Classic VW BuGs, Our Gas Today, Vapor Lock, Beetle OverHeating?

Added May 9, 2014 by Chris Vallone

Our Gas Today, Vapor lock, and Overheating!

We are heading into summer, and like clock work I will get hammered with emails with people telling me that their beetle starts right up and runs great from the “get go,” but after about 15-30min of driving, the VW loses power and is then tough to restart.  If you let it cool down a bit, she will start right up again, drive for a while and go through the same headache, I have heard it 1000 times.

This is a constant issue we have been hearing from VW owners across the country.

I have spoken about these issues within the past couple of years.  I did a video about ethanol, vapor lock, fuel filters, and the quality of our gas today.  I plan on doing another video about this problem in the coming weeks with some updated info, but I would like to get your taste buds going today.

Through more extensive research and testing on our own, we have come up with some solutions to help your VW run better with the present day fuel and hopefully prevent you from experiencing a vapor lock or overheating issue.

You may not know this, but another lil tid bit I found out about our gas today may shed some light for ya, it is its boiling temperature.  We now know that the gas today boils at a much lower temperature than it used to when the beetles were first hitting the roads.  Today’s gas has more alcohol blend with of course the CRAP corn (ethanol) that goes into it, another thing the gas did not have back then.  Do a little research on google and you will see that gas today boils even lower than what it takes for water to boil.  They do this so it runs cleaner.

So what does this mean?  Well when your gas runs too hot, it slows the flow and speed to the fuel pump and then to your carb.  VW like other car makers with their cars, designed the beetle to have the right flow speed.  When you slow that flow, you can starve your beetle. 

When adding one of these


to your fuel lines, it makes the problem even worse!  The fuel filter will act as a reservoir and slow the pace of the fuel down.  In the late 60s VW dealerships added the fuel filter in the engine compartment, this was convenient to see if any dirt was passing through the fuel system and it could catch what came through. 

With the scary risk of a fire, I then always put my fuel filters under the car, technically right under the luggage compartment.  The steel fuel line that travels through the tunnel of the bug pokes its head out right by the tranny under the luggage compartment.  We then attach a small segment of VW braided rubber fuel hose, then the fuel filter, then another section of braided hose, then onward to the steel line that then goes into the engine compartment, to the fuel pump.  All of this splicing and connecting are accompanied by fuel hose clamps to stop the risk of a leak.

Not knowing about the boiling temp of gas today, we did not think that placing the fuel filter in the engine compartment or under the luggage area would contribute what we are experiencing today nor would anyone think about that even back in the day.

What we noticed with today’s fuel, is that having the fuel filter in the engine compartment or even under the luggage area of the VW, could be one of the reasons you could be experiencing vapor lock, or overheating.

Since the gas today boils at a lower temp, and the fuel filters act as reservoirs thus slowing the pace of the fuel down, your VW will run lean much sooner due to the heat in the motor compartment and in the luggage area under the car.  When you run lean, the motor will run HOT. 

I thought running the filter under the car would not face a heat problem, I was wrong.  Fresh air motors with the later style heat boxes omit a lot of heat under that luggage area, so it stays trapped there.  Not to mention that the fuel line and filter run right along side the heat boxes.  If you do not have your heat on in the car, the boxes need to omit it somewhere, and that is right under the luggage compartment.  Sometimes I see fuel lines literally touching the heat boxes, so that fuel is cooking!  At the top of the heat boxes are small slits that allow the heat to escape, you can see this on every fresh air heat box.

I do not face this problem with early style stale air motors because the early boxes let the heat out by the muffler, not under the luggage area.

So what does this all mean?  We probably need to relocate our filters.  We are testing the filters by placing them right under the gas tank, and (if we decide to still keep them under the luggage compartment) moving them further away from the heat boxes.  I plan on doing a video on all of this in the near future.  For now, if you are concerned with your filter, try moving it away from the motor compartment and or heat boxes.

Some of you guys may not ever experience any of this depending on your location in the world.  If you live in a cooler climate, you may have never come across this issue.  You may also live in an area that still sells PURE GAS without any additives.  I live in NY, they change the gas quality through the seasons all year round.  I only seem to experience all this with later style motors and going on long trips.

If you only do a few miles at a time with your VW, you may not go through it either.

You can browse my “Resto Tips” section on my website in regards to topics like this, vapor lock, fuel additives, running hot, engine seals, etc. 

I would love to hear your input on this, feel free to write me on the subject.

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Categories: General News,VW Restoration Tips


On my 67 Beetle, I installed my fuel filter in the front of the car, as it exits the fuel tank. A little less convenient to change filters, but much safer. I also use the marine formula erthanol treatment by Sta-Bil at every fillup. I live in the hot south and it seems to help.



First let me say thank you for all the great VW data you provide!

For my 73 Woodie Super resto, the engine running problem is..... it runs great for 5 minuites then dies....did the sanding of the pump plastic shaft, crocus cloth polished the 100mm pump shaft for a Bocar Pump, put Star Tron ethanol treatment in the regular gas and located the fuel filter under the luggage compartment.

From your latest tip, sounds like the filter should go foward under the gas tank.

I will do this.and also run some non ethanol high test...

Your comments please..




I have found that if you run Non ethanol high test you won't have this problem. You can find this at marinas and gas stations that are located by body's of water. BOATS hate ethanol fuel because it holds water.