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Tuesday, May 26, 2009

Bug Out Vehicle Cooling Systems for Extreme Emergencies, by The Oddshot

Vehicles break down. It’s a fact of life. Most breakdowns can be avoided by following a good schedule of preventative maintenance or with a couple of well thought out modifications. But, try as you might, failures can and will occur, even to the best of us.

Anything can put you on the side of the road. Ever run out of gas? Have a flat tire? Bad universal joint on a drive shaft? Charging system go bad? This one happened to me just a few weeks ago. To get an idea of what can go wrong, just drive to work. Look at the cars stuck on the side of the road. A good habit is to make a mental inventory of what you can see that sidelined these vehicles and prepare for worse.

As I said, try as you might, you just cannot prepare for everything. If you had the time and money, I don’t think it would help. I’ve seen brand new parts, fresh out of the box, break down.

But you can learn techniques and tricks that can get you back up and running when you do not have the time or parts to fix it text-book correct and must get moving as quickly as possible and keep moving in the extreme.

The Cooling System

An internal combustion engine is basically a “heat machine”. In an internal combustion engine a fuel/air mixture contained within a closed cylinder and is set on fire…the burning mixture expands pushing the piston down…and on and on until you have power to the rear wheels. A diesel engine is similar but the fuel/air mixture explodes in the cylinder instead of being burned.

For the record...the difference between the two engines is the spark plug of the gasoline engine. When the spark bridges the gap between the electrodes, the compressed mixture is ignited, and the burning of mixture does the rest. This spark must be repeated over and over to keep the fires burning. This process can be demonstrated by use of a device used to tune British Cars with dual SU carbs, called a Gunson Color Tune. An explanation of the device with pictures of the flame front can be seen at the Gunson Color Tuning web page.

Please note that several time in this article, the author mentions "the flame" and its color. When the mixture is correct...the color of the flame in the cylinder will be the same color as the flame found on your gas burner: a pretty blue color.

A diesel engine has no repeating spark ... The mixture in the diesel engine explodes due to the engine's extremely high compression ratio. To be sure ... a diesel engine has "igniters" or glow plugs which are really just heating elements that that aid in warming up the cylinder before starting so this explosion can occur. But this is just for cold starts. After the engine has started the glow plugs turn off...and the mixture continues to be set off by compression.

A simple proof of this is to listen to a diesel (especially an older Mercedes Benz sedan) when it accelerates...that characteristic rattling sound is indeed the sound of the explosions.

It is possible for a gasoline engine to produce this type of sound. If the timing is advanced to far, or if the temperature in side the combustion chamber becomes too high, then the gasoline mixture will indeed explode before the piston is at top dead center, and we will hear the sound of these explosions. This is sometimes referred to as "ping" or "knock" or "detonation". Sometimes these explosions can become so violent that they can blow a hole in the top of a piston, and cause the ring lands to collapse or pound out a rod bearing.

An engine delivers most power and fuel efficiency at a particular operating range, usually about 180 degrees (more or less depending on the engine specs). Below this range the engine will drink fuel, it will run rough and be way down on power. In the extreme, if there in not sufficient heat in the engine a carburetor may even clog with ice in its bores. At the other extreme, if an engine gets too hot, it will overheat. The coolant’s temperature will climb and so will coolant system pressures. The result: you are stuck on the side of the road.

Over the years I have seen coolant system hoses blown off. I have seen cylinder head gaskets leak. I have seen cylinder heads warp. I have seen piston rings cook themselves into pistons, and I have seen pistons seize themselves into engine blocks, all due to too much heat in the engine.

Keeping coolant temperatures within a correct range is vitally important.

So how does the cooling system work? A thermostat controls the flow of water through the cooling system. The thermostat opens and closes its disc-like valve using an internal wax ball and an external spring. When the engine is below operating temperature the thermostat will shut its valve. When the thermostat is closed, water, moved by the water pump, circulates through the engine block and cylinder head only, allowing the water to come up to operating temperature. The closed valve disc on the thermostat prevents the water from passing through the radiator. When that water in the engine reaches a temp of about 180 degrees (depending on the engine specs) the thermostat’s valve opens and allows the hot water to pass through the radiator where it is cooled by outside air. The thermostat then cycles open and closed to maintain normal operating temperature in the engine.

An engine that runs too cool will only be inefficient. This can be repaired easily by simply blocking off the flow of air through the radiator.

An engine that runs too hot can leave you on the side of the road.

Any number of factors can cause a cooling system to allow an engine too run hot. Assuming you already have the proper amount of coolant in the system, some of these factors include: a thermostat that has stuck completely or even partially closed, a partially clogged radiator, a bad radiator cap, a damaged water pump, a water pump that has a bad seal allowing air into the system causing the impeller to loose efficiency by pumping a water and air mix, a failed head gasket that is allowing hot combustion gases into the cooling system, a broken or slipping water pump drive belt.

These are just a number of factors that will cause coolant system failure.

To properly fill a cooling system, Follow the manufacturer’s instructions. These can sometimes be found in the owner’s handbook or a good workshop manual.

In General: With the engine off and the engine block cool (there danger of showering yourself with boiling hot water if the engine is hot!), remove the radiator cap and fill the radiator. Start the engine and allow the engine to come up to normal operating temperature on the gauge. The thermostat should open. On some (most) vehicles, the opening of the thermostat is preceded by a rising coolant level that may overflow the radiator. Then the coolant level will drop sharply, as now the entire system is open and flowing. once the level drops, fill the radiator to its proper level and put the cap back on the radiator.

On vehicles with overflow tanks the process is slightly different, only in that you fill the radiator fully, put on its pressure cap, and then fill the overflow container to the marks indicated.

Maintenance and Modifications

Because of its importance, a vehicle’s coolant system should be inspected and maintained regularly. In addition to fresh caps, thermostat hoses and clamps, make sure the coolant is a correct mix of antifreeze and water.

Due to its location out in front, the radiator is a particularly vulnerable part of the cooling system. Some radiator problems can be avoided by regularly inspecting the coolant in it and changing it regularly. If this coolant ever becomes brown or rusty in color, get the cooling system, especially the radiator flushed. Remove all bugs, dead baby birds and other debris from the radiator to maintain a good air flow through it.

The risk of holes in the radiator can be lessened by removing that plastic grille and anything else out in front of the radiator and replacing it something more substantial and foreign object-proof.

You can make your own grille easily with some steel bar or rod stock (rebar will work) and a piece of chain link fencing. If you can get one inch square chain link fencing, even better. It might not look real good, but it will keep a lot of branches, stones, and birds from knocking a hole in all that soft brass.

Replacing the front bumper with a taller, sturdier unit, maybe one with push bars, will keep some of the bigger stuff (deer, other vehicles, etc) out of the radiator.

Depending on your states laws, remove all pollution equipment, certainly the catalytic converter. Whatever you can do to reduce under hood temperatures will be a big help. An air pump robs horsepower and builds engine heat with its parasitic drag. That catalytic converter is just a storehouse of heat.

Remove the metal cooling fan and install electric fan for engine cooling. If you take a hard front hit, those metal bladed fans will destroy a radiator. You can do this job with a junk yard fan unit, or find something in the JC Whitney catalogue or any speed shop. As a side benefit, you may see some improvement in fuel economy, due to the reduction of parasitic drag. Wire this electric fan with a sensor and manual override switch on dash.

Consider installing an oversized radiator and coolant overflow tank. Trucks that came with air conditioning generally have the biggest radiators. The more coolant you have in the cooling system, the further you can go if the radiator gets a hole in it and you just can’t stop to fix it right away.

Remove the air conditioning system completely. More flow through the radiator, less drag from the pump.

Incorrect ignition timing can cause overheating. Check with a timing light and set to manufacturer’s specs.

Get rid of all your vehicle's inexpensive “spring tension”-type cooling system hose clamps. Replace them with new “screw type” (Aero-Seal) hose clamps. Never, unless you have no other choice, re-use an old hose clamp. It will just fail on you.

In your “Get Out Of Dodge” kit you should have spare belts, hoses, clamps, caps and thermostats. Always carry a can or two of Stop Leak. Yellow and brown cans of Barr’s Stop Leak have always been in the trunks of my cars. Always keep at least a couple of gallons of water for coolant and a suitable empty container to get more if needed.

Remember this. During the course of my 30 years as a mechanic I have seen many new thermostats and radiator caps go bad in a few miles, hoses that just refuse to stay seated, cylinder head gaskets that go bad for no apparent reason, and on and on and on.

So, an overheat can still happen. What then?

Failures in the Extreme

Symptoms of a cooling system failure include a higher than normal (and sometimes rising) temperature gauge reading, steam coming from under the hood, or a pool of coolant under the vehicle. If you’ve run the engine so hot, so long that you hear a knocking noise, you’ve run it too long.

During the course of 30 years I heard hundreds of times, "I only ran it for five minutes after the temperature light came on," while I was looking at a car that now needed thousands of dollars of engine repair that could have been avoided. This was in the best of times. In the extreme, you must address a cooling system problem as soon as possible to be able to keep moving.

Some coolant system problems are fairly easy to diagnose. A broken, leaking or collapsing coolant hose is easy to spot. A broken belt is fairly obvious.

A water pump can be checked by grabbing its pulley at the top and bottom and wiggling it. It should have no play. If it does the pump has a bad bearing. Water pump seals can also leak: air in, water out. Check that by visually checking its vent hole(s) with the engine off. These will be located on the pump body just behind the pump’s pulley. If you cannot see the hole, run your fingers all along the pump's housing, if your finger gets wet, the pump is bad. Replace it if you can.

A simple test for a radiator cap is just to compress its valve and spring using your hand. If it has “a fair bit” of tension, it should be OK. Otherwise, replace it.

A bad head gasket or cracked cylinder head can be detected by way of a compression test, a cylinder leak-down test. If you have access to an exhaust gas analyzer you can test for the presence of exhaust gases in the radiator while the engine is running. Just take off the cap (very carefully!) and hold the probe over the open radiator. If you detect Hydrocarbons or Carbon Monoxide, you have a cracked head or bad head gasket.

If you have access to a coolant system pressure tester, you can remove all the spark plugs, fill the coolant system with water, pump air pressure into the cooling system, and crank the engine (as if trying to start it). If you have a bad head gasket, water will enter the affected cylinder and be pumped out by the cranking. The coolant will be pumped out with some force, so stand clear of the spark plug holes!

You can check for a bad thermostat by removing and inspecting it when it is hot. In most vehicles the thermostat is located in a housing bolted to the engine block. The upper radiator hose is secured to this housing. A bad thermostat will be one that is stuck partially or fully shut. Replace it with a new one.

A clogged radiator can be checked by getting the engine hot, and then with the engine off, very carefully feeling the radiator core (the cooling fins) with your hand for cool or cold spots. These cool spots are places where clogs are preventing the hot water flowing. Holes in the radiator can be detected by puddles of coolant on your feet!

In the extreme, a holed radiator can be repaired well enough to keep you going by closing off the injured cooling tubes in the core of the radiator. The core of the radiator is made up of rows of these tubes, sometimes as many as 5 or 6 tubes deep. A fast expedient repair is to grab each holed tube with needle-nosed pliers, flatten the tube and fold it over, to prevent your from coolant from leaking from that tube. If you can, fold each damaged tube over twice. Put in a can of stop leak, and top up the coolant, remembering to wait for the thermostat to open. A more “complete temporary” repair would be to solder the tubes closed, but if you don’t have time the pliers will do the trick.

But what can you do if you are in the extreme, and must keep moving? You’ve checked for the obvious, the hoses are dry and tight, the belts are good, the cap seems to hold pressure, there’s no sign of leaks and you have a good level of coolant in the system. But the engine is running hot. Way hot. Or what if you find you have a clog in the radiator, or a bad water pump, maybe even a bad head gasket, and you must keep moving. What to try next?

You could turn on your heater fan. The heater core can act as a secondary radiator. The fan blowing air through it can cool the hot coolant by a couple of degrees. It works! I’ve used this any number of times.

But what if it still runs hot? What next?

I have been able to reduce a high engine temperature by “gutting” the thermostat. This is done by removing the spring and disc-like valve, leaving just the housing. This will look like a fairly large brass flat washer, a brass disc with a large hole in the center. You just install it back where the whole thermostat assembly was. Old time racers call this a “blanking sleeve”.

Never run an engine without a thermostat or blanking sleeve!

So why not just put in a new thermostat? A blanking sleeve will allow the water to flow through the entire system including the radiator. It controls the flow rate so its slow enough to collect the heat out of the engine and get cooled by the radiator.

A blanking sleeve has no valve so it cannot close to allow the heat to build up in the engine. I have reduced engine temperatures by as much as twenty degrees by modifying a thermostat into a blanking sleeve. A blanking sleeve allows water to flow at “just the right speed” slow enough to pick up the engine’s heat and slow enough that it stays in the radiator long enough to get cooled off.

The trade-off is that without a thermostat’s regulatory action, it will take longer engine to come up to normal operating temperature, especially in the winter. In cold weather, the engine might not come up to normal operating temperature at all. You may find you have to stop the air flow through the radiator to warm up by turning off your cooling fans or by covering the radiator core.

So why not just leave the thermostat and blanking sleeve out entirely? Because the water will flow, unrestricted, and very fast through the engine and radiator. Too fast to pick up the heat from inside the engine, too fast to get cooled off in the radiator.

But, a blanking sleeve might allow a 20 degree reduction in temperature, which just might be what you need to keep moving and get where you gotta be, in the extreme.

- OddShot


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