Hello ST4 Snow trac owners ~ Engine Overheating Issue

[William Barrett]

Well the ST-4 went for its first ride made it through some overflow and heated up, to the point she don't wanna go. I was hoping if someone had some info, if Volkswagon ever put out a diesel flat four engine, or a replaceable diesel engine that would work or be compatable...any ideas?

 

[Melensdad]

I've heard of some overheating issues with Snow Tracs.

One thing that I've been told is that the air scoop located behind the fan shroud, and in front of the Variator Belt Pulleys, must be able to get plenty of air through the air vents in the hood. There is a rubber gasket around the air scoop to better seal the air scoop to underside of the hood. I've been told that if the rubber gasket is missing, or if the seal is not very good, then the engine can easily overheat.

I have no first hand experience in this, but it has been told to me by 2 people here on the forums with overheating issues. Maybe Lyndon can give us some insight and detail?

 

[Lyndon]

Greetings Mr. Barrett: I've written this out several times before, but I can't seem to find it here on the Forum. I would be willing to bet that I've explained it to at least a hundred people. FOR ALL KRISTI AND SNOW TRAC OWNERS; When they built both machines, Both manufacturers Violated some of VW's cardinal rules concerning engine cooling.

For their original Bug/Bus/Transporter/Karman Ghia applications VW engines had elaborate tin and rubber seals that drew fresh, cool air over the engine, then thru the engine and exhausted it out the bottom. The single and only saving grace that kept every Kristy and Snow Trac from burning up the engine is that they are operated in cold wether. IT IS IMPERATIVE!! THAT YOU HAVE ALL THE TIN IN PLACE!! In the case of a Snow Trac this means: The intake horn ("V shaped" box that goes between the back of the fan housing and mates to the hood) If it's missing have one made. Other wise your engine will just circulate it's own hot air until it overheats. This will eventually lead to a valve failing, which causes the engine to sieze up. Engine TOAST! This is why, unlike VW cars, Snow Trac's had both the "Idiot Lights" AND a Temperature guage. If your temp guage is broken or missing FIX it! I generally had both oil pressure and temp guages in all of my machines. There is some other tin that helps seperate the hot air exhausted out of the engine. they are like 'Shelves' and go right above the muffler.

Some, in fact ALOT of ST4 owners and some Kristi owners thought that the Air induction intake was a nusiance and discarded it. BIG MISTAKE! Read John Muir's Idiot Book or any other authority like GENE BURG's material and you will see how critical this is. OK, now the 'Tongue Lashing' is over. You can relax, in the next section I'll give you a list of all the 'FIXES'.

 

[Melensdad]

There is some other tin that helps seperate the hot air exhausted out of the engine. they are like 'Shelves' and go right above the muffler.

Lyndon, that is one of the most common 'missing parts' that I have seen on Snow Tracs.

 

[Lyndon]

Snow Trac had overheating 'Issues' right from the start. They tried lots of things. Individuals also tried their own 'FIXES'. Initially the manufacturer added an auxiliry fan to push more air thru the engine compartment. It's noisy and obnoxious! Since it had to turn an additional set of pulleys and a second fan this worked the starter harder and made it more difficult to start. Some people tried putting on an extra oil cooler. This didn't always work so well because the machine was often run on such uneven ground that one could starve the engine of oil.

We tried putting temperature sensors all over the engine and came up with the following DATA: 1) an awful lot of the heat comes from the muffler so re-routing the Exhaust pipe out of the engine compartment, instead of inside the compartment dropped the temperature. 2) punch (4) silver dollar sized(2") holes directly under the muffeler. This drops the engine compartment temperature by 25 to 35 degrees. Don't bother with the Auxiliry Oil Cooler, instead, have your local VW guy adjust the FUEL/AIR Ratio with an engine gas analyzer. That's just a fancy name for a polution testing machine. Most guys that have one will do it for about 50$. It's a 'ONE TIME' Fix, that is you don't have to keep doing it regularly. You need your VW engine to be set to operate at the correct Altitude also. Advance the distributor one degree for each 1000 foot of altitude, starting above 3000 Feet( See John Muir's "Idiot Book"). That means if you live, or Run your machine below 3000 Ft. you don't do anything. An engine running too Lean will overheat, too Rich and it will run cold.

 

[Lyndon]

Lyndon, that is one of the most common 'missing parts' that I have seen on Snow Tracs.

Well Snow Trac put it there for a reason.

 

[Melensdad]

Well Snow Trac put it there for a reason.

I suppose so! But until today, I'm sure that most of us had no clue what the heck their reason was.

 

[Lyndon]

The 'Tin' Shelves that go in the front of the engine compartment are in the owners manual. You can cut them out of sheet metal or have your local HVAC ( Heating/Ventilation/Air/Conditioning) shop fab them up for you. It is wise for any Snow Trac or Kristi owner that has a VW Air Cooled machine to hook up with the local VW Hippie/Guru. Generally they will love to work on your machine as they are such novel machines. I used to 'Show' as many as 6 ST4's at a time at Vintage VW Meets and believe me when I tell you that:"Old VW Hippies Like Snow Trac's" You can use this to your advantage.

To continue with the Heating problems, you can do away with the Auxiliry Fan, but you have to plug the hole in the Air horn so that it doesn't recirculate Hot Air. For Bill Harnish's FBI Rig I made a wooden block that plugs up just the left side of the air induction horn, then we pop the extra fan belt off. IF you want to Groom with your machine or you pull a 2 ton sleed up the "Matterhorn" or your local mountain to your cabin and your machine still seems like it's overheating you can put in an electric fan, right in the grill. You will find that you only need it for long hill climbs of 2 miles or more and that you won't need it the rest of the time. Make it controllable by a toggle switch and switch it on when the guages say you need it. You'll find that when your leaving, going back down the mountain it runs too cool and your heat and defrost wont work with the aditional fan on.

 

[Lyndon]

Old VW guy's like me know that: If the Oil dip stick is too hot to hold continuously, the engine is running too hot.

On single engine aircraft they have adjustable Vernier controls for both the Fuel/Air ratio, & the Spark Advance. You would also find this feature on Pre-War Rolls Royce, like the 20/25. Silver Ghost, or Phantom 1's, 2's, and 3's. You don't have to go to quite this extent. Just getting the exhaust pipe out, punching the holes undr the muffler and having someone adjust the Fuel/Air Ratio is plenty. Pay attention to the Temp Guage when doing long hill climbs. You can always stop and let it cool off. with the Hood open it usually cools right off quite quickly. Here's what can happen if you don't pay attention to he Temp: Electrical wiring will melt and often burn up. Next Hoses will melt and lead to a Fire!

Both the Fuel Pump and the Ignition coil will fail above a certain temperature. Finally the oil seals will give out and it will start leaking. If you really overheat it, or just have the mixture and spark really badly adjusted it will "Suck a Valve". One of the Exhaust valves, almost always cylinder 3, will break off. This will punch a hole in the top of the piston and the engine will sieze. Of course this all happens in a fraction of a second and it will be when your trying to get out of some hole your stuck in or while your pulling out a buddies truck that is stuck in the ditch.

 

[Lyndon]

There is another "side effect" of the overheating. The original Fuel line was copper tubing. The heat will boil the fuel in the line and the machine will vapor lock especially at higher altitudes. If you have a clear fuel filter you can actually 'see' this in progress. The "FIX" is to eliminate the copper fuel line and put the fuel supply up on the fenders instead of under the back seat. People added little electric fuel pumps to deal with this. They are Noisy, Obnoxious, and a bit of a fire hazard. Since Fuel problems are one of the single biggest problems with 30 year old Snow Cats, replacing the fuel system is a good idea. With the Boat Tank on the fender arraingement your machine will still run even if the fuel pump fails.

 

[DaveNay]

There is another "side effect" of the overheating. The original Fuel line was copper tubing. The heat will boil the fuel in the line and the machine will vapor lock especially at higher altitudes.

DING! Bob, have you checked the routing of your fuel line? Vapor lock shows exactly the symptoms you described a couple weeks ago where it wouldn't start, but after resting for an hour during dinner, it started just fine.

 

[BigAl]

Is this one of the pieces of tin you were talking about Lyndon ??? I snapped this picture at Lyndons shop last year .

 

[Lyndon]

YEP, That's it!

 

[Melensdad]

OK so we have a couple different reasons why a Snow Trac might overheat.

Here is another old photo of my engine, but this on clearly shows the heat shield that is mounted over the top of the muffler that BigAl posted the individual photo of, and that Lyndon speaks about. It also clearly shows the air intake scoop with the gasket to bring air into the engine.

 

[mtntopper]

Snow Trac had overheating 'Issues' right from the start. They tried lots of things. Individuals also tried their own 'FIXES'. Initially the manufacturer added an auxiliry fan to push more air thru the engine compartment. It's noisy and obnoxious! Since it had to turn an additional set of pulleys and a second fan this worked the starter harder and made it more difficult to start.

I took some pics of the FBI rig's auxiliary cooling system to help with Lyndon's explanation of the auxiliary cooling fan set up on the Tracmaster.

Auxiliary cooling fan belt installed for extra cooling


Cooling block installed when not using the auxiliary fan


Auxiliary fan belt off and fan not running when extra cooling is not required

 

[mtmogs]

Thanks Lyndon for the comprehensive information on this critical issue, and thanks Bob and Al for the pics.

I was very concerned about overheating yesterday as it was getting so warm in the cab. I stopped several times, each time expecting the hood to be too hot to touch, but found it to be cool. In fact, the engine compartment seemed cooler than the cab. Is that normal? I didn't try the "dipstick test," but that's a good one. Also, I didn't hear the typical clinks, tinks, pinks, you know, hot engines sounds.

Well, mine are all amateur observations, and certainly don't subsitute for an oil temp guage which I DON"T have. Where is the sending unit typically installed? A working oil pressure gauge is currently installed in the spot on the dash where the manual indicates the temp gauge sits. Is there an additional plug where a temp sending unit can be installed, or should I just swap out the pressure sending unit and gauge?

Oh, I'm not clear on why you would remove the aux fan from the intake horn. Doesn't it help draw cold air in?? I guess the good news is I actually have the intake horn and rubber seal, as well as the tin shelves in front.

Many, many thanks Lyndon - Paul

 

[BigAl]

SnowTrac Owners ,
I did make a template of the "Tin " when I was up and saw Lnydon . I think I may still have it . If anyone needs a template of it ,I probably can trace a copy on "Butcher paper" and send it to you to use to make one if yours is missing .
Al

 

[mtntopper]

Oh, I'm not clear on why you would remove the aux fan from the intake horn. Doesn't it help draw cold air in?? I guess the good news is I actually have the intake horn and rubber seal, as well as the tin shelves in front.

Many, many thanks Lyndon - Paul

Paul,
I disconnect the belt to allow the machine to warm up faster. The temperatures are very cold this time of the year in WY. Our temps in WY drop to -20 degrees often and if not working the machine fairly hard it warms up faster and runs much quieter with the belt off and the fan not running. It is also easier to start with the belt off. I do watch the oil temp closely if the belt is removed. It is a very simple task to run or not run the auxiliary cooling system by removing the belt as needed.
Bill

 

[Lyndon]

I'm really pleased that the FBI rig got such a good home! About the Temperature senders: From the very first units right thru about the 1500th machine built they used an obsolete 'Dip Stick' Oil Temperature sender. This was just what it sounds like, an oil dipstick that had 2 wires coming out of the handel. They are still currently available from some specialty VW restoration suppliers. Personally I used a "y" fitting and installed 3 senders. Dual, combination senders are available from VW suppliers that combine the Idiot light for the oil (an oil switch) and a pressure sender in one unit. The Temp sender is available in 1/8th inch threaded pipe or one that threads in to the main oil galley for the bypass spring. This latter model doesn't work well for Snow Trac's as the wire had to pass too close to the muffler where it melts, grounds out and in turn ruins the Meter! Major Bummer! All of the Guages/Instruments and senders are made by VDO and by shopping around you can get them in the correct chrome trim that matches the original Speedo and Fuel guages. Since the first thing I always did was eliminate the internal gas tanks and their senders I was always left with extra holes in the dash. I filled them with VDO Clocks, volt meters... that sort of stuff. I always attempted to keep the original Hours and Speedometer and with a little polishing they came fairly close to matching the New meters.

 

[Lyndon]

Correction: earlier I said that thru the 1500th machine they used the 2 wire dipstick sender. I just remembered that Cold Bay had one and was #1876. I always remembered the machines buy their Number although we gave lots of them other names. Old Red, the FBI rig, Cold Bay, the Ambulance, the Kitten, Red/Yellow, Purple, Nadine, Natasha..... 180, 196 the old Rolls Royce P1 was: The Yellow Peril, a play on the fact that it"Failed to proceed"quite regularly. ( Rolls Royce's never Break Down, they " Fail to Proceed") Anyway the Oil dipstick sender was used for many years after VW stopped using them on their products.Oh yes, #921 & 922, sister Trac Master's of which one is the "FBI Rig".

 

[mtntopper]

Personally I used a "y" fitting and installed 3 senders. Dual, combination senders are available from VW suppliers that combine the Idiot light for the oil (an oil switch) and a pressure sender in one unit. The Temp sender is available in 1/8th inch threaded pipe or one that threads in to the main oil galley for the bypass spring. This latter model doesn't work well for Snow Trac's as the wire had to pass too close to the muffler where it melts, grounds out and in turn ruins the Meter! Major Bummer!

 

[mtmogs]

Thanks for the great photo Bill. I think that setup is the way to go.

All the best - Paul

 

[mtmogs]

I took some pics of the FBI rig's auxiliary cooling system to help with Lyndon's explanation of the auxiliary cooling fan set up on the Tracmaster.

Very nice job on the cooling block. It makes sense now seeing the pic.
Thanks Bill

 

[mtmogs]

Correction: earlier I said that thru the 1500th machine they used the 2 wire dipstick sender. I just remembered that Cold Bay had one and was #1876.
.

Thanks Lyndon. I've got chassis # 1800 so I guess it originally had 2-wire dipstick sender. I think I will go ahead and install the y-fitting as you suggest though.

-Paul

 

[nwerring]

Found some photos of different cooling tin bits I thought I could share as well.... Two different fan shrouds pluss other parts.

 

[Lyndon]

Parts, Left to Right, Top to Bottom: Shelf for Pre-Big Wheel machine, Flats for New Style go down by the drive chains and should bolt on to a center piece(Not shown inthis photo), Old Style Air induction horn, will fit all rigs, but some hoods have larger intake louvers on them, The larger Black intake Horn actually comes in 2 versions, one houses the Auxiliry fan, the other doesn't have the Aux Fan feature. And last is the black "Shield". It attaches to the tin near, and just above the muffeler, and points up out of the engine compartment at 45 Degrees. There is a small strap about an inch wide that goes from this shield to the lower front bolt for the Carb. This piece tends to be the most effective and is shown on some of the service and parts manuals.

 

[Lyndon]

The Air induction "horn" or air box is the single most important part of the cooling system. Kristi's used 6 inch stove pipe for their VW engines. Anyway the air intake rusts out because there is nothing to prevent rain from getting in. They are pretty easy to fabricate and I gave a complete set of the drawings as well as a set of Templates to Warren of Snow Trac. Com. Once you have rebuilt or fabricated a new Air Horn it is wise to throw something over it if your machine is stored outside. This also tends to preclude some rusting of other Variator parts. Some years had an Additional Screen with about 3/8 mesh to keep leaves out. Finding one of these is rare because it was the very first thing to get discarded. Also it doesn't show up in practally any of the parts manuals, and was only found on the machines with the larger Air Horn. The FBI Rig and Cold Bay are the only 2 machines that I have ever seen one on, and Cold Bay's was beyond repair.

 

[mtmogs]

Okay. Had a look at the oil pressure and idiot light senders (see pic) They are mounted in the location shown in Bill's photo, except these are mounted on a 1/8" NPT female brass "T." I never cared for the brass fittings as my experience is they tend to leak when mated with steel pipe fittings in particular. Note there is a small oil leak coming from the the smaller of the 2 senders. I'll replace this fitting with a steel pipe "Y," and add a leg for an oil temp sender so it'll be 3 senders, 2 gauges, and 1 idiot light.

 

[mtmogs]

While we're on the subject of tins and horns, you can see I have the horn with the aux fan setup. Is the yellow vertical plate in the foreground supposed to be what Lyndon calls the "sheild?" It's not the same shape as the sheild in nwerring's photo, but is it in the right spot doing the right thing?

Note the rusty canister with the 2 purple wires coming out of it behind the air cleaner. Enlosed in there is a dropdown resistor to reduce 24 volts supplied by the battery down to 12 volts output to the coil. Kris installed this to convert the 24v ignition components to readily available 12v components. Apparently it is near impossible to fine a Bosch 24v distributor anymore.

 

[mtmogs]

Anybody up for a quiz? I found the pictured brass part wedged behind the brass T that houses the oil pressure and idiot light senders. Kris installed the new carb less than 2 weeks ago so it may have dropped during that process. I looked around above where I found the part and didn't see an obvious home for it. The only thing that looked peculiar was that the throttle cable passes through a similar-sized hole in a sheet metal shroud, an obvious location for cable wear. Could this part be a cable bushing?