Exhaust Fumes In 1st Generation Z Cars

[rzola]

Thanks to all the posters on this forum! After reading through quite a few post on the interior fume issue, I decided to attack the problem on my car. I have a series 1 car in fairly good shape that I use as a fair weather daily driver. I love the car, but was getting sick of smelling like a tailpipe!

Even just cracking the drivers window 1/2" would fill the car with nasty untreated exhaust fumes.. I used to think it was bad aerodynamics of the car. My therory was the rear turbulance from the car would draw he fumes forward along the car and enter the side windows. I was getting ready to buy a BRE rear spoiler and try to modify the aerodynamic wake of the car to resolve the fume issue. Glad I did not do this, my theory was wrong! Another poster mentioned that while the widows are closed, the cabin has positive pressure, from the ventalation system. That is why the Series 1 cars have the rear hatch or later cars the Z logo air extractor vents. This allows a flow through effect for your ventilation. They also serve as a relief valve while slamming the doors. If you did not have these extractors, slamming the door causes pressure that can irratate your ears. The extrators on most all cars have a rubber flap, so they work as exit only valves. Once the windows are opened (even just a wee bit) the cabin changes to a negative pressue at speed. This causes the car to pull air in from any other openings in the body. A list of possible culprits:

1. Firewall openings, boots and grometts may be ripped or missing.

2. Inner shift boot (under console), ripped or cracked.

3. Rust holes in the body structure that go through to the interior.

4. Rear hatch area:

a. Rear hatch inner seal

b. Rear hatch inner trim panel (was used as a air extractor valve on 1970 cars) gasket leaking.

c. Rear hatch edge plugs (were used as vent drains on 1970 cars) missing. Also 2 small holes on outer edge.

d. Tail lamp gaskets leaking

e. Other pass throughs for antenna, fuel vapor system.

5. Leaking exhaust system compnents.

Since I have already adressed items 1 , 2, 3, and 5 when I first purchased the car, I focused on area 4.

A. Rear Hatch Seal: Initial observation showed hatch seals appered to be in good condition. I then checked the gap between the hatch and the seal. I used a trick I learned while working as a vehicle development engineer at Ford. You apply some talcum powder to the seal surface, just a light dusting. Close the panel, and then re-open. The powder will deposit on the mating surface. This will show the contact area with the seal bulb quite well. If there is a thin line or no powder, you have a poor seal! I had a very poor seal along the entire rear edge, and around the lower side sections.

Resolution: I tried to adjust the hatch striker bracket downward to get the hatch to close in tighter. This did not make significant improvement. To remedy this, I applied a strip of EPDM rubber self adhesive seal to the hatch. Another Home Depot product. This stuff is black self adhesive seal bulb 7/16th" wide. I stuck it on the hatch inner surface, along where the body seal meets it. This gave a very tight seal in this region!

B. Rear Hatch Inner Trim/Vent Panel: The rear inner hatch panel's sealing gasket (cork) had disintigrated, and a couple of fasteners were missing.

Resolution: I made a new seal from flat foam 3/8" wide stick-on weather stripping. Cheep stuff $2.59 for a small roll at Home Ddepot. Replaced missing fasteners so the new gasket is compressed. The panel is now well sealed!

C. Drain and Plug Holes in Hatch: My 1970 car has drain tubes in these holes, so not an issue.... I did fill the small holes located on both outer edges with a couple of small rubber bumpers. Not sure why Nissan made these holes?

D. Tail lamp gaskets: These tend to get nasty around the edge flanges on 240Zs, but the mounting surface has many fasteners. This usually holds the seal tight and probably will not leak. I have parted out many terminal 240s and found good seal integrity on the mounting surface.

E. Other Pass Throughs: I inspected antenna, and fuel vapor line grometts. All were in good condition.

Conclusion: A 30 mile commute to work left me very excited. No significant fumes inside of the car. I tried various speeds, and window opening combinations. I could only get slight scents of fumes on slow downs, and throttle back outs. Most of this is due to the fact that my valve guide seals are shot. I feel the issue is 90% fixed at this point. I think the most significant fix was the main hatch seal. This is a critical fit on the 1st generation Z. While my seal fix would not fly on a show car, it still does not look too cobbled. Fine for a driver Z car. When I do a re-paint, I will try to install a new seal, and hopefully eliminate the extra seal on the hatch bottom. The fix is nice and cheep. About $10.00 and 2 hours of time was spent on the fix. Now my wife will ride in the Z again!

I hope this summary, and sharing of experiance will help out other Datsun Z fans. Besides the stench, this could possibly be a deady situation! CO poisoning is quite possible.

This post has been promoted to an article

[Ricklandia]

Excellent write-up. This is the sort of thing we need to include in a ClassicZCar "writ-of-wisdom" CD.

[jmanz6]

Glad to see you got it solved. I know the rear seal is bad on my car, as soon as I get it back together (still haven't got the spindle pin out) I will address the rear hatch seal. I haven't been able to move the pin from either my housing or the one you gave me to try.

[hls30.com]

One more set of openings-the drain holes in the spare tire well.

Will

[v12horse]

Thank you for the write-up Rzola. This is definately something I am going to tackle this summer.

-Ben

[nwcubsman]

Bob,

Excellent article. My initial examination has shown 2 proble areas myself. After tackling these I'll move on to eliminate any others you have mentioned. Keep up the good work, I appreciate it.

[TomoHawk]

There is one more REALLY BIG opening you need to check- the bottom is the rear quarters. I took out the plastic rear 1/4 panels from the inside of my 78 280Z, and I sould see clear to the ground. I don't know why theengineers left it open and relied on those pastic interior pices to keep the water out. I thought the air pressure alone would push them in after so many years of getting brittle.

So I thought somebody would have noticed it in these 30 years gone, and formed a plastic, metal, or fiberglass piece to fit in there.

thx

[mdbrandy]

There is one more REALLY BIG opening you need to check- the bottom is the rear quarters. I took out the plastic rear 1/4 panels from the inside of my 78 280Z, and I sould see clear to the ground. I don't know why theengineers left it open and relied on those pastic interior pices to keep the water out. I thought the air pressure alone would push them in after so many years of getting brittle.

So I thought somebody would have noticed it in these 30 years gone, and formed a plastic, metal, or fiberglass piece to fit in there.

thx

Tomo,

I'm not quite sure what you're seeing, but I'm worried for your car. The inner wheel well (metal) should keep you from "seeing through to the road" from the inside quarter. Having said that, I had the exact same experience with my '75 280Z. Remove the inner plastic panel on the drivers side rear, and you could see all the way to the road. But that is not because Datsun messed up. The inner wheel well had rusted completely away, and separated from the rear quarter! So if you can see the road in this area (other than through small holes like the antenna drain), then yours must be rusted away too.

[TomoHawk]

I'll have another look from the bottom the next time I ge the car on a lift. There may have been something else there, and fell off (Florida car- all the plastic & rubber stuff is brittle). I never had any fumes smell inside the car, but it does get a little odor if you leave it in the sun a long time (which is normal)

thanks

[Arne]

Glad this post came back to the top so I could find it. The series 1 car that I am picking up in two weeks no longer has its original vented hatch. I've been trying to decide if this is going to be a problem or not.

So if I'm reading this correctly, if the rest of the car is properly sealed the issues I may face for having no vents is the pressure "boom" when closing the door, and lack of flow in the ventilation system with the windows closed.

Hmm, I may need to look for an early hatch...

[=Enigma=]

I dont' know if this has been mentioned in other threads or not but there is a real danger here of carbon monoxide poisoning. If you're not familiar with this you might want to read up on it. Basically, the Carbon Monoxide(CO) enters your bloodstream through your lungs and bonds with the oxygen(02) molecules, preventing the O2 from being absorbed by your vital organs which includes your heart and brain. This can lead to all kinds of bad things. Since CO is colorless and odorless, you may already be exposed even if you can smell the exhaust fumes. Take this very seriously.

[beandip]

In my openion , this vented hatch is a design flaw that Nissan saw and fixed with the quarter vents. Personally , I wouldent vent the rear hatch unless you are wanting to keep it a complete '70-71 for shows. Over the long haul of my redo of my '73 , I removed the evap tank and eliminated the vent hoses . all but one , that enter the cabin . I have driven the car now for a couple of hundred miles now . In hot weather and I can drive with the windows open and do not smell any fumes. I have filled the gas tank and again the same no smell inside . the car was parked in the garage overnight with the full tank windows closed , and before it would have stunk to high heaven . No longer. Now, I have replaced all the hatch rubber and new tail light seals . The point I am making is that the evap tank CAN be a sorce of fumes . So don't overlook this as a potential area to concider . Gary