The smoky quest continues...

[Tom]

The exhaust ports have a path to the tail pipe whether the waste gate is open or closed. The majority of it goes into the headers, through the cross-over, through the turbo, through the downpipe, through the cat, and out the tailpipe. To control boost, sometimes a portion of that exhaust leaks through an open waste gate, bypassing the turbo and downpipe, and goes straight to the cat. Either way, if you pressurize the exhaust via the tale pipe, the pressure will find every joint in the system.

I bought a smoke-making machine from Amazon when hunting for vacuum leaks on my old Mercedes. It eliminates all hunting -- every last leak sends up its own little smoke signal you just can't miss.

https://www.amazon.com/AutoLine-Pro-Aut ... 0aWM&psc=1

And it's not harmful to put a leafblower on the tail pipe to blow air into the exhaust system?
If I use a smoke machine (I made one using a cigar and a transfer pump), where do I attach it to? MAF?

Well, I'm not speaking from experience here, but I can't think of any real risk, assuming the air pressure is just a few PSI... Might take the oil cap off in case pressure gets into the crank case via the rings. I was just going off your plan to check the exhaust for leaks, and was thinking smoke in the tailpipe would reveal leaks easier than checking each joint with soapy water. (If you wanted to check for vacuum/boost leaks, then yes you'd put it somewhere before the AFM/MAF...

I once made a smoke machine using cigarettes -- it didn't work nearly as well as the Amazon contraption. Nothing special about the Amazon tool though -- the key is using mineral oil. It creates a ton of thick smoke that you can see from every leak. The cigarette smoke was too wispy to make it all the way out all leaks, and it made my engine smell like a chain smoker for a week.

Remind me why you want to check for exhaust leaks now? Once a car is up and running, exhaust leaks usually make themselves known in fairly short order via soot residue around the leak -- even smallish leaks.

[Belgian951]

The exhaust ports have a path to the tail pipe whether the waste gate is open or closed. The majority of it goes into the headers, through the cross-over, through the turbo, through the downpipe, through the cat, and out the tailpipe. To control boost, sometimes a portion of that exhaust leaks through an open waste gate, bypassing the turbo and downpipe, and goes straight to the cat. Either way, if you pressurize the exhaust via the tale pipe, the pressure will find every joint in the system.

I bought a smoke-making machine from Amazon when hunting for vacuum leaks on my old Mercedes. It eliminates all hunting -- every last leak sends up its own little smoke signal you just can't miss.

https://www.amazon.com/AutoLine-Pro-Aut ... 0aWM&psc=1

And it's not harmful to put a leafblower on the tail pipe to blow air into the exhaust system?
If I use a smoke machine (I made one using a cigar and a transfer pump), where do I attach it to? MAF?

Well, I'm not speaking from experience here, but I can't think of any real risk, assuming the air pressure is just a few PSI... Might take the oil cap off in case pressure gets into the crank case via the rings. I was just going off your plan to check the exhaust for leaks, and was thinking smoke in the tailpipe would reveal leaks easier than checking each joint with soapy water. (If you wanted to check for vacuum/boost leaks, then yes you'd put it somewhere before the AFM/MAF...

I once made a smoke machine using cigarettes -- it didn't work nearly as well as the Amazon contraption. Nothing special about the Amazon tool though -- the key is using mineral oil. It creates a ton of thick smoke that you can see from every leak. The cigarette smoke was too wispy to make it all the way out all leaks, and it made my engine smell like a chain smoker for a week.

Remind me why you want to check for exhaust leaks now? Once a car is up and running, exhaust leaks usually make themselves known in fairly short order via soot residue around the leak -- even smallish leaks.

I think I'll test my cigar machine first and then see how badly I need another new tool.
I want to check for leaks because I failed inspection for high CO emissions. I changed my crossover pipe because I believed it was cracked. Now I want to check if it's fixed and if there are cracks somewhere else.

[Tom]

Understood on not buying more tools, maybe try mineral oil in the tool you made if possible.

High CO most likely means your car is running rich. It's possible an exhaust leak can trick the O2 sensor and cause the car to run rich, so not a crazy idea, especially since you had known leaks, but more often than not these cars will run rich due to something 'off' with the engine management system. You mentioned MAF -- do you have an aftermarket hot-wire MAF or the factory barn-door style Air Flow Meter? If a true MAF, which one and are you sure the chips, fuel pressure regulator, and injectors are all designed to work together? With these cars, all too often people will mix and match those parts -- thinking for example that a higher pressure FPR or bigger injectors will give them more power, when in fact all it does is make the car rich. Oily plugs can causes misses too, which will leave extra CO in the exhaust. Bad engine temp sensors can cause the car to run rich too.

Is your car completely stock -- DME/Chips/AFM/injectors/FPR -- all stock? If not, what mods do you have? And if you have mods, consider getting a wideband O2 sensor so you can SEE if the AFR before heading in for smog checks. After years of guess work and failed tests, I finally installed a wideband on my old 450SL and it made passing the test a breeze....

[Belgian951]

Understood on not buying more tools, maybe try mineral oil in the tool you made if possible.

High CO most likely means your car is running rich. It's possible an exhaust leak can trick the O2 sensor and cause the car to run rich, so not a crazy idea, especially since you had known leaks, but more often than not these cars will run rich due to something 'off' with the engine management system. You mentioned MAF -- do you have an aftermarket hot-wire MAF or the factory barn-door style Air Flow Meter? If a true MAF, which one and are you sure the chips, fuel pressure regulator, and injectors are all designed to work together? With these cars, all too often people will mix and match those parts -- thinking for example that a higher pressure FPR or bigger injectors will give them more power, when in fact all it does is make the car rich. Oily plugs can causes misses too, which will leave extra CO in the exhaust. Bad engine temp sensors can cause the car to run rich too.

Is your car completely stock -- DME/Chips/AFM/injectors/FPR -- all stock? If not, what mods do you have? And if you have mods, consider getting a wideband O2 sensor so you can SEE if the AFR before heading in for smog checks. After years of guess work and failed tests, I finally installed a wideband on my old 450SL and it made passing the test a breeze....

The car is all stock. I just replaced my OEM barn door style MAF with a new / refurbished(?) unit from Bosch. The old one still worked perfectly fine but the PO attached some kind of adapter on it for the cone style filter, which made it impossible for me to restore my factory air box (which it now has once more).

I'm not sure how I can change the richness of the fuel besides the fuel quality button on the DME, but I haven't touched that. It's my understanding that that's also not really desired to touch...

I see a wideband O2 sensor would require a bung welded into the pipe. I'd rather have a non permanent solution, so a clamp on sensor kit may be more useful... Will this WB O2 sensor tell me more than just the ratio? Will it be able to tell CO levels etc?

Update: I did the spray test and wow, I can't believe how fast the exhaust headers are warming up! They are almost immediately evaporating the spray. In any case, I found my problem. The exhaust headers are just leaky at the flanges! I found a pretty big leak on the number 2 flange. It almost looks like the weld is totally gone there. Then another at the other flanges. My crossover seems ok but it's hard to tell because the spray is evaporating so fast. I did find a bubbly leak at the Xover to wastegate connection though... Kinda bummer because I used a Lindsey Racing gasket + the original crush ring. I think I'll try to retighten those bolts but I'll have to be careful because the studs are ready to snap!