I have a 86 mustang lx 4 cil. Engine and it keeps overheating I've replaced belts radiator cap and thermostat I've flushed the radiator and checked for leaks around the thermostat houseing and water pump but found nothing.Does anyone have a clue of what's going on.Or what I should check for next.

If your belt is not slipping and there are no leaks and the system can
Build up pressure than the only other thing to check would be the fan.
Check that the blades are not loose or damaged and if you have a fan clutch
Ensure it is engaging.

Maybe your water pump is going bad.
They are cheap and if you can do the work.
Just change it out and see if it solves your problem.

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Originally Posted by Vandy-1

If your belt is not slipping and there are no leaks and the system can
build up pressure than the only other thing to check would be the fan.
Check that the blades are not loose or damaged and if you have a fan clutch
ensure it is engaging.

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Thanks for your reply?All belts are tight and my fan comes on but I haven't checked it to be loose or damaged I'll do that.

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Originally Posted by Demonspeeding_2005

Maybe your water pump is going bad.
They are cheap and if you can do the work.
Just change it out and see if it solves your problem.

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I checked the water pump but didn't see any leaks.Thanks for your reply.

Check your ignition timing. If it is too far advanced it could cause overheating. Check your lower readiator hose when cold to see if you can collapse it by hand. There is usually a coiled wire in the hose to keep it from collapsing because of the suction of the water pump. If that wire rots away, it could allow a restriction in that hose. Check the front of your radiator for a buld up of crud that might restrict air flow through it. This build up of crud can be especially hard to spot in cars with AC, because the AC condenser sits in front of the radiator, and you can't even see the front of the radiator. I have seen instances where a plastic bag was stuck between the condenser and radiator. Obviously you have checked your water for the presence of oil (usually a white froth) that would indicate a blown head gasket. Good luck.

Thanks I'll try those things.

Even if it is not leaking doesn't mean it not going bad

1986, when it starts to over heat try turning on the heater blower on high and see if this cool thing down a bit if it does, sounds like you have a rad problem even though you have flushed it is still could be plugged and not letting enough coolant though the tubes, take it out and take it to rad shop and check the core

Also, if your radiator fan is thermostatically controlled (goes on and off at idle)
Your thermostat that controls the fan may be bad.

I've flushed it once more but still bad circulation.the bottom coolant tube seems like the springs are bad I'll check them.and the fan comes on as soon as the car is started and stays on.

One simple thing that could be the culprit is a stuck thermostat that would prevent the coolant flow from the engine to the radiator. If you don't wish to just replace it, you can check its functioning easily. Remove it from the vehicle and suspend it in a pot of water, so it does not rest on the bottom. Put it on the stove and check the water temp. You should be able to see it open when the temp approaches the specified temp of the thermostat 160, 180, etc. You can also check the function of a thermostatic fan clutch easily. Sart the car and allow it to warm up. As it heats up, you should be able to hear and feel an increase in air flow.

I took my thermostat out and my fan starts as soon as the car is started and doesn't go off until I cut the car off.

I am assuming that you don't have an electric fan but have one at the end of your water pump. A thermostatic fan clutch will turn the fan at all times but with so much slipage that it won't move much air. As it heats up the slipage will diminish until you have positive engagement of the fan.

So what should I do about the fan?Or is there anything I can do?

If your car has a fan clutch, and it is indeed bad, you should replace it. If the auto parts store offers a standard fan clutch and a "heavy duty" model, spend the extra money on the better one. One from the dealer will probably cost much more. I have seen some people remove the clutch altogether and replace it with a spacer to keep the fan in its original location. With that setup the fan will always be engaged. That may affect your gas mileage and may put more stress on the water pump bearings. Do not let someone talk you into putting on a "flex-fan". I have read of those things flying apart and causing injury to people.

I'll go to the parts house now to get one.and yes the flex fans can hurt you my brother has a scar where one flew off and bit him on the head.

My brother-in-law restores old 70's cars and I asked him about my overheating problem and he told me basically the samethings you people have told me.Then as we were talking I rememberd after I put a new heater core in the car started overheating he sayed for me to unhook the heater core and see if that solves the problem or either that or I hooked my heater core hoses up the wrong way what do you think.

There is no way that an improperly hooked up heater core would cause an overheating problem. It is just a tiny radiator (heay exchanger) that removes some heat from the engine and puts it into the passenger compartment. You can bypass the heater core altogether, with no affect. When you replaced the radiator, are you sure that it was the same as the old one (same number of rows)? Did you perhaps leave off some of the fan shrouds? With the engine running and the radiator cap off, can you see water flow from the horizontal cooling tubes? It seems like you have covered all the bases. I am stumped. Maybe one of the other members will get an epiphany in the dead of night.

Correction: I just noticed that you DID NOT replace the radiator. You might consider removing it and have it rodded by a radiator shop to remove any crud from the cooling tubes, or just buy a new radiator.

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Originally Posted by Dr D

There is no way that an improperly hooked up heater core would cause an overheating problem. It is just a tiny radiator (heay exchanger) that removes some heat from the engine and puts it into the passenger compartment. You can bypass the heater core altogether, with no affect. When you replaced the radiator, are you sure that it was the same as the old one (same number of rows)? Did you perhaps leave off some of the fan shrouds? With the engine running and the radiator cap off, can you see water flow from the horizontal cooling tubes? It seems like you have covered all the bases. I am stumped. Maybe one of the other members will get an epiphany in the dead of night.

Correction: I just noticed that you DID NOT replace the radiator. You might consider removing it and have it rodded by a radiator shop to remove any crud from the cooling tubes, or just buy a new radiator.

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I'm going to blow the radiator out bugs and wantnot I just replaced the water pump this morning and the little fan was corroded and I found two pinched tubes one going from the water pump to the heat core and another from the themostat housing to the heat core so I replaced them.now I've found that when I took my lower radiator hose off the coil spring inside was rusty and broken off so I'm going to buy another.