The usual means of displacing engine heat is by radiator. Most gasoline powered engines can be cooled sufficiently by a radiator through which water and coolant flow leaving the oil free for lubrication purposes. Diesel engines produce much more heat which must be displaced by both oil and water.
I called on the Vanagon Online Community and found this was not an uncommon problem with VW diesels. Various ways of remedying feverish engines were offered, and I embarked upon an aggressive course of action.
First, I removed Westly's radiator. After 30 years, it had become clogged with scale and was beginning to rot away. I found a new radiator that would fit which was constructed of aluminum and plastic. Some say it's a thermodynamic improvement, but I chose to stay with the original brass/steel component. I hauled it in to Seattle Radiator Works to be re-cored. They expertly removed the side tanks and inserted a new high-efficiency 5/8" dimpled tube core (higher cooling capacity than the original). When I retrieved it, it was nicely painted in flat black, and my wallet was much lighter.
|Westly's newly refurbished radiator|
The two holes on the right upper corner are for the auxiliary cooling fan switches.
|Block heater installed|
This handy little device is a 400 watt heating element that keeps your coolant (and oil, by conduction) warm during freezing weather for easier starting and quicker interior warming. I plug it into a timer which activates it around 2 hours before I'll be venturing out into the frozen wasteland or driving to the Handy Mart for the Sunday paper.
While the van is in motion, air flows through the radiator and then out beneath the van. For those times when additional air flow is needed there is a large two speed electric fan mounted behind the radiator, activated by two thermal switches. The low speed comes on when the coolant reaches around 167 degrees, the high speed comes on around 216. I installed a switch on the dash so I could manually activate the high speed fan if necessary (turned out it never has been) and also connected this to the green LED on the gauge pod. The LED lights up dim with the low fan speed, full brightness with high speed.
A decision had to be made about addressing the oil temperature. Some advocate an external oil cooler (like a small radiator) to be mounted underneath the van (with some type of scoop to direct air over it, or electric fans) or up front ahead of the coolant radiator. They both involved lots of hose and fittings, each with the potential to loosen or be cut and/or punctured resulting in a loss of oil which is almost always detrimental to an engine. They also complicated the oil change process what with needing to be drained and altering the oil capacity.
The stock VW diesel engine uses a cleverly designed heat exchanger which allows coolant flow to cool the oil and equalize the temperatures as well. I found that higher performance (like the turbo-diesel) VW engines used a larger version of this component than Westly's engine had come with.
|The new oil cooler (top) is about |
25mm thicker than the original
On the advice of the online community, I searched for and found several of the larger coolers for sale on e-bay, but they didn't come with the corresponding longer mounting tube. Also, because oil and coolant are both flowing inside, if the lining is compromised at all they mix which is ugly and can lead the hapless mechanic on a wild goose chase, replacing head gaskets, looking for a cracked block and so on. So I decided a new one would be best and found one with everything necessary to install it.
Once everything was back in place, it was time to fill and "burp" the cooling system. There is the official Bentley Manual way to do this, and about as many opinions on other ways as there are Vanagon mechanics. The issue is (with both diesel and gasoline engine Vanagons) that an air bubble can get in the system (and invariably does) which impedes the flow of coolant and leads to over heating. I continued to hear air bubbles swishing through the heater core after trying several ways of burping without success. Then I happened upon plans to build an ingenious device invented by a formerly frustrated (and rightly so) Vanagon owner. I had to modify the plans slightly because the diesel engine coolant tank is a little different than the gas one.
|The coolant tower (aka the Libby Bong)|
allows carefree burping of the Vanagon
This device attaches to the coolant tank in place of the pressure cap. It is filled to the top with coolant, (above the level of the radiator - this is key) and you can check the level in the clear plastic tube running along the side. With the engine running and fully warm, you loosen the bleeder valve on the radiator and keep it open until no more air bubbles emerge. Check the tower often to make sure it doesn't run out of coolant, because if it does, you get to start over. When the bubbles stop, close the bleeder valve. Loosen the clear hose on the side of the tower from its holder on top and lower it to drain any remaining coolant in the tower. Then, remove the tower and replace the pressure cap. After a couple of days of driving, top up the coolant overflow tank and you're done.
Finally, I switched to a synthetic engine oil. "Dinosaur" oil (actually from the plants that the dinosaurs didn't get around to eating) has a nasty habit of beginning to break down at around 250 degrees, where synthetic holds its viscosity (thickness) up to much higher temperatures. Too low of oil viscosity means that bearings and other surfaces don't receive the protection they rely on from the oil and they eventually respond in a horribly nasty manner, like causing your engine to seize on a Saturday night in Tucumcari, New Mexico. Be aware of the oil viscosity requirements of whatever you are driving, and don't let it get too hot. Please don't ask how I know all this, just recognize some good advice when you read it. I selected Mobil 1 5W40 Diesel Truck motor oil for the winter months. In the summer, I'll likely switch to Redline 15W40. For more discussion about Westly's oil and other fluids, check out the post Westly's Care and Feeding.
The results have been satisfactory so far. Water temp runs around 190 with the highest observed temp at 210. Oil runs around 220 with the highest observed temp at 250.
Keep in mind that I have not yet driven in an ambient air temperature much above 70 degrees, as I just completed this procedure last fall. I'll report back when I get out to the desert in Eastern Washington this spring, a trip I am very much looking forward to.
|Adventure awaits in Eastern Washington|
Update: Westly traveled to Lake Smokiam in Eastern Washington in mid April, and did very well although it was not yet all that hot there. On the steepest part of Snoqualmie Pass, the oil temp rose to 260 deg f under full throttle, but dropped back to 240 upon cresting the summit. Water temp never rose above 210. See the story about that trip here.