Following the advice of TWO CTZCC members, I have solved (at least temporarily) my complaints about exhaust fumes sneaking into my 240Z cabin. I highly suggest/recommend you try the same:

Under the car, just behind the driver's side rear wheel well, put a piece of tape over the antenna drain hoe plug. It's a rubber nipple which lets water out. Since I don't drive my Z in the rain anyway, I would only have to open this drain while washing the car;

Before closing the rear hatch, lay the edge of a towel over the rear part of the gasket which is closest to the latch. In other words, cover the whole rear-most perimeter of the gasket with the edge of a towel and close the hatch on it. That makes a "second gasket" back there along the trailing edge of the hatch;

In the 1970 carz, tape over those two circular vent holes in the trailing edge of the hatch. NOT the external grilles, but the two holes they lead to on the 'invisible' edge of the hatch.

That combination cured my exhaust problems. I realiZe that is a temporary fix, and perhaps only ONE of those would do the job, but at least this gives me an understanding about where the fumes are sneaking into the cabin so I can plan a more permanent attack.

If you're planning a long road trip and don't want to asphyxiate yourself or your passenger, these simple and free tricks will at least help you survive the drive.

Frank

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1970 240Z

Frank,

There was another potential fume fix outlined on Hybridz recently.

http://forums.hybridz.org/index.php/top ... ntry998983

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Phil
1981 280zxt - Now in the care my son!
2014 370Z Sports Touring Roadster

That's a great article, Phil ~ thanks. Not sure what he's referring to tho ~ I'll have to climb under the Z with a light and feel around under there. It doesn't sound like something you can see from inside the cabin.

Anybody else familiar with the "rear frame rail under the tail lights"?

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1970 240Z

If you remove the rear strut tower covers, and cardboard, you will find a gaping hole in the hatch floor, on each side, that is a direct port into the rear frame rails. Since the rear frame rails are not "watertight" by any means, exhaust is free to enter the rear frame work, and chimney into the cabin from those holes. That's not a commonly known entry point for fumes.

Look at the hole at the base of the strut tower!


That hole connects to the hole shown next.

Besides that, the rear frame directly over the muffler has a 3/4" hole in it. I am sure, that some fumes enter this hole and route their way up into the cabin.



Here is a shot of the rear cross frame where it meets the rear frame rails.


Here is the antenna drain tube.


Don't forget alll the fuel line and vent line penetrations. They are usually "drafty" as well.

Photos of my 72.

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-Dave
76Z Turbo'd
72 In Progress---DONE!

Gee, that was a great photo layout!! Thanks for going to all that trouble.

My Z never leaked fumes when it was new. The rear shock tower struts were never messed with until I bought the car the second time, after the taillights had been removed/replaced. When I replaced some Gurrred-up vinyl with new stuff and upgraded the shocks, I found mice nests and a palmful of Hawaiian beach sand in each one. I never thought to patch up any holes while I was in there (Duhhh).

I have taped up the antenna drain plug. I also taped over the two circular vent holes in the inside of the hatch which lead to the horizontal grilles on the back of the '70 carz (didn't tape the grilles themselves, just the opposite end of that path thru the hatch).

But what REALLY made a great difference was when I laid a towel along the trailing edge of the cargo weather stripping before I closed the hatch. Now I get very little exhaust in the cabin. Some, but not much.

So using your photos and a smoke gun, I need to jack the car up and trace a few more paths.

Frank

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1970 240Z

My car just happens to be on stands right now, so I figured I would go have a look, and snap some shots.

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-Dave
76Z Turbo'd
72 In Progress---DONE!

Another easy fix is getting a longer exhaust tip.

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Clive Bogle President - New York Z Car Club - NYZCC.COM
1971 240Z - LS1/T56
1974 260Z-L30
1976 Fairlady Z

Well, that's true. But Paul in RI tried that, and it nearly killed him. He'll gladly show you his stitches.

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1970 240Z

Ha, true but I didn't say get a sharp exhaust tip

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Clive Bogle President - New York Z Car Club - NYZCC.COM
1971 240Z - LS1/T56
1974 260Z-L30
1976 Fairlady Z

Frank,

One other source which I don't believe was addressed is from leaky tail lights.

As with other old rubber parts, the old gaskets that seal the tail light assembly to the car gets dried out over time. These have been known to cause the leaks as well.

These cars when driven with the windows down can also have the exhaust creep up along the bottom of the LR side quarter window at the body line and come into the open drivers window. This is especially true if you only have the drivers window opened. It is not as serious if both windows are opened. Go figure!

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John Kish
1971 240Z - original owner

Wow ~ I'm trying to picture that. So, if I'm blasting across the parking lot at 65mph, the fumes can actually sneak up the side of my car to get into the window?

There should be some way to aerodynamically break up the back draft which would cause that.

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1970 240Z

Ever notice that they smell worse when you are decelerating or coasting down a long hill?

Besides incomplete fuel combustion or oil sucking...

My theory is that the velocity of the fumes at the exhaust tip is very slow during deceleration, so they can creep back into the car. When you are on the throttle, the velocity of the exhaust shoots it back further away from the car where it gets sent to the car behind you instead.

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-Dave
76Z Turbo'd
72 In Progress---DONE!

Moral of the story, stay on the throttle!

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Phil
1981 280zxt - Now in the care my son!
2014 370Z Sports Touring Roadster