TDI install retrospective: Cooling

Continuing the process of back-documenting what I did to put a TDI engine into an old (1972) air-cooled VW bus. Today I cover the cooling system. Somehow, I managed to not plan for this post when I started this retrospective. Ha. To keep concepts separate, I won't go into the electrical, but I'll cover everything else cooling / coolant related.

Radiator

I started with a Jetta3 radiator I got off craigslist for $20. This met the need, but eventually was swapped out for a Mishimoto radiator designed for a Jetta3. This allowed all of the bracketing work I did for the original radiator to be re-used. Sort of. The bracket design was relatively simple: Add a straight square-tube bar across the leading edge of the radiator, and form brackets which are affixed to the bar, but thread into the radiator mounts. The crossbar then had eye-hooks added so the radiator could suspend from the underside of the bus. To the front of the bar, steel security screening was added to prevent refuse from entering the radiator. See bracketing the radiator and Radiator mounting planned for more details.

On the rear, simple individual brackets were formed for each of the 2 mount holes on the radiator. Each bracket had an eyehook added, similar to the front bar. From the 4 eyehooks, the radiator would hang from the underside of the bus. I used 400# test chain to hold the radiator, and placed it at an angle (front about 4" lower than the rear) so the exhaust heat would be encouraged to vent down-and-rearwards and so that the leading edge of the radiator might scoop some air as it passed beneath. Corresponding eyehooks were added to the frame under the center of the bus, and the chains have threaded carabiners on the ends for ease of connecting / servicing. See rad brackets continued and Radiator test-fitted for more details.

To discourage hot air from recycling into the intake side of the radiator, I cut and attached some sides to the radiator unit with some thin zinc-coated sheet metal used as cold-air return material in houses (See Radiator Shrouded). Underneath, I attached an aftermarket fan:cowling to maximize the suction of the fans drawing air through the radiator (See Cowling the Hapy Radiator). For more details, See Radiator Installed, Back to the Bus Rad Swap 1 and 2.

I have not experimented with lowering the radiator beyond it's current height of about 9" above the ground. I had ideas of adding a scoop to the leading edge bar, or adding a means of lowering the radiator with a lever or something, but the bus now runs cool enough without added complexity. If that changes, those options remain.

I know there are some who will read this and not accept that an under-belly radiator is sufficient. Consider that the Aussies are doing it, and were doing it well before I started my project. They have super-hot, dusty conditions and they drive their under-belly conversions in the outback. So, some gravel from the road or a mid-western summer are not really the factors we may fear them to be. After 10 years, these have not influenced the cooling at all. The keys to keeping the temperature controlled are getting the exhaust air away and getting air to draw through the radiator through cowling and fan suction.

Overflow Bottle

The overflow bottle for the NewBeetle is shaped like a ball with a mounting tab on one side, like in the picture here. That tab has the 2 mount holes. I built a simple angled bracket that aligned with those 2 holes, and attached it to the front-to-back floor support at the front right corner of the hatch I added. The bottle needs to be located height-wise in the same relative position as it appears in a stock TDI install. This places the full line at the top of the head. This height requirement may force you to put in an access hatch just so you can add coolant. I suppose a port-hole could work. Your bus, your choice.

Hoses
Unlike the inter-cooler and vacuum, the cooling system left only a few pieces I could re-use. The runs to/from the radiator were solved with multiple 2' long Goodyear flexible hoses fitted together with metal connectors. These flexible hoses satisfied the run from the engine bay to the radiator, but within the engine compartment, there were other considerations. For example, the outlet from the thermostat housing exits the engine pointing at the passenger-side rear wheel. This needs a 90* downward bend, so I used a short piece of original hose, and mated the bend to the flexible hose with a metal joiner that included a small (1/2") "T" which I routed to a bleeder. I have used this bleeder to get air out of the system while filling with coolant many times. The run from the outlet flange also points to the passenger side, and it needs to include a temperature sensor. So, again, there is a mix/match of TDI hose, a piece of TDI plastic holding a sensor and the flexible hose.

I omitted the EGR, so the plumbing around the EGR needed to be eliminated as well. This actually simplified some of the paths. Last, there was the coolant line run to the overflow bottle.

Extras

nicked from TDI-club

I haven't introduced any changes to the oil cooler nor the oil-to-coolant exchanger, but this feels like the right spot to mention it. I have thought about swapping out the original stock TDI exchanger for the V6 4motion Passat oil cooler or the late model NewBeetle / Jetta / Passat / Toureg (also Audi) oil cooler. Both are larger, and with the amount of concern I've had over temperature control over the years, this is an upgrade I will probably do as part of a Malone tune. The V6 4motion looks a lot like the TDI one, just a little bigger while the later model cooler has the coolant inlet/outlets oriented differently (middle unit in the picture). I got these part numbers from this thread on the TDIClub and only re-post here for my own future reference benefit. The TDIClub thread author (Kennedy) deserves all the thanks and praise for assembling this detail.

V6 4motion Passat
028117021E OIL COOLER (should come with upper gasket)
038117061 LOWER COVER TO OIL COOLER WITH SEAL
*I believe the original lower cover will fit, but I'm not 100% sure

late model
038117021B OIL COOLER
038117061 LOWER COVER TO OIL COOLER WITH SEAL
038117070B SEAL

Heater

image nicked from theSamba

For some, having a heater isn't an extra. Its mandatory. I wanted to remain stock-VW parts as much as possible, so I looked into a real defroster-type heater unit. I couldn't fit anything that big into the space I had, so I bought a used Vanagon rear-seat heater. I plumbed that into the heater/defroster hose loop, placing the heater unit on the extra battery tray, under the spare tire well in the engine compartment. This actually worked fairly well. The coolant lines were very short, and I was able to route an insulated flexible air hose to the front, connecting it to the original bus air system. I removed it all when my original ignition went up in smoke, and now don't have a heater. More importantly, I don't have a defroster. In retrospect, I probably could have retained the heater, and just sourced the 12V elsewhere.

I have considered adding an aftermarket heater closer to the front of the bus, and running longer coolant lines to support it. The long air hose system was slow to respond because the air in the hose needs to warm up or cool down before you can feel the change. That's the beauty of the modern systems: no air hoses. The coolant, however, could cool off before it gets to the front of the bus, and there are would be a need for a bleeder, etc. so this isn't exactly perfect either. So, as much as this is a retrospective, some things clearly aren't really done.

De-Scale
Regardless of what you do, if your engine isn't new, and you don't really know how well it was maintained by the prior owner, it might be wise to de-scale it before you consider your system complete. I ran a Thoroflush procedure and that made a massive difference in the bus' ability to ditch heat. Check out the Now Water-COOLED post for some more detail.

Prior related posts:
Preparation
Fuel System
Physical Mounting
Vacuum System
Air, Inter-cooler and Exhaust
Primary Electrical

Next related posts:
Secondary Electrical
ECU, dashpod and Sensors