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Fri Aug 08, 2003 1:05 pm

Hi All,
:?: I am wondering how much ventilation does the crescent vents on the back on my 74 SB provide? Are they really usefull? Also, how do I get into the ductwork from the vents to the inside to see how much rot is in there? Any Ideas?
Thanks,

Fri Aug 08, 2003 6:12 pm

I don't know of any tests that can answer that question but I think they were more of an EPA concern. The European spec cars had them optional. Pull the plastic and look inside the hole, also in the engine bay you can look on either side of the firewall and up into this area from behind. If your car doesn't have the headliner you can see the condition of the entrance holes on either side of the back window.

Fri Aug 08, 2003 9:32 pm

Take the padding out that is on the inside of the bug that soaks up all of the moisture and rots those vents right out.

Fri Aug 08, 2003 9:47 pm

That could be done but keep in mind that will increase the engine noise that is heard inside the car. What I did was took some undercoating spray and sealed them real good.

The half moon vent and padding was a long term downfall, due to rust, in VW's design.

Sun Aug 10, 2003 2:26 pm

both superbeetles that i have owned had the body behind the vents rotted pretty good. both were sealed off and had extensive bodywork done to correct the rust. i guess thats why mexican beetles dont have the vents.

Brad

Mon Aug 11, 2003 12:07 pm

Superman wrote: but I think they were more of an EPA concern.

What does the EPA have to do with the ventilation of your car's interior?

I've had cars with and without those vents, and they do NOTHING!!!

Mon Aug 11, 2003 2:44 pm

Yes you are correct, it is more of a NHTSA (National Highway Traffic Safety Administration) issue than EPA (Environmental Protection Agency); although both of these departments fall within the DOT (Department of Transportation).

Quote:
The U.S. government is working on amendments to 30 existing Federal Motor Vehicle Safety Standards adopted in the past four years. Some 30 new proposals are being considered for 1971-1975. In it's 200 page book detailing its plan of action for 1971-1972, the National Highway Safety Bureau reports: "Rulemaking actions during the 1967-70 period have provided a minimum level of safety performance for the majority of new vehicles entering the vehicle population. These actions were, for the most part, taken as a result of existing automotive safety technology." The rulemaking plan for the future "depends on a large extent on the generation of useful, quantitative results from the research program now in progress," says the bureau.

By October 1, the government seeks to eliminate all exterior protrusions, such as ornaments, that might injure a person hit by a car. A regulation is proposed for 1971 that would call for improvements that would prevent carbon monoxide from leaking into the passenger compartment. A government regulation proposed for January 1, 1972, considers an interlock device would not allow a car to be started until the driver had buckled his seat belt.

Sources:
http://isweb.tasc.dot.gov
http://www.nhtsa.dot.gov
http://www.dot.gov

Mon Aug 11, 2003 7:41 pm

And exactly how, in the Wide Wide World of Sports would those crescent vents reduce carbon monoxide in the passenger compartment?
I agree that is why they put them in, but my guess is it was more of a desire to "do something" rather than a real solution to this "problem".

Kind of like the Toyota Prius Hybrid gas/electric car which gets 52 mpg, but uses enough energy to consume the equivalent of 20 mpg for the life of the auxiliary batteries to make the batteries themselves. Looks good on paper, but doesn't do SH|T to solve the problem of energy efficiency.

Mon Aug 11, 2003 10:17 pm

I would have to agree that it does little, if anything, to circulate fresh air in the passenger compartment. I'm thinking, as to assume, that it had to of been a requirement by NHTSA as not many of the others in the world market had these (vents).

Good quote by Slim Pickens. :)

Tue Aug 12, 2003 8:22 pm

Superman,
Neat, you caught that Blazing Saddles quote by Slim Pickens.
Pretty sharp, pretty sharp...

Wed Aug 13, 2003 1:20 am

j.pickens wrote: And exactly how, in the Wide Wide World of Sports would those crescent vents reduce carbon monoxide in the passenger compartment?

I agree that is why they put them in, but my guess is it was more of a desire to "do something" rather than a real solution to this "problem".

I don't think it has to do with CO fumes.... they scavange air into the car from out side...

Now the foam had to to do with blocking fumes from coming into the car yes... but bugs never rotted out there till the vents were introduced.

I think they were more for venallation of the rear window area to aid in defogging :?: Why else would the 3 plastic vents be there( on the inside ) blowing air twords/on the rear glass?

Note: you may not see/have those vents unless you have a OG unmolested headliner still installed and the UV's from the Sun/age has not deteriorated them...

Wed Aug 13, 2003 11:48 pm

VW tried so hard to keep up with the times.
The crescent vents were for flow through ventilation.
You had new vents in the dash & the crescent vents.
High pressure at the hood vent & low pressure at the crescent vents did the trick.
They vents also did the trick for rotting out the roof.
When (not if) the roof rots out, cut out the rust, dig out all the foam.
Repair the hole, and without the foam to hold the water that will
come trough the vents, the water will simply drain out.

Thu Aug 14, 2003 8:02 am

From what I have read the cresent vents are just VW's attempt at adding more engine cooling, I have never had a super sedan only a super convertible so I never really checked it out.

Fri Aug 15, 2003 2:29 pm

keifernet wrote: I think they were more for venallation of the rear window area to aid in defogging :?: Why else would the 3 plastic vents be there( on the inside ) blowing air twords/on the rear glass?

The air is not coming in the car there, those vents (on the inside) are the exit as air flows out to the vents on the outside of the car. Any way we are nit-picking this to death and it can be sumed up that they suck.

Fri Aug 15, 2003 3:35 pm

I am puzzled. The vents are kinda aimed the wrong way to accomplish that. They are more like scoops.
But, just to clarify my earlier question. The ducting for the vents consists entirely of the padding behind the headliner. The suggested resolution is to close the vents and seal the metal to prevent continuing damage?

Thanks,
Matt

Fri Aug 15, 2003 4:46 pm

Superman, you may be right but I think the force would push air in the vents, particularly in the winter when the windows are closed...

Maybe some college physics class would like to donate some serious wind tunnel/smoke machine testing to this problem? :wink:

Agreed... they suck.... more than just air... :P

and they damn sure don't have anyting to do with cooling the engine! :roll:

Fri Aug 15, 2003 6:22 pm

:?: Just wondering how one goes about removing these vents??? Do I pry until something gives?

Fri Aug 15, 2003 7:25 pm

keifernet wrote:
Agreed... they suck.... more than just air... :P

and they damn sure don't have anyting to do with cooling the engine! :roll:

LOL...
My Mexican beetle has the modified panel behind the rear windows where the crescent vents go, but thankfully, VW of Mexico gave up on them.
Nothing but solid metal there.
I guess they just kept using the same stamping presses and just didn't cut out the vents.

Fri Aug 15, 2003 8:24 pm

LOL...
My Mexican beetle has the modified panel behind the rear windows where the crescent vents go, but thankfully, VW of Mexico gave up on them.
Nothing but solid metal there.
I guess they just kept using the same stamping presses and just didn't cut out the vents.[/quote]

yeah being in TX I've seen lots of Mexi bugs... sure wish I'd have picked one up and given it the legal treatment like yours a long time back... fat chick or not it would be cool to have one IMO.

VW bob yes just pry on the vents with a thin blade screwdriver, if they are not too deteriorated you can get them out without busting them up...

PS they came in black only and with aluminum trim....

Fri Aug 15, 2003 9:52 pm

keifernet wrote:

yeah being in TX I've seen lots of Mexi bugs... sure wish I'd have picked one up and given it the legal treatment like yours a long time back... fat chick or not it would be cool to have one IMO.

Fat Chick? NOT!
It's a standard beetle, and it IS cool.