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Old March 5th, 2010, 12:49 AM
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Arrow Understanding The Cooling System

This article is about understanding the cooling system.

So... you're having trouble with your vehicle either overheating, not warming up, boiling over, etc.

Don't forget to read the "tips" at the bottom of this page.

the perfect mix of antifreeze (glycol) and water is 50% glycol to 50% water. Actually as long as you have over 40% glycol it's perfect.

Common causes of overheating:
  • malfunctioning radiator cap, if it doesn't hold it's pressure (boiling over) the boiling point temperature will be much lower. Most radiator caps hold at least 14 psi pressure.
  • bad water pump. This happens rarely. Water pumps only go "bad" if the seals start leaking. The actual "propellor" or impeller is usually made of steel or aluminum and rarely of plastic so the actual pumping mechanism never goes bad.
  • slipping drive belts. Check your belts for correct tension and/or cracking with age. Slipping belts will not drive the water pump correctly.
  • only using water and not a glycol mixture... your boiling point will be 100 deg. C and not higher. Your engine block and cooling passages will corrode. Glycol protects the metals in your engine as well as increasing the boiling point and lowering the freezing point. It is a misconception that anti-freeze only keeps the cooling liquid from freezing in the winter time. It also works in the reverse in the summer to keep it from boiling over.
  • malfunctioning thermostat. These are usually located under a small aluminum housing where the upper radiator hose comes off the engine block. They are $5 to replace plus a $1 gasket. They are stamped to indicate the temperature that they open to allow cooling water to flow into the radiator. If they stay stuck closed then no water will get to the radiator and your engine will be re-circulating it's water... hotter and hotter it goes.
  • stop and go traffic and you're running the air conditioner as well. This lets your engine breath even hotter air than the outside ambient air. Turn the air conditioner off if your temp. gauge is going into the red. Idle the engine a little faster. If your fan is belt-drive this will help cool things as well as moving the cooling water faster around the engine/radiator.
  • a collapsing lower radiator hose. Generally they have a spiral spring inside which keeps the hose from collapsing. Sometimes there is no spring or the spring is weak. The vacuum created by the water pump trying to suck water from the radiator can collapse it and it's like sucking water from a straw. The engine gets starved of cooling water. When the motor is hot, open the hood, have an assistant rev the motor up a bit. Watch and see if the hose collapses.
  • broken relay or thermostat that controls the electrical radiator cooling fan. If you car doesn't have a belt-drive fan then the thermostat switch could be broken and not turning the fan on in stop & go traffic.
  • broken belt-drive fan thermostat. Most belt-drive fans have a viscous coupling or similar liquid operated clutch. When it gets to a certain temperature it closes and turns the fan. This clutch is built into the fan assembly just behind the blades and ahead of the belt-drive pulley that the whole thing is mounted to. The clutch can be bought separately.
  • is your radiator shroud missing. I've seen this before. Look at some other vehicles besides yours and you'll see that most have a plastic housing that sort of funnels the air from the radiator towards the radiator fan. If you are missing this shroud (cost cutting of the car manufacturer), when your fan starts rotating it will basically suck the air from around it in a circulating path and not from through the radiator. You may be able to find a fan shroud from an auto-wrecker or as an aftermarket piece at your local autoparts store.

Common causes of not warming up quickly in winter:
  • malfunctioning thermostat. The thermostat is stuck in the open position and is recirculating cooling water to the radiator even though the engine hasn't warmed up yet. Unless you are pulling a trailer and/or going up steep grades in cold weather it will not warm up.
  • it's extremely cold outside and your vehicle is functioning correctly. Diesels have a habit of not warming up very fast, especially if you start it up cold and drive downhill (from the ski lodge for instance) you may find it doesn't warm up until you drive a bit faster and on flat roads or start to go uphill. This is normal because diesels are much more efficient that gasoline engines.... therefore they also waste less of the fuel energy on heat which is a by-product of combustion.
TIP: change your thermostat about once every 2 to 3 years. They are made with a bi-metallic spring which expands at a certain temperature to open a valve to either allow or not allow cooling water to enter the radiator to be cooled. It stays shut until the engine has warmed up to operating temperature and regulated the cooling flow to the radiator to keep the temperature of the engine constant. Changing this thermostat on most vehicles is a snap. Takes less than 1/2 hr. Basically you remove the two bolts holding the aluminum housing on the motor block and remove it. Inside is the thermostat. You'll have to clean or scrape both surfaces to remove the old gasket material. Pop in the new thermostat (facing the right way!!) and a new gasket. Bolt it back up and fasten the upper rad hose. That's it!

TIP: change your coolant mixture every 2 years. Dispose of it safely and find out what the disposal rules are in your area. Please don't dump it down the drain.

TIP: the correct thermostat is critical to proper emissions system performance and correct engine function. A thermostat that is too hot will result in improper combustion (pre-ignition or pinging) which is detrimental to engine performance and can do serious damage to your engine if you keep your foot down heavy on the throttle and let it ping a lot. A little bit once in a while is normal but not if you're not driving down a hill for example. Usually a bit of pinging occurs on cheap pump gas when going up a hill in high gear and the rpm's drop just before shifting into a lower gear. An old adage was to put a lower temperature thermostat in vehicles to increase performance. This was true 10 years ago but not with the modern computer controlled vehicles. The newer vehicles will try to adjust the fuel injection timing and duration and/or ignition timing to counteract the lower temperature thus resulting in worse performance and bad gas mileage plus evil tail-pipe emissions because the fuel injection is dumping too much gasoline into the motor. If your vehicles comes with a 205 degree F. thermostat it's probably ok to go to a 195 degree model but never get a 180 degree model for instance. If you have put in a slightly cooler thermostat and are still experiencing pinging problems try to see if replacement spark plugs are available in a lower temperature heat range. Usually this will cure your troubles, along with some good combustion chamber cleaner.

Article provided by Peter Ferlow

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antifreeze , cooling , f150 cooling system , glycol , radiator , system , understanding

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