Water Level

[agro1]

I have a straight radiator neck running to my water pump with a cap in the middle (you can see it in the photo linked below). I'm always worried that my water level is low because before startup I check it and there is nothing there. If I add a little it comes up (from the radiator). Then, sometimes I add too much and it overflows while running...How can I maintain the perfect amount ??

http://www.clubcobra.com/photopost/s...t=1&thecat=500

Thanks in advance.

[Rick Parker]

Your filler neck should be the highest point in your cooling system to be a true indicator of coolant level. If not the cooling and heating of the coolant and the resultant expansion of the coolant will keep you guessing at the true level.

Rick

[scottj]

For an application like the Cobra, where the radiator is not the highest point in the system, you have to use a surge tank. The surge tank is mounted at the highest point of the system, with the radiator cap on top. Use a 1/2" line to connect the bottom of the surge tank to the inlet side of the water pump. Connect a ¼” line from the side of the surge tank to the highest point of the low pressure side of the radiator. The ¼” bleed line allows for a small amount of circulation through the tank. As coolant flows through it, the surge tank allows air to separate from the coolant. Any air in the system will be forced out if system pressure exceeds the cap's rating. What you don’t want to do is run the cap in the hose on the high pressure side of the system. Running the cap in the upper hose will allow water pump pressure, not total system pressure, to force coolant out the cap at high rpm. When that happens the boiling point of the system is immediately reduce.
Scott

[Bob Putnam]

Scott,

An interesting point about the "excess" pressure from the outlet-side of the pump. Since classical vertical-flow radiators had their caps on the pressure side, they had to compensate for that phenom. It would be interesting to see the local pressures in a complete system. After all, a water pump reduces the pressure on the intake side, as well as increasing the pressure on the outlet. Local pressure is dependant on the total of pressure drops along the water's path...

I don't think that a large surge tank is necessary in the system if the overflow to the reservoir is at the highest point. A properly designed system (with a two-way cap) will always expell air and return water.

[rdorman]

I use the overflow system like Bob describes, much like an OEM system. Worked perfect with never any air in the system. Everytime I take off the radiator cap (in upper hose where you usually see the tank) it is totally full. You couldn't sqeeze and eye dropper full of water in there.

[agro1]

See - that's the problem...When I take the cap off, after it cools down obviously, I can't see any water...The cap is at the top of the hose on a downward angle running towards the radiator, thus, the water seems to settle where gravity puts it, down towards the radiator. When I pour water in it, it comes back up towards the water pump...Could this be a problem ? I've never had it overheat or anything like that...Except for when I blew a head gasket, but that was because of a bad gasket...

[scottj]

Guys,
What I described, when used with a high-flow pump and a high performance (30-31 psi) radiator, would be an optimal system. With that system, water pump pressure is not “excessive”, but desirable. The system is designed to run the highest pressure that the radiator will allow and the highest velocity that the water pump will generate. Higher velocity transfers heat more efficiently, because of increased turbulence, in both the radiator and in the engine. The higher velocity also aids in “scrubbing” hot spots, which cause detonation, from the cylinder heads. Higher pressure transfers heat better than lower pressure and raises the boiling point.
Running a 1qt surge tank on the low-pressure side of the system is the optimal location to separate air from the coolant. That location has the lowest pressure and lowest velocity in the system. Under those conditions air will separate from the coolant more efficiently and expel from the system only when total system pressure (unaffected by direct water pump pressure) is exceeded.
This idea behind this system is contrary to the idea of running under drive pulleys and restrictors to slow the coolant down. The old vertical flow radiators couldn’t use a surge tank so those were necessary means of keeping coolant in that system. A low rpm (street driven) surge tank system should probably use over drive pulleys to reach maximum pressure and velocity. When the cap is in the high pressure hose, the tendency is for the water pump to push coolant out at higher rpms and as a result, reduce the effective “safety factor” that the cap could provide.
If our cars had the radiator positioned higher than the engine, we would all be running radiators with the cap on the top of the low-pressure tank and not even thinking about it. Since we can’t, the surge tank will do the same thing and I would take the position that this is the proper system design.
Scott

[agro1]

Now I'm confused...Is my system set up properly ?? My cap is located between the radiator and waterpump...There is a line running from the cap (overflow) to my puke tank. Is this the best setup ? It was done by the guys at House of Cobras for mostly racing and a bit of street use...

[scottj]

Agro1

If your system was set-up for track use then I would say it is not the best design. It may be sufficient, but it is not the best.

I would suggest that you or anyone else, NOT take my word for it though. Do some research; start with Stewart Components. They are the best in the industry when it comes to cooling.

For what it's worth I used to have the same design as you.

Scott

[rdorman]

For your set up to work you must have one of the vacuum recovery type caps and the line to the puke tank must always be below the fluid level otherwise it will just suck air. A system similiar to what scott is describing can be found in Carroll Smiths books (cant remember which one) if I am understanding him correctly. But it sounds as though you have what you need, just for some reason the system is not exchanging fluid with the puke tank on cool down.

[rdorman]

I would agree with Scott that the OEM type set up is not the ultimate, but is works for most of us. If your system is exchanging fluid with the overflow, then you could have a couple of other issues. Leaking head gaskets, steam pockets, water pump cavitation come to mind. Head gaskets you know how to fix! Steam pockets are often fixed by running a lot of block pressure (restriction on the exit). Water pump cavitation usually is helped by a quality high performance pump and by slowing the pump. A swirl tank will help remove air from the system no matter where it is coming from (address the problem first). By the way, it can often take a dozen or more heat and cool cycles to eleminate all the air in a system.

The only time I remove the radiator cap is either to test it or to refill the system. I know the system level by the over flow tank.

[scottj]

Don't slow the pump, a good pump like an Edelbrock Victor or a Stage 3 or 4 Stewart should turn 6000-7000 rpm. That will maximize pressure and velocity. Don't restrict flow at the exit of the block or you will slow velocity. Velocity gets you the turbulance that prevents steam pockets.
Again I'm talking about an optimum system not merely an adequate one.
Scott

[agro1]

I have an Edelbrock Victor that should be adequate...Yesterday I wanted to test the overflow line from the cap to the puke tank...I unplugged the puke tank and lifted the lever on the cap to vent pressure and coolant came rushing out of the bottom of the puke tank onto the ground...Could one assume from this that my system is working properly ?

[rdorman]

The pump should be fine. Slowing helps with less adequate pumps. You test shows no more than the hose is clear. I am assuming the car was hot. It does seem as though you are sending fluid to the overflow but two items I mentioned about the cap or the tube earlier may be an issue. But to be honest, I forget the exact procedure for testing the vacuum recover since it has been so bloody long since I had to test one. The system is full, the overflow level rises when hot, lower when cool, looks good!

I disagree on the block pressure and velocity. With that said, don't raise the block pressure unless you need to. If you increase velocity you reduce pressure which reduces boil point with increases the chances of steam pockets. Fluid dynamics. At the wild end of the scale it is possible to pass coolent over a surface so fast that inadequete thermal transfer occurs and the coolent becomes ineffective. It takes time for the transfer to occur. What period of time that is I have no clue

[Mr.Fixit]

The radiator cap is the highest point in your system. If the cap sees too much pressure, it will send the overflow into your "catch can" where it will not be recovered. If you had an "expansion tank" then the coolant would be recovered back into the system, the difference is a expansion tank sits ABOVE the rad cap. Your setup is fine, but you need to check your water level more frequently, as if you boil any out, it is gone. I have the same exact setup on all my cars, it has worked fine for decades, just not as idiot proof as the recovery tank setyups.

[agro1]

Thanks Fixit...I check my water level everytime before I start the motor...It is just annoying cause everytime I open the cap there is no water visable - I add a little and it comes right up to where I can see it. Should I be doing that EVERy time ??

[Mr.Fixit]

How much do you have to add? If it is a quart or less, that is normal as the coolant heats up, it expands and pushes the last bit out the top.

[agro1]

I never add more than a quart, usually about a cup or so...I guess I am fine...

[Back in Black]

http://www.cobrakit.com/Chassis/Chassis%20Front%201.htm

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For those of you that have been following my saga:

She will be on the way to me tommorrow, Wednesday.. almost completely finished.. will be here by the weekend..just have to modify the steering sheel adaptor (machining) to install my LeCarra wheel, and get the EFI going (She is coming initially with a demon carb)