cooling system questions

[Jim Rosenthal]

I have been at building this car so damn long that I am probably repeating questions I posted years ago (this is what happens when you get old, and when you take nine years and counting to finish a project like my GT40), only this time I am asking these questions because we are actually DOING this stuff, so forgive me if, like a lot of old folks, I repeat myself:

Today we installed the pipes and hoses which connect the cooling system- the water pump to the main coolant tubes, and the main coolant tubes to the radiator. I also have the overflow tank, which will install on the engine room bulkhead on the starboard side. It hass a neck for a radiator-type cap, and also three NPT or some kind of threaded holes in the inner side. My car does not have a heater. There are also two short stub pipes coming out of the Ford water pump. One of them would ordinarily be used for a thermostat bypass, like on my 289 Cobra's 302 engine, but the bypass into the manifold is blocked off- the casting is not drilled for it.

So, it seems to me that we will have to drill a couple of bypass holes in the thermostat itself, first off. But the real purpose of this thread is to ask about how to do all the cooling system plumbing. The engine and the radiator which cools it are at opposite and high ends of the system- the transfer pipes are in the middle and they enter the radiator at the bottom of it. There are also two threaded holes in the radiator top tank which I assume are for bleed hoses.

The questions are:

-where do the air bleed lines run, and how are they hooked up?
-how do I fill the system? (we are thinking fill the engine manually first off, and then everything else, and install petcocks to permit us to burp the air out of the radiator at least)
-how do I ensure that all the dissolved air, once it coalesces into bubbles, can get to a high point in the system, specifically the overflow tank?

I would appreciate it if you all would share your experiences and advice. We are actually getting close to a point where we could put water and oil in the car and fire it up. (well, we'd still have to wire it, wouldn't we) and I would like to do this right the first time if I can.

By the way, the coolant tubes were made by Safir GT40. They are stainless steel, I think 316L, beaded at the ends for hoses and clamps, and they fit very nicely. (everything that was made by Brady Pack at Safir has fit the first time out, I am happy to report) We used silicone hoses and double-clamped some of the ends. The hoses were wrapped with exhaust pipe wrapping and over that high-temp heat shrink tubing was applied, which we hope will keep the heat inside the tunnel pipes and not radiate it all into the occupants of the car.

 

[Jac Mac]

This is Mk2, but you get the idea. ideally the bypass passage must be drilled to allow this to function & piped via the header tank to make coolant flow pass by the T/Stat bulb to correctly function.

 

[Mark Clapp]

Jim, like in Jac Mac's illustration, one bleed line (small diameter) is plumbed from the top of the radiator to the expansion tank using one of the npt pipe thread bungs. Sounds like you could run one from both top sides of your rad. If there is an outlet at a high place on the intake manifold, run a bleed line from there and tee into the ones from the rad. My tank has a 1" threaded bung on the bottom that fills the system with a heater hose line (5/8") to one of the water pump inlets. Sounds like the other inlet on the water pump will be capped off on your system since no bypass. As the system circulates, trapped air will be rushed into the expansion tank through the bleed lines. As the coolant expands and overflows into your overflow tank (which you will also need) the air will be vented there. Once cooled, a vacuum is formed and the system will suck back coolant from the overflow tank. The system should be self bleeding and will not need petcocks to bleed with. It will continue to burp out the air and you just keep filling through the expansion tank until it finally stays full. Hope this helps some.

 

[Jim Rosenthal]

Very helpful. I think we can adapt all that to my car. I may drill the gooseneck for the thermostat bypass. But I think the above diagram tells me what I need to know.

I didn't see this when I wrote the original posting today but the radiator top tanks fittings are different; the left hand side one is a small internally threaded one, about 1/4" or so, and the right-hand one is considerably larger and externally threaded. I think that is where the radiator bleed hose back to the overflow tank originates, and runs back through the tunnel to the tank. I am not sure I need TWO radiator bleed hoses especially since they would be at the same height. I will use one and close off the other bleed hole unless I really need it.

It will be interesting doing all this plumbing. We are very keen to get all this going, and of course months from doing it....

 

[Neal]

Jim,

One should be sufficient. I used a 3/8" ID bleed. Works like a charm.

 

[Jim Rosenthal]

I do have enough bungs on the tank to use one to fill the system using the heater inlets on the water pump. I think we ARE going to drill out the gooseneck and put in the bypass hose aorund the thermostat- not having it makes me kind of nervous. I suppose I could just drill a couple of holes in the thermostat itself....I think I ought to have it the way it was originally designed, though.

 

[Jac Mac]

Original bypass works better than drilling holes in T/stat, with By-Pass coolant does short loop thru pump/engine..... drilling holes sends coolant fwd thru radiator & takes forever to warm up as it actually interferes with correct operation of T/stat...... Now we wait for the anti -thermostat gang to arrive with how they drilled 3.9 3/32" holes at 89° intervals & havent had a problem.

 

[Terry Oxandale]

The hoses were wrapped with exhaust pipe wrapping and over that high-temp heat shrink tubing was applied, which we hope will keep the heat inside the tunnel pipes and not radiate it all into the occupants of the car.<!-- google_ad_section_end -->

Could we have some discussion on this as well. I've heard tid-bits from time to time, but still do not have a grasp on the heat issue with tubes down the middle (successful and unsuccessful methods of keeping the heat down). I'm contemplating running the tubes through the side pods (remember, it's a McLaren wanabe) rather than down the middle, or under the passenger side seat (yes my wife wants to ride in it periodically, and the tubes in their correct location would give her the red-..., and I do that well enough without the extra heat.

ox

 

[Jim Rosenthal]

Well, basically cars that have the engine in the back, the people in the middle, and the radiator out front are hot in the passenger space.The engine is right behind the people, the coolant tubes run through the backbone, typically, and the radiator radiates a lot of heat into the air which then washes back over the middle of the car, heating it further. So they tend not to be too comfortable for the people in them, unless you have such a large amount of cooling air that it very easily carries off all the waste heat and hot air etc.

If you look at second-generation mid-engine Ferraris, they have the radiators in the back along with the engine- cars like the Testarossa and 348 and their successors. These cars are much more comfortable to be in than the ones that came before them- the 328s and Mondials, for example. The 365 and 512 Boxers also had the radiator up front like a GT40 does, and the amount of heat coming backwards from the hot air coming through the radiator is impressive.

I don't think there is enough space in a GT40 to put the radiators in the back. The way Ferrari did it was to use multiple small radiators and a lot of fans (the only thing up front in the Testarossa and 348 is the AC condenser, which of course works rather well since it isn't around anything else), and there isn't room for that in a GT40. Maybe it could be engineered but what would the point be....so we all end up trying to minimize the amount of heat that gets into the passenger space of a GT40. Insulating the coolant tubes and the bulkheads between the engine area and the passenger space is what most folks do. Getting some air moving through the tunnel is also helpful as it carries off heat. Using SS tubes helps a lot (see Adam's posts, I think it was him, in an earlier thread a few years ago about the heat transfer properties of various tubing materials, and you wouldn't pick aluminum if you'd read it). I may try to duct some air through the tunnel as well if it seems to need it. And having a lot of ventilation in the rear space helps, as heat trapped there will make its' way forward if it is around long enough to do so.

 

[Mark Clapp]

Terry, run the pipes down the outsides if you can. My GT replica has the coolant pipes running down the side pods in notches that run the length of the gas tanks. I love it because I have no additional heat in the interior coming from the pipes. This also leaves more space for wiring, vacuum tubing for power brakes, throttle cable, etc in the tunnel and no insulation worries. I realize not all cars are made to run the pipes down the sides.

 

[Doc Kaler]

I'm wondering. Since ceramic coating exhaust headers helps to cool down engine compartments, why not coat the SS coolant tubes? Every little bit might help.

 

[Jack]

Header wrap is useful too..

 

[Jim Rosenthal]

We used header wrap. (low tech, but made to take the heat). We also shrinkwrapped the tubes after the header wrap went on, to keep it in place. (hope this works). I am sorting out all this plumbing now- of course, none of the items in question have the same kinds of threads etc etc

 

[Jim Rosenthal]

Well, here's another cooling system question, as follows. I'd be interested in anyone's advice or input on this, as the choices I make now will no doubt have some bearing on how my car's engine acts and lasts in days to come.

While we were running bleed lines and installing fittings for same today, I discovered that 1) my car's engine has no thermostat in it 2) nor does it have the recess machined in the thermostat housing which would allow me to put one in. I mentioned in an earlier post that the part of the thermostat housing which is a spigot that goes to the upper small water pump fitting is also not drilled out.

My question is this: in a street engine, it seems important to me to have a thermostat or at the very least a restrictor in that position so that the flow of coolant is about where the engine designers intended it to be. I can understand why an engine in a car which is only driven on the track wouldn't have a thermostat, just a restrictor, but seems to me that an engine which has to warm up quickly, idle in traffic without overheating, and drive at slow car speeds some of the time needs to have a cooling system that is suitable for street use.

Please comment as you see fit. As you all know, I don't do this for a living and I have no false pride about being told what to do. I'd much rather get some guidance than blow something up by not asking for it.

 

[Jim Rosenthal]

I forgot to mention that I think I can take the housing down to the machine shop and have them flycut the mounting surface so that a thermostat CAN be installed. And I can drill out the blank spigot on the drill press, I am at least that good.

 

[John]

Jim,

This post is so old I don't know whether it's active. I see you're in Annapolis - I'm in Rockville, Md.

I'm having an overheating problem and noticed a bleed line from the radiator was suggested to you! Can this simply be a small plastic line or does it need to be as solid line running to the purge tank?

John
:thumbsup: