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MG Midget and Sprite Technical - It's that time again -- any better ideas?

It's about that time in a North Carolina Spring when I
need to re-plumb the coolant system to bypass the
heater core but run coolant past cylinder 4. I have to
unscrew the clamps on two hoses and re-route them
so that the cockpit stays cool when I turn on the fan.

Must be a simple plumbing device/valve that would let
me toggle back and forth between heat and no heat
when the flap is open and the fan is on. Probably
need one valve each side of the heater core. In one
position water goes thru the core, in the other
position water shunts out one valve and in the other
to bypass the core. I can draw it; just can't find
the hardware.

suggestions??

chuck
c c

Chuck,
If you have a good relationship with your local autoparts store, they will frequently let you leaf through the old book of heater valves. I know I have seen one which is Y-shaped and allows you to select the path you want it to take. Theoretically, it would need another Y (without a valve) to re-join them, but the one valve should suffice as you would get minimal backfeeding. When I looked at it before, I wasn't ready to do anything, so I wasn't interested in special-ordering a valve. BTW, Which way is the water flowing there? A spare choke cable could probably work as a control...
David "out of roundtuits" Lieb
David Lieb

Chuck, try taking a look at the heater valve from around an 87 or 88 Jeep Cherokee or Comanache with the 4.0 engine. It's controlled by a vacuum solenoid, but it appears that you could remove that and mount a cable actuator. I think it's the type vavle you're looking for that will bypass the heater core while still passing coolant back to the radiator from the port in the rear of the head.


Bill Young

But will it fit 1/2" heater hose?
David Lieb

My 1275 midget has a valve at the back of the cylinder head that I close to stop the water from flowing to the heater core. It came from the factory that way & is available from MG parts suppliers. Also the 1969 Chrysler Station Wagon with the 440 engine had a heater control valve that fit inline on the heater hose & was cable operated so you could also adjust flow for those days where you need a little heat.
Mike G

Mike,
You are correct about the factory setup. The reason for the original post, however, is that there is a firmly held belief that turning off that valve can lead to poor circulation of coolant around cylinder 4 with resultant overheating of that end of the engine and sediment buildup to exacerbate it further. Therefore, many people are reluctant to turn off the tap, preferring to use a hose to bypass the heater core. Since I live in the Chicago area, I find it hard to decide exactly when it is prudent to bypass the heater core, because our weather just ain't that reliable. A diverter valve would be much nicer, especially if controllable from the cockpit.
David "hot toes" Lieb
David Lieb

Id use a brass garden hose "y" spliter, with the built in valves,,and use that to by-pass the heater core with a 2nd "y" splitter.

http://www.amazon.com/LR-Nelson-Two-Hose-Shut-Off-N80C/dp/B0009NES92/ref=tag_tdp_sv_edpp_i/105-1090516-8462013


prop
Prop

Prop,
I think they heard you...

"Currently unavailable.
We don't know when or if this item will be back in stock."
David Lieb

David, I'm not sure about the hose size. I used a cable controlled valve from an AMC on my Midget and it took a 5/8" hose but I was able to stretch the 1/2" hose over it with a little lubrication and cussin. It was only a simple on / off valve so wouldn't return water to the radiator when off, but I didn't have any cooling problems during the one summer I used it on the 1275. The same valve is now on the V6 and still working.
Bill Young

I assume that the water comes OUT of the block, right? Is there another car with a similar design with a simple flange with pipe that attaches there instead of the tap? If I were to put a valve there, the extra room would be welcome and the absence of several potential leaks would be a benefit.
David "tapped out" Lieb
David Lieb

All of which reminds me of the attached photo...

;-)

-:G:-


Gryf Ketcherside

Gryf,
Thats a beautifull mod!!
I have always closed the factory valve in the summer, but based on Davids reasoning I'll probably look for some kind of diverter valve.
Phil
Phil

In googling various permutations of pertinant words, I came across a site from a guy in Florida with a Miata. He claims that the Miata always circulates water through the heater matrix to keep from overheating the rear of the engine... Sound familiar? Anyhoot, he got tired of re-routing his heater hoses every year to keep from cooking his accelerator foot, just like Chuck. His solution was to find a marine 3-way ball valve that transitions from shifting the flow from A>B into A>C. This, with a T in the return line would do just what I want, and might even be converted from a lever to cable actuated. His dissertation is at http://mymiata.paladinmicro.com/MiataHeater.htm

Bears looking into as far as I am concerned.
David "now to find the 1/4" version of that valve..." Lieb
David Lieb

My summertime concern has mostly been a desire for increased cooling
capacity. So I leave the valve open like "ol hot toes". (could always close the flap on my side and let mama have hot toes.)
Maybe a cutaway in the back cover of the heater core box would allow
the summer heat out in the engine compartment, with the added effect of "ram air".
off to look for a new heater valve knob! too cool, Gryf!
D Ramsay


Interesting... I drove my car for 3 years in Medford, Oregon, during the summer. It was regularly over 100 degrees, with quite a few days over 110 degrees, and never had an issue with just turning the valve off at the back of the engine. Never had an overheating problem and the engine never seemed to suffer. This is a '68 with 1275.

These days I just leave the heater on all the time and don't open the vents in the summer because I live in a bit cooler area.
Scott Linn

This thread was discussed between 02/04/2008 and 05/04/2008

MG Midget and Sprite Technical index

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