Triumph Sports Cars

I am getting close to being done and I am examining everything that I am not completely satisfied with the design and layout.

So my situation is the outflow pipe from the engine is about 1 inch higher than the corresponding inlet on the radiator. So the hose slants down a little to the radiator (one of the 8 million variables that I didn't account for, but I would rather not hack up of purchase a new radiator). The radiator cap and vent is the highest point in the system but since the radiator cap is installed on a 45 degree corner on the radiator it creates an issue when filling the system. When the radiator is filled, as much as the location of the radiator cap allows, there is about 1-1.5 inches of air in the top of the radiator and because there is an up slope to the engine from the radiator (top hose) it is questionable if the top hose is filled.

The motor is a reverse flow motor where the thermostat is on the bottom of the engine and controls when coolant is allowed into the engine. When the thermostat opens, coolant is allowed in from the bottom pipe, the water pump pumps the coolant up and out of the top hose to the radiator.

With the radiator filled as much as allows the coolant level is several inches above the water pump. So my question is this, will the system operate properly and keep the block full of coolant as long as the coolant level is higher than the water pump? I think over time it will eventually siphon in enough coolant to top off to the top the radiator and keep the top hose full, but I am not sure. I have attached a couple of pictures to get an idea of what I am trying to explain.

Or do I need to install a surge tank at the high point on the return hose to insure that the top hose is always full of coolant from the initial start and not worry/chance with it topping itself off via the vent.

If I don't need to add more crap to the engine compartment I would rather not.
I am sure this is all clear as mud. Any help, opinions are welcomed.






Edited 1 time(s). Last edit at 12/21/2008 10:28AM by crj7driver.

I have an aftermarket setup in the TR8 with a similar issue (I bought it that way, so don't flame me).

Despite the fact that whenever I look in the hoses, they are all empty, and I have no idea how it can all work, it seems to do just that. - work. Based on my slightly skewed experience, I'd say "suck it and see" rather than "it'll never work".

I'd love to be able to be more helpful, but in my case, the PO set it all up - as far as I'm concerned, against all logic, it seems to just work. Good luck, btw.

Ryan, this is going to be a REALLY nice conversion!

As Alan said, the system might work fine as is... but I suspect your concerns are well founded. A header tank on the firewall would ensure that the cooling system works well in all situations. Besides the points you mentioned, I've read several places that radiator pressure caps don't work well unless there's an air gap under them. I like the transparent bottles that European OEM's use. (I know I've seen them on BMW, Saab, Volvo, and VW.)

Jim Stuart used a Volvo 240 tank:

(The Volvo 740 tank is smaller and more cylindrical, as I recall.)

I used a Volkswagen Jetta VW Jetta (~1992) tank:


If you don't have a remote tank, it might be helpful to install a plug closer to the top of the system for topping up.

Robert Milk's shows one approach to that:

With reverse flow all bets are off unless you can find an expert on that type of system. About all we can do is guess. But to start with, as the coolant heats up it will expand some, raising the fluid level a bit. The pump will push as much fluid through as comes into it and that means there's a small volume at the pump inlet that gets pushed through as well. Not much to rely on for circulation but at least it's something. Originally cross-flow radiators were designed to have an air space at the top bot that doesn't help if they are top feed to the water pump. (Personally I don't know why you'd want to do that since heat goes up.)

There are two types of extra tanks used with coolant systems, surge and overflow. You can use either, both, or neither. A surge, (or header) tank seems called for. It's purpose is to keep the radiator full under all conditions. With a properly designed header tank an overflow recovery bottle is largely superfluous.

Jim

I installed a radiator cap in my top hose, with a aluminmum in line filler. Don't remember the brand but it was a lot like this one from Jeg's.
[www.jegs.com]

Thanks for all the input. I might do a little of it all. It just occurred to me that I might be able to cut and re-weld the water neck on the engine to drop it and give it a positive rise to the radiator inlet. Since the radiator cap is the highest point it should be able to take care of topping itself off via normal means. If that won't work, it looks like I will either install some sort of topping off port or surge tank. Now I just need to get home to try it out. Why does work get in way of all my projects?

The most effective surge tank I've ever seen was on an old ford sedan with a 390. It was in the form of a separate tank that the upper radiator hose ran through and was above the radiator. It was filled 2/3 full and the rest of the system was kept air free, and there was no overflow, so no recovery tank was needed. There was an overflow tube on the tank's filler neck, but the header tank acted as the fluid recovery tank.

With your reverse flow, the trick is going to be keeping a supply of coolant at the pump inlet. A similar arrangement could work for you but I feel your system is always going to be extremely sensitive to coolant level. If you have a crossflow radiator you could just as easily feed the pump from the bottom of the supply side tank, and I think this would be better for always assuring a supply of coolant even if the level goes down.

Jim

BlownMGB-V8 Wrote:
-------------------------------------------------------
>
> With your reverse flow, the trick is going to be
> keeping a supply of coolant at the pump inlet. A
> similar arrangement could work for you but I feel
> your system is always going to be extremely
> sensitive to coolant level. If you have a
> crossflow radiator you could just as easily feed
> the pump from the bottom of the supply side tank,
> and I think this would be better for always
> assuring a supply of coolant even if the level
> goes down.
>
> Jim

The radiator is actually a cross-flow and the water pump is fed off the bottom hose (I am certain water will be above the pump). I was concerned with an air pocket on the upper return side and how that would affect the top hose and coolant circulation. But if I can drop the neck on the topside of the engine enough I think I will be good.

Sorry Ryan, I misunderstood. Then if supply is good the next issue is removal of air from the system. You said this was reverse flow. If that means the water from the pump goes into the heads and comes out from the block then there is great concern with removing air and steam bubbles from the head. There should be some sort of bleed passages from the heads back to the low pressure side of the system (pump inlet side or surge tank) then the use of either a surge tank or recovery tank to maintain a fluid filled system should about do it. This should be tied in at the high point in the system and should be even higher than that point. This would preferably be a low flow area.

Jim