What pressure cap are you running?
The return line to the reservoir does actually come from the top of the radiator, or at least very close to it. The more I think about it, the more I agree with you that it is an airlock problem because (and please correct me if I'm wrong) if the water pump was moving coolant, then there would be coolant returning to the reservoir through the small hose.
This is the case.
But if there is air in the system, where is it? Shouldn't be in the rads because it would be returned to the reservoir through the existing return hoses. If there is air in the water pump, wouldn't it bubble up into the head?
I think there are two factors.
1 A small amount of air will swell to a larger volume at 200F, and if it will tend to impede flow.
2 The more linear feet you move liquid through a tube, the greater the resitance to flow, and you are at 9? times what the water pump was ever meant to see. Corners are bad too, but velocity is low, so who knows.
If resistance is great enough to let water boil in the head, all bets are off, coolant flow stops.
This is beginning to make sense. Back when I had a radiator in the engine compartment, it had a return to the reservoir that was above the cylinder head level, and in fact the hose went directly up and over the engine to it. Now, both returns are well below cylinder head level. I bet I need a bleed valve near the top of the engine...
the reservoir needs to be at the top of the cooling system to perform the bleed function properly. a seperate bleeder may work, but adds complexity, and service difficulty, esp. on the side of the road.
and wouldn't you know it, googling "vanagon engine air bleed" pulled up this:
http://www.relitech.com/tech/19wpump/hsbleed.jpg
I feel so stoopid now.
Did yo also read the Vanagon bleed procedure?
2200 RPM on a 23 degree slope to 5 minutes?
this was conceived by a brilliant person with an engineering degree?
You are not the dumb one.
As for series/parallel, I did consider the latter but that arrangement requires more fittings/hoses and it cannot be guaranteed how much water will go to each radiator. Also staging the fans would not work as well. Temp differential would be the same as you still have the same amount of water flowing across the same area of radiator either way, but some say that heat will transfer better if the coolant is moving more slowly, which would be a benefit to the parallel arrangement. I may try it someday.
-David
Ease of flow is also a factor at play, Your radiator resistance will be half, as will coolant speed. If you run a Y pipe at each end of the rad pair, the only difference between the two will be relative deposit buildup in the tubes, and flow will be pretty well equal. As is, i think rad #2 is not doing much more than acting as a tank. if you can access an IR temp gun, you can check for yourself(a lot of things).most emission shops will have one if a friend doesn't. The first 1/4-1/3 of a rad sheds about as much heat as the rest. Run the fans so they are triggered by either or both switches, extra safety factor
Between the big transfer pipes, and 2 rads, you have almost double stock coolant capacity, I think if the stuff were moving, you'd be fine.
Once you get flow dialed, it will be worth your time to do some experimenting with air dams encouraging flow. done right, the E-fan probably won't need to run on the highway.
Taking the Chevy RV I had for awhile as an example... a 454 in a low perf application only needs 3/8fuel line, but since it is 30 feet from tank to motor, GM used 1/2" for that run. Why? Straight line friction would have let 3/8 line perform like 1/4. You might run a slightly larger line on the bleed hose.
Can you tell I have fought this battle before? My Volvo VW diesel came from the factory with over 32 hose clamp coolant connections
there is a theme here...
I added a very similar aux rad to a friends 350 Chevy converted Mercedes 309D bus, and it worked pretty well.
Topic: Overheating problem in TD bus (Read 5186 times)
