Those of you who have been around the Volkswagen scene for a while can hopefully shed some light on this one.  Recently I replaced the heads on my 65 (top end rebuild) and noticed the heat coming out of my tail pipes is extremely hot (equally on both sides).  I know the manifold and heat riser tubes are not plugged, the car is running smoothly, and the fan built appears to have the correct tension.  However I have nothing to compare this to since I'm quite new to the Volkswagen scene.  Is this typical of most air cooled Volkswagen engines?  Even the rear apron is extremely hot to touch.  Is this normal?  If not, what would be some of the root causes?

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MY72BUG
Welcome to the world of VW.  There are a few simple things that you should take great care with when it comes to working with these old air-cooled engines.  Some of these are as follows:
1.  With the engine cold, remove and examine the spark plugs.  ( NEVER pull a spark plug from a hot engine as the aluminum head's threads will have a death grip on the steel spark plug's threads.  This can lead to stripping a thread. )  The plug's condition will tell you if the engine is in fact running hot.  A bit of grey or reddish ash is normal.  If the ash is very white you are running hot.  This could be a sign of a too lean fuel mixture.  Correct this in a hurry or you will be toasting the valves of your new heads.  When you put the plugs back in, use a swipe of never seize compound on the threads but do not foul the electrode.
2.  Make sure that you used ALL of those engine cooling tin pieces.  They direct the flow of cooling air over the fins of the heads.
3.  Make sure that ALL of the rubber engine compartment seals are in place and are undamaged.  This includes the rubber seals around the engine compartment lid,  spark plug holes in the tin and the two critical seals at the back of the engine compartment and around the sides of the engine compartment.  These establish a highly concentrated flow of air from the cooling air louvres on the engine compartment lid ( or above the engine compartment lid depending on your year ) through the cooling fan and over the fins on the heads and out the underside of the engine.
4.  Make sure that the fan shroud louvres are either wired open, as many VW owners do, or that the movement of the louvres by the  thermostat is unimpaired.
5.  I imagine that when you did your engine work you made sure that there was no accumulation of debris in the fins or the engine fan shroud.

Follow all of the above and you should have a happy engine.  Let us know how the situation turns out.   Dan ( MY 72BUG) in Goderich, Ont.

I'd rather have a partial bottle in front of me than a partial frontal lobotomy.
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68autobug

As Dan pointed out....

all that hot air and exhaust is normal for a beetle engine....

The number 3 cylinder is the one that gets hottest, and the VW distributor retards number 3 cylinder to help keep it cool...

The oil cooler is in the flow of cooling air to number 3...

The best thing You can do to Your Beetle is to open the top of the engine lid with "stand offs"... there are alloy ones or steel ones...

even quick release ones...

These capture the cool air coming over the roof and make the world of difference to the VW engine bay....

In the summer I couldn't touch virtually anything in My engine bay after driving down the highway....

Now, with the lid open about 2-3 inches.... Wow... Big difference...

I'd recommend it to anyone....

Only problem is your engine will get wet when the car is stationary...

I haven't had that problem as yet.... drought over here....

but I'm thinking about it.... maybe an aluminium or even plastic or rubber strip to stop the rain but let the air in....

I have seen egine lids open 5-6 inches... even....

 

Lee -- 68AutoBug -- Australia --

 

http://community.webshots.com/user/vw68autobug

 

Lee Noonan
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Wayne

Do you have the factory thermostat still installed on your Beetle? A lot of people take them off but this is wrong. The Beetle is designed to operate with a thermostat and it is important for cooling and engine wear due to uneven heating of the different metals used in the engine.

 

See Cooling 101 by Jake Raby:

 

http://www.superbeetles.com/Tech_talk/jan2.htm

 

If you don't have an oil temperature guage you can tell if your engine is running too hot by taking the dipstick out at operating temperature. If it's too hot to handle, you're running too hot.

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Ryan

The dipstick test is flawed.  My oil can be right at 190F (considered optimal) and I have to juggle the dipstick from hand to hand and I have a pretty high pain threshold.

The comment about the timing retarded on the #3 cylinder is only partially true.  VW stopped doing that with the introduction of the doghouse style fanshroud.  With the oil cooler removed from the air stream in the shroud, the #3 cylinder's cooling was improved enough to do away with the 'special' distributor.

Hot exhaust is normal.  EGTs at the head can easily reach 1200F.  The gasses obviously cool by the time they reach the tail pipe, but not as much as the cars you're probably used to with front mounted engines.  Excessively hot exhaust, say hot enough to bubble the paint on the rear apron (I've done this) is caused by having your timing retarded too much.  The cylinder fires so late that the mixture is still burning in the exhaust pipes.  So you see you can't just cool an engine by retarding the timing.

I would actually venture to say your engine is running just fine.  If the apron was hot, but you didn't actually drive the car, i.e. it was just idling in your driveway, then that's normal too.  You need some movement of air around the car (like from actually driving) to remove the hot air from under engine.

If you want to be sure, I'd suggest you do the usual maintenance items, timing, point gap/dwell, valve clearance check, and so on.  If it all checks out, then I'd say 95% chance your fine.  If you want that extra 5%, get some gauges.  Oh, and pick up a Bentley manual for a complete maintenance checklist.  --Ryan

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Ditto on all of the above.  I had this same thing happen only my spark plug boots melted (if you smell something like burning chocolate, pull over).  My problem was a stuck oil pressure piston.  It wouldn't open up due to a bunch of gunk on it and therefore wouldn't allow any oil to cirulate.  Hence, it overheated.  If you don't have smoke, you probably are ok.

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