ok im not getting any heat out of my heater, 1955 with the heater that you can see, and touch the heater core right in front of the passengers seat on the fire wall. i have a 351 cleveland and the valve is in the upper tube on the heater outlet and goes to the water pump fitting on the engine. does the water pump hose go to the top of the heater core or the bottom and does it make a difference which hose the valve goes in.

 

De leg bone connected to dee kneee bone.....

Ok all the heater tubing routes the same. On the Cleveland motor, it runs:

Out of the intake manifold to a shut off valve - if you have one. Then;
From the shutoff valve to the LOWER tube of the heater core. Then;
Out of the heater core and back to the nipple in the water pump.

Check:
1) to make sure that if you have a stop valve, it is opening (honestly, if you have one I'd just take it out-completely unnecessary);
2) the nipple coming out of your intake manifold is not plugged or rusted shut; and/or,
3) the nipple at the water pump is not plugged or rusted shut - both are infamous for that.
4) you have a thermostat in the engine and it is operating at the correct temp (195 degrees).

You may also have a "Bypass" type of valve. A "Shut off" valve will just stop the hot water from traveling up the hose to the heater. A bypass valve will allow the hot coolant to travel up the hose but when closed, re routes the hot coolant via a seperate hose to a "T" in the line that returns the coolant from the heater core to the nipple on the water pump.

Many after market valves have to be opened by hand while standing at the engine compartment - they are not automatic. If you have a stock original shut of valve, it should open by pulling the "Temp" cable on your heater control.

 

yeah i think one of the nipples is rusted almost closed.

 

I've seen this question come up a few times and it has gotten me thinking... does it matter which 'side' of the heater core is the inlet? Its just a heat exchanger, right, so the flow through it shouldn't be directional. I bring this up because I would think I'd put the inlet at the top, so when the valve is closed (no hot fluid flowing through it) whatever fluid left in it would be allowed to drain as much as possible back to the water pump. Am I missing something?

I don't remember how I hooked mine up (though I would image I used the logic above) but I do know it seemed to work fine.

 

I think Julie and I agree on the thermodynamics, hot water rises, so the hot go’s into the bottom of the core and is sucked out of the top by the water pump.

 

There is nowhere for it to drain, it's a closed loop system. Normally you put hot water in the lower connection, so it will force any air out of the heater core. To answer your question precisely, sometimes they are arranged so that hot water goes in the air outlet side of the core, and the cooled water goes out on the air inlet side. That way there is a more or less constant temperature differential between air and water. On the simple Ford box heaters, not sure they bother with that. When they work right, they'll set your shoes on fire!

 

Sure, hot water rises, but thats really only relevant to a stagnant situation. This system is flowing when the heater is on, so it'll be pushed/pulled anyways, probably with negligable thermodynamic effect (especially since as soon the thermostat opens, the coolant should be at constant temp, so there is no 'hot water').
I understand purging the core, and subsequently the system, since air in the cooling system isn't too good, and that is the quickest way to the vent. Mine's been installed for so long I would think what air may be in there has already worked its way out. I'll check mine out anyways.
I guess the obvious other question is, whats the harm if the hoses are backwards? And isn't the radiator a top inlet, bottom outlet...and the heater core is just another 'radiator'.

 

if it just stopped workin' all of a sudden, if it has a cable controlled heater valve.... check that the actual lever that the cable pushes hasn't come stripped off of the axis of the valve mechinisim.... had this happen only opposite couple of summers ago on my vw eurovan..... was cold in the morning had the heater on for the drive into the city, coming home ate afternoon though it was like 30c and couldn't shut the heat off....made for an uncomfy drive home....couldn't even pinch the heater hose off nuff' with a pair of vise grips to make the heat stop.
mikie
near ottawa canada
58 merc 100 panel & 64 econo p/u

 

Heatere trivia:
The industry standard now in the US is called the "Ford heater", which runs hot water all the time, but bypasses all or some of the air around the core. This givbes much finer control of air temp than trying to regulate the water side. As Economan notes, 10% of water flow is enough to make a bunch of heat, in mild weather the valve would be almost completely closed, which quickly destroys the seat in the valve.

 

There are a couple of key points in all the discussions that need to be brought together.

First, Ross is absolutely correct in that driving the water up from the bottom to the top ejects any air that could be trapped or bypassed if the water flow were aided by gravity. Air trapped in the heater core can be very bad if there is any type of water hammer effect caused by sudden heat increases (like opeing the shut off valve). Also, being driven against gravity the water tends to flow more to all parts of the core and not just "rush" through it.

True also that the heater core is a small radiator. But the flow from top in (hot) to bottom out (cool) on a radiator is safetied by a pressure relief cap on the radiator that the heater does not have. That makes the trapped air and possible pressure a more significand problem in the heater.

You also have to remember that the heater is completely independent of the thermostat and it's operation. The heater flow bypasses the thermostat intentionally to allow hot water to flow from the intake manifold through the heater to the water pump, when the thermostat is closed and forcing the coolant to stay in the engine until it is at the right temp.

The basic box heaters didn't use a shut off valve. Theory was if the fan was not on, the heat in the core would stay in the box. Or, you were lucky to have heat so shut up if it's a little warm in the summer.

Some of the Magic Air heaters had shut-off or bypass valves and some did not. I think the difference was in the physical configuration of the doors in the body of the heater itself (the "Ford" heater air flow Ross mentioned) and how they controlled engine heat to get distributed via the heater.

In mine there is no heater control valve, the temperature control **** opens and closes a door which isolates the warm core inside the box. It works quite well as I can draw cool air in from the outside vent, blow it into the cab and it does not heat up.

On other heaters, perhaps the temperature was controlled by the valve instead of a door to isolate the warm core.

One of the biggest killers of the valves is the same thing that causes those rust/plaque blockages in the manifold and water pump nipples. It's electrocatalytic conversion of the heavy metals/minerals (sodium, iron and especially calcuim) in some of the tap water found in the US. Most of the folks with the mild pHs in their water are ok. But from Texas west, and Colorado south, the water has high amounts of minerals and metals in it.

The heat of the engine, plus the constant electrical charge the metal is subjected to, turns the inside of the engine into a quasi annode and tends to convert and combine these off metals and minerals into harmful (to your engine) compounds. Calcium carbonate is the biggest culprit. For those of you who live out west, that is also what encrusts your faucets and shower fixtures. Calcium carbonate is caustic (like lye) and will "eat" just about anything - especially the shafts and seats on the shut off/bypass valves (and for that matter, water pumps). It also will cause iron to oxydize (rust) which when mixed with a dash of oil, is how you get the rust/plaque.

So here's a suggestion for all you folks doing restorations. You've spent anywhere from $100 to $500 on a new radiator or recore. $100 or more on a water pump(s) and $100 on a new heater core. Spend $5 to go up to the store and buy 3 gallons of Distilled Water to mix with a high grade coolant (which may cost you another $20 over the lower grades). Mix your coolant at the recommended concentration for your temps (50/50 or maybe even as high as 70/30 for Buffalo in the winter) and add 1/2 cup of white vinegar to the cooling system. The vinagar is quite acid and will neutralize any minerals or metal in the water, plus it will disolve any mineral deposites that may be in the engine. It'll save the seals and shafts of the water pumps and heater control valves.

For new or rebuilt engines, after 2000 miles, completely drain, flush and replace the engine coolant mixture. This will expell any residual oils from remanufacture (that causes rust/plaque), left over free floating gasket compound or sealants, and any flash rust the engine may have had from sitting with air in it when it was re built.

Never EVER allow any part of your cooling system to be subjected to air for more than half an hour.

Just a suggestion.

 

so confusing, glad i sold the truck last week, the new owner can figure it out.