The smoky quest continues...

[Belgian951]

Hi everyone,

I should probably change my username to Belgiancrossoverpipe by now but I have another problem, and thus another set of questions after the installation of my new crossover pipe (which you can read about in my very first thread on this wonderful forum).

So the status of my car:

- 1986 Porsche 944 Turbo
- Car hasn't actually properly been driven since November 2022. I did drive it to the technical inspection but that's about 10 km
- All original, no modifications
- Yesterday, I completed the installation of my 'new old stock' crossover pipe. This pipe should be 100% leak free as it is new (it also does look new)
- I torqued the crossover to exhaust header bolts to 20+2 nm (besides the 2 bolts I couldn't reach, I just tightened these a bit more)
- I torqued the crossover to wastegate nuts to the same spec
- I restored the original OEM Air filter box, removed the cone filter
- I added a brand new coolant reservoir and replenished the spilled coolant (from decoupling the turbo water pump to get at the crossover bolts on turbo side)
- I removed two spark plugs and sprayed a bit of WD40 in it to help lubricate the first start up. I then primed the car's oil system by removing the spark plug wires and cranking the car. After a few cranks, I reconnected the plugs and started normally. Car started right up. The two spark plugs I removed had very much black tips and had dark black oil on them.

And... the problems after my test run (idling in the driveway):

- At first start, there was still a lot of smoke coming from the exhaust headers/crossover pipe
- This may however have been oil spills burning off, as I know the pipe had a bit of oil on it because I have a leak from what I believe to be the oil pan (God help me)
- After shutdown and a second start, the smoke from the exhaust area and crossover pipe was almost gone, barely noticable. After a while it did start up again but way less
- I believe smoke did increase if I revved
- I can see the gasket on my exhaust header (the one closest to the front window) bubble. These gaskets are definitely rotten
- There was a lot of white smoke coming out of the tail pipe
- There was also some black slurry sprinkling out of the tail pipe, leaving a track on the driveway

What I plan to do next weekend:

- Start up car and check again visually for leaks
- Spray soapy water on exhaust headers to find leaks, especially seal area but also pipes themselves
- Spray soapy water on crossover to find leaks
- If leaks found on crossover flanges, tighten bolts
- (If leaks found on actual crossover pipe, find cliff and destroy car)
- Change engine oil
- Add coolant and do coolant compression test

My worries/questions:

1- If smoke is coming from the exhaust headers to head, would this be enough to fail emissions? Last time my CO was "7" while it should be "4".

2- Is changing the exhaust header gaskets possible to do without actually removing the pipes and studs?

3- On a scale of 1-10 how hard is it to remove exhaust headers and reinstall them? Do I need to remove intake manifold etc to get at the crossover to turbo bolts so I can get the crossover pipe aligned again when I replace the exhaust headers?

4- Would you suggest to get an induction heater to heat up the studs of the exhaust headers, will this ensure they won't snap? Or lower the chances at least?

5- If exhaust headers are leaky (90% chance they are since I can spot bad welding on them), should I replace them? With what? I'm eying the lindsey racing exhaust header but these are one piece connected, so can I easily replace them? Will they fit my crossover or will this complicate crossover installation even more?

6- Can I use a sort of liquid gasket to fix the exhaust headers gaskets temporarily? Will this hold? How hard is it to remove afterwards?

7- The white smoke from the tailpipe: is this a head gasket failure? Temperature outside was about 55 Fahrenheit (13 celsius). No noticable coolant loss (but haven't driven much), I'll know more when I change the oil. Dipstick oil looks normal though.

8- The spark plugs are brand new, I only drove a few kilometers. They are already black and oily. What can cause this?

9- If the connections between crossover and exhaust manifold are leaking smoke, can I just tighten them beyond the torque spec?

[Tom]

Let's see....

1. Yes, an exhaust leak can throw off the emissions. An exhaust leak at the header let's exhaust gas out, and fresh air in. When fresh air trickles into the exhaust, it will cause the oxygen sensor to think the car is lean, and the DME will try to add more fuel and the car will run rich. High CO readings generally mean the car is running rich. I assume your car has an 02 sensor, right? Either way, when exhaust leaks into the engine bay, some of it will get sucked into the HVAC inlets, and then into your lungs.

2. You need to pull the headers off to change the gaskets (at least without cutting up the gaskets and compromising their integrity).

3. R&R'ing the headers is, on average, 6.38 on a scale of 1 to 10. However, it can be fairly easy if everything comes apart easily, or a nightmare if studs snap off in the head, etc.

4. Heat can help at times. Propane torch works too, just be careful around the fuel lines. You don't necessarily need to get every last stud. I'd start with penetrating oil first, give up on the ones that don't budge, and break out the heat if needed once the easy ones come out.

5. I'd replace them with good used headers from Porsche. Welding stock headers is hard to do right, and aftermarket headers all tend to introduce new fitment and quality issues. I'd only do aftermarket headers (in the style of SFR headers) if I already had a high-output motor and was looking for incremental gains after doing all the common hot rod stuff.

6. No, don't put goo on an exhaust leak. It won't work and the Porsche gods will curse your car.

7. White smoke/steam can be a bad head gasket, but if the car has been sitting for nearly a year, the crankcase has probably accumulate a lot of condensation/moisture. If, after you get the car running, you keep getting white smoke/steam, even after a long drive, then I'd start to worry. See the first few paragraphs of my HG replacement guide for that to look for... viewtopic.php?t=351

8. Oily black plugs after a few miles is concerning. Unless they are sopping wet, I'd get the car running and see what happens once the car has been run a while. After you burn off the one-year hibernation, if those plugs are still getting oily fast, then time to start running some mechanical tests.

9. If the header-to-crossover flanges are leaking, you might try loosening them all up an re-torqueing them. You can get away with a little extra torque (say 25% over spec) but if the headers leak with all the fasteners torqued to spec, something else isn't right. Since your headers were welded, I'm guessing they are the issue.

Other stuff: very common to burn off oil and grease after replacing exhaust parts. Should go away after running the motor long enough. If it doesn't, then worry. Watch for oil dripping onto the crossover from a leaking rear main or oil pan onto other hot exhaust parts. That's a fire hazard. Hopefully, the white smoke is a year's worth of condensation, but time will tell. The black spitting from the tail pipe is just normal soot in the exhaust mixing with the moisture that's spitting out the tail pipe -- it's the byproduct of a potential problem, but not its own problem.

[Belgian951]

Thank you Tom! My responses are in bold below your answers.

Let's see....

1. Yes, an exhaust leak can throw off the emissions. An exhaust leak at the header let's exhaust gas out, and fresh air in. When fresh air trickles into the exhaust, it will cause the oxygen sensor to think the car is lean, and the DME will try to add more fuel and the car will run rich. High CO readings generally mean the car is running rich. I assume your car has an 02 sensor, right? Either way, when exhaust leaks into the engine bay, some of it will get sucked into the HVAC inlets, and then into your lungs.

Yes I have a completely new Bosch O2 sensor installed. I actually have a new theory for my whole crossover problem. I always wondered why I didn't notice the car smoking during my inspection when I purchased the car back in November 2022. It got me thinking and today I formulated this theory:

The car is leaking oil that drips on the crossover pipe (this is a fact). The PO still drove the car up until I purchased it (he said so himself). This means that at the time of purchase, the crossover was oil free! This means, no noticeable smoke since the oil spill was burned off.

When I started the car in May 2023, after a timing belt and waterpump change, the car immediately developed the smoke, clearly coming from the crossover. I thought it was a leak, but it may have been oil burning off as the car had been sitting for months, and thus had the time to accumulate the oil on top of the pipe.

I may have proven this theory already, since when I 'fixed' the pipe with some exhaust paste a week later, the smoke was immediately less and after a few minutes practically gone. The oil must've burned off again, making it appear that my bandaid fix resolved the 'leaky pipe'.

After this fix, I went to the DMV and failed emissions testing. I thought my bandaid didn't work and that the pipe was too far gone. But it may be that the CO issue is caused by another part of the engine. I never did the soapy water test because it looked so obvious where the leak was.

I may have spend about 2K on crossover pipes I didn't need to!
However, seeing my old pipe, the new crossover definitely is an upgrade so.. yay?

2. You need to pull the headers off to change the gaskets (at least without cutting up the gaskets and compromising their integrity).

Thought so, unfortunately.

3. R&R'ing the headers is, on average, 6.38 on a scale of 1 to 10. However, it can be fairly easy if everything comes apart easily, or a nightmare if studs snap off in the head, etc.
Do you have a recommendation regarding a set for this job? Or perhaps a type of studs? Rennbay sells a kit that has a hex head stud which seems popular. Do you think it's good?

4. Heat can help at times. Propane torch works too, just be careful around the fuel lines. You don't necessarily need to get every last stud. I'd start with penetrating oil first, give up on the ones that don't budge, and break out the heat if needed once the easy ones come out.
Not sure I need to remove the cam tower for this job (opinions seem to vary) but using a torch would probably melt the gasket there, no?

5. I'd replace them with good used headers from Porsche. Welding stock headers is hard to do right, and aftermarket headers all tend to introduce new fitment and quality issues. I'd only do aftermarket headers (in the style of SFR headers) if I already had a high-output motor and was looking for incremental gains after doing all the common hot rod stuff.
I could look for some used headers but I'm scared of buying cracked ones. There are also a few types of headers for 944 turbos and I'm not sure if I should keep my 86 accordeon header(s) or get some others.

6. No, don't put goo on an exhaust leak. It won't work and the Porsche gods will curse your car.
Roger that!

7. White smoke/steam can be a bad head gasket, but if the car has been sitting for nearly a year, the crankcase has probably accumulate a lot of condensation/moisture. If, after you get the car running, you keep getting white smoke/steam, even after a long drive, then I'd start to worry. See the first few paragraphs of my HG replacement guide for that to look for... viewtopic.php?t=351
I'll check out your guide! I hope it's condensation, and frankly, would be kinda surprised it had a blown gasket... But I'll check for the signs this weekend. An oil change would tell me everything, right?

8. Oily black plugs after a few miles is concerning. Unless they are sopping wet, I'd get the car running and see what happens once the car has been run a while. After you burn off the one-year hibernation, if those plugs are still getting oily fast, then time to start running some mechanical tests.
I'll keep an eye on it.

9. If the header-to-crossover flanges are leaking, you might try loosening them all up an re-torqueing them. You can get away with a little extra torque (say 25% over spec) but if the headers leak with all the fasteners torqued to spec, something else isn't right. Since your headers were welded, I'm guessing they are the issue.
Thanks, I'll double check if there is smoke coming from them with the soapy water test.

Other stuff: very common to burn off oil and grease after replacing exhaust parts. Should go away after running the motor long enough. If it doesn't, then worry. Watch for oil dripping onto the crossover from a leaking rear main or oil pan onto other hot exhaust parts. That's a fire hazard. Hopefully, the white smoke is a year's worth of condensation, but time will tell. The black spitting from the tail pipe is just normal soot in the exhaust mixing with the moisture that's spitting out the tail pipe -- it's the byproduct of a potential problem, but not its own problem.

I'm pretty sure my rear main and oil pan are leaking... This car is a long-term project for sure! Good that the black spitting issue is not really an issue. Thank you for all the help!

[ROB III]

"R&R'ing the headers is, on average, 6.38 on a scale of 1 to 10."
Love the detail!!!!

[Tom]

When I started the car in May 2023, after a timing belt and waterpump change, the car immediately developed the smoke, clearly coming from the crossover. I thought it was a leak, but it may have been oil burning off as the car had been sitting for months, and thus had the time to accumulate the oil on top of the pipe.

Possible, but in my experience, oil drips mostly after you drive the car and the oil is hot and thin. Once the car cools down, most leaks don't just keep dripping forever. If a leak were that bad, I'm thinking you'd know that by now. Maybe the seller just cleaned off the cross-over so it wouldn't smoke when he showed the car?? Or, like when my rear main was leaking on the cross-over, the oil leak could be hit or miss. I could go weeks with no smoke, then just a couple drops onto the crossover and it would smoke like crazy.

I may have proven this theory already, since when I 'fixed' the pipe with some exhaust paste a week later, the smoke was immediately less and after a few minutes practically gone. The oil must've burned off again, making it appear that my bandaid fix resolved the 'leaky pipe'.

Agreed. Also, exhaust leaks alone won't create thick oily smoke (unless that's also coming out the tailpipe). You are more likely to hear and smell an exhaust leak. If you are getting heavy oily smoke from an exhaust pipe, that typically means there is oil or grease on the outside of the pipe, rather than exhaust gasses leaking out.

After this fix, I went to the DMV and failed emissions testing. I thought my bandaid didn't work and that the pipe was too far gone. But it may be that the CO issue is caused by another part of the engine. I never did the soapy water test because it looked so obvious where the leak was.
I'd be inclined to pull the O2 sensor and see if it's covered in oil like those spark plugs. If it's bad, it can easily cause you to fail emissions. Also, if there is that much oil in the exhaust, then maybe the smoke you are seeing at the tailpipe is indeed oily exhaust smoke rather than condensation. Oil smoke is smelly and blue-ish and lingers in the air, whereas condensation is white and tends to evaporate rather than blowing down the street. Maybe post a video if unsure...

Do you have a recommendation regarding a set for this job? Or perhaps a type of studs? Rennbay sells a kit that has a hex head stud which seems popular. Do you think it's good?

The primary benefit is for 'next time' since those studs have an Allen socket to remove them. Particularly nice if you take the headers off a lot. If the studs end up sticking in the head, however, not sure an Allen socket would hold up.

Not sure I need to remove the cam tower for this job (opinions seem to vary) but using a torch would probably melt the gasket there, no? Not if you just put the flame on the stud...

I could look for some used headers but I'm scared of buying cracked ones. There are also a few types of headers for 944 turbos and I'm not sure if I should keep my 86 accordeon header(s) or get some others. Yes, that is the risk, unfortunately. On the other hand, I've yet to see aftermarket headers that are anywhere near as high-quality as the factory -- short of custom made tube headers that cost thousands and take months...


I'm pretty sure my rear main and oil pan are leaking... This car is a long-term project for sure! Good that the black spitting issue is not really an issue. Thank you for all the help! Ouch, sorry about that...but at least you'll really get to know the car.

[Belgian951]

I already changed the O2 sensor because well why not. It was greyish if I remember. I can make a picture this Saturday. Replaced it with a brand new one. I'll also get a vid of the smoke. It's not blueish, just white. I'll also do an oil change and get a pic of the oil, I'll be sure to clean out the oil catch pan first.

I ordered a set of Rennbay studs and the exhaust headers gaskets, they'll arrive on Tuesday.

Would you say the Lindsey Racing headers are good? If I buy a new set, it's probably theirs. I'll keep an eye out for Porsche headers though. I know a store that sells new headers for cylinder 2 & 3 but not 1 & 4.

[Tom]

I already changed the O2 sensor because well why not. It was greyish if I remember. I can make a picture this Saturday. Replaced it with a brand new one. I'll also get a vid of the smoke. It's not blueish, just white. I'll also do an oil change and get a pic of the oil, I'll be sure to clean out the oil catch pan first.

I ordered a set of Rennbay studs and the exhaust headers gaskets, they'll arrive on Tuesday.

Would you say the Lindsey Racing headers are good? If I buy a new set, it's probably theirs. I'll keep an eye out for Porsche headers though. I know a store that sells new headers for cylinder 2 & 3 but not 1 & 4.

I have never tried Lindsey's headers, so no first-hand experience to share, and have not seen much online about people actually using them. I see that they are not equal length headers, and do not have any mechanism to accommodate expansion/contraction like the factory accordions and/or the slip-fit joints used in the Speedforce Racing headers. I assume they'd work, but all things equal I'd rather have a good set of factory headers -- very few parts like this match the quality and fitment of the factory parts in my experience. You could buy quite a few sets of used headers on eBay for the cost of the LR or SFR headers. That said, I'm pretty jaded about aftermarket parts like this.

[Belgian951]

Thanks!
I got another question concerning identifying the leaks in the headers.

Without taking anything off, I wanted to put a leafblower on the tail pipe to get air to blow so soapy bubbles would be more easy to see. But I'm wondering if that would work on a turbo car since the wastegate is probably closed and would keep the air from reaching the crossover and the exhaust headers. Or am I wrong?

[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

[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?