stevescivic

my friend has a 92 accord and recently it started developing some overheating issues. He says that when he was driving that his car would all of the sudden have the temp gauge start rising and stay at the 3/4 to hot range and then just drop and then rise again and drop.

When he came by my house the lower rad hose was cold so logically I thought it to be the thermostat no opening up. I replaced the thermostat for him and bled the air out of the cooling system. All was good until we went for a drive and then the overheating issue started all over again. The cooling fan sensor works b/c the fan did kick on every now and then when the cooling system was actually working.

so... as the engine temps starting rising again I thought that maybe there may be some air in the cooling system. So I bled the coolant out of the air bleed port and then all of the sudden the lower rad hose became hot again and coolant was flowing normally. Again we went for a drive and it was okay until we stopped and let it idle for 5 minutes. Once again the temp started rising.....

So I know it isn't air in the system causing the coolant to flow.
I also know that the coolant mixture is right.
I also know the rad isn't clogged (its new)

My only conclusion here is....

blown head gasket but I think that would cause constant overheating
bad rad cap but if that were the case the hoses would feel pressurized
faulty water pump but again why would that cause the rad hose to be cold then all of the sudden hot and then cold again...

What could it be?

Thanks

dockersguy

I have a 92' Accord too. I bought a brand new Stant brand thermostat and it was one of the reasons why my car overheated. I replaced it with a Honda OEM thermostat and it hasn't overheated since. Your overheating may have a different cause, but a non-oem thermostat IMHO is definately worth looking into. Can you confirm that both fans are or are not coming on when they're suppose to? I would also go ahead and check the radiator and condenser fan relays, fuses, coolant temperature switches, and the hoses.

stevescivic

strange thing is that when I purge the cooling system the lower rad hose gets hot again and everything works fine. I drive it for 5km's or so then the rad hose becomes cold again... Then a purge and the it flows.

It almost suggests to me that air is getting into the cooling system via a blow head gasket.

Is there any way I can determine a blown headgasket via compression test?

I know for a fact the fans work b/c they did cycle on several times while idling before the overheating started acting up.

Thanks

dockersguy

Do a pressure test on your system to determine if there's an actual pressure leak. Or look at the color of fumes coming from your exhaust. I forget which color means what, but you basically have white smoke, blue smoke, or black smoke. They each mean you're burning something different (oil, coolant and....) Can anyone else chime in on this? I would also check the hoses for little leaks. Check under the car for any coolant loss after a drive. From what you're saying, it seems logical to me that air is getting into the system somewhere. How's your reservoir bottle doing? Does the coolant level change after a long drive? Sometimes after a long drive the coolant in the reservoir bottle/overfill bottle will rise some.

JimBlake

If you're burning coolant, your exhaust will smell sweet, like antifreeze.

A pressure-check will be good. Sometimes the leaking coolant evaporates & you can't find the leak. Pressurizing it cold will make it leak liquid.

Check the hose from the radiator cap over to the reservoir bottle. Whenever the engine runs up to temperature, some antifreeze pushes out to the reservoir. When the engine cools off, it's supposed to suck back in. If there's a break in that hose, it's like drinking thru a straw with a hole. You get lots of air. Heat up & cool down the engine a couple times & that draws air back into the cooling system.

stevescivic

there are no obvious leaks and cracks and the hoses are all new.

Its like the water pump isn't moving any of the water in the engine b/c the hoses don't feel firm. I changed the rad cap and I still have no luck.

I think I will have to get the system pressure tested to really know.

Thanks