Itinerant Air-Cooled

Regarding flooding after heat-soak.... Look at this ad on oldbug.com. Scroll down to the photo that shows the open engine cover. What is that gizmo on the engine cover? It appears to be some sort of thermostat that opens up air flaps that would be hidden behind the license plate. There's wiring running to it too, is that for an electric fan? I've never seen anything like that before!

Is it to try to keep the carb from getting too hot??

http://www.oldbug.com/jimsun.htm

vwlover77 wrote:Regarding flooding after heat-soak.... Look at this ad on oldbug.com. Scroll down to the photo that shows the open engine cover. What is that gizmo on the engine cover? It appears to be some sort of thermostat that opens up air flaps that would be hidden behind the license plate. There's wiring running to it too, is that for an electric fan? I've never seen anything like that before!

Is it to try to keep the carb from getting too hot??

http://www.oldbug.com/jimsun.htm

A young friend of mine with a '74 super also has this rectangular vent. I thought it had been a P.O modification (his poor bug is rather hacked), but looking at those photos of the Sun Bug, it's clearly a factory piece. It's just a vent. There aren't any flaps or thermostat.

I'm going to hazard a guess here and speculate that it's intended to draw off heat from the EGR valve, which is mounted to the back of the carb. No fan, though, the wires would be for the license plate light. Since it's behind the license plate, I'm wondering if there isn't also supposed to be some sort of stand-off for the plate mount to allow for air circulation.

Interesting.... But look again at the close-up shot of just the engine cover. It looks like there is an expanding thermostat similar to the ones that run the regular cooling fan air flaps, and it's got an actuating rod attached....

Let's revive this topic a bit.....

I still have the problem of the carb flooding after heat soak. I found this article interesting.....
http://www.edelblog.com/tech-tips/resolving-heat-soak
Just for fun, yesterday I made up a spacer from 1/4" oak plywood to try. It doesn't help - the engine compartment is just too enclosed and the vents in the decklid just can't get rid of the heat fast enough after shutdown.

I've been thinking about cutting holes in the decklid behind the license plate and mounting small fans there (if there is room). I found a 12v thermostatic control board with temp sensor on Amazon for $10. Mount the sensor near the carb, set it to 120degrees, and let the fans bring in fresh air to cool off the carb.

Thoughts?

How many rows of vents does your engine lid have on it? Two or four rows? Which fuel pump are you running currently? Have you checked the current fuel pumps PSI and Volume output? I know some aftermarket fuel pumps put out 6 pounds plus so the volume of the pump must be a lot more than stock as well. What's the float bowl level at on this carb? Has been measured?

It would be interesting for you to install a VW/Pierburg square top pump on this engine with the fuel shut off valve built into it. I'm running this style pump on my VW's in hot as hell Phoenix and am not experiencing this issue. One of the engines has a German Solex 34-3 that had the throttle shaft bushing redone and then I rebuilt it.



IDK, I don't think this is a heat issue inside the engine compartment. You could shove a tennis ball under the deck lid lock to get a lot more air into the compartment to see if it had any effect. For shits and grins, you could consider trying another known good needle valve.

4 rows of vents. It's a convertible, so no vent under the rear window like a regular Super Beetle. Aftermarket fuel pump without the shutoff. Where can I get one of the square-top pumps?

I swear it's a combination of the fuel blend around here (with ethanol of course) and the heat in the engine compartment. Please note that in the past, I have TOTALLY DISCONNECTED the fuel line to the carb after shutting the car off and it STILL floods.

vwlover77 wrote:4 rows of vents. It's a convertible, so no vent under the rear window like a regular Super Beetle. Aftermarket fuel pump without the shutoff. Where can I get one of the square-top pumps?

I swear it's a combination of the fuel blend around here (with ethanol of course) and the heat in the engine compartment. Please note that in the past, I have TOTALLY DISCONNECTED the fuel line to the carb after shutting the car off and it STILL floods.

Then I'd be REALLY curious to know what the float level in the carb is? Why don't you do this.. Start it up and let it idle. Shut it off. Unscrew the 6 screws and pull the top cover of the carb off. Measure from the top of fuel bowl down to the level of the fuel. Let us know.

Old thread but I'll add my $.02. My otherwise perfect rebuilt-by-Volkzbitz 34PICT was flooding after shutdown. Gas mileage was worsening, also. Way back in my fading memory banks I recalled Muir mentioning this problem. His solution was wacking the side of the carb body with a plastic handled screw driver. Purpose: free up a sticking float . I wacked the carb and the problem was solved.

VW tried a number of solutions, including that four-nipple anti-percolation valve that stood off from the fuel pump and carburetor. Check float level for sure and make sure you have a quality needle valve, those valves with the little spring loaded ball at the float contact point are pretty good.

Also, you may need to double check that you have the restrictor style heat riser gasket on one side only (the side closest to the exhaust port).
Colin

I will definitely check the float level....... Restrictor style heat riser gasket??????? What does that look like? I'll definitely check but I believe the left and right side gaskets are identical.

vwlover77 wrote: ↑

Thu Mar 09, 2017 5:53 am

I will definitely check the float level....... Restrictor style heat riser gasket??????? What does that look like? I'll definitely check but I believe the left and right side gaskets are identical.

It looks like a heat riser gasket but with only a pencil sized hole in it.
Colin

Hey, what happened to my post from yesterday?

Anyway, here's a photo of the fuel level in the carb immediately after shutdown. I got a little "Pfft" and squirt of fuel when I removed the fuel hose from the carb. From that I concluded that the needle valve must be closing properly.

vwlover77 wrote: ↑

Wed Mar 15, 2017 5:49 pm

I got a little "Pfft" and squirt of fuel when I removed the fuel hose from the carb. From that I concluded that the needle valve must be closing properly.

For fun, you can try to install a tee in the fuel line to the carburetor and read the residual pressure during heat soak.

So, nice picture and all, but what was the fuel level (in mm's)?
Colin

I was discussing this issue with an old time VW shop owner from the 60-'s through the 80's. His first thought was the needle valve as well. His second thought was a crack or flaw in the carb body causing the leak after shutdown. You mentioned you experienced this same condition with the craptastic EMPI carb as well.

What I haven't seen mentioned is your engine temperatures. Have you measured your oil temp after shutdown in ambient air temperatures that cause this problem?

My 67 bug was vapor locking in 100* temps. The engine only had 3k miles on it after I rebuilt it. I shot the oil sump plate with a laser temp gauge and was hitting 235ish. I found an old thread that talked about high oil pressure causing the oil to not go to the oil cooler as quickly with tight bearing tolerances, especially on small oil passage, single relief and single port engines. I lowered my oil from 10w-40 to 10-30 and saw close to a 10 degree oil temperature drop. I then installed a 67 convertible engine lid with two rows of vents in it and saw a further drop of oil temperatures. I think I got it down to around 220 with those two changes.

One thing that was VERY noticeable with the additional of the vert lid is the engine compartment wasn't nearly as hot when touching the fan shroud or other ancillary engine parts after coming off a freeway run. The good news is it cured the vapor locking. For good measure, I cut a piece of rubber hose and wrapped it around the fuel pump feed line where it goes by the heat risers to the carb manifold.

wcfvw69 wrote: ↑

Sat Mar 18, 2017 10:53 am

I cut a piece of rubber hose and wrapped it around the fuel pump feed line where it goes by the heat risers to the carb manifold.

Interestink . . . .