Overheating (Engines)

You got those 3.8 (60,000-80,000 miles) Blues. Could be a thermostat. Are you going through coolant? If so, the technician is probably right. The 3.8 motor wants head gaskets every 70,000 miles or so. Plan on machining the head flat again too. If you are not going through coolant, it would sound more like a thermostat or possible blockage in the system.

Check the condition of the radiator, the water pump, the thermostat, and the pressure cap. I had a similar problem with my 1991 Chevy Cavalier (4 cyl, 2.2L). When all is well it normally runs about 180-200 degrees F (the electric fan clicks on at about 200 and shuts off at 180, fan runs continuously w/AC on). Because I neglected to flush the system for about 3 years, the radiator clogged and the water pump was on the way out (all but three of the blades had eroded away). The car was running 230 degrees (about 3/4 of the way up the gauge). Even after the water pump was replaced, it still ran hot even though the T-stat and cap were ok and there was plenty of coolant. I flushed out the system and replaced the radiator. This cured the problem instantly. Running temp fell from 230F to 180F (about 1/4 of the way up the temp gauge on my car). I don't know many particular problems that occur with '90 Cougars, but these are several generic problems that cause overheating. Check the T-stat by removing it and boiling it in water on the stove. If it is good you will see it open as the water temp in the pan increases. While the t-stat is out of the engine, start it and run it for the length of time it takes for it to overheat. If the t-stat is the problem, with it removed, the temp gauge won't even lift off the peg. (Don't run the engine without a thermostat longer than it takes to verify the problem). Also check water flow through the system by warming up the engine with the cap off and looking into the radiator fill pipe. With the engine at running temp, there should be a strong water flow out of the tubes (water turbulence for a vertical radiator). Also make sure the fan works.

Bear in mind that any air (as well as gunk) trapped in the coolant lines will cause overheating, particularly higher up around the head gasket. This overheating can definitely cause warping and result in a blown gasket. This is especially common in cars with aluminum head gaskets. (I don't know how the Cougar was designed.) Always "burp" your coolant system after flushing.

It is really a bad idea to even crank the engine over if the timing belt is broken. Engines can be either so-called "interference" engines or "non- interference" engines. In an interference engine the valves at their lowest are lower than the pistons at their highest, so if the timing belt breaks the valves and the pistons can collide, badly damaging the engine.

If it's a non-interference engine this type of damage can't occur, but w/o a timing belt powering the valves the engine won't run at all.

If the broken belt isn't a timing belt, but simply a drive belt for the water pump, then the engine can be started w/o a belt. But it is very likely to overheat rather quickly if you actually drive the car that way.

no coolant or you have a bad thermostat and or bad water pump .

Coolant could be low. Thermostat could be broken. Water pump or fan may not be working.

I had a 2002 Vauxhall Corsa which was running hot and it turned out to be the water pump which needed replacing.

Causes for an overheat: low coolant, failed water pump, plugged radiator, failed headgasket, inoperative radiator fan, stuck thermostat, missing belt, etc

First confirm that the engine IS actually overheating - steam, no heat to the interior etc. Sometimes a temperature sensor will fail and give a misleading 'overheat' reading on gauge. For that matter sometimes the gauge can fail and give the same misleading reading. Check that the cooling fan comes on when the engine temperature starts to rise above 'normal'. If not check (in order) fan fuse, fan relay, fan sensor, fan. Real overheating is caused by a lack of coolant AND/OR lack of coolant flow. Modern cooling systems are 'closed'. In other words there should be little or no loss of coolant. If the level is significantly low you have a leak....either external or internal. With the coolant topped up to the correct level and the radiator cap on, run the engine and look for visible leaks...hoses, valves, radiator etc. Internal leaks, eg. head gasket will usually be accompanied by white exhaust smoke (steam), hard starting, rough running and bubbles in the expansion tank. Sometimes, though NOT always, you will find the engine oil has a milky look and/or engine oil will be mixed in with the coolant. == == Lack of coolant flow can be caused by anything in the system that causes an obstruction......in order of common occurance......thermostat stuck closed, radiator blockage, heater core blockage, water pump failure. One last point. because of design considerations many vehicles have the radiator mounted at a different level than the uppermost coolant passages in the engine thus trapping air in the coolant passages. In short the system must be bled of air in order to properly fill with coolant. Such systems will incorporate bleed screws usually in either the top/side of the radiator, the top hose, the thermostat housing and sometimes in all of these points. To bleed out the air do NOT run the engine as you fill the radiator. Instead, open all bleed screws. As you fill the radiator coolant will run out of one or more bleed points. Close this bleed point(s). Continue to fill until coolant escapes from the next bleed point then close that one. Proceed until coolant has escaped from ALL bleed points then continue to fill to the correct level. The expansion tank will have minimum and maximum level markings. Fill only to the minimum level mark with the engine cold. Explaining how to check each of the individual components would take up more space than I have so if the above doesn't help email me at seahog@btinternet.com.

Check the oil level add as needed. Check the water (and antifreez) add as needed Check the rediator cap. re-place if it's old or missing the seal gasket Check the thermostat. replace if old or not working See that the belt to the water pump is adjusted properly Check to see if the water pump is working. Check the radiator. Make sure it isn't clogged

It's a good idea to visually check the oil, water, belts and hoses everytime you fill up. It takes less than 2 minuites and could save you large amounts of money and headaches.

In that case, (Fans not running), it may be a blown fuse, bad fan motor, or a bad thermal sensor.

Answer. If fans are not coming on, check coolant temp switch. I ahd same problem with my car. I had my cooling fan direct. Had a bad coolant temp switch

Answer:

I experienced one time an engine that was overheating due to a slipping overheating transmission. Although some diagnostics can be obvious, sometimes there is a curve ball.

If the fuel economy has dropped also?

We've seen a few older cars with cracked head gaskets - the combustion stroke, gasse are 100's of PSI. And that pressure blasts into the water jacket during operation, causing the coolant to stop circulating - normally due to extreme over-pressuring.

This should show itself as bubbling through the radiator cap - but to diagnose properly, you need a small test kit to check. (Eric the carguy and Scotty Kilmer have a video about it on ewe toob) Being that I've rebuilt only three engines in my life, it's safe to say that all the answers above are more likely - especially for a japanese car, but the septic-tank-mobiles and our aussie rubbish - this is pretty comon.

Also, check to see if the fan shroud or parts of it are missing.

For a normal radiator cooled engine:

Lack of coolant

Punctured radiator

Radiator fins clocked with debris

Corrosion inside radiator that leads to blocked galleries in the radiator

Lack of engine oil

Lack of airflow around the engine block (contributory)

Cracked Head(s)

Head gasket failure

Warped engine block

Old coolant

Water pump failure

Oil pump failure

Blocked cooling galleries in engine block and head(s)

Thermostat failure

Cooling fan failure

Air cooled engine:

It depends on the cooling design. Mostly it's due to lack of airflow, or in some cases oil, cracked head/gasket failure.
When you drive too long.

You didnt say if the water pump was changed. No hot air means no circulation.

Anyways, Coolant is a fluid that keeps a car from getting too hot among other things. If there is low coolant the car will overheat. When the coolant ciculates through the engine it will also go through a thing in the dash that is like a small radiator called a heater core. A fan or blower move air through this part and pushes the hot air from the heater core into the passenger compartment. This heater core is usually the highest point of the coolant flow. Since fluid seeks it's lowest level, the heater core is the first to lose the hot coolant. Therefore your blower blows accross a cold heater core and gives you cold air.

If you don't have a leak, then when the thermostat was replaced, the coolant may have not been bled of the air in the system.

I would first fill the coolant and check for any leaks first. There is a common problem with the Buick centuries if you have a 3.1 motor. The intake manifold gasket is common for leaking.

In any event, don't run the engine if it goes into the red. Overheating can cause headgasket problems. See othe posts regarding this issue.

Let me know how you make out.

The heater core does not need to be removed to be checked. If the hose going into the heater core is hot and the one coming out is cold, the tells you it is retricted. Another way to verify is to remove the hoses going to the core, hook up one without installing into the car and run it. It should get hot-very hot, and then see how hot the hose is coming out of the core is like now.