OK, kids, this is it. If you have a clunker and you want to trade it in and get a $3,500 or $4,500 rebate for a new vehicle under the Car Allowance Rebate Systems (CARS) program ... STOP WHAT YOU'RE DOING.

Do it right now, today, and get to your dealer no later than 4 pm. Today. But call first, to make sure the dealer is still doing clunker deals at all. Some dealers and chains stopped taking clunkers altogether as of Friday or sometime this weekend.

As we reported on Thursday, eager buyers have used up the latest $2 billion allocated by Congress for Clunker funding. That same day, the Obama administration announced that the program would end today at 8 pm.

Allow at least four hours

Consumer advocates suggest you allow at least four hours at your dealer. Dealers have reported heavy showroom traffic all weekend, and that is likely to continue today.

Among other things, your salesperson will need to make sure your clunker is a qualifying model, inspect your registration and insurance documents, and actually sell you the new car.

Then you'll need to make financial arrangements, do the paperwork, and the dealer must submit the paperwork online--all by 8 pm.  The Department of Transportation said that applications for clunker reimbursements will not be accepted after that deadline.

Dealer complaints: delays, cashflow

Dealers have complained about long delays in processing, and rejected applications, especially after the initial allocation of $1 billion was used up in just a single week in late July.

Congress managed to approve a second allocation of $2 billion, which was expected to last until Labor Day, before leaving for its summer recess.

The DoT did say car dealers can resubmit rejected applications after the deadline. But it also cautioned them not to make clunker sales over the weekend unless the buyer had all necessary paperwork in hand.

Dealers have also complained about long waits to be reimbursed, and General Motors, Chrysler, Mazda, and other automakers have stepped in with short-term loans to help dealers manage their cashflow.

Telephone before you travel

As a buyer, that's not your problem--unless a dealer has already stopped doing clunker sales, as many have, including the large AutoNation chain. Make sure you call and confirm your dealer of choice is still taking clunkers up to the deadline before you visit!

Dealers who have stopped taking in clunkers fear not getting reimbursed if money runs out, and a few have now run entirely out of new cars with high enough gas mileage.

Clunkers application rates varied widely among states, but carmakers nonetheless have started to run out of their most popular high-mileage models, including the Ford Focus. Only one hybrid--the 2010 Toyota Prius--was initially among the Top 10, and it too is almost sold out.

More cash? Unclear

As of Thursday, according to the Department of Transportation, dealers had already submitted 457,476 transactions for $1.91 billion in rebates. Those numbers are expected rise by another $1 billion, or close, by the end of the day.

The White House declined to say on Thursday whether it plans to ask for a further appropriation to continue the program after Congress returns in September. The original legislation introduced this spring had proposed a program totaling $4 billion.

GreenCarReports.com will assess the final impact of the unexpectedly popular Cash-For-Clunkers program after all the data has been gathered and analyzed. We've already looked at results from the first week, which we concluded had worked unexpectedly well,

Meanwhile, if you're in the market ... you should have stopped reading long before this. You have been warned.

Cash for Clunkers tradein: Mercury Sable

Cash for Clunkers tradein: Mercury Sable

Cash-for-Clunkers engine destruction, using sodium silicate solution, from Wayzata Nissan

Cash-for-Clunkers engine destruction, using sodium silicate solution, from Wayzata Nissan

Cash-for-Clunkers' online buzz (from Nielsen)

Cash-for-Clunkers' online buzz (from Nielsen)

Clunkers

Clunkers

[The New York Times, Washington Post, Automotive News (requires subscription)]