[Fot] TR coolant pressure/flow

[Larry Young]

Greg,
I don't have an answer to your question regarding pressures, but I had a 
similar arrangement in my TR3.  The Chevy style radiator is a great 
idea, because it eliminates the worry of overheating. I cut off the 
radiator fill cap and plugged it off, since it is unreachable anyway.   
I put the expansion tank in (from Pegasus I believe) so that I would 
have a way to fill it.  I wanted to have water flowing thru the 
expansion tank to effectively increase the volume of water in the 
system.  I went with the return to the suction side of the pump with 1/8 
inch pipe and small diameter hose to keep the flow rate down.  I drilled 
and tapped the thermostat housing for a drain valve so I could bleed all 
the air out.  It worked very well and was one of the best upgrades I did 
to the car. Some would argue that you should have a cap to regulate the 
pressure downstream from the thermostat, but I found that it worked fine 
with something like a 7 lb cap on the expansion tank.  You would think 
this would open up due to pumping pressure.  I think if I did it over 
again, I'd just put a cap somewhere downstream from the thermostat and 
eliminate the expansion tank.  I could probably find some photos if 
you'd like to see them.
Larry Young

On 2/7/2013 9:08 PM, Greg & Alison Blake wrote:
> Anyone out there every gauged coolant pressure on the TR block?  I'd love to
> see the results.
>
>   
>
> I am going through the process of adding a surge (expansion) tank on my TR3
> and I am starting to wonder if I am plumbing the return line in the correct
> spot.  I have installed the tank in the battery box with a line entering the
> top of the tank that originates at the heater port in the rear of the head.
> For the return line, off the bottom of the expansion tank, I have added a
> welded fitting in my top radiator hose between the thermostat housing and
> the radiator to accept the return line.  I use a cross flow Chevy style
> radiator so I have a metal radiator pipe between the thermostat housing and
> the intake for the radiator.  I thought it would be better to introduce the
> hot coolant from the expansion tank back into the radiator vs dumping
> directly back into suction side of the water pump via the return heater
> port.  My thinking was that I should not introduce hot coolant into the
> suction side of the pump and re circulate it back thru the block.  The way I
> have it plumbed (if it works), the hot coolant from the expansion tank will
> first go thru the radiator then into the pump and back thru the block.  I am
> guessing that downstream of the thermostat housing (I use a thermostat) the
> pressure will be lower than at the back of the block.
>
>   
>
> My questions are:
>
> Has anyone measured pressure between the thermostat housing and the
> radiator?
>
> Has anyone measured pressure at the back of the head heater port?
>
> What is the difference?
>
> Am I going to get coolant to flow from my expansion tank back into the top
> radiator hose or is the pressure higher in that top hose than the back of
> the block?
>
> Would it be better to plumb the return line into the return heater port?
>
>   
>
> Thanks,
>
>   
>
> Greg
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