Intermittent Exhaust Fumes in Cabin - '66 SWB

[304093]

Hey guys,
Over approximately the last 2 summers' worth of driving, I've had occasional exhaust fumes (black smoke, etc.) coming thru the floor vents into the cabin.
It's an intermittent problem, and when I see it, I open the windows to air the car out and the problem "goes away".

Visual inspection yields nothing.

Engine completely rebuilt/restored 2014-2015, returned to me 2016.
Heat exchangers & hoses are brand new (2015).
Heater valves were blasted & painted, and the heat works fine.
Original Leistritz Muffler blasted, recoated.

I've driven the car approx. 6,000 miles or so since 2016. I've only driven it about 250 miles this year, in part because of this problem.

Could there be a blockage of some kind in my muffler?

Could there be a bad weld inside the heat exchangers - but it would have to be both, since the smoke is visible on both sides of the car, passenger & driver.

Do I remove the heat exchangers to inspect?

I'm really stumped here, and don't know where to start - but I know it's a serious problem and needs attention.

Thanks all for any help.

[edmayo]

And the engine has NO oil leaks??

[jim amato]

I have a 67, this is common at first start up after sitting due to oil seepage onto heat exchangers, I have never seen a 100% leak free 2.0, best thing to do is drive the car up to temp to burn off oil, fumes will subside

[304093]

Thanks for responding guys.

No, my engine is leak free. The oil tank to cooler line leaks at the cooler fitting, so some drops of oil have burned on the fitting. After a hard run, there’s usually a drop of oil hanging there.
The problem occurs when the engine is warm, and although I said fumes are present from both vents, it seems worse on the passenger side at times.
Would a leaking exhaust gasket cause this (something that can’t readily be seen by looking at the under side)?
Should I check the muffler for a blockage of some sort?
Is it worth removing the exchangers and visually checking them? Maybe a leak test with air pressure?

[NZVW]

I agree with what jim amato has said.
In all honesty 250 miles per year is a ridiculously low annual mileage.
Fill the car up with gas and go for a good spirited drive, when the petrol tank is at a 1/4 fill it up again and drive home.
Easy Peezy way to have fun and I am sure it will resolve your issue.

[1969911T]

Very interesting!
Intermittent, then goes away
When this happens, does black smoke come out the tail pipe?
Is the heater valve on?

My guess is both the carbs have issues to make black smoke, there is a leak in the headers inside each of the heat exchangers, and the heat is on.
Steve

[356rider]

To answer a few of your questions...
- A blockage in your muffler would not by itself cause smoke in the heater vents. A blockage would also cause the car to run poorly under load.
- There should be no welds inside the heat exchangers unless they are the rare early original type. Pretty sure you don't have these as you say they are new.
- The exhaust gaskets are also outside the heat exchanger so unlikely to introduce smoke in the heater system Also a leak which caused noticeable smoke would definitely be heard. BTW, does your car emit noticeable smoke out the exhaust pipe?

Are you sure it is exhaust fumes you are smelling and not burning oil? Oil dripping from the cooler fitting or anywhere else can get on the heat exchangers and find its way inside as it is blown around forcefully by air currents. If you have a visible drip forming on the cooler fitting, you can be sure that it is dripping and leaking as you drive or as it sits in storage. After you start up, it will take a bit for the sheetmetal of the exchanger to get hot enough to burn oil that is sitting on the inside bottom. Once that happens you get the familiar smoke through the heater vents that others have mentioned and which is fairly common. It really doesn't take much oil inside the exchangers to cause the smoke. Fix your leak at the cooler and also carefully inspect above the driver side heat exchanger for *any* evidence of oil. After that, take it for a long drive as mentioned to burn off any remaining oil in the heat exchangers.

[304093]

Hi 356rider & group,
Thanks for responding.

1. If it matters, the heat exchangers are SSIs and were new in 2015. I sent them to Jet Hot to have them coated, and we used them in my build.

2. I don't see any black smoke from the exhaust pipe at any time, other than the typical puff of smoke on startup after a few weeks of sitting.

3. The car runs great when fully warmed up. Of course it runs a little rough when stone cold after sitting, but I think that's normal.

4. My distributor could probably use a refresh, but I can set the timing acceptably and in the correct range. It advances as it should, but it could be a little "tighter".

5. My carbs were completely restored to show condition by Paul Abbott. The throttle bodies match each other, and I sourced an original pair of sand-cast manifolds. These were coated in the original olive grey coating as found in March-April 1966. They are correctly tuned to the engine & work fine.

6. I don't see any visible exhaust leaks on the outside of the exchangers, which leads me to believe the gaskets are OK.

This leaves the oil line fitting at the cooler. I purchased a new line (pic attached), but it is much longer, and I couldn't figure out how to get it to work. I couldn't get the bend where it should be. Do you have any hints?

Is it OK to use this (new) hose (the original is not availabe anymore and supercedes to this one), and if so, how do I get the bend right? I posted this question last summer, but I gave up because I couldn't get it to work. So I put the old line back on - which leaks like it did last year.
[*Note, Ed said to send my old one to Brad Davis. I'll probably do that this winter, if Brad is not too busy.]

So, it appears the drops on the exchanger are just enough to cause the smoke in the cabin?

You're saying this oil somehow gets past the weld and goes inside, causing the smoke, correct?

Thanks again.

[1969911T]

What seems most curious is that the black smoke in the cabin is on both sides. Since the exhaust does not smoke, the smoke has to come from oil.
I presume the heat lever is on when the smoke occurs. Does the smoke happen only if the blower fan in the front trunk is on?

Once the air comes through the engine fan/alternator, it goes to each heat exchanger. So, either the oil is appearing and starting to smoke under the shroud behind the alternator or the black smoke is coming from one heat exchanger getting mixed by the blower fan(I cannot see how this could happen, but my 69 could be different than your 66) or the smoke just comes on one side and you think it is coming out both sides. Handheld CO monitors are pretty inexpensive($40) and might help to find out which side is worst. If the worst side matches the oil leak, case solved!

[silverc4s]

Those look like the always leaking Exhaust Valve Covers (Original Porsche Design) that has been improved upon over the years by many folks, not without good reason.