Before we go further, let me say that the small tubes of the Intake manifold, which connect to the muffler, direct heated air to the aluminum-blanketed portion of the Intake manifold. The aluminum, which acts as a “heat sink”, quickly heats and transfers its heat conductively to the steel manifold, below the carburetor. The heated manifold pipe helps to vaporize the air-fuel mixture which is headed to the cylinder heads.
Where each small pre-heat tube departs the engine compartment to connect with the muffler, provides an opening where heated and/or exhausted air can enter the engine compartment—as well as opportunity for precious intake air to escape the engine compartment, thus robbing the Fan which is supplying cooling air to the oil cooler and across the cylinder and cylinder head fins.
Volkswagen invented a method for blocking this opening: the heat riser or pre-heat tube cover.
These are right and left, with 3 holes each for securing using engine tin screws.
Since metal-to-metal doesn’t seal well, and, since we are dealing with heated air, provision was made by Volkswagen engineers for hot-temperature insulation. With time, this asbestos (I assume) insulation becomes impregnated with oil and dirt and begins to fray. With each removal and replacement, the insulation further deteriorates and the insulating property lost.
Wolfsburg West markets an insulation kit just for this purpose: Part# 113-119-597. The kit contains enough pieces for one pair of covers (enough for one engine).
In all of my years of working with VWs, I have not had opportunity to completely restore a heat riser cover! I’ve always been blessed with good covers which, when cleaned and repainted, were good as new. But, my time came this past week as I sought to do some engine-tin-cleaning. Whoops!
Richard, at Wolfsburg West, assisted me with the order. Cost of the kit was $7.50 plus shipping. (note: in order to spread shipping costs, order multiple items) Richard shipped the part USPS Priority. It was here in a couple of days.
I noted that the thin metal insert in genuine VW Cover Insulation is unnecessary with this replacement kit, since there is a new metal stiffening strip embedded in the new insulation material. Also, note that the new material is not asbestos but has the same or similar properties.
I removed the old insulation and scraped away residue. If you are going to clean using a blasting technique, removal of oil and grime is essential to keeping the medium as clean and viable as possible.
I scraped and picked to remove stubborn dirt and rust from the seams and crevices of the Covers. I used sandpaper to do the rest.
Using a steel block, a small hammer and a couple of flat-ended drifts, and pliers, I straightened dents and bends. I cleaned both covers using compressed air, followed by a good washing in mineral spirits. Paint ready!
I did multiple coats of rust inhibiting black paint. The weather was hot so each coat dried quickly, enabling me to paint the covers in record time.
I hung each cover on a bent wire and left them for a few days so that the paint could cure.
Now came the simple task of installing the insulation. This is straight-forward.
The result, as you can see by the photo, is very pleasing. My car will love the attention it receives from everyone who views the improved engine compartment.
Great little piece.
A huge thanks to Jay Salser!
Any info on efficient techniques to clean out clogged heat riser tubes?
I know Chris Vallone has a video on it. Also, Jay might have some knowledge on the topic.
I have always enjoy reading the articles in the 1967beetle.com esp the ones by Jay Salser. They are both informative and interesting.
Keep up the good work. You are all making this hobby that much more enjoyable.
Eric you have a great website. Congratulations.
Oh, Hendrik…I wish that I had a quick and toil-free method for unclogging pre-heat tubes! Sometimes we get lucky and find a manifold that is lightly clogged. Hurrah for that one!
One method is to use an old clutch cable. First, I knock on the tube along its length and shake out debris. Use compressed air to blow into the openings to help to remove loose stuff. Better wear eye protection and a particle mask!
I unwind the outer wires on the clutch cable to make a smaller cable. I cut a short length. At one end, I bend a few strands up to create a scouring tool. Inserting the other end into an electric drill motor, I begin, carefully, inserting just a bit of the cable at a time into one pre-heat end. You don’t want to do a lot of forcing–that could wind and lock the cable inside the tube! This also is the reason for a short piece of cable to begin with. Hopefully, this will unclog one end. Repeat the process on the other end. Use plenty of compressed air to remove debris. If you are fortunate, you may be able to penetrate from one side to the other. That mid-section is the toughest!
Note that this could take a lot of time–maybe even hours!
Once you have breached the tube…use successively larger cables to scour the inside of the tube. Don’t try to put a cable all the way through. go no more than half-way. Then scour from the other end.
There are other methods, I am sure. Let’s hear from some others.
Here’s what my buddy Chris does.
Here’s another. Same process.
If you can invert the tube, and get partially through it with anything, such as cable ?
A product iv used is a cold parts cleaner. ( carb cleaner ) best product iv found is time.. I think it is spelled differently but my I pad won’t let me. Just soak the whole thing,plugged solid…. or inverted you can funnel it into the tube if it has some opening. Works great, and virgin steel clean.
Richard…The carbon turns into rock-hard stuff towards the middle of the manifold. Also, know this–the two pre-heat tubes are not continuous. They actually do not meet in the middle of that aluminum blanket, at the center. This “rough” area tends to hold the carbon and allow it to solidify. We have tried all sorts of carb cleaners, etc. One shop I know, soaks, as per your method, for a lengthy period of time. This tends to “soften” the carbon. it then takes an inordinate amount of time to cable-clean the passage. This shop charges about $120 to clean the pre-heat passage, then to media-blast the entire manifold, including reaching into the manifold openings as far as possible. I know of two mechanics who by-pass this lengthy and costly procedure and use a long drill bit to open a passage from one side to drill the carbon…then to clean the residual. The hole must be welded closed.
After-market single-port manifolds usually do not fit properly and must be tweaked to fit. This makes having a German manifold preferable.
I wish that I had better news, Richard!
Well now. Took you no time to shoot that down… Lol
But it looked good on paper.. Iv done this with small block passages with great success, but they are larger, and can be worked from both ends.
Well now back to the drawing board. But I’m thinking the drilling, and welding up sounds like about the fastest.
Oh, Richard…I didn’t mean to “shoot you down”! Anything is possible and it is possible that there is a solvent out there which would do the job. Just because I haven’t found it means little, actually. It’s just that in my little experience I have had nothing but hard work trying to open the passage. And the fact that a couple of good mechanics whom I know, have decided that in the interest of time/labor, they best can drill a hole in the heat riser tube and drill away the carbon deposit, weld the hole closed and be done with the job. Knowing you–you probably will come up with a method to do the job! I sure hope so, anyway! jay
Oh Jay, iv taken no harsh feelings to comments on my ideas. My idea of humor may be taken as sarcasm, but not intended that way. It’s the experience of you, and Eric, as well as all the others on this whole site that keeps me reading, and thinking. As I sit reading, and gaining a belly, my brain is in overdrive… Lol
We will keep the lights on for you!
Hi, Back to the caps. I am having a bad time getting them to get together. The insulation sticks soo far out I’ a bit off to be able to get the tin screws in. Any suggestions?
Still having issues?
Hello, Chris…As you can see in my photos, tehe insulation DOES protrude from the metal cover. But, if you are having difficulty installing the insulation so that the screw holes are aligned properly, make certain that there is no residue of old material still inside
the metal cover. If the metal cover is clean, maybe you can try whittling the edge of the insulation which fits inside the cover to allow the insulation to fit better. I have learned that there apparently are two sizes of the metal covers–which can affect the way the insulation fits. I do not know if there are 2 kits available–at this point, I know of only one source (which is probably where you obtained your insulating pieces). At any rate–try my suggested remedy above and let us know how it goes, please. jay
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