Can't Get Enough
Join Date: Mar 2000
Location: So. Jersey
Thanked 0 Times in 0 Posts
First off I apologize for not replying/posting something earlier. Time, health, working on other cars, etc. My Jeep has been the mainstay. KISS principle – Keep It Simple Stupid. Four wheels, a carbureted engine, and a manual transmission.
Now from here on in the word “coolant” will be used in place of the word “water”. This is an attempt, albeit feeble, to help my self and other old schoolers enter into modern times. You have a coolant pump and not a water pump. There are always exceptions to the rules and this one is when one is creating the 50/50 coolant solution one has to mix water and the concentrated coolant.
Through the years cars have had heater control valves. These are either vacuum or mechanically operated. They stop the flow of coolant to the heater core (and sometimes return it to the engine). They started to appear when air conditioning became more popular. A direct result of engines being forced to run hotter to help emissions. Who wants that really hot coolant coming into the cabin area if it won’t be used, possibly fighting the air conditioner? Move the heater controls to a/c and the valve would close. If you can figure out what year, make, and model of a vehicle heater control valve will work please share. I chose not to go this route because there is a reason auto parts stores carry them. They start leaking or freeze up.
I chose to use good old home type ½” brass valves. No bleeder. Replaceable neoprene/rubber washers. ½” copper pipe is measured at the inside diameter. The outside diameter is about 5/8” If you then solder a ½” coupling onto the pipe then the coupling’s outer diameter is about 3/4”. This size works good for standard heater hose and the use of the coupling combined with sliding the heater hose far enough over the coupling will provide a ridge to help keep the hose from sliding off of the coupling. Now let’s realize that the average cooling system will only build up something like 16 p.s.i. The use of all stainless steel worm gear hose clamps with moderate clamping force will be adequate. Silicone hose and lined clamps would be the cat’s meow! Do it once and do it right.
Please refer to the attached documents. The 258 cu.in., errrr 4.2 l., AMC engine likes to use the heater as a bypass. That is a thermostat bypass. In the past I have just slightly delved into internal combustion cooling theory. I think it is designed with a bypass for two reasons. Some pumps like to flow liquids and get real upset if the flow is stopped while they are trying to pump. Internal pressure may build blowing past the seal or perhaps cavitation or that other word I can’t remember when gas vapor is mechanically forced to come out of solution causing erosion of hard surfaces. Or in the unlikely, but not impossible, event of the thermostat failing in the closed position some cooling will be provided through the heater core to let you limp her home.
When I first tried this I did not provide a bypass path and simply used one valve to stop the flow of coolant to the heater core. I started the Jeep and watched the temperature gauge. It sat at stone cold while the engine got hotter and hotter and hotter. Finally after the thermostat got hot enough, from convection not from coolant circulating next to it, it opened up and the temperature gauge went from stone cold to overheat in a New York City minute.
I made the Valve/Manifold assembly with the ½” copper pipe and fittings. The valves are directional with some kind of markings showing this. If there are no markings the flow should be against the face of the washer, not from behind the washer. Look in the end to see the face of the washer in the closed position. When you are soldering disassemble the valve so the rubber washer, packing seal, and gasket are not melted. Experience is the best teacher. You’ll need two tees, a couple of elbows, and four couplings. Design it any way you want but leave enough space between the valves to get your fat hand on the handles. My second design took this into consideration. A nice touch is to have red handles indicating they could be hot.
Coolant flow is straight forward as far as the coolant comes out of the engine at the thermostat housing and goes back into the engine at the coolant pump. (I almost wrote water pump.) Now’s where it gets a little fancy. My ’79 engine strictly adhered to the KISS principle. Hot coolant from the thermostat housing to the upper heater core nipple and cooler coolant from the lower heater core nipple to the coolant pump. I don’t think it really matters whether the coolant goes in the top and comes out the bottom of the heater core but this is the way I think it was originally set up. Perhaps the engineers were smoking something illegal or perhaps with the hot coolant coming in the top there will be a little natural flow with it cooling in the heater core and sinking and coming out the bottom nipple. Its natural flow helping the coolant pump’s forced circulation. That’s my story and I’m sticking to it! Now here’s where it can get a little complicated. The ’85 engine I currently have has a heated intake manifold. I think this was designed to help drivability and also to help reduce emissions by helping the engine warm up faster. If you notice on the cooling system drawing it shows the hot coolant coming from the thermostat housing first going to the intake manifold. What is not shown is it then coming from the intake manifold to the heater core then to the coolant pump. I think everyone knows Jeep heaters, especially from this era, are notoriously marginal at best. So knowing my ’79 motor without intake manifold heating worked just fine I wanted the hottest coolant possible going to the heater to keep my tootsies as warm as possible. I also have a full soft top. Can you say drafty? I switched a couple hoses around so the hot coolant goes first to the heater then to the intake manifold. Looks good lasts long time! This intake manifold also has an electrical heater in the floor directly under the carburetor. I disconnect this during the summer and reconnect it in the winter.
Operation is close one valve open the other and vice a versa. Open the upper (in the drawing) valve to supply hot water to the heater core and close the lower valve to stop any bypass action. Close the upper valve to stop all hot coolant to the heater core and open the bottom valve to provide bypass for a gradual (normal) engine heating.
Today's mighty oak is just yesterday's nut that held its ground!