White Exhaust Smoke 911SC 3.2 HOT Start

[Porsche904Guy]

I've read almost all of the white exhaust smoke posts but they are all cold starts or cars that have been sitting.

Yesterday, after a 40 minute highway drive, I parked my car for 20 min and started it with a plume of smoke coming from the exhaust. Did a quick drive to a local market, and it smoked again on start.

Not seeing smoke while driving or when I park. I only have one small oil leak that ends up on the pavement. Top end was supposedly rebuilt at 1500 miles ago. The person I purchased the car from seemed very trustworthy, and the work included rings/lapped valves/valve guides.


Started it today and no smoke. After some spirited driving, smoked on the next two hot starts (within 15 min of eachother). One lasted for a few minutes of driving.

Car dies when I remove oil cap to check level. Was around the middle so I did add some oil today, there's a chance she's a quart over but at most its that.


Here's a quick video showing the amount of smoke. She is currently straight piped.

https://www.youtube.com/shorts/UK7_60XemEQ

[eholster]

If, after getting the car up to temp, I park my 79 SC on anything that even suggests having the driver side a few mm lower than the passenger side for more than 10. minutes I blow an offensive amount of smoke... just ask the folks on the patio of the Gucci taco shop I parked in front of this afternoon! I was informed this is likely valve guides... I have found that by idling for a bit before shutting down minimizes the smoke on the next hot start.

[Porsche904Guy]

Originally Posted by eholster

If, after getting the car up to temp, I park my 79 SC on anything that even suggests having the driver side a few mm lower than the passenger side for more than 10. minutes I blow an offensive amount of smoke... just ask the folks on the patio of the Gucci taco shop I parked in front of this afternoon! I was informed this is likely valve guides... I have found that by idling for a bit before shutting down minimizes the smoke on the next hot start.

Gucci taco shop? Gotta find one of those myself.

Certainly possible but I believe the top end work was done, and guides were included.

I recently pulled the master cylinder because the front plastic fitting had cracked. Decided to fix it and put the old one back in. I have read about brake fluid getting past diaphragm and into vacuum line, and into exhaust.

Well, I pulled the line and it was wet. I'm assuming that should be dry as a bone?


Started it this AM and it smoked like the video. Left exhaust pipe is moist. Going to clean that and run with no vacuum for a few days. Should be ok around town?

[EC900]

That’s a lot of oil getting into the cylinder and mighty fast. Ring failure or completely trashed guide?

I had the same with a high mileage, gradually worn and leaky valve guide(s). It’s a slow process which oil seeps past into the cylinder(s) but that it takes a long time to accumulate, perhaps several weeks of sitting without starting to generate that much smoke.
When I would get this symptom usually overwintering storage, smoke lasts for a couple minutes but goes away if I start and drive drive more frequently and regularly.
Check compression and leak down would be first to have checked.
I can’t see a situation where a complete top-end wouldn’t include new valve guides…but not the rings…hmmm?
You can easily check brake fluid theory inspecting the vac line but that’s has to be a lot of missing fluid and it’s a long way to travel, the exhaust smell should be different than motor oil too.

[Porsche904Guy]

Originally Posted by EC900

That’s a lot of oil getting into the cylinder and mighty fast. Ring failure or completely trashed guide?

I had the same with a high mileage, gradually worn and leaky valve guide(s). It’s a slow process which oil seeps past into the cylinder(s) but that it takes a long time to accumulate, perhaps several weeks of sitting without starting to generate that much smoke.
When I would get this symptom usually overwintering storage, smoke lasts for a couple minutes but goes away if I start and drive drive more frequently and regularly.
Check compression and leak down would be first to have checked.
I can’t see a situation where a complete top-end wouldn’t include new valve guides…but not the rings…hmmm?
You can easily check brake fluid theory inspecting the vac line but that’s has to be a lot of missing fluid and it’s a long way to travel, the exhaust smell should be different than motor oil too.

Rings were done as part of the top end. Does smell like oil to me. I'll do a compression and leak down as well. Important data there.


Lets say there is an issue with the top end. Would you not see more smoke will driving or idling?

[EC900]

I’d say the top end condition is the issue and it’s the smoke that’s the symptom.
With the leak (seep) the more oil in the cyl equates to more smoke out the tail pipe, engine heat acts as it’s own seal somewhat but not always, smoke is just less obvious while driving than at idle unless oil is really pouring down at either idle or driving.

If the smoke at idle doesn't dissipate after a few minutes, the leak is greater than one or two seals/ring can handle. This is the common wear issue that shouldn’t come after a 1,500 mi top end.

I take it there’s no odd or difference in engine noises or idle/running issues other than that smoke.

But it’s a sudden appearance of constant smoke that would worry me about driving any further as it could lead to engine disaster when or if the lubrication is compromised as oil is burned off quicker burned than you can refill or keep the tank full.

[JSV798]

White smoke: is this brake fluid being sucked in from the servo?

Roy

[Porsche904Guy]

Originally Posted by EC900

I’d say the top end condition is the issue and it’s the smoke that’s the symptom.
With the leak (seep) the more oil in the cyl equates to more smoke out the tail pipe, engine heat acts as it’s own seal somewhat but not always, smoke is just less obvious while driving than at idle unless oil is really pouring down at either idle or driving.

If the smoke at idle doesn't dissipate after a few minutes, the leak is greater than one or two seals/ring can handle. This is the common wear issue that shouldn’t come after a 1,500 mi top end.

I take it there’s no odd or difference in engine noises or idle/running issues other than that smoke.

But it’s a sudden appearance of constant smoke that would worry me about driving any further as it could lead to engine disaster when or if the lubrication is compromised as oil is burned off quicker burned than you can refill or keep the tank full.

No other issues with sound or drivability than smoke. Going to be doing a leak down, won’t be driving it much until I see the results.

I will also keep an eye on my brake fluid level just in case.

[Porsche904Guy]

Originally Posted by JSV798

White smoke: is this brake fluid being sucked in from the servo?

Roy

The vacuum line was wet. But level seemed normal and amount of smoke & smell makes me lean towards oil.

[Schulisco]

I see white fumes in the video, and white/grey smoke is not oil. Either old fuel (attracts water) or one or more leaking fuel injectors after shutting down the engine leaking fuel into the cylinders and exhaust. This superfluous amount of fuel will be burned or dried in the exhaust due to hot exhaus fumes when restarting the engine after a drive before. Check the spray pattern of all injectors. After shutting down the ignition all injectors have to remain tight. There's some residual pressure in the system (to enable hot starts by pressurizing the fuel to prevent fuel bubbles). But this can cause also leaking the (bad) injectors.
How is the start of the car after sitting some days? Also that much of smoke? I suppose not because then the fuel has vaporized...
If the smoke would be dark/blue only then I would expect either burned engine oil or a way too rich mixture. But the mixture is quite good after a few seconds running the engine while no more smoke and engine seems to run happy...

Thomas

[targa80]

The engine should not die when warmed up and oil cap removed. You have an issue with false air getting into the vacuum of the fuel system. Suggestions to check for leaking fuel injectors is just one part of the equation. Do a smoke test and a cis fuel pressure tests, along with injector spray and fuel delivery tests.

The title says 911SC with a 3.2 motor is this a transplant or a typo in the title?

[TibetanT]

Just a thought, and I am no expert, but were the head bolts checked after the rebuild was done? Usually done about 1,000-1,500 miles after engine is rebuilt and installed.

Good luck, and I hope you find it to be something simple instead of complicated !

Subscribed.

[proporsche]

if this is :Car dies when I remove oil cap to check level" you are most likely missing the air restrictor in the breather hose to the tank..
here is some reading for ya..
Breather Hose Restrictor

regarding the smoke ..most likely your piston rings did not seated in correctly..Did you do piston rings break procedure , after the semi rebuild?

Ivan
btw, the mechanic has check the pistons and cylinder measurements for ovality ??

[Porsche904Guy]

Thank you everyone for the tips. Will go through each one and try to rule parts out. Few things in general. One is I recently replaced the fuel pump and swapped master in/out a few days prior to these issues (perhaps just a coincidence) and in the car you do smell a "sweet" fume. Might not be the best way to describe the smell but in the car driving home from work I could smell it most of the time.

It does run either a bit rich or lean, as I do have a little more than a few pops on deceleration.

I am no engineer, but I do hail from a family of them. The fuel injectors is interesting, and would make sense when you think about the car making similar levels of smoke at various time intervals. If it was oil seeping into combustion chamber, you would think smoke volume would rise after more time as passed.

How is the start of the car after sitting some days? Also that much of smoke?

This is an issue that just presented itself in the past few days. Today, going to work and leaving, I got the same amount of smoke you see in the video. Then nothing at idle or driving. Pretty much starts the exact same as you see in the video, cold or hot.

The title says 911SC with a 3.2 motor is this a transplant or a typo in the title?

It is a 3.2 motor in a 79 chassis.

Just a thought, and I am no expert, but were the head bolts checked after the rebuild was done? Usually done about 1,000-1,500 miles after engine is rebuilt and installed.

I am at the point currently, and had this week planned to retorque heads and check valves.

I did follow the break in procedures I read online, but I'm sure I could have done a better job. And I'm not sure exactly what the seller had done in the 50-100 miles he had used it after top end.

Good luck, and I hope you find it to be something simple instead of complicated !

Thank you! Fingers crossed.

[Porsche904Guy]

Originally Posted by proporsche

if this is :Car dies when I remove oil cap to check level" you are most likely missing the air restrictor in the breather hose to the tank..
btw, the mechanic has check the pistons and cylinder measurements for ovality ??

Car sat for 10 min after getting home from work, before going outside to grab these two photos. Started her up to see if she'd die after I cut some cracked line away, and I got the smoke plume you see in the video. Starting to shy away from it being an oil problem, but certainly not ruling it out.

It looks like I do have the restrictor. There was some oil in the tube but I imagine that is somewhat normal. No idea if he did that with the piston. From what I remember, this guy had built many engines but I'm not sure how many Porsche engines he had ever worked on.

[proporsche]

are you sure..i do not see any restrictor inside the breathing hose?It is cone shape copper piece...you have some interesting engine set up , do not see much but i see many tubes and extra el.cables??
Ivan

[EC900]

For what it’s worth my restrictor is on the end of the hose going into the air box (2.7L) not sure about the 3.2. - that said if his restrictor is missing can the hose be plugged so oil level be checked w/o engine dying?
The air box would have some oil residue in it, not dripping or pooling unless the oil tank is well overfilled, drawing oil in and dropping into the cylinders. You say you added a quart more and that could be the problem - overfill.
Again this is burn off that should subside. So but let it warm up, check level on flat surface while running, then drain excess to just below the full mark if needed.

Good luck, hope it’s just an overfill.

[proporsche]

[QUOTE=EC900;12064086]For what it’s worth my restrictor is on the end of the hose going into the air box (2.7L) not sure about the 3.2. - that said if his restrictor is missing can the hose be plugged so oil level be checked w/o engine dying?
I`d say NO it is a breather hose for the engine....it should really have the restrictor inside the hose which goes to the breather cover on top of the engine

ivan

[Schulisco]

If the engine dies on oil level checking then either the restrictor is missing or there are other issues, like vacuum leaks and therefore a misadjusted mixture and idle. Keep in mind: Even with a (unindentified) vacuum leak you can adjust mixture and idle in that way that the engine will start and run somehow. But far away from perfection in all rpms in the sense of performance and fuel economy or even engine start behviour. It's a widely spread misunderstanding that if the engine starts and idles good or run good at cruising speeds that everything is fine...especially on CIS cars, but also on 3.2's.

Thomas

[Porsche904Guy]

Alright folks, I think I have found the problem.

It's brake fluid getting into the vacuum line.

Was on the highway and had to do a slightly hard stop, and after I filled the entire interstate with smoke. It was bad. Luckily no accidents.
RPM's dropped to almost nothing and car almost stalled out. Let it clear up in the breakdown lane and drove home fine.


Near my house, did another medium-hard brake to see if I could replicate it. And it did the same thing. I'll pull the vacuum line and do a little driving but it looks like I need a new booster & master.

Sucks, just had them out of the car.