Blocking the air to heaterboxes

The fan is cooling the engine, FL. is HOT, keep the fan.Block it at the heater out box.

I didn't mess with the fan, I plugged the fan housing where the down tubes go to the heater boxes. In my mind the fan is then not having to push air anywhere other than inside the housing more better for cooling no?

I'm not sure since at this point there is no temperature gauge installed

Which leads me to the another question, do I want to have one? I recently saw that someone on TheSamba had offered the classic dipstick temperature sender for around $40.00

In the past I've had a lot of aircooled VW's none had temp gauges and none except the bay window ever overheated. But the present set-up has a few mods on the engine and I'd like to be able to keep it together, I've got about 800 miles on the build

Thanks I agree there's a huge amount written on the most common causes of cooling problems leading to melt down.

according to Gene Berg the main thing to monitor is oil temp,he says gauges can be off up to 50 degrees. He's got a sensor that attaches to the dipstick or replaces it and causes an idiot light to start to blink @ 210 degrees and come on steady @ 230 other people have used a wide range of devices including candy thermometers in place of the dipstick--must be fun to stop run back and check the temp!

I'm just trying to figure out if I did the right thing in blocking the heater tube outlets on the fan shroud.

Thanks for that info!

I basically can unscrew the top heater tube connections to the fan shroud and pull the plugs I fabbed and turn it back into normal heaterbox set-up.

Thanks also for the feedback on the Gene Berg dipstick! I'll probably go with that for starters

So when the flap in the heater box is closed the air goes into the heater box and stops there except for what leaks out from the tin pressed around the manifold.

Are you saying that the air coming into the boxes is cooling the heads?

If anything it would be cooling the manifolds and possibly the connections at cylinder#3 & #2

the plugs I used were modified fence post caps, the concave crown of which is force fitted facing into the shroud

I don't have "j" pipes are you referring to the manifolds that are part of the boxes?

Obviously I don't want to beat-up my motor and I certainly respect your opinion and experience. My heat exchangers I believe are aftermarket and don't have all the flaps and stuff that the stock VW ones have. I don't have a thermostat either. I just want it to run as cool as is possible down here. Average temps are around 80-85 right now.

Typical VW heat exchanger air flow valve.



How air flows. The flapper shown in red will either block the vent to atmosphere {heat goes into car} or block the tube leading into the car {heat is dumped under car}



Heat exchangers work on the principal that heat is naturally attracted to cold. The heat of combustion gasses heats up the pipe which heats the aluminum fins. Cool air blowing over the fins is heated as it passes through the exchanger. In the process it cools the fins and the pipe. It also draws heat from the heads through convection of the pipe.

When the air supply to the exchangers is removed there is no cooling of the exchanger fins/pipe/head. As a result engine temps go up. Also heat radiated from the exchanger raises head and valve cover temps which is transferred to the engine oil.

Think of it this way. On your newer liquid cooled ride, what happens when you block the airflow in front of the rad...same thing.

If your flappers are not functioning properly or only blowing heat into the car, DO NOt remove the air supply to the boxes, disconnect the tubes between the exchanger and the body.

As for the thermostat flaps and removing them.
This DOES NOT make your engine run cooler. They DO NOT control the max engine temp. They control MINIMUM eng temp.

This writeup is for liquid cooled but the same holds true for air cooled. Now edited for those that cannot relate to the different components.

Changing thermostats to a different rating or removing them cannot cure overheating; it can only cure overcooling. To understand why, you need to understand why a thermostat determines only the minimum operating temperature. Let me repeat that: A thermostat determines only the MINIMUM operating temperature, not the maximum temp. Keep reading to see why.

An engine takes energy stored in fuel and releases it by burning the fuel. Some of the energy (less than 25%) gets converted to kinetic energy (motion) to turn the engine and ultimately the wheels. A little bit of it gets turned into vibrations (actually, another form of motion) that we can feel and hear. The largest part of it gets turned into waste heat. This thermal energy flows into the engine parts to be carried to the cooling fins (or remains in the combustion gases to be carried out the tailpipe). The cooling fins send it into the atmosphere. Any energy that makes it to the cooling fins is lost, having done you absolutely no good whatsoever. Under normal conditions, a cooling system in good repair can shed heat faster than the engine can produce it, so you need something to limit the capacity of the cooling system to dump heat. That's the thermostat's job.

Imagine an engine that is at normal operating temperature. Say, for instance, that you're driving along a ridge road in the mountains. At the moment you're neither climbing nor descending, there is a lot of air going over the cooling fins, and the thermostat is open. Now suppose you turn off the ridge road and start descending a steep hill into a valley. The cooling system is dumping heat like mad and the engine is producing very little, so the engine starts to cool down. The thermostat notices this (it sees the air temperature falling) and begins to close. Because there is now less air flowing through over the fins, there is less heat being disposed of. The thermostat keeps the engine from becoming too cold. Because the thermostat is limiting the amount of heat being shed by the fins, after a while the engine temp starts to rise again. Once it's high enough, the thermostat opens.

Now you've reached the bottom of the valley, and you start up the hill on the other side. The engine is really working hard now, and there's less air passing over the fins, because you're going slower. Since the engine is making heat faster than it's being carried away, it begins to get hotter. The themostat is already fully open, so there's nothing it can do. The engine gets hotter and hotter. If this carries on long enough, damage will happen. It has overheated.

Another way to think about it is this: Imagine that you live in Florida in a house with no air conditioning. On a sweltering August afternoon, turning the furnace thermostat down from 68ºF to 60ºF won't make you feel any cooler!

So you see, a thermostat cannot prevent overheating. It only prevents overcooling. A thermostat can only be the cause of overheating if it is defective and doesn't open as it should.

The fix then, if your engine is truly overheating, is obviously not to put in a cooler thermostat or remove it, but to fix the fault in the cooling system. A cooler thermostat or removing it with the shroud flaps is just a band-aid that at best can only temporarily mask the problem. If the cooling system is marginal, it might buy you a little time before the engine overheats, but not much. Find the real problem -- a clogged air intake, a bad fan, siezed flaps and or linkages, too much buildup on the cooling fins or oil cooler, a loose belt missing tins, or a bad distributor {timing}.

I should have known I would get this type of response. It happens all the time on the samba, people cannot relate the similarities between liquid and air cooled.

As I originally stated this writeup was for liquid cooled and that the same holds true for air cooled. It was used to demonstrate and explain the importance of the thermostat and related componrnts.
It is now edited for those that cannot relate to the different components.

I guess my point was that if someone is not familiar with aircooled engines and is questioning possible overheating concerns then throwing in examples/suggestions of general cooling theory of internal combustion engines doesn't help in my opinion.

Telling an inexperienced person that cooling issues can be the result of a "clogged radiator", while true in water cooled cars, really isn't applicable in this case at all. Telling them it could be a "water pump with a defective impeller" may just send the inexperienced person off to google "water impeller vw aircooled". That would be a wild goose chase.

Its kinda like when someone asks about a lawn mower stalling and you give a long winded answer about proper fuel pressure, clean fuel injectors, proper sensor readings, and functioning of the ecm. All great stuff but absolutely no applicability. In that example the person might be a little less confused if you stated: check to make sure your gas is fresh, your air cleaner isn;t plugged, your fuel filter (if equipped) isn't dirty, and your carb is clean.

A long winded answer is not always the best answer.

Good idea to go back to a stock shroud. A lot of aftermarket shroudsare not engineered to produce the airflow that a stock shroud does.

I noticed in your pic that you do not have any tinwork separating the hot side from the cold side. Adding this will make a big difference.

Here is how I did my Ghia. There is a foam "water pipe" insulation going around the engine tins with the stainless over it.



Here you can see how I did it with my air cooled Corvair.

Dan: I can see the apron part on your Ghia but what did you use directly around the block, cylinder shields and heater hoses? Do you have a pix that will show that detail?