BritishV8 Forum

Hello all! I am getting closer and closer to starting my long-term MGB project. Finally found some time to get working again, and I have a plumbing question for you learned folk.

I am planning on using the old MGB coolant overflow tank, albeit somewhat polished up. I wanted to ask about where I can route the bottom line that returns coolant to the system. I understand that these are (typically?) connected with a T fitting in the lower radiator hose, but my mustang radiator came with some nifty bungs that I wanted to utilize (see photo).

I have gone ahead and plugged the left bung, and was planning on using a brass 90 degree fitting to run the coolant return from the bottom of the overflow tank. Does anyone know if this would be problematic? I am assuming that enough suction from the water pump will circulate coolant through the line via the bottom radiator tank. However, I want to make sure that nothing bad will happen from having the overflow tank directly plumbed to the radiator.

As always, many thanks for everyone's expertise! This is my first custom car project, and I will never cease to be amazed at the complexity of this process.

Hey John, unless I'm mistaken, those nifty little ports on the bottom of your radiator are for cooling automatic transmission fluid and don't go into the water tank, or at least they're not designed to.


Paul

Paul,
Thanks for the info. So it is likely they are a closed loop between the two ports? That certainly wouldn't be good for my application.

John, Put a T where your drain plug is.

On a stock MG that line goes to the top of the radiator.

I suppose maybe I should reconsider it, but I have an aluminum cross-flow radiator and don't have an expansion tank.


Paul

John, I use an early Mustang radiator along with the stock overflow tank in the stock location.  I plugged the tube in the neck of the tank, ran a hose from the other tube in the overflow tank to the tube in the neck of the radiator.  I removed the rubber seal in the filler cap on the oveflow tank.  Works great for me.

Photo attached............

John, don't know if it helps but I used the old 1800 header tank and put as high as I could near the firewall. The hose runs from a fitting at the top of a standard MGBV8 radiator by the filler to the tank. Which is I guess is the same as Phils.  I keep the tank about 1/3 full and bleed all the air out the system via a bleed screw in a copper pipe fitting on the heater pipe and it seems to work well.

I did a heater delete and put the tank in its spot.

I did a heater delete as well (Gen II Mini system) and plan to move my odyssey battery there. As there's room for an over-flow tank as well, I'm seriously considering that addition, thanks Rick, hadn't thought of that.  BTW, I just installed my RV8 bonnet and the new struts, I love it, and can now close my hood with the carb installed.  Thanks again Rick, I love the way it looks.


Paul

How many ports are on the coolant tank?   If there is a third one that I can't see in your pic, the hose tee would be a good choice.  With three ports, one should be connected somewhere in the lower radiator hose/water pump inlet.  Another is connected to the very top of your cold side radiator tank.  The slight pressure drop in your lower radiator hose creates a delta-p in your top tank.  This creates a little flow and actively pulls air from the top of the radiator.  This works extremely well.  Probably not the best description, but I can sketch it if you want.  

If you only have one hose (plus the burp hose in the neck)  I'd say it can go anywhere on the "cold" tank of the radiator.

The stock MGB tank only has two ports.

One on the neck (see clear/white tubing on my picture) and one at about 4 o'clock as looking directly at the tank (see black hose).

Hey yall, thanks so much for the fantastic insights. My understanding of the system is that the surge tank is part of the active circulation of coolant - as it expands and contracts beyond the radiator's holding capacity, coolant should flow through the surge tank (what Mike is describing methinks).

Running only one line to the tank would make it merely an overflow tank, which may be the least complicated option for me at this point (like Phil's application). Would I then need to run the other line, near the cap on the surge tank, to an open air hose for overflow drainage?

Sounds like there are many ways to do this.... Sometimes I wonder if "custom" car really means "arbitrary" car?

John, it is an expansion tank as the pipe at the tank goes to the bottom of the tank which is why you only keep it part full. The cap on the radiator is a blank and the rad cap is put on the expansion tank. So as the water expands it blows into the expansion tank and then gets sucked back as it cools.
Depending which year tank you have the inlet pipe fits near the top and then has an internal pipe to the bottom of the tank, or earlier ones had the pipe go to the bottom of the tank.
They do work.

Regards Ian