Heat Discussion

I really want to get the exhaust/heating system squared away before the cold weather returns. I noticed last time I had the rear seat out that the plastic tube running along the side to the heater channel is all smashed it's no wonder there's no air up front! I would like to take that whole assembly out on either side of the back seat and replace it with a single length of pipe, if that's possible. I'm not worried about heat in the back -- I need/want it up front and on the windshield.

Also under the backseat -- I took the insulation off of the heater tube on the left (driver's) side and exposed the Y shaped metal tube that feeds the vent under the rear seat and then connects to the heater channel carrying heated air to the front. I was VERY surprised to find the metal Y piece perforated over it's entire length with holes!

If it's possible to get a straight pipe replacement for the heater channels it sure would help pump that air up front.

I think that the holes in the Y-tube are supposed to act as a sort of muffler for the fan noise. The construction is very similar to muffler construction where you have a tube full of holes with an absorbent material around the outside (like the VW peashooter tailpipes for example). If you are able to fix the heater as you suggest, you might find that the fan noise is increased a little with the heater on.

Also, the plastic piece that the Y-tube attaches to at the rear is broken badly.

I have to replace one of these pieces on my car too. I guess the heat must eventually send them brittle.

Also the tubes that run from the fan down to the heater boxes (fresh-air tubes) fell apart in my hands when I removed them -- real junk. I need to find some good substantial ones. The pretty silver ones lasted less than a year!

The originals on my car lasted for about 15 years, but the replacements seem to last just 3-4. No quality to them. :-(

Seems like a strange design to me -- a tradeoff (less noise, but also less air to the front because of leakage through the holes).

It is supposed to be surrounded by lagging/padding which absorbs the sound whilst sending ALL the air through to the heater channels. The lagging on mine is wrapped around the tube and held in place by thin metal straps which are crimped tight.

The black paper (silver inside) fresh-air tubes seem to last better than that, but still not as good as the originals. I'll have to replace all mine after the accident -- two got split, and they were getting past it anyway.

My bug has no heater system, so the heater channels don't work as that. They are there just for structural manners...My floor pans have to be changed and so my running boards...so what do you think of my heater channels? How can I know if they need to be replaced?

If the heater channels are not rusty, then you won't need to change them.

Usually replacing the floor pan leaves the outer edge in place (with the line of attachment bolts) and just replaces the actual floor parts.

You can get replacement heater channel sections (www.aircooled.net or www.motorworks.com for example) but it takes a lot of experience with cutters and MIG welders to fix them. It has to be a good job because the channel under the door provide a lot of stiffness to the floor pans, and the alignment is important so the doors close properly, and the body stays straight.

The running boards are held by bolts in the heater channel with captive nuts inside. If the nuts twist out of the channel when you undo the bolts, then the heater channels might need replacing. When undoing these bolts, use plenty of WD40 or even a better penetrating oil like Kroil (www.kano.com I think) and let it soak for a day so the bolts don't snap off - they are always rusty and stuck.

If the channels look rusty, or you can push a screw driver through them, then they are probably rusty enough to need replacing.

Autumn is here and the nights are noticeably cooler. I can’t fix the cabin heater until I either work the paper tube past the header exhaust system to connect to the heat exchangers, or replace the muffler so the correct fittings are in place (remember that stuff we talked about where there is a tube-over-a tube arrangement for the rear cylinder header pipes, to take the heater air past those exhausts to connect to the heat exchangers just underneath). You don't have them with your muffler if I remember, and if I left these headers on I'd have to work around the rear cylinder exhaust pipes like yours - to get to the heat exchangers.

It's more pricey if I go "standard muffler" but this (plus a replacement heat riser manifold section) will also give me carby de-icing, which I will need occasionally in winter. A present I have neither cabin heat nor heat riser connections available with this weird exhaust.

My Bug has great heat inside the cabin, but I need to improve the right side black-hole pipe to get some more heat to the right side (driver of course) windscreen.

The outlet ends on my Bug were in good shape -- if they are rotting it's a real sign the rest of the exchanger is going bad.

Like my older Bug -- the ends just fell off when I removed his old muffler a few weeks ago to cut a good piece out of the heat riser curved pipe to repair the heat riser on my other car.

While I'm at it I'm going to order a pair of hot air tubes (the tube between engine and body -- near the gearbox), assuming that they have the interior insulation and baffles.

My Bug has this "bellows" style -- they are plain rubber inside I think, though I haven't taken them off to look. My older Bug still has his original padded flexible metal tubes there. The padding on these is on the outside (insulation) the tube itself made of spiral wound metal strip -- like the exposed flexible exhaust pipe you see on some hot-rods. So these would transmit sound, yet my older Bug wasn't noisy from the fan whine.

Under the back seat my newer Bug has plain metal Y-tubes for the heater (no sound deadening), but the older car has the perforated padded type. I think that changed in 1969.

My newer Bug seems to carry a fraction more of the fan whine, but it's hard to tell, since I haven't driven this car for over 2 years. The newer Bug doesn't seem over-noisy though, not as noisy as the early bugs I've driven.

Those straight-shot tubes I put in (to replace the Y-tubes under the rear seat) carry the fan noise right up into the car. I may put some heavy-gauge steel wool in the tubes under the rear seat too (Bob Hoover’s recommendation) -- pass the air but not the noise.

That would still restrict the flow somewhat -- I wouldn't do that until after you've tested the under car bellows type tubes -- might be enough.

With the padded perforated Y-pipe and the lined heater pipes gone, we have a lot of fan noise when the heater boxes are open. I hope to be able to find a pair of the lined heater pipes (heater boxes forward) to replace the el cheapo's this summer -- I'm sure that will help.

I'm sure it will. Bob Hoover says that most of the engine noise in the beetle is fan noise, and so it makes sense that some gets through the heaters.

I took the original heater tubes (heater boxes forward) out because they were VERY smelly, and I was afraid the smell would be transmitted into the cabin. I replaced them with plain plastic concertina tubes without the internal padding -- and got increased fan noise in exchange.

The ones in my '68 Bug are not original, they LOOK like plain plastic concertinas, but have padding inside, so maybe they have two types, or maybe the earlier replacement ones were better designed. The heat tubes in my ’70 Bug are the original flexible padded metal pipe ...

Our original ones were flexible and padded on the inside, but they were made of plastic. They also had a wire mesh inside of them to hold the padding in place.

That's what the heat tubes in my ’68 Bug look like, so maybe VW replaced the metal ones (like those in my ’70 Bug) with a padded plastic version, and THAT's what my ’68 Bug has.

Making three designs -- original padded metal pipe, then internally padded plastic/rubber, then the unpadded type.