Proper Engine Cooling

Eric of 1967beetle.com messaged me recently with a diagnostic situation. Eric explained that he was hearing a strange sound in his engine. He even made a short video of his running engine.

I listened, heard “something”, but could not come to a conclusion. Had it been the Generator bearings, I would have suspected a growling. I could not hear that. I suggested that it could be something to do with the Fan—maybe the Fan Nut on upside down?—maybe a cracked Fan? It did not sound like a Fan rubbing the Fan Shroud. Someone else thought that it might be a connecting rod. I asked Eric if, after accelerating, then letting off the gas, he heard a heavy thumping. No. Well…that seemed to limit our attention to the Fan. In the end, Eric’s mechanic was called upon to diagnose and remedy the problem. The Fan had succumbed to metal fatigue and had cracked where the Fan Hub seats on one side and the Wave Washer, on the other.

Eric wanted to install a new Generator which he had on hand—which turned out to be a good thing because the original one was quite troublesome to disengage from the Fan and was rendered useless in the end. With the replacement Fan and the new Generator installed, the Savannah Beige was, once more, purring down the roadways!

In choosing a good German Fan to send to Eric, I looked at several which I had on hand. I found one similarly cracked. Another was severely rusted at the Hub. Rust does a number on metal, weakening it. That one also was discarded.

Yet another problem which can occur to the Fan is “wallowing”. If the Fan Securing Nut is not properly torqued onto the Generator Shaft against the Fan Hub, the Fan will begin to “rebound”, causing the opening for the Hub to become distorted. When this happens, the Fan must be discarded and a fresh one installed. The Hub, also, must be inspected for damage.

Once, on a VW cruise, one of the drivers told us that he could hear a strange noise in the engine compartment of his Beetle. We gathered around his car while he started the engine. As we listened and pondered, one of the group remarked: “I bet that the Fan Nut is on upside-down!” He asked that the engine be shut down. Reaching behind the Fan Shroud and into the Fan opening, he could feel the Fan Nut.

Sure enough the Nut was on upside-down. In subsequent photographs, it will be come evident why an improperly installed Fan Nut will cause problems. The Nut cannot be properly torqued when installed upside-down.

Also, the Fan Nut Wave Washer can be improperly installed upside-down. Both the upside-down Fan Nut and/or the upside-down Wave Washer can contribute to Wallowing.

Our 1967 Beetles use the “skinny” Fan, VW Part# 131-119-031. This Fan began to be used from Engine Number F0 958 001 and continued for all 1500 and 1600cc engines through 1970. It often is called the 32mm Fan (rough measurement across the Fan’s edge). There are some minor variations which I will not discuss in this paper. The depictions in this article, I believe, match those Fans which came with our ’67 Beetles.

Beginning with the Generator Shaft at the Fan Shroud, components include the following: Woodruff Key—VW Part# N 012 705 1. There are two of these, of course, since there is one at the other end of the Generator at the Belt Pulley. The Hub—VW Part# 111-119-123. This Hub began to be used during the 36Hp Engine era, at least, and persisted into February, 1968.

The Carrier Plate (also called the Thrust Plate)—VW Part# 111-119-131. The Hub and the Carrier Pate work as a unit. In February, 1968, Volkswagen introduced a new one-piece Hub (VW Part# 111-119-123A) which eliminated the Carrier Plate. The New Hub will retro-fit previous Fans and surely was a cost-saving measure. For our ‘67s, the earlier two-piece version was used.

Next on the shaft, IF any are needed, come the Shims (also called Washers). According to the VW Manuals, three Shims generally are required. We’ll discuss this aspect shortly.

At this point, comes the installation of the Backing Plate Assembly. This is a three-piece Assembly which began with the 1500 engine series. That means that it first was used with T-2 Vehicles prior to 1967.

For 1967 Beetles, this was a new part. Previous Beetles (’66 and earlier) had a one-piece Backing Plate. My discussion will focus upon the three-piece Backing Plate Assembly for the ’67 Beetle.

The Backing Plate Assembly consists of three parts:

The Outer Backing Plate—VW Part# 131-119-261 for the 105mm Generator (the diameter of the 12 volt Generator which came on the ’67 Beetles)–is mounted onto the two 6mm Generator Studs.

Next, the Center Reinforcement Ring is installed—VW Part# 131-119-271

Followed by the Inner Backing Plate—VW Part# 131-119-259

Install the two small Generator Stud Wave Washers, followed by the 10mm Generator Stud Nuts. Tighten firmly.

Now, install the Fan onto the Hub. The Fan is secured to the Hub using a stout Wave Lock Washer—VW Part# 111-119-135 and a large 36mm Special Fan Nut—VW Part# 111-119-141A

The Wave Washer must be installed with the two elevated edges facing the Nut. The Nut, then, must be threaded onto the Shaft with the grooved side against the Wave Washer.

Failure to install the Wave Washer and the Nut properly can result in damage to the Fan and Fan Hub as mentioned above (wallowed Fan Hub opening and grooved Fan Hub). Cooling will be affected since the Fan will be rendered less than effective. Eventually, there will be a failure which can result in major damage to the engine.

I strongly recommend running a 12mm X 1.50 Tap through the Fan Nut to ensure cleaned and straightened threads in order to achieve proper torque.

At this point, proper clearance can be set between the Fan and the Backing Plate Assembly. None of the Fans seems to be perfect. These were mass-produced and, although an attempt was made to balance the Fans, they do have some run-out. Balancing was effected by spot-welding tiny bits of metal to the inner surface of the Fan edges between the fins. Usually two of these bits will be present. At first glance they may appear to be affixed debris, but do not make the mistake of loosening or removing these bits.

Clearance can be achieved by the use of the Shims. Clearance usually will be no more than 2mm (eighty thousandths of an inch) or slightly less. If the proper clearance cannot not be achieved without Shims, place one Shim between the Carrier Plate and the Fan. Reassemble the Fan onto the Generator Shaft and tighten the Nut to 40-47 Ft. Lbs. Check the clearance again. Continue to adjust until the Fan’s run-out clears the Backing Plate. If the Fan is bent or has significant run-out (wobble) it is advisable to acquire a replacement Fan.

The Official Manuals call for placing unused Shims between the Fan and the Wave Washer. The Manuals indicate that only one Shim will be necessary between the Carrier Plate and the Fan in order to adjust the clearance. In this case, of the three Shims which the Manuals call for, two will be left for placing between the Wave Washer and the Fan’s inner surface. Obviously, use of one’s judgment will be necessary when adjusting the clearance.

Sometimes no Shim will be necessary.

I sat with Barry Blythe, a 32 year veteran Volkswagen mechanic, to discuss the use of Shims. Although the Official Manuals call for placing the Shim between the Hub and the Carrier Plate, he told me that this was not a good idea. The Shim should be placed between the Carrier Plate and the Fan itself.

David Brown, a veteran VWoA trained mechanic, and I discussed this same issue. As David told me—“There is no mechanical advantage to placing the Shim other than at the Fan.”

As well…both mechanics advised against placing any extra Shims between the Fan and the Wave Washer. Again, this gives no mechanical advantage and offers opportunity for loosening of the Fan Nut. Better to store any “extra” Shims in the tool box.

It has become popular to install a dust cover on the Generator.

During our study of the Cooling Fan, David Brown brought to my attention the disadvantage of this practice. Here’s why.

You will notice that at the fore and aft ends, there are openings in the Generator. This is not for the purposes of “weight reduction”. These openings furnish passages for air to circulate through the Generator body for cooling purposes. The two openings (top and bottom) which serve as access ports to the Brushes, also allow circulating air to escape the Generator. Closing one or both access openings, diminishes maximum air circulation to the internals of the Generator.

But, what is the source of this circulating air? Let us review the facts:

The Louvers in the Body of the Beetle above the Decklid allow air to enter the Engine Compartment. The Decklid Rubber Seal keeps this air from escaping the Compartment. As well, the large Rubber Engine Compartment Seal, which encircles the Compartment, contains the valuable incoming air.

The Fan sits inside the Fan Shroud. The round opening of the Fan matches the round opening of the Shroud. The Fan is turning clockwise with the turning of the Engine (trace the Engine Crank Pulley to the Generator Pulley via the V-belt). The fins, or vanes, of the Fan are angled so that as the Fan turns, the fins are “cutting” air, drawing air through the Louvers and into the Shroud. This air becomes “pressurized” inside the Shroud.

A large volume of air is needed to push through the Oil Cooler Radiator inside the Shroud. As well, the forced air is directed across the Cylinder Fins and Cylinder Head Fins to cool them. Air also is forced through the two large-diameter Fresh Air Duct Hoses on the back of the Shroud. This forced air through the Fresh Air Hoses will serve to heat the Cabin, when the Heat/Defrost Levers are pulled to allow the air to course through the Heater Boxes and into the Cabin.

Looking at the Backing Plate Assembly, we see that it is a three-piece affair. The Outer Plate, which goes directly against the end of the Generator, fits snugly against the Generator Housing but is open to the end of the Generator. Note the 4 openings in the end of the Generator for circulating air.

Next comes the Reinforcing Ring which fits the contour of the inner surface of the Outer Backing Plate. The Outer and Inner Plates are contoured so that there is space between them for air to circulate. The Reinforcing Ring prevents the two Plates from collapsing when they are bolted together

But, the Inner Backing Plate does not have a large central opening in it as does the Outer Plate. Once it is bolted to the generator, it is closed—except for a flared area at the bottom. Air is pushed by the Fan through this flared Air Slot and, thus, through the Generator. Any impedance, including Generator Dust Covers, offers resistance to the flow of cooling air across the Generator windings.

Note that the Inner Plate has an Air Dam at the upper portion. The Air Dam prevents air from simply circulating round and round between the two Plates. The air pushed through the Inner Backing Plate Air Slot MUST pass through the Outer Backing Plate opening into, then through, the Generator.

Volkswagen engineers spent an exorbitant amount of time and energy—not to mention monetary expense–to perfect the Cooling System. The belt-driven Cooling System has proven itself time and time again—even in the most extreme Zones of this Planet. Yet, the System is so simple that it is easily maintained by minimally trained vehicle owners.

Acknowledgements:

Most of what I write stems from conversations and interchanges with others of the 1967 Beetle Community. My thanks to ALL who contribute! Especial thanks go to the following persons

• Many thanks to David Brown who spent hours on the phone with me exploring the workings of the Fan and its components. David had at hand the components, as I did on my end. Thus, we were able to compare, measure and discuss the components, piece-by-piece. David also proofed the Article to find any discrepancies. Find many pages of David’s Used and NOS VW Parts by going to thesamba.com and entering the following into the Search Box under User Name/E-mail: mountain bug
• Barry Blythe, who has been working on my Volkswagens for years, patiently answered my many questions and guided me through the maze of parts—both relevant and irrelevant. Barry has operated a VW shop in Garland, TX, for well over 30 years. He possesses a wealth of VW information and practical application.
• Doug Smith of R & D Engineering, using his professional cleaning station, cleaned the Fan which was demonstrated in the Article. Afterwards, Doug gave me a tour of the shop to demonstrate all of the many other VW services which R & D offers. See: RD-Eng.com
• I showed some aspects of the Fan to our son, Kevin, who was visiting us recently. Kevin literally grew up in VWs, learned to drive them and did constantly, even through his college years. He not only helped me endless hours when I was working on the family VWs but worked on his own VWs as well. He pointed out and emphasized the “pressurizing effect” of the Fan in the Shroud. He suggested doing a simple test to prove or to disprove the flow of air through the Generator. Using a strip of paper towel held above the upper brush opening of the Generator, with the engine running, we clearly could see that air was coming through the Generator from the Fan Shroud. The paper towel flapped as air exited the brush opening.
• Neva, my ever-patient wife, used her photography skills to capture images of
  the props for this Article.

Technical Notes:

Fan: From Engine # F 0 958 001 and all 1500 and 1600 thru 1970: 131-119-031
Single-Port; 30.16mm or 1-3/16ths” wide—measuring across the Fan’s edge.

Early Hub : # 111-119-123, includes most 36hp also. (the newer 1 piece version is 111-119-123 A)

Fan Hub Carrier Plate 3.5mm Thick : 111-119-131—sometimes called “Thrust Washer” by Volkswagen Manuals, not needed when using the redesigned Hub 111-119-123 A

Some Fan History…….. Chassis # 118-600-001 was designated as the change-over for the Fan Hub with the dropping of the Carrier Plate. (The day that 111-119-123 grew up and became 111-119-123 A)

Shim for Hub: 111-119-133 B Approximately .012” thickness and 1.790 OD. Sometimes called “Spacer Washer” by VW Manuals.

Backing Plate, Outer : 131-119-261 for 105mm Generator

Center Reinforcement Plate: 131-119-271 for 105mm Generator

Backing Plate, Inner: 131-119-259 for 105mm Generator

Generator Shaft Keys (2): N 012-705-1

36mm Fan Nut: 111-119-141 A

Lock Washer (Wave Washer) for 36mm Nut: 111-119-135

Torque for 36mm Fan Nut: 40-47 Ft. Lbs.

For Added Information:

Workshop Manual Volkswagen 1200 ’61-’65, M-4 page 5 and M-4 page 14.

Official Service Manual’66-’69, Engine, page 13.

Be aware that not only is there some “missing information” but also some conflicting information in the Manuals. Perhaps poor proof-reading?—perhaps some things lost during translation?