I have a '96 4V and I am not sure if the coolent is flowing thru the radiator because of the "U" tube that connects the two heads. Does anyone have this problem and what would you do to correct this flow?
What gives you reason to believe the coolant is not circulating? Have you noticed abnormally high engine temps? Why would you expect the problem (if there actually is one) to be a result of the crossover tube instead of something more common like a bad thermostat? After all, its just a tube. Are you aware that the 1996 Cobra cooling systems were sufficiently bad that the factory issued a TSB that covered a free replacement radiator when the car was under the 3yr/36k mile warranty? Do you know the service history of your car well enough to say if that TSB was performed on your car?
The motor overheated the other day, This was a swap into a '96 GT just did it 2 weeks ago. I was told that the same radiator was used, the radiator hose that goes from the U pipe to the top of the raidiator seems like it is empty for a while and then coolent will finally work its way into it, I put some water wetter and new coolent and it was cooling fine now but i have not had a chance to drive it much. The radiator and the other componnts seem to be doing a good job but because of that u tube it makes me think that the coolent just circulates around that and back through the pump, bypassing the radiator. because I just did the motor swap there might have been air still in the cooling system that could have gotten really hot, but I had put like 250 miles on it since then so I just don't know why it just did it because it was fine thus far.
Well, in that case my first thought is that you've got an air bubble or two in your system. The Cobra owners manual gives a specific order of operations for filling the coolant system in order to avoid bubbles. When the car is cold, you should make sure that the overflow tank cap is off and then remove the fill plug from the crossover tube. If the tube is dry, add water until you see the level come up (the level in the overflow bottle should be at the same height.
Start the car and let it idle with the fill plug installed but with the overflow bottle cap off. If there is an air bubble in the system, it should eventually vent to the overflow bottle, and you will notice a drop in level. Top off the bottle to the FULL line and you should be fully burped. If you are confident that there are no air pockets in the cooling system and the car is still overheating, I would look into whether that 1996 radiator is sufficient. Most 96 cars were given a 97 spec radiator during the TSB, but there might be a few cars out there that didn't get the update.
BTW- the 4.6 DOHC cooling system is a much different flowpath that what you would see on the earlier cars and 2V cars. It looks weird, but it does work.