If the fumes are coming from under the hood and into the passenger compartment then one way to find out would be to remove the hood and drive it around for a day. The fumes then would not be forced into the cabin, they would dissipate into the air.
My boss had a leaking hose under the hood of his 97 Caravan and that's how we narrowed down where it was coming from. With no hood there were no fumes in the cabin so we knew it was under the hood somewhere.
Drill tiny holes in the hinges before removal, then place a nail in the holes to realign the hood for reinstallation.
I know it seems like a drastic move but it worked for us.

 

I read everyone of these posts and not 1 mentioned anything about gas fumes as I have the same problem with my 2000 dodge grand caravan. it's coming from the vent tube and it's not always doing that.it seems it only does that when the tank is full(and no, there is no leaks as I had a new fuel pump put on). hope that help solved the mystery fume bandit.

 

There may be a reason it hasn't been mentioed. Here's a quote from the first post:

" I don't smell any fresh gasoline."

 

well it couldn't be CO because you ruled that out in almost all your posts and gasoline is the only other thing that can make you light headed. just because you don't smell it doesn't mean it's not there

 

Gasoline is not the only other thing that can make you light headed. Blow-by, which can come from various places under the hood can do that as well as hot oil which can also come from various spots under the hood can make you light headed.
Worn, rotten or split rubber hoses, loose connections or hose clamps on the egr, there are many things under the hood that when worn or damaged can release fumes which can get into the cabin, especially on a 10 yr old van. These fumes all contain CO.

 

Thank you all!

Paddy, if I were going to keep the car, I'd follow your advice
about removing the hood for a day. But there are so many
possible sources for the fumes, as you pointed out,
that we're now searching for a new used car.

Huffman, I appreciate your idea, but it's definitely not fresh gas
coming in, in my case.

Cougar, thank you for reminding Huffman that we ruled out fresh gas
coming in. Fresh gas has an unmistakable smell, and it's not our problem!

Paddy, thank you for the wise words that you wrote, namely:

"Gasoline is not the only other thing that can make you light headed.
Blow-by, which can come from various places under the hood
can do that as well as hot oil which can also come from
various spots under the hood can make you light headed.

Worn, rotten or split rubber hoses, loose connections or
hose clamps on the egr, there are many things under the hood
that when worn or damaged can release fumes
which can get into the cabin, especially on a 10 yr old van.
These fumes all contain CO."

If anyone knows a super good mechanic in the Denver area,
who'd like to buy my minivan, to be a demo for mechanic students,
etc., let me know.

Carol (cell: 970-531-5000, fsds@rkymtnhi.com)

 

Just a thought. You live in the mile high Denver area where there's less oxygen. Given the fact something in the van is making you light headed, I wonder if you sold the van to someone living at a much lower altitude where there's more oxygen if they would even notice the problem. Then again there's the smell. That may not be effected.

 

Hi Cougar,

Actually, we live up higher than Denver,
in the mountains, at about 8500 feet above sea level.

We're pretty sure that it's most likely (at least)
leaking oil being burned, that is entering the cabin
from under the hood, and poisoning us.

This would happen at any altitude, and since it would
cost too much to analyze and fix (we've priced possible
fixes), we're looking for a new minivan.

We hope that some mechanic might want to
buy the car, as a "demo", for diagnosing car
problems, but not to drive. If not, it will
probably go to salvage.

Even when the car is off--not running at all,
I can detect a distinctly bad smell inside,
that also makes my eyes "smart" (burn).

I believe that Paddy is right--One or more
toxic fumes are coming in, and the prime
suspect is burning oil.

Sincerely,
Carol

 

There are really only 2 ways the fumes can enter the cabin, both are relatively cheap fixes you may be able to do yourself.

First, replace the rubber seal around the hood and ensure the hood is adjusted to allow the seal to, well, seal.
If the hood does not seal, especially along the underside of the windshield, fumes may enter the cabin via the hvac fresh air intake. This is a simple job to replace. You won't fix the fume issue but you will prevent them from entering the cabin.

If there are still fumes, the next fix is a bit more involved but not much and that is applying a layer of Dynamat to the cabin side of the firewall which involves peeling back the carpet to expose the metal firewall...you may have to remove the seats for better access, but they are only 4 bolts each. Cover the whole area up to under the front seats. The Dynamat is a peel and stick sound deadener which will also seal up any tiny holes which may be letting fumes in.
Installing the Dynamat is simple and is covered in several YouTube video's.
You could do it a few other ways but with the Dynamat you get the added benefit of some good sound deadening as an added benefit for the work involved in pulling back the carpet.
When I did my Dynamat install I did the whole floor front to back and removed the entire carpet and had it professionally cleaned while it was out...looks and smells like brand new. (didn't even know it smelled until it came back clean!)

Do both fixes and you can sell the vehicle with confidence that you won't gas the next owner. The fumes will still be there but will not enter the cabin.

Fumes like this are very common in older vehicles so there is no guarantee the next vehicle you get won't give you the same grief. You may have now become super sensitive to the fumes and a very small amount will be noticeable to you.

Do this fix, drive it for a while to see if it works for you, then you may sell at market value, or without fumes in the cabin you might keep it. If it happens on another vehicle, you know the fix.

Good luck!

OH, Altitude has zero to do with your problem...zero.

 

Hi Paddy!

Thank you!

We'll check into all your great advice, as we can.

I also agree with everything you wrote,
including how I'm now more sensitive to
any kind of fumes (dang!).

Meanwhile, we're looking for a new (used) minivan
that is newer than my old one.

I appreciate everyone's input, too!

Carol