1990 Toyota Camry 4 cyl manual

Never had leaks, still no leaks, 205,000 miles

heat stopped working this year, so I bypassed heater control switch and put new hose between engine and heater core

heat worked great for a week

then car starts overheating

have changed thermostat and radiator cap

car runs fine and doesn't start to overheat until I really get on the gas

oh yeah, the heat doesn't work yet again

fans are working

is this a clogged system (fluid was rusty lookin)

or air in the system?

or something else completely?

 

Did the engine temp gauge needle ever get into the red?

Start the engine leaving the radiator cap off. As the engine warms up observe the coolant, it should start to circulate. Wear safety or other eye protection in case the coolant blows out the filler port.

When the engine is warmed up the upper and lower radiator hoses should be hot.

Once the engine is warm, if no circulation and or one hose is hot and the other cold the water is not circulating properly.

If the coolant spews out the filler port the head gasket could be blown.

If all OK drain out all of the coolant. Look into the radiator cap fill port for signs of clogged radiator tubes from rust.

Remove the upper radiator hose at the radiator and lower hose at the water pump.

Back flush the radiator by applying water to the hose going to the water pump. Flush the radiator until the water is clear.

Remove the thermostat and apply the water to the outlet pipe on the head to back flush the engine.

There is a drain port on the right rear of the engine block. When draining open this port and allow all the coolant to run out, then allow the flushing water to come out.

You should be able to apply a full open garden hose to one of the radiator hoses or hose ports (or openings in the block) and have the water run out the other without backing up.

For the heater remove the hoses going to the heater core. Suggest not removing them at the firewall as the metal hoses can easily be damaged. You want to be able to apply the garden hose to one heater core hose, preferable the return coolant hose. Watch the water coming out the other hose for debris and run the water clear.

On rare occasion the water pump impeller will fail causing over heating. If the pump is working the coolant should be circulating.

When filling the coolant system burp the large radiator hose of air to allow as much coolant into the engine as possible.

If the radiator and engine are not clear of rust and other debris, the coolant circulates, etc and the engine still overheats do a block test for exhaust gases in the coolant caused by a leaking head gasket.

 

Great tutorial on flushing the system.
I've never done this but wanted to a time or two before.
Now I know how it's done.
Thanks!

 

Start the engine leaving the radiator cap off. As the engine warms up observe the coolant, it should start to circulate. Wear safety or other eye protection in case the coolant blows out the filler port.

When the engine is warmed up the upper and lower radiator hoses should be hot.

Once the engine is warm, if no circulation and or one hose is hot and the other cold the water is not circulating properly.

If the coolant spews out the filler port the head gasket could be blown.

well, if the head gasket has leaks, you will see something that looks like a beer foam, forming in coolant. it can be very vigorous formation, along with coolant gushing out of radiator neck. coolant that does not have any exhaust leak into it, may have some bubbles shwoing, but normally circulates pretty clear and uniformly.