get to the cat. Some sealants are marked catalyst safe and should be used on parts that can connect with the exhaust system.
However if you don't run the car for 24 hours until the sealant has completely cured there is no issue anyway. The noxious emissions cease once curing is complete.
Personally I think your chances of creating a problem are close to nil unless you actually use non cat friendly sealant on an exhaust manifold joint immediately above the cat.
However if you don't run the car for 24 hours until the sealant has completely cured there is no issue anyway. The noxious emissions cease once curing is complete.
Personally I think your chances of creating a problem are close to nil unless you actually use non cat friendly sealant on an exhaust manifold joint immediately above the cat.
bertelli_1 said:
I fitted some aftermarket manifolds to a Covette a while ago. The kit came with new aluminium gaskets & the instructions stated to use a silicone sealant on the new gaskets! Needless to say I ignored it.
By the way, it isn't the cats that are affected, it buggers up the o2 sensors.
Quite right, nothing to do with the cats or the acetic acid given off during curing. The silicone leeches out continually long after curing is complete and will destroy the lambdas. Remember that incident a couple of years ago when some dodgy petrol detroyed the lambdas on thousands of cars. That was some fitter in the refinery who used silicone sealer on a pipe joint.By the way, it isn't the cats that are affected, it buggers up the o2 sensors.
bertelli_1 said:
I fitted some aftermarket manifolds to a Covette a while ago. The kit came with new aluminium gaskets & the instructions stated to use a silicone sealant on the new gaskets! Needless to say I ignored it.
By the way, it isn't the cats that are affected, it buggers up the o2 sensors.
You're quite right but what it usually says on the product is "catalyst safe" or similar. I've actually got some Loctite 598 sat next to me ready to do an exhaust job and the words on the tube are "suitable for use on catalyst equipped engines".By the way, it isn't the cats that are affected, it buggers up the o2 sensors.
However it is indeed the O2 sensor that gets fouled not the catalyst itself. Same odds to whoever's engine ceases to run of course if they use the wrong stuff. High temp silicone sealant is definitely the best thing to use on exhaust joints as your instructions told you but it must be cat safe of course and that means a lot more money than basic DIY silicone.
fatjon said:
bertelli_1 said:
I fitted some aftermarket manifolds to a Covette a while ago. The kit came with new aluminium gaskets & the instructions stated to use a silicone sealant on the new gaskets! Needless to say I ignored it.
By the way, it isn't the cats that are affected, it buggers up the o2 sensors.
Quite right, nothing to do with the cats or the acetic acid given off during curing. The silicone leeches out continually long after curing is complete and will destroy the lambdas. Remember that incident a couple of years ago when some dodgy petrol detroyed the lambdas on thousands of cars. That was some fitter in the refinery who used silicone sealer on a pipe joint.By the way, it isn't the cats that are affected, it buggers up the o2 sensors.
Pumaracing said:
High temp silicone sealant is definitely the best thing to use on exhaust joints
I certainly prefer it on manifold flanges as it will take the exact shape of any porting, without spending ages trimming gaskets. The big BUT is however that many people seem to think when it comes to any use of sealant that more is better, and all sealants are the same... then dismiss all sealants as being ineffective / incompatible??Pumaracing said:
fatjon said:
bertelli_1 said:
I fitted some aftermarket manifolds to a Covette a while ago. The kit came with new aluminium gaskets & the instructions stated to use a silicone sealant on the new gaskets! Needless to say I ignored it.
By the way, it isn't the cats that are affected, it buggers up the o2 sensors.
Quite right, nothing to do with the cats or the acetic acid given off during curing. The silicone leeches out continually long after curing is complete and will destroy the lambdas. Remember that incident a couple of years ago when some dodgy petrol detroyed the lambdas on thousands of cars. That was some fitter in the refinery who used silicone sealer on a pipe joint.By the way, it isn't the cats that are affected, it buggers up the o2 sensors.
james0 said:
So standard silicone sealant on the intake is bad then? Best remove it and sort it out.
I was talking about exhaust manifolds, but yes, its also bad on the intake and even parts of the oil system (cam covers etc.). The oil breather will normally vent back into the intake, through the cylinders and down the exhaust. The risk of damage is very small though as long as you allow the sealant time to cure. Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff