Cooling System Function and Operation Part 4
Before continuing to the thermostat section, I must regress to some things about the heater that I have omitted.
If a heater fails to keep your car comfortable in the winter, you may want to check out a few things. Is the coolant temperature correct to the thermostat rating? If not check engine temperature and change the thermostat to correct it. Is the hose into the heater hot? If not check for a plugged heater core or a heater control valve that’s not working. If the heater core is clogged, it may not be repairable and require replacement. Heater cores are constructed in a "two pass" design, meaning that coolant enters on one side of the core and flows to the bottom then turns upward to the outlet fitting making a "U" turn internally. In the top tank there is an internal divider to separate inlet from outlet passages. Should the solder bond at this divider separate, it will allow the coolant to take the path of least resistance (in one side/out the other) instead of sending heated coolant through the entire core. This can be determined by checking hose temperature to the touch, if both hoses check hot and you are not getting much heat in the car the internal divider may be the problem.
Insufficient airflow from the heater box is another reason for poor heater performance. The fan motor may be tired and unable to turn fast enough for an adequate supply of air. The core it's self may be blocked, leaves, grass, mouse and bee nest have been found in heater boxes. Make sure the box and core are clean before condemning the fan motor.
Thermostat
The thermostat is much maligned, often misunderstood, and seldom credited for its mostly reliable service.
Thermostats in proper working order, control only the minimum operating temperature at which engine coolant is allowed to heat. A properly operating thermostat has absolutely nothing to do with how hot the engine becomes. If you are experiencing an over heating concern, changing to a colder thermostat will not correct the condition, it only allows the coolant more time to over heat. A thermostat once fully open can do no more to control temperature the overheating cause lays somewhere else.
Some believe that removing the thermostat completely can remedy over heating concerns. This can be deceiving, with out some flow control coolant can pass through the radiator without slowing enough to cool, returning to the engine hotter with each circuit of the liquid.
Usually washer type flow restrictions in place of the thermostat are only acceptable in racing applications. They can control neither minimum or maximum temperatures, only flow capability. The only exception is in racing application where it may become a restriction, to slow coolant flow through the radiator. You can see that removing a thermostat, going to a colder setting, or using flow restriction washers is not suitable for street driven cars.
A thermostat has a metal (brass or stainless steel) valve operating open and closed by a temperature reacting spring. The spring is in the flow path of the heated coolant. Its cycling is determined by the temperature of the coolant it is in contact with, opening by small increments as the coolant starts to reach the rated temperature, closing down as the coolant becomes colder.
Coolant must be in contact with the thermostat for it to work properly. An engine low on coolant may experience a thermostat not opening because steam is present in the top of the engine. Air trapped in the system by a closed thermostat when refilling with coolant may cause a violent boil over.
Having been severely overheated a thermostat needs replaced, overheating of the reaction spring tends to change its effectiveness. It may not fully close causing slow warm up. A sticking thermostat is one that will over temp or under temp momentarily and then suddenly operate normally. Debris in the coolant can effect the thermostat operation. Mentioned earlier RTV, gasket parts, block casting wire, or hose parts all will cause thermostat problems also. Poorly maintained coolant can attack the thermostat damaging it and reducing it effectiveness.
Thermostats come in many varying quality levels, as important as they are to our engines, please purchase only top brand names like Stant, Robert Shaw, or original Motorcraft. The price of a quality thermostat will not usually exceed $8.00, making it not worth the trouble a cheap one can cause.
Some thermostats will have a giggle valve in the mounting plate. This valve is not an indication of the quality of the thermostat, but merely an added feature. The valve is oriented at the top when installed in a vertical position. Its true function is to allow air to escape from the top of the cooling system, aiding filling, and avoiding steam pockets. If your thermostat does not come with a giggle valve, a 1/16" drilled hole near the outer diameter of the plate will work with the same effect.
The factory specification on most 60's Ford cars thermostats are 165* for normal use. This temperature is not set in stone. In northern climates it was common practice to use a 165* in summer and change to a 185* in winter. The use of the cooler thermostat in summer had nothing to do with over heating problems, but was an attempt to reduce under hood heat in the summer. These cars had very little insulation to keep the heat out of the interior. Lower engine temperatures contributed directly to driver comfort even if the car was equipped with air conditioning. Thermostats have stock temperature tolerance variation up to + or -5* and will start to open at about 150*, completely open by 180*. At these operating temperatures, combustion by products and acids will be eliminated from the lubricating oil. Lower temperature or no thermostats can cause engine damage and loss of fuel economy. Sludge build up starves oil pumps and creates more wear. At respectively higher temperatures engines operate more efficiently. In more extreme winter conditions a 185* thermostat will provide better interior comfort. We need to note that the temperature coming from the heater core is only variable in proportion to the temperature of the coolant that passes through it, since the physical size of the core is fixed.
Thermostat Installation
Installing a thermostat is very simple, yet often done incorrectly. Always place the temperature sensing spring towards the engine. On engines with vertical installation, (289-302-351W-FE) make sure to stick the thermostat in place with either a small amount of wheel bearing grease or RTV to prevent it from dropping from its mounting counter bore. Should the thermostat fall from its location while tightening the housing bolts, it will surely crack and ruin the thermostat housing. Should your housing become damaged, new stock replacements are readily available at most professional auto parts stores.
It is very important to look upon the thermostat as a periodic maintenance item on your car. Even though a very reliable part they can fail in time. Most people look upon the cooling system as a no maintenance area. If it's working," don’t mess with it". Like oil changes, tune-ups, and fuel filters some things need attention before they make you a pedestrian. I have seen many cars operated over 10 years or more with the factory thermostat still in place. Ignoring the thermostat is like not checking your engine oil level.
Thermostat Housing
The thermostat housing bolts to the intake manifold on most Ford engines. The exceptions being the 351C/351-400M, they bolt directly to the engine block. The front of the intake manifold or the face of the thermostat housing has a machined counter bore that is the locating feature for the thermostat.
Some thermostat housings also have a water pump by-pass hose nipple on them. These housings can be of cast aluminum or iron, each being susceptible to corrosion damage. Gasket sealing surfaces and hose nipples are prone to deep pitting making them unusable.
Besides being a servicing access for the thermostat, the housing is the main flow restriction in the coolant flow returning to the radiator. Even with the thermostat at full open position, more coolant is being pumped into the engine than can be expelled from the top hose casting to the radiator. This is evident in the hose sizes on most engines, the lower hose being a larger diameter than the top hose. The design provides a steady supply of positive pressure on the coolant at the top of the engine, helping eliminate air bubbles or steam pockets from forming.
If you are planning to replace your stock housing with one of the nice looking chrome after market dress up parts, you should be aware that most of these are of poor quality. The "O" ring sealed housings being susceptible to leaking.
Water Pump By-pass Hoses
The water pump by pass hose connects the water pump to a fitting on or near the thermostat housing. Coolant may flow in either direction through the by pass hose, depending on rpm and degree of open of the thermostat. When an engine starts cold, before the thermostat begins to open, coolant moves through the engine with out an exit route. We know that we want the coolant to stay in the engine block until fully warmed, but some coolant must circulate. If stagnant, unable to circulate, localized areas in the cylinder heads can boil coolant then super heat it and cause metal failure. The by-pass hose offers a partial escape route for coolant to circulate back through the engine while the closed thermostat will not allow it into the radiator.
At high water pump rpm more coolant is pushed into the engine than can be exited, allowing it to be by passed from the water pump through the hose directly into the thermostat area for return to the engine.
Another condition is present when pump impeller cavitates. At high pump rpm the lower radiator hose can be sucked shut, not getting the volume it needs, this creates a negative pressure at the pump impeller, pulling coolant through the by pass hose. That is the reason for the coil spring inside the lower radiator hose, to prevent collapse.
It has been suggested in some automotive magazine tech. articles that blocking the by pass hose can gain you up to 30% increase in flow. While this is basically true, removing the thermostat will achieve the same flow gains. If other parts of the cooling system are operating at maximum flow (radiator) and still can not cool your engine, then increases in flow will offer an advantage. Similar to having after market water pumps claiming greater flow capability, stock pumps will supply all the flow that is needed. These are things best left for racing applications, not practical in street cars.
Radiator Hoses
Radiator hoses are subjected to extreme conditions, pressures over 18 psi and temperature ratings of 275* are normal. Many are not rubber alone but may have reinforcing cord in them similar to the side wall on a tire.
Upper and lower radiator hoses connect the engine to the body of the car, in every case the radiator is bolted mostly solid to the core support. Hoses must be flexible enough to allow for slight movement of the engine on its rubber mounts. Hoses must clear engine accessories and frame/chassis obstructions. Hoses can and will fail prematurely if not properly installed. Always make sure hoses can not contact belts, steering, frame, or engine block. Abrasion can saw a hole through a hose in a very short time.
Molded hoses provide the best fit and flow capacity, having smooth bends and gentle internal corners. Flex hoses or "fit all hoses" should be avoided except in an emergency when nothing else is available. Many discount auto parts stores rely on a few flex hoses to cover many molded hose part numbers. These parts like most other things are a compromise and asked to do many jobs, in most cases they do none of them very well. Top brand name hoses such as Gates or Goodyear always being the best choice for fit and quality.
Previously I mentioned the importance of the coil spring in the lower hose, always verify that a new hose has one, as they sometimes fall out. In some older cars having been poorly maintained, the lower spring may have rusted away, been broken or otherwise missing. Parts of this spring can and will move through the entire cooling system. I have found pieces of spring lodged in the thermostat, rendering it inoperative. Water pump impeller damage may also result from passing spring pieces. Pieces of spring in the radiator top tank, protruding from core tubes restricting flow. The lower area of the engine block is where most of the spring parts will accumulate, being almost impossible to remove without engine disassembly.
Fabricating Custom Hoses
If you have ever considered an engine swap to something not normally found in your year Failane, one of the problems encountered is trying to get radiator hoses that match your current radiator to the new engine. Here is a Tech. Tip that will help. Many professional auto parts stores have illustrated hose catalogs (this will not be in the computer) that show all their available hoses. The catalog that I use is CarQuest CQ-2040 RBR issued in 2000. The molded hose dimensions are in the very back. If you know the sizes you need the catalog list them in progressive sizes from 7/32" to 3 1/2" I.D. and 4" to over 50" lengths. Hoses are in many shapes with unique bends. Going through this catalog you may find exactly what you need. If not, there are ways of fabricating hoses in any shape or bend. Using short pieces of tail pipe tubing you can join hose sections together. If the hose does not turn exactly where you need it too, pre-bent pieces of tubing in 45* or 90*, can also be used to gain a radius. I use a cut off saw to get straight clean cuts on the tubing. These short pieces of tail pipe can be found at your local muffler shop, sometimes free if retrieved from the scrap bin. Hose clamps are used to join the rubber hoses to the tubing. If the tubing is visible in the engine compartment it can be, painted, powder coated, or chrome plated for an extra dress up quality.
The after market now offers chrome plated copper flex tubing that can be utilized in many applications, being offered in various diameters and lengths.
Hose Clamps
Hose clamps vary in design and Ford changed them often in the Fairlane-Torino years.
The band clamp used in the early models, was a good design with even clamping force around the entire hose. It has a small bolt and nut that pulls the two ends together. The band style allowed the ends of the clamp to slip under each other, providing 360* sealing. Their only negative aspect was the slot head screw, that almost never loosened with out cutting them, replacement was required.
Tower clamps are a solid band having the clamp bolt perpendicular to the band. Tower clamps have an unusual method of operation, one end pushes in and holds stationary, while the other is pull up. Over torqueing the bolt makes this clamp unusable, as the band becomes dimpled. Most of this type clamp will not be reused because the bolt will usually snap off while trying to remove them. Cutting the clamp off is the only option when this occurs.
Many Fairlanes used the double wire clamp with the clamp bolt parallel with the O.D. of the hose. This clamped is still in use by Ford today, possibly because it is a very good clamp providing 360* clamping and a hex head screw for ease of installation. I would assume this clamps production cost is low, it is constructed of wire. Ford gained a cost reduction on the production assembly line, stapling the clamp to the hose eliminating rotating clamps and fumbling to get them in the correct location. When removing this type clamp from the hose always cut the staples, forcibly removing the clamp may damage the hose.
The last clamp is the worm drive screw type. It is used almost exclusively by the automotive repair industry as an after market replacement clamp. Its main advantages are its stainless steel construction, 360* clamping force, and hex head tightening screw. This is a very reusable clamp if not over torque.
The after market makes some very good clamps, the worm screw drive foremost of these. Some high tech. clamps available now that are installed using a method similar to heat shrink tubing on electrical wiring. Slipped over the hose and the hose slid over the connection, a heat gun is used to apply heat until the clamp shrinks down tight. This is a very clean looking clamping device, that will streamline the look of your hoses. There are two negatives to this clamp method, difficulty in accessing some hose locations with the heat gun and that they are very hard to remove. If you must remove this clamp, hose damage may occur trying to separate it.
Many auto manufactures even today use the spring clamp. Constructed of spring steel and formed with the inside diameter of the clamp smaller than the outside diameter of the hose. Compressing the tabs together facilitates installation. It provides the advantage of having full contact around the hose and being able to compensate (maintains clamping tension) for temperature extremes. Some hose clamps can leak under extreme temperature changes, many must be retighten occasionally.
Mike the Radiator Man